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Richard L.
2007-Dec-31, 08:05 PM
I love a good mystery, and recent astronomical observations have created a mind bending controversy. All galaxies rotate, and when astronomers began to measure the orbital velocity of individual stars within a galaxy, they noted something entirely unexpected. Some distance from the galactic center, individual stars moved with orbital velocities independent of their distance from the central mass. Rather than follow the basic gravitational rule that as distance from a central mass such as the sun increases orbital velocity must decrease, individual stars defied Newtonian rules and all moved at the same velocity. Such unorthodox behavior created a huge paradox for science, and only three possible choices could explain the observations. Either the data is faulty, or Newton was wrong about gravity, or there is some mysterious gravitational stuff out there that causes the stars to orbit faster than they otherwise should. The data has been confirmed by many astronomers using diverse instruments and methods, so the anomaly is real. The second possibility, that our gravitational theories are wrong, is offensive to most scientists who refuse to give this possibility credence. While most scientists will freely admit that we really do not understand gravity, it is scientific heresy to claim that Newton and Einstein were wrong describing this fundamental force. To preserve these time honored theories, most scientists have opted for the third possibility and assumed the existence of a deep space ghost; an enigma they call Dark Matter, so named because it is invisible, undetectable, and its nature uncertain.

Most scientists accept Dark Matter as a real despite the fact that they cannot see or measure it or even agree on what it is. It is theorized to be some enigmatic matter that gravitationally affects large-scale systems such as galaxies or galactic clusters, but does not interact in other ways with ordinary matter. All we know is there must be an awesome amount of it throughout the universe to account for our observations and theories. Without Dark Matter most of the universe is missing.

Dark Matter is ubiquitous yet displays no measurable attributes such as electrical charge, inertia, spin or other of the usual properties of matter. It does not absorb or emit electromagnetic radiation or interact with atoms or other subatomic particles; exchanges that might betray its presence. In other words, it will be very difficult to prove that it exists at all.

If Newton and Einstein’s descriptions of gravity are complete (and this may be a big assumption), all matter in the universe must follow these laws without regard to scale or distance. The laws of celestial mechanics dictate how an independent body such as a planet or spaceship should move inside a gravitational well. Einstein theorized that gravity is not a force between two objects but the bending of space-time as a property of mass. The further away an object is from a large central mass, the shallower the slope of the gravitational well surrounding that mass. In other words the further away from a mass, the weaker gravity field will be. Celestial mechanics requires an object nearby a central mass to move at a greater orbital velocity than if the same object were at a distance. If it moves slower than that required by its position in the gravitational well, the object will spiral into the central mass, and if it moves faster it will move away from the central mass. A popular way to describe this law is to imagine the central mass has less pull (less bending of space-time) on a body as it moves further and further away from the mass. For instance, because of its proximity to the Sun, Mercury races about its orbit in 88 days just to keep from spiraling into the Sun and burning up. Earth, being further away, orbits with a lower orbital velocity, and poor Pluto way out there in the boondocks of the solar system, has an orbital velocity that is the lowest of all the planets taking that frozen world hundreds of years to complete a single orbit. Newton’s laws of celestial mechanics are well understood, so much so that his equations are used to sling a spaceship from Earth to Saturn with the precision required to orbit that planet and send a probe to the surface of Titan. That is like firing a rifle at a target placed on the Moon and hitting the bull’s eye. If Newton’s equations work this well, most scientists argue that they must be a correct description of nature.

Nevertheless, for me the concept of Dark Matter to explain a fundamental process of the universe is nonintuitive and unsatisfactory. When scientists invent some mysterious substance to preserve their overall concept of the universe, one has to suspect the theory they are striving to protect could itself be fundamentally flawed. One infamous example was Einstein’s invention of the cosmological constant to explain an inevitable consequence of his equations that contradicted his intuition. Einstein believed that the universe was static, neither expanding nor contracting under the influence of gravity. A consequence of his theory demanded that the universe was expanding, and this was so unsatisfactory that he invented the cosmological constant (lambda) to preserve his idea of a static universe. Later on when Hubble proved that the universe was indeed expanding, Einstein called lambda his “greatest blunder”. The recent discovery that the universe is experiencing an accelerating expansion has revived the concept of a cosmological constant and thus change Einstein’s greatest blunder into possibly his greatest intuition.

In the 19th century scientists invented another mysterious substance they called the Ether. It was known that light traveled in the form of a wave, and the Ether was necessary to explain how an electromagnetic radiation such as light could travel through empty space. After all, what was waving in the vacuum of outer space? They reasoned it had to be an invisible substance, the Ether. The Ether could not been seen or measured, but it was necessary to preserve the electromagnetic wave theories in vogue at the end of that century. Sound familiar? By the 20th century, Einstein and Max Plank obviated the need of the Ether by explaining light as both a wave and a particle that traveled in packets or quanta. This explanation doomed Ether to a historical notation in textbooks.

The observed constant velocity of stars within a galaxy may help explain another mystery that has been debated for years; the diverse spiral shape of galaxies. Intuition and experimentation can be used to help explain galaxy formation and geometry. Let a bucket of white paint simulate the spiral formation of independently moving particles in a viscous material. Gently stir the paint until the entire bucket of paint assumes a constant rotational velocity, then pore a cup of black paint into the center. Note the black paint begins to form spiral arms as propelled by centrifugal force it moves out from the center. Spiral arms of black paint form because those individual particles further away from the hub have a longer distance to travel to complete a revolution than those closest to the center. Because of the viscosity of the paint, the black particles at the leading edge attain a certain terminal velocity and at some distance from the center they all move with the same velocity, a velocity that is not fast enough to remain synchronized with the inner particles. A spiral arm forms as distant black paint particles lag behind, taking longer and longer to make a complete revolution. On the other hand, if the particles were locked into position and unable to move independently as they are in a wheel, the particles at the periphery of the wheel will have a greater velocity than those nearest to the hub, each making a complete revolution in equal time. If the particles were allowed to move slower and slower as they moved from the center, spiral arms would not form. Another example of this is a line of ice-skaters performing a rotation about a central point. If the skater at the end of the line cannot increase his or her speed proportional to the distance from the center, they will lag behind and the entire line will sag. If the skater can keep balanced and assume the required speed, the line will remain straight but the end skater will be traveling faster than they might wish. They will also have to hold tight to their companion (an analogy of gravity) or the affects of centrifugal force will tear them away from their friends and fling them out of the rink. If the skaters were allowed to move independently, slower and slower as their distance from the center increased, then they all would assume asynchronous positions around the ring.

I also have a problem with the explanation that Dark Matter forms a halo outside of each visible galaxy. This halo of Dark Matter’s is presumed to gravitationally attract individual stars and cause them to move faster than they otherwise should. Nonetheless, what force keeps this halo of Dark Matter in place outside the main body of the galaxy? When the galaxy originally condensed from a presumed cloud of both normal and Dark Matter, why would Dark Matter remained outside the main body of the galaxy and not migrate toward the central mass along with ordinary matter and stars? Conversely, how could the galaxy form in the first place with a massive halo of matter opposing the gravitational pull of the central mass on migrating matter? It seems likely that a halo of Dark Matter, many times the mass of the visible galaxy, would tear the galaxy apart.

Finally, we must explore the third possibility, the one that admits we do not fully understand gravity. Did Newton and Einstein have it wrong about the nature of gravity? The anomalous velocity of stars rotating in a galaxy can be explained equally well by a tweak to a famous equation, Newton’s second law of motion. Newton’s law of motion linearly relates force, mass and acceleration in the formula F=ma. This formula is valid on the scale of our solar system, yet may need to be tweaked on a galactic scale. One scientist, Mordehai Milgrom proposed just such a tweak to Newton’s second law of motion. He calls his theory MOND, or MOdified Newtonian Dynamics. This theory conjectures Newton’s second law is incomplete for extremely small accelerations, those less than 10 billionths of a meter per second each second. This sounds like an infinitesimally small number, one that can be easily ignored in everyday life. Yet even a small tweak can have profound effects for galactic distances and masses. MOND adjusts the second law to be F=ma2/a0 Within our solar system, Newton’s conventional formula works well to the 6th decimal place, but at galactic radii MOND predicts the observed the flat line velocity verses distance data that astronomers measure.

MOND explains another dilemma that has puzzled scientists for decades. As the Pioneer 10 and Pioneer 11 spacecraft climbed out of the Sun’s gravitational well, something inexplicable was observed. They are not following the gravitation law that dictates the velocity as their distance from the Sun increases. The variation from the law is small, at the limits of our ability to measure, but the further those spacecraft move away from the Sun, the more their speed deviates (speeds up) from the predicted value. Unless something is wrong with our measurements, the only other explanation is that gravity is stronger at the limits of the solar system than Newton and Einstein formulas predict and the spacecraft are being accelerated from the predicted values.

However, all is not well with MOND. MOND is itself a contrived mathematical solution (as was Lambda, Einstein’s cosmological constant) and as such seems nothing more than another convenient fudge factor. MOND is best described as a math adjustment rather than a theory. It has not been derived from basic physical principles such as E-mc2 or F=ma has. Milgrom simply adjusted the value of a0 until the results agreed with the measured velocities of galactic stars. Nevertheless, it is interesting that if we divide the speed of light by the age of the universe, we arrive at the value of a0 . This may have some cosmological significance, or just be a coincidence. At this point no one knows. Another sticking point is that MOND cannot be easily related to relativity, although there has been some recent success by another researcher in doing so.

As in the history of other controversial theories, MOND has yet to gain wide acceptance among Physicists or Astronomers. It is considered too radical and Dark Matter has been able to solve other cosmological problems such as the “missing mass” of the universe. Another example where Dark Matter can explain observations is with the phenomenon known as Einstein lensing, where the mass of a galaxy cluster placed between the observer and a distance object causes that object to be magnified or split into multiple images. Such lensing requires many times the amount of visible mass in those clusters, but adds in copious amounts of Dark Matter and the results match observations.

Much about the behavior and origin of gravity has yet to be discovered, and to presume that we know all there is to know about this mysterious force (or the bending of space-time) is arrogant. Presently the fact remains that Dark Matter lacks existence proof. Essentially, we have no idea what it is or how it originated. The conjecture is that we are bathed in a flood of seldom interacting subatomic particles, yet after spending hundreds of millions of dollars and years of dedicated work to build and operate huge instruments designed to detect them, no one has captured a single Dark Matter event. If these mysterious particles exist in such huge and ubiquitous numbers, where and what are they? Elusive as these particles may be, I have a problem accepting the existence of Dark Matter until scientists can prove WIMPS (Weakly Interacting Massive Particles) or some other exotic “stuff” actually exist in sufficient quantities to explain astronomical observations. In the meantime, I consider Dark Matter in the same category as the Ether of the 19th century; a theoretical speculation designed to preserve historic theories.

AstroRockHunter
2007-Dec-31, 08:27 PM
I'm not sure about MOND. I haven't read enough about it. But I will agree on one point.

We do not know what gravity is.

I'm an older student (50+) studying Physics and Astronomy. My physics prof. at the local CC where I went (a PhD. in cosmology) made an incredible statement the first day of class. She held a box of tissues at shoulder height, then let it drop to the floor. After it hit she exclaimed "science cannot tell us WHY that happens!"

Later, (this past semister in fact) I took a class at Arizona State University (where I intend to get my degrees) entitled 'Intro. to Stellar and Planetary Astrophysics'. The prof. (PhD. in astronomy) agreed with my former physics teacher on this point.

I believe that this is something that we need to address before we can really start to understand these anomolies that we observe.

Ken G
2008-Jan-01, 07:58 AM
The second possibility, that our gravitational theories are wrong, is offensive to most scientists who refuse to give this possibility credence. That statement exposes a profound lack of understanding of how science works, and how scientists think. It's completely baloney, in fact. Any scientist would be thrilled to find a way to "fix" our gravitational theory, and collect their Nobel prize. Where this absurd idea comes from that scientists are "offended" by modifications to their theories I have no idea, but a little scientific history study might be of some use.
If Newton’s equations work this well, most scientists argue that they must be a correct description of nature.
Um, I'm sure you didn't really mean that.


Nevertheless, for me the concept of Dark Matter to explain a fundamental process of the universe is nonintuitive and unsatisfactory.You are more than welcome to try and find a better alternative, as many have tried and failed.
In the meantime, I consider Dark Matter in the same category as the Ether of the 19th century; a theoretical speculation designed to preserve historic theories.Again, this is what science does, not "preserve", but build on past success until something better comes along. Nothing new here.

George
2008-Jan-01, 07:49 PM
However, all is not well with MOND.
Yes, it has an even bigger problem than what you stated; MOND may work nicely for galactic rotations, but it fails in modeling glactic cluster rotations. However, this might be solved with the addition of...... dark matter. :) So, MOND appears even more contreived.

undidly
2008-Jan-03, 10:08 PM
Richard L.
>Rather than follow the basic gravitational rule that as distance from a central mass such as the sun increases orbital velocity must decrease, individual stars defied Newtonian rules and all moved at the same velocity. Such unorthodox behavior created a huge paradox for science, and only three possible choices could explain the observations. Either the data is faulty, or Newton was wrong about gravity, or there is some mysterious gravitational stuff out there that causes the stars to orbit faster than they otherwise should.>

Do they travel faster?.Maybe the inner stars travel more slowly than some
expect them to if all the galaxy mass was in the center.It is not but is distributed.Halfway out suns orbit slowly because the outer suns counteract the gravity from the inner suns.The lower orbital speed is just right to balance the reduced force toward the center.

Too simple an explanation?.Surely someone else has thought of this.

Spaceman Spiff
2008-Jan-04, 03:34 AM
Undidly - Astronomers do not model galaxies as if they were point sources of mass with other point masses orbiting them. They take into account the distribution of mass (of stars, gas clouds, dark matter).

Richard L. - well, what to do about neutrinos, then? They don't have charges, and as such do not interact via the electromagnetic force. They interact VERY weakly with matter that is charged. So nature makes such forms of matter, but neutrinos aren't on top of the list of candidates for dark matter because (a) the sum of their rest masses (3 flavors) is fairly well constrained to be < 1 eV, and (b) being nearly massless they are "hot", in that they move at speeds approaching c.

However, in that last regard, what about the neutrinos in the cosmic neutrino background left over from the leptonogenesis in the first 3 seconds of the hot big bang? Are they, too, still hot? Anybody (Ken G?) know about these? They should greatly outnumber the relativistic neutrinos emitted by stars in nuclear reactions.

In any case, there are several potential candidate particles (supersymmetry) for dark matter, and we might find one or two in the LHC experiments over the next several years of measurements.

lalbatros
2008-Jan-04, 12:59 PM
If you have some time to read these papers:

Significant reduction of galactic dark matter by general relativity (http://arxiv.org/abs/astro-ph/0602519)

General relativistic velocity: the alternative to dark matter (http://arxiv.org/abs/0712.0019)

maybe you find these useful for this discussion,
and I would be interrested by your comments.

loglo
2008-Jan-04, 04:02 PM
Another hit and run? Gee.. the traffic is bad already this year. :)

Richard L.
2008-Jan-04, 07:30 PM
Uh...you are right. That is not how science should work, but often humans mess up the process with closed minds. A study of history turns up countless examples. When someone such as Milgrom proposes a radical idea, he may be right or not, yet some experts attack and call such ideas wacky. There are many examples, not limited to the 19th century. Read about how Tesla's ideas of alternating current transmission lines and induction motors were attacked rather than accepted by Edison. Only Westinghouse listened.

Richard L.
2008-Jan-04, 07:43 PM
Spiff:
Yes, I agree that nutrinos will not fill the missing matter gap. Perhaps some heavy particle like WIMPS is required, but after heroic efforts to detect such, nothing. Nor have the experiments to detect gravitational waves yet suceeded. Perhpas my great-grandchildren will laugh at our sorry attempts to expain such a fundamental force.

frankuitaalst
2008-Jan-04, 09:53 PM
Quote :Some distance from the galactic center, individual stars moved with orbital velocities independent of their distance from the central mass. Rather than follow the basic gravitational rule that as distance from a central mass such as the sun increases orbital velocity must decrease, individual stars defied Newtonian rules and all moved at the same velocity. Such unorthodox behavior created a huge paradox for science, and only three possible choices could explain the observations. End Quote
I had the same opinion a while ago that stars should move (orbit) slower as they are further from the center of the galaxy . Till someone told me this is "normal" . Point is that a galaxy is not a point mass , in fact it is a collection of point masses orbiting each other . The further away from the center the bigger the mass inside is and the greater the attraction . So the attraction decreases not 1/r² but will decrease slower , more like 1/r , making that a galaxy rotates more as a wheel .

Spaceman Spiff
2008-Jan-05, 02:49 AM
frankuitaalst:

Astronomers model the v(r) (or sigma(r)) vs. r curves of galaxies with models that take into account the mass distributions of various components (stellar pops and gas clouds) and then do the integral. All of these effects of mass distribution of the galaxy are taken into account - and still a dark matter component is required.

The point the person you quoted was trying to make is that in the case of the MW galaxy, at the location of our Sun the vast majority of all of the luminous mass lies interior to the Sun's orbit. So to a pretty good approximation, stuff beyond the Sun should have orbit speeds diminishing in a Keplerian like fashion. See here (http://homepages.wmich.edu/%7Ekorista/stargal-images/MW_rotcurve.gif), for a start. It's a little schematic, but it gets some of the important ideas across.

Your "rotate like a wheel" analogy holds within the inner bulge region only.



Yes, I agree that nutrinos will not fill the missing matter gap. Perhaps some heavy particle like WIMPS is required, but after heroic efforts to detect such, nothing. Nor have the experiments to detect gravitational waves yet suceeded. Perhpas my great-grandchildren will laugh at our sorry attempts to expain such a fundamental force.

We've just begun scratching the surface of both investigations. I was simply commenting that neutrinos are known particles that have the type of weakly interacting properties you were poo-pooing in your post.

Ken G
2008-Jan-05, 03:36 PM
So nature makes such forms of matter, but neutrinos aren't on top of the list of candidates for dark matter because (a) the sum of their rest masses (3 flavors) is fairly well constrained to be < 1 eV, and (b) being nearly massless they are "hot", in that they move at speeds approaching c.

However, in that last regard, what about the neutrinos in the cosmic neutrino background left over from the leptonogenesis in the first 3 seconds of the hot big bang? Are they, too, still hot? Anybody (Ken G?) know about these? I don't know much about them, but I am told that such neutrinos are indeed numerous but would not amount to a significant total mass, and would indeed be very "hot" (i.e., too relativistic to form galaxies).

frankuitaalst
2008-Jan-05, 05:18 PM
Thanks for the reply Spaceman Spiff .
The picture you posted tells a lot about the problem of missing matter .
It must have taken a lot of effort to make this comparision . Is there any reference how the calculations were done ?

Spaceman Spiff
2008-Jan-06, 12:15 AM
I don't know much about them, but I am told that such neutrinos are indeed numerous but would not amount to a significant total mass, and would indeed be very "hot" (i.e., too relativistic to form galaxies).

This site (http://www.astro.princeton.edu/%7Edns/MAP/Bahcall/node6.html), while a bit dated, does comment on the cosmic neutrino background - apparently, it's still the "wrong stuff".

dgavin
2008-Jan-06, 03:39 AM
I seem to remember some show last year stating dark matter wasn't needed for Galaxy Spin explanation. The the spin could be tied to fact that the stars are gravitationaly bound toghther, and as the inner part of a spiral moves, the rest of the spiral moves at a similar speed because of this gravitational dragging.

It went on to say the DM was needed to correct other things that didn't pan out however mathmatically.

Ken G
2008-Jan-06, 07:19 AM
I seem to remember some show last year stating dark matter wasn't needed for Galaxy Spin explanation. The the spin could be tied to fact that the stars are gravitationaly bound toghther, and as the inner part of a spiral moves, the rest of the spiral moves at a similar speed because of this gravitational dragging.

I know of no such valid view, involving "gravitational dragging". Certainly normal GR effects like frame dragging won't work, the scale of GR effects in the galaxy is vastly too small.

dgavin
2008-Jan-06, 10:31 AM
I know of no such valid view, involving "gravitational dragging". Certainly normal GR effects like frame dragging won't work, the scale of GR effects in the galaxy is vastly too small.

No it wasn't frame dragging, if I remember the way they explained it was that the core influences the stars out to a certain point, after that the stars have more of an gravitational influence to each other then the core does. If I remember this is the point that bars and spirals structures can form. Basically the bars, arms, spirals and spheres rotate based more on the principle akin to liquefaction dynamics, then Newtonian dynamics.

In other wards there is enough gravity in say a galaxy arm, that it moves around the core as is it was a semi solid structure, because all the stars in it are gravitationally chained together after a fashion.

At least thats the way I understood their explanation. Weather it's right or not, I haven't a clue.

Ken G
2008-Jan-06, 02:27 PM
No it wasn't frame dragging, if I remember the way they explained it was that the core influences the stars out to a certain point, after that the stars have more of an gravitational influence to each other then the core does. If I remember this is the point that bars and spirals structures can form. Basically the bars, arms, spirals and spheres rotate based more on the principle akin to liquefaction dynamics, then Newtonian dynamics.But the only force of significance between stars is gravity, which is a long-range force, unlike the van der Waals force that holds liquids together, which falls off much faster and is more conducive to nearest-neighbor interactions. The analogy would not seem to hold. I think it's pretty clear that current physics cannot explain the galactic rotation curves.


In other wards there is enough gravity in say a galaxy arm, that it moves around the core as is it was a semi solid structure, because all the stars in it are gravitationally chained together after a fashion.That certainly isn't true-- spiral arms are density waves that move differently from the matter that is in them.


At least thats the way I understood their explanation. Weather it's right or not, I haven't a clue.It sounds bogus to me, it probably wasn't an authoritative source, or it was that recent paper that tried to use GR effects to explain it but came under fire as not doing the GR calculation in an appropriate way.

Spaceman Spiff
2008-Jan-06, 04:45 PM
Yes, it's bogus. Dark matter is still postulated (based on a wide array of observations and theory, from galactic dynamics, dynamics of dwarf galaxies near big ones, and early galactic dynamical evolution) on the scales of galaxies.

lalbatros
2008-Jan-07, 06:25 AM
I like to always go back to the basics.
That's why such articles always catch my eye:

General Relativity Resolves Galactic Rotation Without Exotic Dark Matter (http://arxiv.org/PS_cache/astro-ph/pdf/0507/0507619v1.pdf)

Would it be true that a careful use of known physics could eliminate the need for dark things?
I am new to this topic, therefore I would gretly appreciate a good review on the subject. Do you know some reference showing a comprehensive analysis of galactic rotation data?

Ken G
2008-Jan-07, 03:28 PM
That article has been widely discredited, and in fact it just clearly wrong from the most basic principles of physics. The gravitational interaction between any two stars in the extended galaxy is clearly highly Newtonian, that's just obvious. So it is equally obvious that GR corrections to Newtonian gravity in an extended galaxy cannot amount to a hill of beans. What is far less obvious is where they went wrong in their calculation-- I'll leave that up to the GR experts, but apparently it has something to do with subtle implicit assumptions being made.

Spaceman Spiff
2008-Jan-07, 04:22 PM
I like to always go back to the basics.
That's why such articles always catch my eye:

General Relativity Resolves Galactic Rotation Without Exotic Dark Matter (http://arxiv.org/PS_cache/astro-ph/pdf/0507/0507619v1.pdf)

Would it be true that a careful use of known physics could eliminate the need for dark things?
I am new to this topic, therefore I would gretly appreciate a good review on the subject. Do you know some reference showing a comprehensive analysis of galactic rotation data?

Yes, it would be true if such careful use actually revealed something useful. However, the paper you link and several others of theirs have never been published in peer reviewed journals.
Here are three papers that directly refute their model as being unphysical: 1 (http://adsabs.harvard.edu/abs/2007JPhA...40.7087K), 2 (http://adsabs.harvard.edu/abs/2006NewA...11..608F), 3 (http://adsabs.harvard.edu/abs/2006CQGra..23.1391G).
All 3 of these have been published. A shortened version of the first can be found here (http://arxiv.org/abs/astro-ph/0508377), and freely available versions of the other two can be found here (http://arxiv.org/abs/astro-ph/0604022) and here (http://arxiv.org/abs/gr-qc/0511082).

And let's just think for a moment. GR devolves to Newton in the limit of weak gravity fields, and while we can observe GR effects under these conditions (e.g., earth, our solar system) we do so with ultra-precise measurements - effectively as high order corrections to Newton. The effect of Dark Matter observed in galaxies and galaxy clusters is not some high order effect - it is the effect. It seems as though these guys got lost in the trees, or who knows what.

kzb
2008-Jan-07, 06:45 PM
When Mendeleev put together the periodic table of the elements, he left gaps where he predicted hitherto undetected elements. Not olny that but he predicted many chemical properties for the missing elements which were born out when they WERE discovered.

So if non-baryonic DM IS detected and proves to have the necessary properties, that would be powerful evidence that we are doing something right. However I've got to admit to a bit of a skeptical feeling about it myself.

lalbatros
2008-Jan-07, 08:08 PM
Spaceman Spiff,

I totally agree with you.
It is indeed difficult to conceive that the Newtonian limit would lead to a non-Newtonian result.
However, I would also be very interrested in a review about dark matter related to galactic rotation.
This is -I think- what this threat was about.

In such a paper, I would check many things.

First, what is defined as "non-dark" matter: is it based on optical observation, and if yes how is the "visible" mass estimated? Knowing that should already offer many possibilities for "classical" dark matter, isn't it? Or is "classical" dark matter (like planets) not really dark matter?

Second, I would -by curiosity at least- review how exactly the Newtonian limit is defined and how large the discrepancies could be depending on the space scales. The diameter of the milky way is about 100000 ly: naïvely speaking, how much does GR affect physics on such scales with the actual density of the MW? I know at least that on billions ly GR should be taken into account with the current density in the universe. Am I right?

Thanks a lot already for the references, that will avoid me spedning too much of my (free) time on deceiving ideas.

Nereid
2008-Jan-07, 08:53 PM
Spaceman Spiff,

I totally agree with you.
It is indeed difficult to conceive that the Newtonian limit would lead to a non-Newtonian result.
However, I would also be very interrested in a review about dark matter related to galactic rotation.
This is -I think- what this threat was about.

In such a paper, I would check many things.

First, what is defined as "non-dark" matter: is it based on optical observation, and if yes how is the "visible" mass estimated? Knowing that should already offer many possibilities for "classical" dark matter, isn't it? Or is "classical" dark matter (like planets) not really dark matter?

Second, I would -by curiosity at least- review how exactly the Newtonian limit is defined and how large the discrepancies could be depending on the space scales. The diameter of the milky way is about 100000 ly: naïvely speaking, how much does GR affect physics on such scales with the actual density of the MW? I know at least that on billions ly GR should be taken into account with the current density in the universe. Am I right?

Thanks a lot already for the references, that will avoid me spedning too much of my (free) time on deceiving ideas.
Why not read this thread: What is the observational basis for (cold, non-baryonic) dark matter? (http://www.bautforum.com/questions-answers/42223-what-observational-basis-cold-non-baryonic-dark-matter.html)

While it doesn't address galaxies (elliptical, spiral, dwarf, ...), many of the techniques described apply also to (non-baryonic DM in) galaxies ...

Jerry
2008-Jan-08, 12:38 AM
That statement exposes a profound lack of understanding of how science works, and how scientists think. It's completely baloney, in fact. Any scientist would be thrilled to find a way to "fix" our gravitational theory, and collect their Nobel prize. Where this absurd idea comes from that scientists are "offended" by modifications to their theories I have no idea, but a little scientific history study might be of some use.Um, I'm sure you didn't really mean that.
You are more than welcome to try and find a better alternative, as many have tried and failed.Again, this is what science does, not "preserve", but build on past success until something better comes along. Nothing new here.
I am afraid what Richard said about gravity is true: The scientific community will not entertain the notion that Newtonian physics is more than Einstein's pencil tip from reality. If you want to see eyes glaze over, try explaning how big the cracks are, how there may be a common thread, and how it is all woven together. You might get as far as 1) the first time you mistate a fact; but the listener will also tune out if 2) you are not considered a peer (for a PHd that requires a PHd) or 3) you quote data that is at odds with the listener's understanding of observational facts.

(Trying to introduce new physical concepts to an educated physical science audience is one subject I am an expert on:)

Ken G
2008-Jan-08, 03:30 AM
I am afraid what Richard said about gravity is true: The scientific community will not entertain the notion that Newtonian physics is more than Einstein's pencil tip from reality.A dubious claim like that requires support. I suppose there's little point in my wasting my time to cite for you all the peer-reviewed and published papers that entertain precisely the notion you ignore.

If you want to see eyes glaze over, try explaning how big the cracks are, how there may be a common thread, and how it is all woven together. You might get as far as 1) the first time you mistate a fact; but the listener will also tune out if 2) you are not considered a peer (for a PHd that requires a PHd) or 3) you quote data that is at odds with the listener's understanding of observational facts. I'm trying to understand your complaint here. It sounds like you are frustrated that just because you don't have an advanced physics education, and you are describing unconventional theories whose observational support is flimsy (which you instead blame on being "unfamiliar"), and are vague or complicated and cannot be made understandable to a scientifically proficient audience, you are experiencing frustration-- and want to blame your audience for it? Is that pretty much what you are saying here?

Don't get me wrong, I personally am glad there are people doing what you are doing, because if a new theory is needed, you might help promote the attitude that finds it. I just think your chip is showing-- and blaming your audience is a bit one-sided. It might be that many don't see your way as the more productive way, and it might not be-- or it might.

lalbatros
2008-Jan-08, 03:05 PM
Has any link been suggested between the "galactic rotation anomaly" and the "pioneer anomaly"?
Any relation, or no possible link?

Ken G
2008-Jan-08, 04:08 PM
Those who look for modifications to Newton (MOND) do indeed consider the pioneer anomaly to be an important local test. So far, MOND models have not successfully bridged the gap from the solar system to galaxy rotation curves to galaxy cluster data (this is my impression, I haven't a citation to back it).

George
2008-Jan-08, 04:55 PM
So far, MOND models have not successfully bridged the gap from the solar system to galaxy rotation curves to galaxy cluster data (this is my impression, I haven't a citation to back it).

This (http://arxiv.org/PS_cache/astro-ph/pdf/0607/0607142v1.pdf) seems to be one related paper.


The MOND hypothesis, as a stand alone solution, has proven to be unable to solve the
missing mass problem at the clusters scale. An added hot dark component is needed to rescue
MOND, massive neutrinos for instance. As the amount of hot DM needed is up to [/FONT][FONT=CMR10]80% of the clusters mass, this turns the MONDian cosmological framework more into a mixed DM cosmology.
[Added: Here is another more current paper...On the Proof of Dark Matter, the Law of Gravity and the Mass of Neutrinos (http://arxiv.org/abs/astro-ph/0609125), which uses lensing techniques.]

Ken G
2008-Jan-08, 07:41 PM
Thanks for fleshing that out.

Stuart Sweeney
2008-Jan-11, 05:30 AM
This post picks up on a comment by Phil Plait in his great collation of astronomy images for 2007:

http://www.badastronomy.com/bablog/2007/12/13/top-ten-astronomy-pictures-of-2007/

My thanks for the effort and knowledge that went into compiling the list (and the also-rans). It brightened my morning more than somewhat.

However, like another poster, Jingchun Chen, I didn’t find this comment by Phil helpful:

“Many people — who don’t understand the science — claim dark matter doesn’t exist, and that astronomers are making it all up. Well, there’s a giant smoke ring in the sky indicating they are quite wrong.”

The alternative, albeit minority view, MOND, has been discussed, but my concern is more a philosophical one.

Secondly, as a devotee of Karl Popper’s philosophy of science, what I have read of “Dark Matter” gives me pause for thought. Popper’s central concept is of scientific method as a series of conjectures and refutations. Scientists make conjectures that generate predictions which can then be tested experimentally. If the experiement agrees with the prediction, then the theory is corroborated, but never proved; there’s always another experiement round the corner which may result in a refutation of the theory. Thus did Newton’s theory of gravitation prove wanting after a few hundred years of nothing but corroborative observations, although it remains a primary computation tool in non-relativistic situations.

Popper also draws attention to those theories that make tough predictions that turn out to be correct eg General Relativity predicted that light would be bent around the Sun, an effect that had not been observed at that time that Einstein made his prediction.

Dark Matter theory clearly started life as a patch to hold existing cosmological theories together. That is a series of observations on the motions of galaxies could not be reconciled with existing theory and a conjecture made to account for the anomoly. Patches can be OK, but Popper counsels caution when the patch creates additional problems of verification. The lack of progress in identifying the Dark Matter is just such a problem of verification

The situation reminds me of the Taniyama-Shimura conjecture, which provides links between the branches of mathematics known as algebraic geometry and complex analysis. This was stated, without proof, in 1955 and became an important building block for further analysis, but researchers using it always had to state “assuming that the Taniyama-Shimura conjecture is true,” rather like an auditor’s exception to a set of financial accounts. As far as I understand, and the maths involved is beyond all but the most gifted in the field, in 1994, Andrew Wiles proved the T-S conjecture (unlike science, you can prove things in maths, as it is an axiomatic structure) on the way to proving Fermat’s Last Theorem and thereby put a whole raft of mathematics on a sounder basis.

While accepting that mathematics and science have key structural differences, we seem to have be at an analogous stage with Dark Matter, but without astronomers acknowledging that it remains less well verified than most other key scientific theories. In particular, the failure of the many attempts to detect candidate particles for dark matter is a concern.

To sum up: “Many people….claim dark matter doesn’t exist…” Well, this person believes that dark matter remains the best candidate around as an explanation of what astronomers observe in the motion of galaxies. But guys: while it’s fine to devote your professional lives to lines of research that depend on the dark matter hypothesis, beware of overstating the theoretical verification of your dark matter patch on cosmological theory.

Jerry
2008-Jan-11, 05:40 AM
Don't get me wrong, I personally am glad there are people doing what you are doing, because if a new theory is needed, you might help promote the attitude that finds it. I just think your chip is showing-- and blaming your audience is a bit one-sided. It might be that many don't see your way as the more productive way, and it might not be-- or it might.

Very few physicists are comfortable enough with their own discipline to actively entertain discussions which impose on their personal world view.

One example: I have probably pointed out at least a dozen times in BA threads alone that there is a curious juxiposition in the gravity anomalies of Mars and Venus (Venus peaks are under-dense, and Venus valleys over-dense; while on Mars the measured observations are exactly and consistently opposite.) Not once has anyone commented on this curious fact; one I have used as a representitive example of how screwed-up Newtonian physical explanations are.

On the other hand, by bringing up this same argument (which has never been challenged or refuted), I am at some risk of censorship and I have often been personally attacked.

jeff Mitchell
2008-Jan-11, 05:48 PM
To Richard L.

To answer the question you posed in at the start, Is Dark Matter for real. The answer is NO. The bb boys have come to a wall in their theory and to make it work they have to rely on the dark side; dark matter and dark energy. The problem is, if you use dark matter and darkenergy in your theory you can come up with any nonsense you want. IE. Everything is ran and controlled by a purple unicorn Where is he? Can't see him, dark matter. How does he do things? Can't tell you, dark energy. Jeff Mitchell (The Galaxy Spin Guy)

Spaceman Spiff
2008-Jan-11, 06:27 PM
Wow. :(

So astronomers and astrophysicists (along with the data we have gathered) are completely clueless and resort to 'dark matter' merely to patch our beloved theory ("Big Bang"). I can think of a word in the dictionary that sums up the statement made just above.

sophomoric (from the MW Collegiate Dictionary): conceited and overconfident of knowledge but poorly informed and immature <a sophomoric argument>.

To those of you who have asked, your best bet toward understanding how astronomers construct models of mass distribution in individual galaxies can be found in Galactic Dynamics (http://www.amazon.com/gp/product/0691130272/ref=wl_it_dp?ie=UTF8&coliid=I2GLMAYSCJYX26&colid=BIVZN5GWGXPX), by Binney & Tremaine.

Stuart Sweeney
2008-Jan-11, 08:42 PM
I assume that Spaceman Spiff's comments are directed in my direction, but I was surprised by his comment: "So astronomers and astrophysicists (along with the data we have gathered) are completely clueless..." I re-read my post above and found no use of the word "clueless". But, for the avoidance of doubt: I certainly would not use that term to describe Messrs. Taniyama and Shimura for coming up with their unproved, but brilliant mathematical conjecture, which spawned a new direction for mathematical investigation. Similarly, those who came after and based their research on the T-S conjecture are not "clueless".

And just as it was always likely that the T-S conjecture was correct, I went out of my way to say that chances are that the Dark Matter hypothesis will also be vindicated; thus I certainly don't consider those working in this area "clueless". But, whereas the T-S conjecture has now been established, the failure to identify Dark Matter, despite heroic efforts, must surely mean that the jury remains out on its existence; sorry if that makes some uncomfortable.

I'm also sorry that the word, "patch" causes such alarm and despondency, but when hypothetical, unidentified material is introduced to make a theory work, that is, not to make predictions, but to account for observations that don't accord with a current theory, then "patch" does not seem unreasonable. It may well be that this particular patch turns out to be correct, but from some astronomers/astrophysicists, I don't see the modesty that mathematicians displayed when using the T-S conjecture, pre-Wiles.

The use of a pejorative like "sophomoric" suggests a surprising defensiveness on the part of Spaceman Spiff. Have to say, though, that it would be great to be sophomore age again, but that's a long way downstream for me.

antoniseb
2008-Jan-11, 09:31 PM
I assume that Spaceman Spiff's comments are directed in my direction...
I don't want to speak for S. Spiff, but I took his comments to be directed jeff Mitchell.

Ken G
2008-Jan-12, 03:23 AM
The problem is, if you use dark matter and darkenergy in your theory you can come up with any nonsense you want.

This is an uninformed claim. Dark matter and dark energy have to unify the physics we see, or there would be no point to them. Unification means you can use them to understand a wide array of phenomena without introducing very many new parameters to the model. For example, the simplest form of dark energy is just one parameter (Lambda), and the simplest form of dark matter is also just one parameter (density, assuming it is cold enough to undergo the kinds of gravitational instability you can get without radiating). You probably don't understand anything I've just said, so just rest assured that including dark matter and dark energy introduces as few as just two new parameters, and coupled with existing observations, allows you to understand:
the H/He in our universe
the CMB and its ripples
galaxy rotation curves
galaxy clustering
cosmological redshifts of supernovae
galactic collision dynamics
and a host of other things I haven't named (others can add to the list). So if your logic is "you can always explain dozens of independent things with just two new parameters", you are mistaken.

Cougar
2008-Jan-12, 05:09 AM
I didn’t find this comment by Phil helpful:

“Many people — who don’t understand the science — claim dark matter doesn’t exist, and that astronomers are making it all up. Well, there’s a giant smoke ring in the sky indicating they are quite wrong.”

Welcome to the board, Stuart. An impressive first or second post. But I think what Phil's quote means is that the evidence for dark matter is considerable and not limited to the "odd" dynamics of galaxies in rotation. More recently we've got additional observations like the bullet cluster (http://en.wikipedia.org/wiki/Bullet_cluster) as independent, confirming observations. As you say, no assertion is 100% conclusive, but the existence of some form of dark matter is considerably better supported than you seem to allow.


...but my concern is more a philosophical one.
Well, that's a turn off to many scientists, ;) but you'll probably get some reaction on this board. :whistle:


Dark Matter theory clearly started life as a patch to hold existing cosmological theories together.
Here's the problem. "Patch" is highly derogatory and evidences a somewhat biased understanding of the motivations of scientists.


Popper counsels caution when the patch creates additional problems of verification. The lack of progress in identifying the Dark Matter is just such a problem of verification.
Well, here you're just a little behind in the literature. And weak lensing is not the only additional component of the giant smoke ring in the sky supporting the dark matter hypothesis. The cosmic background radiation encodes a remarkable amount of information....

.

.

Ken G
2008-Jan-12, 05:44 AM
One example: I have probably pointed out at least a dozen times in BA threads alone that there is a curious juxiposition in the gravity anomalies of Mars and Venus (Venus peaks are under-dense, and Venus valleys over-dense; while on Mars the measured observations are exactly and consistently opposite.) Not once has anyone commented on this curious fact; one I have used as a representitive example of how screwed-up Newtonian physical explanations are. And you think no one has commented simply because it challenges Newtonian gravity? No, no one has commented because they have nothing at all to say on the matter, knowing neither the observations (or more importantly, the systematic errors present), nor the proposed explanations, whether Newtonian or non-Newtonian. On the other hand, we've all seen MOND claims on the far-better observed Earth (deep wells and whatnot) consistently go up in smoke as irreproducible. Once burned, twice shy. Furthermore, it is widely known that none of the MOND corrections suggested to explain local data successfully generalize to include both galaxy rotation curves and galaxy cluster data. Why are you not the one commenting on that little challenge to your personal world view? I think the pot is calling the kettle black, when you maintain that most people reject MOND because they don't like it-- rather than because it doesn't work.


On the other hand, by bringing up this same argument (which has never been challenged or refuted), I am at some risk of censorship and I have often been personally attacked.If you count counterarguments as "attacks", I suppose you'll claim that once again here. Or if you are talking about personal attacks not framed in the form of a counterargument, then they are unfortunate but irrelevant, as they could not come from anyone whose opinion matters.

Ken G
2008-Jan-12, 06:15 AM
Dark Matter theory clearly started life as a patch to hold existing cosmological theories together. But what is a "patch" to one person is a "huge discovery" to another. For example, you have probably heard that neutrinos were predicted by Pauli before they were observed, because there was energy strangely missing in otherwise mundane nuclear reactions. So postulating neutrinos was a "patch" to the principle of conservation of energy-- but because that principle had already proved itself vastly useful in a wide array of contexts, it seemed likely that the universe would find a way to preserve it in those nuclear reactions-- and sure enough, it did. Now no one knew that there would be either neutrinos or conservation of energy, but it was the guess most consistent with existing observations taken all together, and more importantly, it motivated the successful search for neutrinos. I believe most astronomers see dark matter in precisely that same light, even if their views are often mischaracterized as professing jealously guarded beliefs.


That is a series of observations on the motions of galaxies could not be reconciled with existing theory and a conjecture made to account for the anomoly. Patches can be OK, but Popper counsels caution when the patch creates additional problems of verification. Again, who are you going to pay attention to-- Popper or Pauli? To Popper, the neutrino would have to be considered an "additional problem of verification", but to Pauli, it was the spectacular discovery of a lifetime. Be a little patient on dark matter.

While accepting that mathematics and science have key structural differences, we seem to have be at an analogous stage with Dark Matter, but without astronomers acknowledging that it remains less well verified than most other key scientific theories. The working astronomers I know are aware of the uncertainties in dark matter, but they are also aware of its growing list of accomplishments, like the bullet cluster, the smoke ring, the history of galaxy formation, and the density waves in the CMB. It is still a young model, going through growing pains-- but its viability appears to increase with every new generation of observations. Can any alternate theories say that? It seems to me it is they that represent the obvious "patches".


To sum up: “Many people….claim dark matter doesn’t exist…” Well, this person believes that dark matter remains the best candidate around as an explanation of what astronomers observe in the motion of galaxies. But guys: while it’s fine to devote your professional lives to lines of research that depend on the dark matter hypothesis, beware of overstating the theoretical verification of your dark matter patch on cosmological theory.But also, be aware of all the observational evidence-- not just a vague impression of the weakness of the model. Most of the criticisms of dark matter I see would have been much more appropriate about ten years ago-- and seem largely unaware of the observations since.

Stuart Sweeney
2008-Jan-12, 09:44 AM
Many thanks to Ken G and cougar for your carefully considered responses to my posts. You've provided plenty of food for thought on the topic, which I should now consider carefully.

Augustus Vox
2008-Jan-12, 01:47 PM
That statement exposes a profound lack of understanding of how science works, and how scientists think. It's completely baloney, in fact. Any scientist would be thrilled to find a way to "fix" our gravitational theory, and collect their Nobel prize. Where this absurd idea comes from that scientists are "offended" by modifications to their theories I have no idea, but a little scientific history study might be of some use.

I’m sorry but (in defense to Jerry’s earlier statements) I beg to differ with you here and perhaps I’m not the one to point it out but many men and women of science have (and in some cases still do) default to condescension when their theories are challenged or when they’re presented with new ones. That is to say, they’re not all the open and free thinkers as you portray. This is because the scientific process does require some measure of challenge by its contemporaries and a measure of that challenge stems from the amount of mental discipline that goes into becoming a scientist. It is the duty of these contemporaries to try to find the faults in the logic of newly presented theories so that the one presenting the challenge can see the defects and either scrap it or to polish it up. As a result some scientists will – as I said before – default to condescension whether they are exposing the faults in a theory or receiving the criticisms from their peers.

I should know something of this as my daughter is well on her way to receiving a PhD in Physics (this being her last year and all) and she’s constantly being challenged by peers, professors and contemporaries. It’s frustrating to watch say the least; I can only imagine what it must be like on the receiving end.

I think Jerry’s responses were quite neutral to say the least because I certainly detected no chip. Of course this is my opinion but then as you so eloquently put it “they could not come from anyone whose opinion matters.” A markedly condescending point and as I understand it this forum is chiefly hallmarked by it’s allowance to the expression of opinion. :whistle:

Ken G
2008-Jan-12, 04:49 PM
Many thanks to Ken G and cougar for your carefully considered responses to my posts. You've provided plenty of food for thought on the topic, which I should now consider carefully.

Thanks to your thoughtful questions. Wouldn't we all like to come back in 200 years and see how this all turned out? Maybe we'll know a lot more a lot sooner...

Ken G
2008-Jan-12, 05:09 PM
This is because the scientific process does require some measure of challenge by its contemporaries and a measure of that challenge stems from the amount of mental discipline that goes into becoming a scientist. It is the duty of these contemporaries to try to find the faults in the logic of newly presented theories so that the one presenting the challenge can see the defects and either scrap it or to polish it up.That is certainly the duty of all scientists, not just a small set of mavericks, and although it is an imperfect process it is carried out constantly. The mavericks and contrarians play a role in doing that, but often not a central role-- the main role is played by those mainstream scientists who see the observations, educate others, and never turn off their capacity for independent thought, despite unsubstantiated accusations to the contrary. For example, please note that the exact process you described is exactly what happened when the outmoded steady-state cosmology was replaced, under the weight of many observations, by the expanding cosmology. That expanding cosmology was challenged at every step, and countless observational campaigns were undertaken to see if it could be falsified, because that's what observations do. Every time someone claims that mainstream scientists are not being suitably skeptical of their ideas simply because they want to believe they are right, I notice how the contrarians are actually the ones who cannot be skeptical of their own objections, because it is they who want to believe they are right. If someone just says, "the evidence does not yet convince me, I need to see more", that is a perfectly skeptical attitude-- and indeed, they will see much more in the coming years. But when they say "I feel that an alternative theory should be pursued for such-and-such a reason", I look at those reasons and think "you have lost your objectivity and skepticism-- the evidence indicates the cause you champion should be discarded as nonviable." I say nonviable, not falsified, as that is very hard to do, but at the least discredited by the available data. In science, discredited ideas take a very long time to actually vanish. I'm sure they sometimes even return, and no one should be faulted for the effort (isn't there a patron saint of lost causes?), but neither should they complain that their cause is lost for any reason other than the weight of the evidence against it.


As a result some scientists will – as I said before – default to condescension whether they are exposing the faults in a theory or receiving the criticisms from their peers.Most scientists do not "condescend", instead they cite evidence. On this very thread, for example, countless examples of evidence backing the mainstream idea have been cited, and the excuse for the alternatives having no evidence is "we would have the evidence if we could get funded", or "people would believe my evidence if I could only get them to listen to it without pre-judging." That kind of "convenient" argument represents a breakdown of skepticism in the clothes of a plea for skepticism.


I should know something of this as my daughter is well on her way to receiving a PhD in Physics (this being her last year and all) and she’s constantly being challenged by peers, professors and contemporaries. It’s frustrating to watch say the least; I can only imagine what it must be like on the receiving end.I'm sorry, I don't see the connection-- are you now talking about sexism in science, and using it to say something about clinging to mainstream models of cosmology?


I think Jerry’s responses were quite neutral to say the least because I certainly detected no chip. Of course this is my opinion but then as you so eloquently put it “they could not come from anyone whose opinion matters.” A markedly condescending point and as I understand it this forum is chiefly hallmarked by it’s allowance to the expression of opinion.
It appears you completely mistake my meaning. Did you think I was saying that anyone who disagrees with the mainstream cannot have an opinion that matters? I suggest you read what I actually said a bit more carefully-- I said that anyone who would launch a personal attack on Jerry, rather than present a counterargument, cannot have an opinion that matters. And I continue to stand by that opinion, and see no evidence to the contrary.

Spaceman Spiff
2008-Jan-12, 05:11 PM
...

I think Jerry’s responses were quite neutral to say the least because I certainly detected no chip. Of course this is my opinion but then as you so eloquently put it “they could not come from anyone whose opinion matters.” A markedly condescending point and as I understand it this forum is chiefly hallmarked by it’s allowance to the expression of opinion. :whistle:


Augustus - First off, welcome!
Second, let's just say that Jerry has a long "track record" which Ken G, myself and many others have been "exposed to". Nevertheless, I do recognize some truth in what you say - and that's because individual scientists are human beings with all the pluses and minuses that come with that. As scientists we do work towards looking at the world differently as we openly inquire with universe, but as individuals we are not immune to human foibles (ego, arrogance, bias, etc) even as we as scientists know that the scientific process has little use of them (or rather, that in the collective effort of the scientific process we make progress in improving our understanding of nature in spite of these human characteristics). And believe me - these foibles are not just found within scientists who happen to find that the preponderance of data happens to side with the current working model.

With best regards.

Spaceman Spiff
2008-Jan-12, 05:33 PM
I don't want to speak for S. Spiff, but I took his comments to be directed jeff Mitchell.

In a word, "yes". But more accurately - they were directed at the statements of jeff Mitchell.

And to Stuart Sweeney - I apologize if my comment appeared directed at you or your postings. It was not. However, it was not a display of "defensiveness" on my part. I purposely displayed the official definition of that word to convey precisely what I thought of the content of jeff Mitchell's post. And as Ken G has so eloquently described (thank you), we are far from being forced to "hang up our hats" on the dark matter issue. And even if the time would come that we had exhausted all avenues of identifying the agent of dark matter, the dark matter model would not be retired until and unless a model came along that better explains and unifies the wide ranging observations and consequences.

Cougar
2008-Jan-13, 01:01 AM
Again, who are you going to pay attention to-- Popper or Pauli?

That's worthy of a tagline somewhere, I think.


Augustus - First off, welcome!

Yes, quite. Tremendous handle there, Augustus Vox.

Jerry
2008-Jan-13, 04:53 PM
And you think no one has commented simply because it challenges Newtonian gravity? No, no one has commented because they have nothing at all to say on the matter, knowing neither the observations (or more importantly, the systematic errors present), nor the proposed explanations, whether Newtonian or non-Newtonian.
The gravity anomalies of Mars and Venus were determined by a number of orbiting probes that use perturbations of the orbits to determine variations in surface density - you can find maps and explanations used in many college planetary geophysics courses.

None of the explanations include the possibility that Newtonian physics - using orbiting probes to accertain surface density - may be wrong, even though we have not directly tested the Newtonian equivalance principle outside the earth-moon domain.

The point i need to make in this thread is that the discussion and development such a theory is eschewed by the physical science community. The BAUT considers such a proposal ATM; and development of ATM theories is not allowed on this board. Doug Ellison will immediately erase suggestions that Newtonian physics must be altered to explain the surface of Titan or the heat generating capacity of Enceladus from his board; and sanction the poster.


On the other hand, we've all seen MOND claims on the far-better observed Earth (deep wells and whatnot) consistently go up in smoke as irreproducible. Once burned, twice shy. Furthermore, it is widely known that none of the MOND corrections suggested to explain local data successfully generalize to include both galaxy rotation curves and galaxy cluster data. Why are you not the one commenting on that little challenge to your personal world view? I think the pot is calling the kettle black, when you maintain that most people reject MOND because they don't like it-- rather than because it doesn't work.

I reject MOND because it has always been sold as phenomenological - a mathematical model with no physical underpinnings. Since the equations work in many situations, it may be useful to use them in the development of a more cognitive model; just as Copernicus used Ptolomec principles to refine his sun-centered system.


If you count counterarguments as "attacks", I suppose you'll claim that once again here. Or if you are talking about personal attacks not framed in the form of a counterargument, then they are unfortunate but irrelevant, as they could not come from anyone whose opinion matters.
Nice point. I have a teaser from Scientific American saying Newtonian physics has come into serious doubt; and I can read about that in a free issue if I will purchase a subscription. So maybe those of us who have been arguing for years 'dark' solutions do not add up are making some progress. But until the day I can go before NASA and argue probes like the Phoenix Mars mission operate at the edge of design because Newtonian physics are incomplete; no one is really taking the issue seriously.

Ken G
2008-Jan-13, 05:20 PM
The gravity anomalies of Mars and Venus were determined by a number of orbiting probes that use perterbations of the orbits to determine variations in surface density - you can find maps and explanations used in many college planetary geophysics courses. And you claim there are not significant uncertainties in the systematic errors in these remote observations on other planets?


None of the explanations include the possibility that Newtonian physics - using orbiting probes to accertain surface density - may be wrong, even though we have not directly tested the Newtonian equivalance principle outside the earth-moon domain.
I would think there's a pretty good reason that the possibility that physics works differently on Mars and Venus than in the Earth-Moon system is treated as an ultra-low priority hypothesis.


The point i need to make in this thread is that the discussion and development such a theory is eschewed by the physical science community.What do you mean by "such a theory"? What theory? MOND? MOND is discussed constantly, and its problems are its own fault, not that of mainstream physics.

Halcyon Dayz
2008-Jan-13, 06:44 PM
That is certainly the duty of all scientists, not just a small set of mavericks, and although it is an imperfect process it is carried out constantly. The mavericks and contrarians play a role in doing that, but often not a central role-- the main role is played by those mainstream scientists who see the observations, educate others, and never turn off their capacity for independent thought, despite unsubstantiated accusations to the contrary. For example, please note that the exact process you described is exactly what happened when the outmoded steady-state cosmology was replaced, under the weight of many observations, by the expanding cosmology. That expanding cosmology was challenged at every step, and countless observational campaigns were undertaken to see if it could be falsified, because that's what observations do. Every time someone claims that mainstream scientists are not being suitably skeptical of their ideas simply because they want to believe they are right, I notice how the contrarians are actually the ones who cannot be skeptical of their own objections, because it is they who want to believe they are right. If someone just says, "the evidence does not yet convince me, I need to see more", that is a perfectly skeptical attitude-- and indeed, they will see much more in the coming years. But when they say "I feel that an alternative theory should be pursued for such-and-such a reason", I look at those reasons and think "you have lost your objectivity and skepticism-- the evidence indicates the cause you champion should be discarded as nonviable." I say nonviable, not falsified, as that is very hard to do, but at the least discredited by the available data. In science, discredited ideas take a very long time to actually vanish. I'm sure they sometimes even return, and no one should be faulted for the effort (isn't there a patron saint of lost causes?), but neither should they complain that their cause is lost for any reason other than the weight of the evidence against it.

To big for a sig, but very well put.

Jerry
2008-Jan-14, 06:50 AM
And you claim there are not significant uncertainties in the systematic errors in these remote observations on other planets?

Yes - many orbits involve in gravity field mappings. I can't open any pdf files at the moment but this search function will provide many references:

http://www.dogpile.com/dogpile/ws/results/Web/Bouguer%20Gravity%20Mars%20Venus/2/0/0/Relevance/zoom=off/qi=21/qk=20/bepersistence=true/_iceUrlFlag=7?_IceUrl=true



I would think there's a pretty good reason that the possibility that physics works differently on Mars and Venus than in the Earth-Moon system is treated as an ultra-low priority hypothesis.

I have NEVER found a geophysical paper that even suggests that the anti-correlations should be considered anything other than correct: Mars has dense volcanos and under-dense ravines, While Venus has light volcanos and very dense chasma. It is a very big step to suggest that the Newtonian equivalence principle is suspect, or as you stated:


Every time someone claims that mainstream scientists are not being suitably skeptical of their ideas simply because they want to believe they are right, I notice how the contrarians are actually the ones who cannot be skeptical of their own objections, because it is they who want to believe they are right.
That is a very broad assumption made by almost everyone, and it precludes series evaluation of alternatives. Contrast your statement with that of my mentor:


Now that you know the existing theories are wrong, you have to go to the literature, and search through all the hair-brained and rejected theories, and go through them one by one, and make sure they were not rejected because of something you have learned, and if they were, try to disprove them yourself.

You cannot apply infinite weight to prevailing theories in spite of their flaws and expect any fledging theory to develop: The universe is very complex, and no one will get it all right in one stroke.

I found the juxiposition in the gravity anomalies when I realized that if the Newtonian equivalence principle is wrong, then using orbital mechanics to determine the masses of other planets will lead to a bogus value for the distribution of mass within every other planet; and this will be obvious in the evaluation of masses above and below the mean surface density - that is exactly what we find in Mars, Venus and Ganymede; and will eventually realize for Titan and possibly other moons of Saturn.


What do you mean by "such a theory"? What theory? .
The theory I have been trying to develop, but as I said, it is very frustrating because when you start with the assumption 250 years of Newtonian physics are far from correct, you will be labeled a kook. Serious physicists cannot claim Newton is wrong and escape that label -

Very simply, the acceleration of a mass is a function of both the mass and distribution of mass in the system: It takes more energy to accelerate a given mass near the sun to a given orbital velocity than it does to accelerate the same mass to the same velocity near the earth. Conversely, it takes much less energy to accelerate to a given velocity at greater distances from an object as massive as the sun. When we send a probe such as Cassini to Titan with a given trajectory, it achieves a higher orbit than it would if Saturn contained the same mass closer to the sun - so our Newtonian physics under-estimate the masses of Saturn and all of her moons. This means that the moons orbiting Saturn are at least twice as dense at the Newtonian calculations predict - and that is why the surface of Titan appears so terrestrial - it is very terrestrial - Titan is not composed primarily of water and hydrocarbons as Sagen and other predicted.

I can pull together a lot of evidentuary trails that support this assertion, but as Antoniseb noted, I have been off on several tangents. But since the BAUT prohibited using the board for theoretical development, I've been more of a gadfly than a serious theorist. But I can get galactic orbitals to behave without injecting Dark Matter.

Ken G
2008-Jan-14, 08:39 AM
I have NEVER found a geophysical paper that even suggests that the anti-correlations should be considered anything other than correct: Mars has dense volcanos and under-dense ravines, While Venus has light volcanos and very dense chasma.I am willing to accept the data is incontrovertible, if that is indeed the case, my issue is in attributing that to a difference in the laws of physics instead of just asserting that Mars volcanoes are different from Venus'. Indeed, the former hypothesis requires that the latter hold, so the latter is always the minimal hypothesis that can explain the data.

You cannot apply infinite weight to prevailing theories in spite of their flaws and expect any fledging theory to develop: The universe is very complex, and no one will get it all right in one stroke.I certainly agree with that, nor would I ever apply overdue weight to a theory simply because it is "existing". The issue has nothing to do with what is existing or what is mainstream, it has to do with the way science works: whenever you have new data that doesn't agree with your previous expectation, the next step is always to find the minimal hypothesis that can explain that data. Call it the "Occam's Razor" approach to modifying expectations.

For example, if I have a theory that says objects taken out of the oven will
burn me, and then I pull out some aluminum foil and find that it does not burn me, I do not say "I guess the rules of thermodynamics were suspended in that experiment", I say "perhaps I'm making an assumption that does not apply to aluminum foil". So if Mars volanoes appear dense, do we say "gravity must be working differently there", or do we say "maybe it was wrong for me to assume a uniform volcano density"? The latter is simply how science is done, it has nothing to do with bruised egos or getting grants. Only when you discover via independent data that Mars volcanoes are not more dense do you begin to wonder if the gravity physics is altered.


I found the juxiposition in the gravity anomalies when I realized that if the Newtonian equivalence principle is wrong, then using orbital mechanics to determine the masses of other planets will lead to a bogus value for the distribution of mass within every other planet; and this will be obvious in the evaluation of masses above and below the mean surface density - that is exactly what we find in Mars, Venus and Ganymede; and will eventually realize for Titan and possibly other moons of Saturn.
I'm sorry, I'm not following here. Are you claiming that the distribution of the masses within the planets can be explained better by using different gravity laws, than it can by including apparent density variations in the most straightforward way? You can't mean that because it would be asking a lot for anyone to swallow based on what has been presented here.


The theory I have been trying to develop, but as I said, it is very frustrating because when you start with the assumption 250 years of Newtonian physics are far from correct, you will be labeled a kook. In my experience, the "kook" label comes not from trying to modify existing theories, it comes from doing it with non-minimal hypotheses. We see it all the time, trust me-- someone says "I don't think photons are particles, I think they are mood swings" or some such thing. Now, maybe photons are mood swings, but to establish that, one first has to develop a model that can explain all the existing data on photons, and then one has to show the model does a better job on the problematic data it claims to resolve. When that doesn't happen, the "kook" label comes out. That's usually how it works, anyway.


Serious physicists cannot claim Newton is wrong and escape that label -
And that is a very convenient apologetic for failure to demonstrate that a new hypothesis is minimal (by which I mean, it succeeds everywhere the old hypothesis did, and explains the new stuff, all without introducing extraneous or unproven aspects that have not been demonstrated to have scientific value.)


Very simply, the acceleration of a mass is a function of both the mass and distribution of mass in the system: It takes more energy to accelerate a given mass near the sun to a given orbital velocity than it does to accelerate the same mass to the same velocity near the earth.Now show that hypothesis is minimal. That's the hard part, but is required for it to have any scientific value. (And I think it would be on ATM at that point.)
This means that the moons orbiting Saturn are at least twice as dense at the Newtonian calculations predict - and that is why the surface of Titan appears so terrestrial - it is very terrestrial - Titan is not composed primarily of water and hydrocarbons as Sagen and other predicted. An interesting theory, but you always have to take theories to the limit-- explore every ramification, not just the ones you like. What does your theory say about the density of Pluto and Charon, or the internal models of the gas giants, or the orbits of Phobos and Deimos around the elliptically orbiting Mars?


I can pull together a lot of evidentuary trails that support this assertion, but as Antoniseb noted, I have been off on several tangents."A lot" won't cut it-- a single severe flaw is all that is required to sink your theory. A single prediction that is obviously and categorically wrong-- that's what the present theory does not suffer from. A minimal hypothesis cannot make the situation dramatically worse anywhere in its domain of application.



But since the BAUT prohibited using the board for theoretical development, I've been more of a gadfly than a serious theorist. But I can get galactic orbitals to behave without injecting Dark Matter.
The BAUT has the ATM section for that. But again note, a theory is not judged by cherry-picking its successes, it is judged by a lack of disastrous failures. I wager such disastrous failures of your theory would be very easy to find if that's what you were looking for. Start with the orbits of Phobos and Deimos around Mars as Mars' distance to the Sun varies.

Richard L.
2008-Jan-14, 08:26 PM
lalbatros:

I read the papers you cited and found them very interesting. This just goes to prove that there are alternative solutions to the galatic rotation problem other than dark matter or MOND. Others have suggested that due to the distribution of mass in galexies, it is incorrect to assume newtonian laws as if the galexy core was a point source and therefore 1/r2 law does not apply. Considering the solar system's position some distance from the Milky Way core, most of the galatic mass lies within our sun's orbit. I wonder if our orbital speed is what one would expect from this fact. This would be a tremendous modeling task for even a supercomputer. Few have addressed the anomoly of the Pioneer 10 and 11 velocity, where the sun should be considered a point source. My only point is that all this is evidence that we do not fully understand gravity, and dark matter as a solution is akin to the
19th centurn invention of the Ether. Alhough I didn't intend to impune scientific objectivity, my comments raised some defensive responses.

Ken G
2008-Jan-14, 09:22 PM
Alhough I didn't intend to impune scientific objectivity, my comments raised some defensive responses.

The problem is not intent to impune, it is misinformation. If there actually were "alternatives" to dark matter and MOND that solved the galaxy rotation problem, as well as the galaxy cluster problem, as well as dark matter does, you may be absolutely certain that they would be the mainstream view-- because that's exactly how the mainstream view gets determined (any student of scientific history will see this). Furthermore, it is simply false to suggest that the people doing galactic rotation simulations are so poorly adept at their craft that it hadn't occured to them that not all the matter in the galaxy is concentrated at the galactic core-- rather, the mass distribution in the simulations is indicated by the light produced (with an assumption of an observationally determined mass-to-light ratio). So once again, we see that the "alternative views" suffer not from neglect by the mainstream, but by their own unsubstantiated or ignorant claims. Be informed, then judge-- not the other way around.

Spaceman Spiff
2008-Jan-15, 04:10 PM
I think it's called an "argument from ignorance"...Start from a false (and ignorant) premise about what science understands as best it can within a useful theory (one that unifies our understanding of a large amount of observational data), come to an absurd conclusion, and then declare that this current working theory of some natural phenomenon must be false and those who do research in the field who happen to find the theory to be most useful to be ignorant. It's a prevalent human condition that I do not pretend to understand.

Jerry
2008-Jan-16, 12:23 AM
I am willing to accept the data is incontrovertible, if that is indeed the case, my issue is in attributing that to a difference in the laws of physics instead of just asserting that Mars volcanoes are different from Venus'. Indeed, the former hypothesis requires that the latter hold, so the latter is always the minimal hypothesis that can explain the data.
I certainly agree with that, nor would I ever apply overdue weight to a theory simply because it is "existing". The issue has nothing to do with what is existing or what is mainstream, it has to do with the way science works: whenever you have new data that doesn't agree with your previous expectation, the next step is always to find the minimal hypothesis that can explain that data. Call it the "Occam's Razor" approach to modifying expectations.

This is a great criteria, but are dark matter and dark energy really minimal hypothesis? Is claiming 95% of the universe is not understood and not locally testable a truely scientific approach to the problem? If so, how low can we reduce the percent of the universe we think we have a good handle? How little can we profess to understand, and remain convinced there is nothing fundamentally wrong?

transreality
2008-Jan-16, 12:57 AM
If models based on the theory match reality there is good evidence that enough of the story is known for the theory to be at least usable. Jerry has described his theory, KenG has suggested a test; so model the darn thing, its not hard, do science, satisfy yourself it produces usable results, and make the displays and show the world; trying to convince by sheer force of argument is futile, because the 'other side' can and routinely does produce functional tests that succeed.

Nereid
2008-Jan-16, 02:51 AM
This is a great criteria, but are dark matter and dark energy really minimal hypothesis? Is claiming 95% of the universe is not understood and not locally testable a truely scientific approach to the problem? If so, how low can we reduce the percent of the universe we think we have a good handle? How little can we profess to understand, and remain convinced there is nothing fundamentally wrong?
But Jerry, the list of things that are 'not testable locally' is, we estimate, 99.9999...... % of the universe!

Or do you have a practical method by which a chunk of 'rock on moon which goes round planet which goes round star which is in galaxy which is in cluster' that we estimate is 234.5 Mpc distant (say), can be tested locally?

Goodness, we can't even 'test locally' stuff which is a mere 1,000 km beneath the Sun's photosphere, or even our own feet!

And let's look at 'not understood', shall we?

May your statement be read as implying 'we understand 5% of the universe'? Do you mean to imply that two of the seven Clay Millennium Problems (http://www.claymath.org/millennium/) have already been solved (Yang-Mills and Mass Gap (http://www.claymath.org/millennium/Yang-Mills_Theory/), and Navier-Stokes Equations (http://www.claymath.org/millennium/Navier-Stokes_Equations/))?

Or even that how certain quantities of C, H, O, N (etc), under certain conditions, give rise to the expression, by certain assemblages of said elements, of 'consciousness'?

Perhaps you 'understand' quantum mechanics (QM); good for you! I certainly don't, and many of the 'greats' have said they didn't either (in one way or another).

May we conclude, using Jerry logic, that QM is 'fundamentally wrong'?

Ken G
2008-Jan-16, 03:26 AM
Is claiming 95% of the universe is not understood and not locally testable a truely scientific approach to the problem?Absolutely-- if the evidence tells you that you don't understand what 95% of the universe is made of, then so be it. That's pretty much how all of the constituents that we do know of were discovered! Are you saying we now live in special times where we should, by rights, understand most of what the universe is made of, whereas, say, 200 years ago, we had no right to make that claim?


If so, how low can we reduce the percent of the universe we think we have a good handle?As low as appears to be the case?
How little can we profess to understand, and remain convinced there is nothing fundamentally wrong?Very little, for sure.

Launch window
2008-Jan-17, 08:46 AM
Why not read this thread: What is the observational basis for (cold, non-baryonic) dark matter? (http://www.bautforum.com/questions-answers/42223-what-observational-basis-cold-non-baryonic-dark-matter.html)

While it doesn't address galaxies (elliptical, spiral, dwarf, ...), many of the techniques described apply also to (non-baryonic DM in) galaxies ...

I think LISA would have proven the existence of Dark Matter (NASA's Gravity Waves Mission) the mission was unfortunately canceled.

Jerry
2008-Jan-18, 02:04 AM
Cancelled or postponed? With gravity antenna it has always been the next generation that will pick up the vibes.

If you look closely at the Faulcutt pendulum anomalies observed during a total solar eclipse; you will see that they are consistent with a severe shear plane disruption of the gravitational 'signal' at the moment(s) that the 'rate of darkening' is changing the quickest. I'm not certain whether this is due to an actual event, or poor control of temperature variables and such, but if it is gravitational in nature, we should be able to observed gravitation waves from catastrophic events within our own galaxy. Something is not understood.

Jerry
2008-Jan-22, 01:51 AM
Jerry
Is claiming 95% of the universe is not understood and not locally testable a truely scientific approach to the problem?
Absolutely-- if the evidence tells you that you don't understand what 95% of the universe is made of, then so be it. That's pretty much how all of the constituents that we do know of were discovered!

This is where we depart, philosophically. This is where, based upon the Copernicus principle, I say something fundamental is more likely wrong, or perhaps something simple, such as the estimates of distances based upon supernova magnitudes. Or both.



May we conclude, using Jerry logic, that QM is 'fundamentally wrong'?
Yes and no. Probably yes;)

Quantum mechanics provides us with a vehicle, a way to keep track of known dependencies, and predict future behavior. Epicycles did the same thing. In both cases any theoretical assumptions made about the root causes may or may not be correct. I could pick a less inflammatory example, such as finite element code, but you should get the picture: I don't think QM mechanics as currently defined represent a truly fundamental conceptualization of matter.

Ken G
2008-Jan-22, 05:34 PM
Quantum mechanics provides us with a vehicle, a way to keep track of known dependencies, and predict future behavior.And what else do you want from physics? That's all it has ever done, sometimes more successfully, sometimes less so, and sometimes what we mean by "success" is a moving target.


Epicycles did the same thing.Absolutely, epicycles were a successful physical model for more than a millennium. Good stuff, that.


In both cases any theoretical assumptions made about the root causes may or may not be correct. You seem to be using a nonscientific meaning for "correct".


I don't think QM mechanics as currently defined represent a truly fundamental conceptualization of matter.And what is the scientific prescription for identifying a "truly fundamental conceptualization of matter"? What aspects of physics can you list that you think can be described that way? And how would you know if it was?

Jerry
2008-Jan-23, 03:55 AM
And what is the scientific prescription for identifying a "truly fundamental conceptualization of matter"? What aspects of physics can you list that you think can be described that way? And how would you know if it was?
Good question.

In chemistry, we were able to divine molecular structure from macro-scale patterns: Snowflakes reveal the structure of frozen water, X-ray defraction revealed the structure of metals and even DNA. We combine NMA, IR and many other clues to develop good models.

In thermodynamics, fluid mechanics and electromagnetics we often find relatively straightforward relationships – Gaussian distributions.

In the quantum mechanical realm, the rules seem much more ambiguous and arbitrary; requiring at times apparent violations of real time and space coordinates. There is no marriage between the quantum and relativistic world without 'renormalization': The ultimate black box. Something is wrong.

How would one know what is 'right'? I don't think we ever will – but it may be possible, if correct principles are used – to push our level of understanding to a deeper level. Sometimes, the correct principle is to abandon approaches that lead to black boxes and dead ends.

And what else do you want from physics? That's all it has ever done, sometimes more successfully, sometimes less so, and sometimes what we mean by "success" is a moving target.

New ideas blossom when old ideas are proven wrong and summarily rejected. How wrong is wrong enough? 96% is wrong enough for me and start over, but that is a philosophical choice.

Have you looked at the UT article about a possible explanation for the Pioneer family of gravity anomalies? Did you even know there were so many solar observations that defy reason? Carl Sagan coined the term “tholins” to explain the atmosphere and surface of Titan, but what we are seeing is very unlikely the nitrates Sagan imagined, and very like the Earth, moon and Mars. Something is wrong here, too.

folkhemmet
2008-Jan-23, 05:15 AM
Jerry said: "How wrong is wrong enough? 96% is wrong enough for me and start over, but that is a philosophical choice."

Jerry, you are jumping the gun here. As usual, your philosophical choice is one of naysaying radical skepticism with a topping of self-refutation and dogmatism. Dark matter could be discovered any day now and then you would be the one who is wrong, flat out. You've been wrong before, have you not?

I agree with Jerry to the extent that if dark matter searches continue, year after year, to rule out the most viable models, then cosmologists should stop stubbornly clinging to the idea. On the other hand, if dark matter particles turn up, then the 96% of the Universe is unknown figure will be reduced to ~70% of the Universe is unknown. The entire is dark matter real debate will disappear and dark matter particles will be added to the box labeled 'known types of matter' which currently contains the chemical elements.

It is safe to conclude, based on his vitriolic distain for modern astrophysics, that it will certainly be a bad day for Jerry when iron-clad evidence for the existence of dark matter comes about, as this will entail that his radical skepticism position and all of his complaints about cosmologists being wrong vis-a-vis dark matter will be rendered dead wrong/anachronistic ont he spot. Jerry, are you prepared to concede defeat, or, out of shear frustration, will you try to slander the discoverers of dark matter by saying that they are faking the data?

Ken G
2008-Jan-23, 09:03 AM
In chemistry, we were able to divine molecular structure from macro-scale patterns: Snowflakes reveal the structure of frozen water, X-ray defraction revealed the structure of metals and even DNA. We combine NMA, IR and many other clues to develop good models.
Right, we interact with the object in as many ways as we can think of, and use the results to help us build a model. But the model is only as good as the interactions that we have at our disposal. We know about nuclei because we can probe them with a beam of energetic particles. But what if we don't have an interaction at our disposal, as with dark matter? That could be just like the status of our understanding of nuclei before Rutherford.


In thermodynamics, fluid mechanics and electromagnetics we often find relatively straightforward relationships – Gaussian distributions.
And these are powerful expressly because they are so ubiquitous that we need know very little about the species exhibiting them. Much like models of cold dark matter-- we can predict its behavior without knowing much at all about its properties.


In the quantum mechanical realm, the rules seem much more ambiguous and arbitrary; requiring at times apparent violations of real time and space coordinates. There is no marriage between the quantum and relativistic world without 'renormalization': The ultimate black box. Something is wrong.There is always a black box at the end of any physical theory, this is not a flaw. The black box is called "reality", and the paradox is, any physical theory that does not connect to that black box is not worth a thing beyond a kind of intellectual pastime.


How would one know what is 'right'? I don't think we ever will – but it may be possible, if correct principles are used – to push our level of understanding to a deeper level. Sometimes, the correct principle is to abandon approaches that lead to black boxes and dead ends.Again, a "dead end" is not contact with a black box as you imply, it is the absence of meaningful contact with a black box.


New ideas blossom when old ideas are proven wrong and summarily rejected. How wrong is wrong enough? 96% is wrong enough for me and start over, but that is a philosophical choice. Yes, there is room for all approaches in science, and it is important to have someone covering all the bases. The real issue, though, is how much resources should society as a whole commit to each base. That isn't a matter of personal philosophy, it is a matter of what has proven to work-- it is a matter of finding the minimal hypothesis that fits all the data.


Have you looked at the UT article about a possible explanation for the Pioneer family of gravity anomalies? Did you even know there were so many solar observations that defy reason? Carl Sagan coined the term “tholins” to explain the atmosphere and surface of Titan, but what we are seeing is very unlikely the nitrates Sagan imagined, and very like the Earth, moon and Mars. Something is wrong here, too.
I do not dispute that there are unanswered questions here. I merely point out that the job of science, when confronting unanswered questions, is to find the minimal, not maximal, hypothesis. That way you don't lose the 99 successful predictions in the process of solving the one that is not working out. The properties of Titan are a good example-- your resolution of that yields far more significant problems with things we already do understand, like the composition of Pluto, and the orbits of the moons of Mars.

Jerry
2008-Jan-24, 04:48 AM
...
I agree with Jerry to the extent that if dark matter searches continue, year after year, to rule out the most viable models, then cosmologists should stop stubbornly clinging to the idea. On the other hand, if dark matter particles turn up, then the 96% of the Universe is unknown figure will be reduced to ~70% of the Universe is unknown. The entire is dark matter real debate will disappear and dark matter particles will be added to the box labeled 'known types of matter' which currently contains the chemical elements.

I can deal with that. Give me chemical properties or give me an new theory! What I cannot condon, is that in so much of the published literature out there, (especially in the NASA outreach programs), so many in the field are still insisting that dark matter is a proven concept; and doing that in spite of forty years of NEGATIVE results. Millions of astrophysical dollars have been spent looking for hot/cold/warm/machos/cheetos in a futile search.

And what about the study of the Pioneer anomalies? How much has been dedicated to this effort? When space missions and research funding are slim, conservative proposals muscle-out long-shots that would require new physical theories. We need to look more carefully for unexpected patterns - I think they are there - patterns of anomalies.

Look at it this way: Forty years of looking for gravitational waves and Dark Matter with no positive results - that is more than twice as long as Michealson & Morley searched for aether before Relativity was proposed. It is past time to focus research dollars elsewhere. Proofing our existing theories within our own solar system is a good place to start.

Celestial Mechanic
2008-Jan-24, 05:07 AM
[Snip!] And what about the study of the Pioneer anomalies? How much has been dedicated to this effort? [Snip!]
Since you hang out at arxiv.org (and so do I!), I'm sure you can't help noticing that hardly a month goes by without at least one article about it. Maybe not a big bux effort, but somewhere in all this speculation there might be the insight that leads to the solution of the problem. But which one? :think:

Jerry
2008-Jan-24, 05:44 AM
Yes, the rock is slowly rolling:

http://xxx.lanl.gov/PS_cache/arxiv/pdf/0801/0801.3407v1.pdf

Tests of general relativity in the solar system


The present lecture notes discuss the current status of tests of general relativity in the solar system. They describe metric extensions of general relativity which have the capability to preserve compatibility with existing gravity tests while opening free space for new phenomena. They present arguments for new mission designs and new space technologies as well as for having a new look on data of existing or future experiments.

I think we have given it a little push, don't you?

Kaptain K
2008-Jan-25, 05:22 AM
Yes, the rock is slowly rolling:

http://xxx.lanl.gov/PS_cache/arxiv/pdf/0801/0801.3407v1.pdf

Tests of general relativity in the solar system



I think we have given it a little push, don't you?
So, now you're taking credit! :sick:
Surely you jest! :lol:

Ken G
2008-Jan-25, 02:58 PM
Millions of astrophysical dollars have been spent looking for hot/cold/warm/machos/cheetos in a futile search.
A little truth in advertising, please. First of all, you are requiring that dark matter be found in the laboratory-- everything that can be done to find its signature in deep space is already being done! So apparently you are now claiming that "millions of dollars" has been spent over 40 years to find dark matter in the laboratory? But the big money (billions of dollars) has gone to finding its signature in deep space-- and guess what, the results have not been negative. One merely needs google "bullet cluster dark matter" to find one of the most striking possible successes in the astrophysical search for dark matter.

Now, I agree with you that the dark matter model will never be complete until it is found in the laboratory. But let's not pretend that all these "astrophysical dollars" are being "wasted" in a "futile search" for it, because those dollars have indeed found it, to whatever extent that is possible in astrophysics. Very little, comparatively, has so far been invested in finding it in the laboratory. I point out that orders of magnitude more money has been spent looking for the Higgs boson, and it has not yet been found-- is that a "futile search" as well? How about the vector boson, was that a "futile search" right up until the moment it was found, and then what did that search become?


And what about the study of the Pioneer anomalies? How much has been dedicated to this effort? When space missions and research funding are slim, conservative proposals muscle-out long-shots that would require new physical theories. We need to look more carefully for unexpected patterns - I think they are there - patterns of anomalies. It is certainly arguable that a more concerted effort should be undertaken to explain that anomaly, if for no other reason, to quiet this kind of objection. But such a search may not be a search for new physics-- but rather a derivative study into the errors of data interpretation in solar-system probes.

undidly
2008-Jan-25, 04:28 PM
The Pioneer anomalies are thought by some to be caused by DARK ENERGY not
DARK MATTER.These both do not exist.There is a simple explanation for both and the dark energy explanation can be experimentally tested.

If relativity is properly applied it is obvious that there is no missing matter to be
accounted for.So many well paid scientists have got it wrong,or play along to get their money.Nothing to find = no grant.
Galaxies are behaving as they should according to Einstein .Sorry Newton you
almost got it right,good enough for local use though.

antoniseb
2008-Jan-25, 04:50 PM
If relativity is properly applied it is obvious that there is no missing matter to be accounted for.

You have made a rather bold ATM statement in the Mainstream part of the forum. You are pretty new here, so perhaps you haven't taken time to read the rules yet.

Continuing to do this sort of thing will eventually get you suspended or banned altogether.

On the other hand, if you think you have something new to show that can replace some mainstream science, everyone here would like to be among the first to see it. Take your idea to the ATM section, and let us ask you questions to help you clarify your idea, or find out if it has a giant hole in it.

Jerry
2008-Jan-26, 08:26 PM
A little truth in advertising, please. First of all, you are requiring that dark matter be found in the laboratory-- everything that can be done to find its signature in deep space is already being done! So apparently you are now claiming that "millions of dollars" has been spent over 40 years to find dark matter in the laboratory? But the big money (billions of dollars) has gone to finding its signature in deep space-- and guess what, the results have not been negative. One merely needs google "bullet cluster dark matter" to find one of the most striking possible successes in the astrophysical search for dark matter.

No, I don't think it is necessary to quantify Dark Matter in the laboratory to prove its existence. Spectrography, multiwavelength telescopes- radar, X-ray, infared - all extend our laboratory capabilities into space. Yes, this is where Dark Matter searches have been concentrated, and this is where they have been UNSuccessful.

The 'bullet galaxy' analysis is one of the NASA propagated evidentuary trails that leave me grinding my teeth. They are making multiple assumptions about the transitory paths of two galaxies, and in any case only demonstrate that the gravitation prediction of mass is inconsistent with the observational evidence of mass.

There is some discussion of this here:

http://www.bautforum.com/astronomy/45700-nasa-announce-dark-matter-discovery-2.html

Ken G
2008-Jan-26, 09:10 PM
No, I don't think it is necessary to quantify Dark Matter in the laboratory to prove its existence. Spectrography, multiwavelength telescopes- radar, X-ray, infared - all extend our laboratory capabilities into space. Yes, this is where Dark Matter searches have been concentrated, and this is where they have been UNSuccessful.I'm really missing your point there. You just listed a bunch of ways of detecting light, then asserted they've been unsuccessful in finding dark matter? Obviously such an approach can only be used to look for indirect evidence-- a whole bunch of which has indeed been successfully found. Can you suggest a single "negative result" in the search for dark matter, other than in the laboratory? Because in space, it does everything it is expected to do-- it is a vastly successful model. The only knock one could have against it is that it is not the minimal hypothesis-- which requires suggesting one that is more minimal. That has not happened, ergo dark matter is our best theory.


The 'bullet galaxy' analysis is one of the NASA propagated evidentuary trails that leave me grinding my teeth. They are making multiple assumptions about the transitory paths of two galaxies, and in any case only demonstrate that the gravitation prediction of mass is inconsistent with the observational evidence of mass.Methinks thou doth protest too much. We see two galaxy clusters in obvious collision, and we see a gravitational signature that does not match the gas, ergo we need a source of gravity other than the gas. Furthermore, the signal would match weakly interacting material-- which fits dark matter. No other model that has ever been suggested even remotely works in this situation. Yes, one could say that it's just a single instance and could be a rare coincidence of some kind, but that argument, like so many others, will fall away with more and more data of the type that is actually being pursued at the moment, despite your worries that it's all being swept under the rug. If the bullet cluster is atypical in some way, we'll soon know, there's no need for a course correction in that regard.

Jerry
2008-Jan-27, 05:31 AM
I'm really missing your point there. You just listed a bunch of ways of detecting light, then asserted they've been unsuccessful in finding dark matter? Obviously such an approach can only be used to look for indirect evidence-- a whole bunch of which has indeed been successfully found. Can you suggest a single "negative result" in the search for dark matter, other than in the laboratory?


Experimental searches for these dark matter candidates have been conducted and are ongoing. These efforts can be divided into two broad classes: direct detection, in which the dark matter particles are observed in a detector; and indirect detection, which looks for the products of dark matter annihilations. Dark matter detection experiments have ruled out some WIMP and axion models. There are also several experiments claiming positive evidence for dark matter detection, such as DAMA/NaI and EGRET, but these are so far unconfirmed and difficult to reconcile with the negative results of other experiments. There have been lots of negative, constraining searches

In astrocast, Pamela describes Dark matter as a place holder, a generic pair of words we us to describe something we really to not understand. "Super gravity" could have been the chosen as a desciptive term the emphasizes that dark matter is really the difference between using Newtonian physics to explain the motions of galaxies, and what we actually observe. We really have three choices: A weird form of matter, a poor law of gravity, or still undetected but quit normal mass.

folkhemmet
2008-Jan-27, 12:41 PM
One of the main objections raised against the CDM theory has been, according to many astrophysicists, that CDM simulations predict approximately an order of magnitude more satellite galaxies surrounding the Milky Way and other large galaxies than are actually observed. This objection is referred to both as the missing satellite problem and the substructure problem.

The results are still preliminary, but SDSS and KecK observations of very tiny very faint conglomerations of stars around the Milky Way show that the satellites do in fact probably exist in large enough numbers to solve this important problem with the CDM model. Albeit, the satellite galaxies found were found in one part of the sky, but when the study extrapolated to the entire sky they found that the number of miniscule satellite galaxies indeed roughly matches the number produced in CDM simulations! Obviously more work will be needed to confirm (or call into doubt) and extend these observations, but they do at least for now strongly suggest that a major stumbling block in the way of CDM has been removed.

Of course, no indirect observation will compare to the direct detection of the dark matter in terms of settling the issue. It is important to realize that although there have years of negative results in this arena, it has only been in the past few years that the relevant experiments have become technologically capable of testing the most favored dark matter models. Also, GLAST and LHC will definitely have something to say one way or the other wrt this matter, soon. So, let's wait and see before jumping the gun either way. If DM has not been found and unambiguously identified by 2015-2020, then the theory should be abandoned. All the while alternatives should and are continuing to be explored.

Ken G
2008-Jan-27, 05:43 PM
There have been lots of negative, constraining searchesI see what you are saying, there have been efforts to detect the astrophysical annihilations of various types of things. I know of no astrophysical experiment mounted expressly for that purpose, but I might not be aware of the money spent on that. To me, speculating a slight possibility, and then not finding it, is not what I would call a "negative" result.


In astrocast, Pamela describes Dark matter as a place holder, a generic pair of words we us to describe something we really to not understand. And that has happened many times before. Take "neutrinos" for example-- a place holder for a particle whose attributes are still being discovered today, called, well, neutrino.

We really have three choices: A weird form of matter, a poor law of gravity, or still undetected but quit normal mass.That rather overlooks the last ten years of results.

Cougar
2008-Jan-27, 07:02 PM
In astrocast, Pamela describes Dark matter as a place holder, a generic pair of words we us to describe something we really to not understand.
I got no problem with that. But the place its holding can't be just anything. It has to stay consistent with what's observed.


All the while alternatives should and are continuing to be explored..."

Also fine. But it should be pointed out that Jerry's continuing argument wrt the Bullet Cluster is inconsistent with what is observed there. The observations provide evidence against the sort of modified gravity theory he's alluding to.

Jerry
2008-Jan-28, 05:22 AM
To me, speculating a slight possibility, and then not finding it, is not what I would call a "negative" result.

In 2004, Jim Peebles called the failure of the concentrated search to nail down Dark Matter "embarrassing".


We really have three choices: A weird form of matter, a poor law of gravity, or still undetected but quit normal mass.
That rather overlooks the last ten years of results.
In what way? It is fair to say that all of the searches for DM have confirmed there is a big difference for what Newtonian gravitational theory predicts, and what we have observed. Either we have a poor theory, poor methods or exotic matter - you can add to that list of options if you like.


Also fine. But it should be pointed out that Jerry's continuing argument wrt the Bullet Cluster is inconsistent with what is observed there. The observations provide evidence against the sort of modified gravity theory he's alluding to.
We don't know what these things looked like before they collided, if they collided. We don't know the internal kinetics, time frame, compositional distribution, or even the parent galaxy types. I don't think it is reasonable to examine anything so peculiar as the bullet cluster and say look at this: We can use this very odd looking thing to prove beyond any doubt that dark matter exists: It is like claiming understanding of a eddy without knowing what lies underneath or what falls upstream.

I don't advocate the MOND solution: I think Newtonian methodology grossly underestimates the mass of many systems, and that the viral theory which relies upon Newtonian estimates of mass demonstrates just that: there is more mass in galactic system than can be accounted for using Newtonian rules.

matt.o
2008-Jan-28, 05:48 AM
The 'bullet galaxy' analysis is one of the NASA propagated evidentuary trails that leave me grinding my teeth. They are making multiple assumptions about the transitory paths of two galaxies, and in any case only demonstrate that the gravitation prediction of mass is inconsistent with the observational evidence of mass.




We don't know what these things looked like before they collided, if they collided. We don't know the internal kinetics, time frame, compositional distribution, or even the parent galaxy types. I don't think it is reasonable to examine anything so peculiar as the bullet cluster and say look at this: We can use this very odd looking thing to prove beyond any doubt that dark matter exists: It is like claiming understanding of a eddy without knowing what lies underneath or what falls upstream.


These sorts of comments make me wonder if you even know what the Bullet Cluster is, let alone whether you should be critiquing the analysis of people who study these things day in day out.

The Bullet Cluster is a cluster of galaxies, not a galaxy, and things like internal kinetics, time frames, whether they collided etc. can be constrained from observations.

knomikos
2008-Jan-28, 06:40 AM
We should all applaud those in who oppose the leading belief in a "placeholder" like DM, even if only for their contribution to the necessary contention for good science and empiricism.

Personally, I dislike dark matter. That doesn't mean I categorically deny its existence. But I would PREFER a more elegant solution.

For those of you who judge a preference to be inferior to a conclusion, those who believe that emotion has no place in scientific discourse, you should study a little outside your "hard" fields. The bottom line is, human thinking is emotionally based. It is only through forums like these that we can distill and filter our most commonly occuring thoughts to a "reasonable" thread...if we're all willing. The miracle of language is that is allows us to share thoughts.

Nothing is more important.

But to the point: I have a question.

Has anyone considered the pressure which must surround a galactic core? There must exist a difference in gas pressure between the volumes near the center vs the outer arms of a galaxy...even if both measure infinitesmally small and the difference is even smaller. Could this account for any of the discrepancy between theory and perception?

I also wonder if many of the ideas presented here for speeding the outer stars in a galactic system don't COMBINE to tell the whole story...if, just like in living systems, several "special cases" conspire at once to explain complex behavior? No, I'm not proposing a "living" galaxy (although I would welcome a debate for or against such a concept), but when a system exhibits behavior which differs from the simplest expectations, emergence is showing itself, and that in itself implies at least a quasi-chaotic system.

Doesn't it?

Ken G
2008-Jan-28, 07:27 AM
In 2004, Jim Peebles called the failure of the concentrated search to nail down Dark Matter "embarrassing".
Sounds like a statement taken out of context to me. Or are you claiming that Peebles is skeptical that dark matter is a good theory?


In what way? It is fair to say that all of the searches for DM have confirmed there is a big difference for what Newtonian gravitational theory predicts, and what we have observed. Either we have a poor theory, poor methods or exotic matter - you can add to that list of options if you like.What you are missing is that all three of those possibilities have been followed vigorously over the past decade or more, and one has had resounding success, while the others have met with dismal failure. That's just the fact. Granted, even the one that had resounding success has not found the "smoking gun" of direct laboratory and astrophysical decay into something observable. But to equate all three approaches after all that has been learned is to have one's head firmly in the sand. But you are already there, when you continue to talk about these non-Newtonian mass estimates without admitting that your alternative theory fails quite completely to properly constrain something as mundane as the orbits of Phobos and Deimos (yes I'll keep bringing that up if you keep trotting out this non-Newtonian mass hooey).



We don't know what these things looked like before they collided, if they collided.To imagine that they are not colliding is quite a stretch. But no matter-- time will provide the further observational support needed. It is the telltale sign of a good theory-- the observational evidence just grows and grows. I predict that by the time it is found in the laboratory, which could be decades from now, it will have been so firmly established that people will say "duh, we already knew that, but it's nice to see it confirmed". Just a prediction.

Jerry
2008-Jan-29, 02:59 AM
Sounds like a statement taken out of context to me. Or are you claiming that Peebles is skeptical that dark matter is a good theory?

Still looking for the exact quote - somewhere between 2002-2004, but here is a perceptive paragraph:


We have little empirical guidance to the physics of the dark sector: we are working in the dark. We accordingly adopt the simplest physics we can get away with, which is good strategy, but certainly need not be the whole story: consider that polytropic ideal gas spheres were good enough for Eddington’s analysis of the structure of the Sun, but helioseismology reveals a host of new details. If our model for the dark sector is missing details that matter it will be revealed by problems in fitting the observations. And there are hints of problems, from observations of the structure and formation of galaxies. My list is headed by the prediction that elliptical galaxies form by mergers at modest redshifts, which seems to be at odds with the observation of massive quasars at z  6; the prediction of appreciable debris in the voids defined by L galaxies, which seems to be at odds with the observation that dwarf, irregular, and L galaxies share quite similar distributions; and the prediction of cusp-like dark matter cores in low surface brightness galaxies, which is at odds with what is observed. These are Rowland-type problems that draw on the rich phenomenology of astronomy, from the latest observations by the Hubble Space Telescope to the vast accumulation of lore from decades past. Sorting through all this takes time, but I expect will show us whether the problems with the standard picture for the dark sector will be resolved by better understanding of the observations and theory, or will be promoted to a Kelvin-level cloud.

http://xxx.lanl.gov/PS_cache/astro-ph/pdf/0209/0209403v1.pdf


These sorts of comments make me wonder if you even know what the Bullet Cluster is, let alone whether you should be critiquing the analysis of people who study these things day in day out.

The Bullet Cluster is a cluster of galaxies, not a galaxy, and things like internal kinetics, time frames, whether they collided etc. can be constrained from observations.
Your walking right past my rather large point: A bunch of stuff in interacting in an unusual way on a massive scale with no local equivalents, and somebody is looking at this and saying: 'Will you look at that! Proof positive of Dark Matter!'

What if the gravity wave people would have looked at this first, and assuming there are interactions between multiple 'black holes'; made appropriate assumptions and ran-out numbers that are consistent with distortions due to gravitational waves? Who would be right?

You can't look at something that is so massive, so totally unique and use it as a one-of proof of a pet theory. Or as Peebles spelled it out in 2002:


...But the present precision of the evidence allows considerably more complicated physics in the dark sector, and more complicated physics may be indicated by the observational challenges from galaxy structure and formation. In short, significant adjustments to the CDM model would not be surprising, and a major shift not inconceivable. Until this is sorted out structure formation is a hazardous basis for cosmological tests.

My bold

http://xxx.lanl.gov/PS_cache/astro-ph/pdf/0208/0208037v1.pdf

Jerry
2008-Jan-29, 03:23 AM
Open Problems in Cosmology

http://xxx.lanl.gov/PS_cache/astro-ph/pdf/0311/0311435v1.pdf


It is also worth bearing in mind that observational advances have ruled out elegant ideas; the steady state cosmology is an example. And for all we know other ideas have survived only because we have not yet found out what is wrong with them: longevity adds a patina of respectability.

In short, we should respect the ideas behind the standard cosmology, because elegant ideas sometimes lead to aspects of reality, but we should use caution in adding ideas to the established cannon, because the universe is quite capable of surprising us.

Also, a useful reference:

http://xxx.lanl.gov/PS_cache/arxiv/pdf/0711/0711.4996v2.pdf

Dark Matter Candidates: A Ten-Point Test

Marco Taoso, Gianfranco Bertone, and Antonio Masiero

folkhemmet
2008-Jan-29, 05:33 AM
Jerry, thank you for providing us with the link to this excellent DM reference, as it gives us an expansive overview of the different possibilities for particle DM as well as a list of the various experiments designed to test them. The paper implicitly underscores the notion that if DM exists in any of the forms mentioned, then there is a good chance that it will be identified in the next decade. Indeed, how could such a steadily improving and multi-faceted experimental regime fail to find the stuff if it actually exists? A discovery of DM would easily place among the top five greatest scientific revelations on par with germ theory, DNA, plate tectonics, chemical elements, etc. We will reduce the ignorance of the 'dark sector' from 96% down to 70%! Many skeptics and MOND adherents will sob. Alternatively, it should be equally interesting to see what the reaction of mainstream astro-physics community is if DM is not found by the end of the next decade. How long will the denial last? What will the coming around look like? What form will the desperate attempts to cling to CDM take?

antoniseb
2008-Jan-29, 03:57 PM
Alternatively, it should be equally interesting to see what the reaction of mainstream astro-physics community is if DM is not found by the end of the next decade. How long will the denial last? What will the coming around look like? What form will the desperate attempts to cling to CDM take?

Given that the next decade will also include increasingly accurate maps of mass distribution in nearby galaxies, dark galaxies, colliding galaxies, dwarf galaxies, and clusters, improved knowledge of the distribution of dust, gas, and machos, increased understanding by observation of the space near event horizons... I think that if we do not observe some kind of WIMP, that we will at least have a much narrower picture of what else could explain the phenomena.

I'm guessing that if we do not detect WIMPs in the laboratory in the next twelve years that the WIMP explanation will not go away without something specific and calculable in its effect being supplied as an alternative.

matt.o
2008-Jan-29, 08:41 PM
Your walking right past my rather large point: A bunch of stuff in interacting in an unusual way on a massive scale with no local equivalents, and somebody is looking at this and saying: 'Will you look at that! Proof positive of Dark Matter!'


No I haven't. As I said in my last post the 'bunch of stuff interacting in an unusual way' can have its interactions constrained by the observations (ie. X-ray, optical spectroscopy etc). There are a few good papers on the radio, x-ray and optical observations of the bullet cluster - just go search ads.abs.harvard.edu for '1e657-558' or 'bullet cluster' and look for authors like Markevitch and Barrena.

Also, it's not as if this is the only evidence for the existence of CDM. It was predicted before the bullet cluster that CDM should be weakly interacting - the bullet cluster is a good evidence of this. You should also check out other evidences of weak lensing mass distributions differing from the light distribution (eg. Abell 520 and CL0024+17, although A520 is more complicated than the bullet).


What if the gravity wave people would have looked at this first, and assuming there are interactions between multiple 'black holes'; made appropriate assumptions and ran-out numbers that are consistent with distortions due to gravitational waves? Who would be right?




I don't think you understand the mass and size scales at work here. And so what if the gravity wave people came along and had a go at solving this? They haven't, and at the moment cold dark matter fits the bill the best, so what is the point of this idle speculation?

Ken G
2008-Jan-29, 10:18 PM
Yet Peebles pretty much summed up my point when he said, in your quote, "We accordingly adopt the simplest physics we can get away with, which is good strategy, but certainly need not be the whole story". Science never has been, nor ever will be, required to provide "the whole story", that will always be a work in progress. The issue at hand is, which is our best current theory, what is the minimal hypothesis that agrees the best with the existing observations and provides the most predictive power and guidance into future observational needs. That is dark matter, and logically, that is also where the lion's share of the research resources should go. I see nothing in Peebles' statements that would suggest otherwise.

Jerry
2008-Jan-30, 01:52 AM
I don't think you understand the mass and size scales at work here. And so what if the gravity wave people came along and had a go at solving this? They haven't, and at the moment cold dark matter fits the bill the best, so what is the point of this idle speculation?
I agree that the bullet cluster studies put forward a good case for CDM. If you read Peebles concerns, and the papers of Milgrom, McGraw and others, there are also many galactic gravitational observations that are difficult to explain with CDM. Weakly interactive CDM should be observable locally. My concern is this is an odd cherry; not a smoking gun.

We need to do the local studies before anyone declares victory. Cassini scientist are scratching their heads over the Titan atmospheric, gravitational, and INMS data. Likewise Enceladas and Iapetus are providing difficult puzzles - planetary geologists are vexed. We need Mossbuer analysis of the outer solar moons, solar Cavendish expirements and other baseline studies.

Ken G
2008-Jan-30, 04:27 PM
If you read Peebles concerns, and the papers of Milgrom, McGraw and others, there are also many galactic gravitational observations that are difficult to explain with CDM.I don't know about those others on your list, but Peebles was pretty clear, I think, that his concern was not that the observations are difficult to explain with CDM, but rather that they require additional features to be added to the CDM models. His point seems to be that CDM is only a "first cut" solution, and that future versions will need to include richer phenomena. Note that it is perfectly normal for science to progress in that fashion, far from the "we're on the completely wrong track" position you are taking. Hence citing Peebles comments as support for your position is misleading.

matt.o
2008-Jan-30, 08:38 PM
I don't know about those others on your list, but Peebles was pretty clear, I think, that his concern was not that the observations are difficult to explain with CDM, but rather that they require additional features to be added to the CDM models. His point seems to be that CDM is only a "first cut" solution, and that future versions will need to include richer phenomena. Note that it is perfectly normal for science to progress in that fashion, far from the "we're on the completely wrong track" position you are taking. Hence citing Peebles comments as support for your position is misleading.

You've hit the nail on the head Ken G. In fact I saw Peebles give a talk on dark matter a couple of years ago where he proposed a form of evolving dark matter to solve the halo and elliptical galaxy age problems.

Ken G
2008-Jan-31, 12:05 AM
In fact I saw Peebles give a talk on dark matter a couple of years ago where he proposed a form of evolving dark matter to solve the halo and elliptical galaxy age problems.He's an amazing guy, I took statistical mechanics from him. It sounds like he's well ahead of the pack in his thinking on dark matter.

folkhemmet
2008-Jan-31, 08:49 PM
Right now a variety of methods, independent of each other, come to the same basic conclusion [within reasonable precision] about the Universe's matter density--namely, that it is 20-30% of the critical density. The discovery of dark matter particles, if it occurs, in the quantity that agrees with these other indirect methods will be, whether radical skeptics (like Jerry) like it or not, a super-strong validation of 25% of the current cosmological model (the CDM part of LCDM). It would be stretching credulity for the skeptics to say that "oh, well, it is just a coincidence that the direct dark matter searches, the CMB, galaxy cluster measurements, lensing, etc all arrive at the same conclusion wrt to the Universe's matter density." Now, this ultra-confirmation may not happen, but if it does Jerry and other radical skeptics will have been massively discredited and, most likely, because they are naysayers, massively dismayed. I for one will be along side those "crazy" people who will call such an event a triumph of humanity. There are plenty of things not to be proud over wrt to our civilization; however, our artistic and intellectual achievements are not among them.

Jerry
2008-Jan-31, 11:57 PM
The discovery of dark matter particles, if it occurs, in the quantity that agrees with these other indirect methods will be, whether radical skeptics (like Jerry) like it or not, a super-strong validation of 25% of the current cosmological model (the CDM part of LCDM).
It will/would be wonderful confirmation...just as the actual local observation of gravitational waves will/would validate the Nobel effort of Hulse.

What is good for the goose is good for the gandor: As the local detection limits improve, the lack of any local detections of either Dark Matter or Gravitational waves can render the current explanations for distant gravimetric analysis null and void. (As you have said: I am of the opinion they already have. My world-view requires thermaldynamic balance - that is a philosophical choice.)

Richard L.
2008-Feb-04, 09:15 PM
The point about distributed gravitation on a star within a galexy is well taken, However, if the individual stars in a galexy were locked in place and rotated as points on a wheel as you suggest, then how is it be possible for galexies to look so different from what one would expect of a wheel? How do we explain spirals all those arms and bard spirals with stars trailing from the ends like water out of a rotating sprinkler. They don't look like wheels do they? Note my analogy about the bucket of rotating white paint where black paint is poured into the center and because of the viscosity of the paint, forms spiral arms as the black paint works its way from the center.

Jerry
2008-Feb-06, 05:56 AM
The point about distributed gravitation on a star within a galexy is well taken, However, if the individual stars in a galexy were locked in place and rotated as points on a wheel as you suggest, then how is it be possible for galexies to look so different from what one would expect of a wheel?
I've never suggested that. I have hypothesized that the permiability and permitivity of a vacuum are not constant, but rather a function of the total mass of the system. This would generally (using Newtonian mechanics) cause the baryonic mass of the system to be underestimated.

nutant gene 71
2008-Feb-06, 08:19 PM
Here’s where ‘missing dark matter’ is really missing. NewScientist article: Galaxy without dark matter puzzles astronomers (http://space.newscientist.com/article/dn13280-galaxy-without-dark-matter-puzzles-astronomers.html) says this galaxy, NGC 4736, doesn’t exhibit any dark matter. Curious that they should say:

” Even then, one exceptional dark-matter-less galaxy would be a great puzzle. "The current picture is that galaxies form inside of dark matter halos," Diemand told New Scientist. The dark matter's gravity attracts ordinary gas, which can then coagulate into stars.
"It is unclear how one would form a galaxy without a dark halo, or how one could remove the halo without destroying the galaxy," says Diemand. "A galaxy without dark matter really does not fit into our current understanding of cosmology and galaxy formation."
Nor can galaxies with declining rotation curves be easily explained by MOND, says McGaugh. So for now, it seems that some of our missing mass is missing.”
However, if the ‘missing dark matter’ attracts cosmic dust and gas into stellar combustion, it may have been either consumed or somehow ‘modified’ into non-dark matter, and now acts as ordinary baryonic matter instead. Either way, dark matter was instrumental in coagulating into stars out of ordinary gas, since it acts gravitationally on a higher order of magnitude than ordinary matter gravity, but per this article it is no longer detectable. This could be, however, because of the assumptions involved in measuring hydrogen gas on galaxy’s perimeter, which may be a flawed assumption, so expected declining rotation curves are not self evident. I for one think so called ‘dark matter’ is merely non-luminous higher G ordinary matter, for the record. ;)

Buzz-Lite-Punch
2008-Feb-06, 08:54 PM
There’s a bit of discussion on NASA TV at the moment, about (Dark Matter and Chandra), most of this is way over my head for clear understanding on how our universe works?

Can (Dark Matter), be consumed by a (Black Hole)?? Or is (Dark Matter) a member or family to (Black Holes)??


http://i232.photobucket.com/albums/ee18/DemolitionMan3417/NASATVdarkmatter.jpg

Jerry
2008-Feb-07, 03:05 AM
Here’s where ‘missing dark matter’ is really missing. NewScientist article: Galaxy without dark matter puzzles astronomers (http://space.newscientist.com/article/dn13280-galaxy-without-dark-matter-puzzles-astronomers.html) says this galaxy, NGC 4736, doesn’t exhibit any dark matter. Curious that they should say:

Such a galaxy is easier on Dark Matter theories than other alternatives: Dark Matter could be missing, modified gravity could not.

Still, one galaxy, and a number of assumptions about this rare, exceptional observations does not make or break a theory, any more that the unusual 'bullet cluster' provides proof positive of dark matter. Curious objects are observed. Normal objects look curious when they are shouded in gas or warped by [distance effects].

Ken G
2008-Feb-07, 08:12 AM
Such a galaxy is easier on Dark Matter theories than other alternatives: Dark Matter could be missing, modified gravity could not.
That's a pretty good point-- and how ironic, it is in effect a true case of the exception that proves the rule!

Jerry
2008-Feb-10, 01:00 AM
A theory (I won't mention who's) that hypothesizes that Newtonian mechanics underestimate the mass of galactic centers has a chance of surviving, if this galaxy core is truly undermassive relative to the core luminosity - that could be true if the baryonic mass in the core is burning much more brightly than the norm. This is certainly a system worthly of further study.

schlaugh
2008-Apr-17, 07:16 PM
Physicists Renew Claim, in New Experiment, of Detecting Dark Matter Particles (http://www.nytimes.com/2008/04/17/science/space/17dark.html)


By DENNIS OVERBYE (http://topics.nytimes.com/top/reference/timestopics/people/o/dennis_overbye/index.html?inline=nyt-per)
Published: April 17, 2008
A team of Italian and Chinese physicists on Wednesday renewed a controversial claim that they had detected the mysterious dark matter particles that astronomers say swaddle the galaxies in halos and direct the evolution of the universe.

The team, called Dama, from “DArk MAtter,” and led by Rita Bernabei of the University of Rome, has maintained since 2000 that a yearly modulation in the rate of flashes in a detector nearly a mile underneath the Gran Sasso mountain in Italy is the result of the Earth’s passage through a “wind” of dark matter particles as it goes around the Sun. Other groups of hunters of dark matter have just as consistently failed to find any evidence of the putative particles.

At a meeting in Venice, Dr. Bernabei reported that a new, bigger experiment named Dama/Libra had now observed the same modulation. “No other experiment whose result can be directly compared in a model-independent way is available so far,” she said. The findings increase the chances that the modulation is real, outside dark matter experts say.

Dark matter has taunted astronomers and physicists ever since the astronomer Fritz Zwicky of the California Institute of Technology (http://topics.nytimes.com/top/reference/timestopics/organizations/c/california_institute_of_technology/index.html?inline=nyt-org) pointed out in the 1930s that clusters of galaxies appear to be missing enough visible matter to hold them together gravitationally. Speculation has centered on the possibility that the dark matter consists of hypothetical elementary particles left over from the Big Bang — so-called WIMPs, or weakly interacting massive particles, that are immune to most forces of nature and so can pass through us and the Earth like ghosts.

borman
2008-Apr-18, 02:12 PM
DAMA paper

For those who would like more details, the paper has been posted on the arxiv:

First results from DAMA/LIBRA and the combined results with DAMA/NaI

Abstract: http://arxiv.org/abs/0804.2741

loglo
2008-Apr-19, 01:02 AM
They are reporting an 8 sigma confidence limit of detection with the combined data. That seems fairly significant. Is there any other experiment of similar sensitivity being run that will be able to confirm?

borman
2008-Apr-20, 05:31 PM
They are reporting an 8 sigma confidence limit of detection with the combined data. That seems fairly significant. Is there any other experiment of similar sensitivity being run that will be able to confirm?

There are other WIMP seaches going on such as CDMS and XENON and they have not detected anything yet and so place limits on the supposed cross section of WIMPs. It is a quiestion of WIMPs or NIMPs where the latter only interact gavitationally and do not go "bump" in the night.

To verify, there would need to be other LIBRA testing sites at differeing lattitudes and orientations. The DAMA team suggests their setup is different from the other searches and their null results do not impact as much upon their results.

The signal does seem believalbe, but it is a different thing to conclude that it is Dark Matter. For example they may be successfully monitoring neutral spallation byproducts from UHECR striking dust from the ISM that is not deflected by the solar magnetic field and is allowed entrance into the solar system.

One thing to keep in mind though is that, from planetary ephemeris, no Dark Matter Effect is seen within the solar system while it is apparent in the paths and velocites of stars moving in galactic orbit. The effect is also seen on scales as small as globular clusters. So one is left wondering why WIMPs cluster at that scale and not others.

One of the other branches of theories hold that maybe gravity is altered, either a dotG theory like MOG or a threshold theory like MOND.

While there are a variety of theories each of which has had some success in capturing the Dark Matter Effect, whether LCDM or the modified gravity or modified inetria theories, they all also have their failures. Many times the failure of one is covered the success of another, but there exists at least one example where they all fail at the same time. So a final correct theory may still be off in the future yet.

01101001
2008-Apr-21, 05:08 PM
Cosmic Variance Blog: Juan Collar on Dark Matter Detection (http://cosmicvariance.com/2008/04/21/guest-post-juan-collar-on-dark-matter-detection/)


I’ll start with the most negative, so as to end up on a brighter note:

The modulation is undeniable by now. I don’t know of any colleagues who doubted these data were blatantly modulated already back in 2003, when “the lady” (DAMA) decided to keep mum for a while. However, to conclude from something this mundane that the experiment “confirms evidence of Dark Matter particles in the galactic halo with high confidence level” or that there is “an evidence for the presence of dark matter particles in the galactic halo at 8.2 sigma confidence level” is simply delusional. There is evidence for a modulation in the data at 8.2 sigma, stop. Compatible with what would be expected from some dark matter particles in some galactic halo models, full stop. Anything beyond this is wanting to believe, and it smears on the rest of us in the field. Of course, of course… there is no other observed process in nature that peaks in the summer and goes through a low in winter, so this must be dark matter, right? [...]

loglo
2008-Apr-23, 08:56 AM
Cheers borman and 01, that sounds far more reasonable.

I liked this bit from 01's link, says it all:

(Occam is turning in his grave, rusty razor still in hand. He is thinking a remake of that opening scene in “Un chien andalou”, with help from this little lady. I am channeling him loud and clear).

borman
2008-Apr-24, 01:43 PM
While it is important to run more controls and calibrations to strengthen the reality of the signal, one can not rule out just yet that it is Dark Matter. As WIMPs it is hard to reconcile with the other experiments who are out to see the WIMPs too.

As the article linked by 01 mentioned, it may be that the single hit event is detected at the atomic or possibly even lattice level considering how pure the NaI is.

One thing that seems missing from the DAMA data is whether there is a modulating role for the time of day apparent in the data. When the detector travels in the direction of enhancement during the summer, does the fact that the Earth is in the path of detection every 12 hours cause a fall off of the signal only to see it get stronger when only around 2 km is overhead 12 hours later yet? Sizeable particles such as alpha and neutrons may get scatttered by the planet from the energy of the signature seen. There could well be a modulation signature upon all WIMPs travelling through the Earth as opposed to the little bit afforded by being in a deep mine.

The absence of the daily modulation upon the signal could help point to what is being seen. Most useful would be the data from the WMAP mission where the direction and speed of the Earth figure into the temperature variations. What WMAP sees are the cosmological photons that have been stretched to where they are in the microwave range. At the same time, there were generated cosmological neutrinos that also have stretched in presumeably the same ratio. Unlike photons, neutrinos can pass easily through Earth from the bottom up as from top down without giving any strong evidence of scattering or modulation.

However, in recent years, experiments have suggested that neutrinos appear to oscillate through their three flavors. There is still an outstanding problem of how they do this without a rest mass to permit them to move at light speed. Nevertheless, the signal appears at the low end of the detector energy range, around 2-6 keV. And so one should wonder if LIBRA is somehow able to detect the oscillation into the more massive flavor of neutrino as it passes into one of the detector bars. At least the cosmological neutrino density profile should have something incommon with the WMAP results as regards how Earth's movement affects the observed temperature variations that would correlate with the signal seen by DAMA.

borman
2008-Jul-08, 09:43 PM
A standard isothermal galactic halo of WIMPs is ruled out for the DAMA/LIBRA annual modulation signal.

Experimental constraints on a dark matter origin
for the DAMA annual modulation effect

Abstract: http://arxiv.org/abs/0807.0879

PDF (4 pages): http://arxiv.org/PS_cache/arxiv/pdf/0807/0807.0879v1.pdf

pie33
2008-Jul-09, 12:32 AM
"Einstein theorized that gravity is not a force between two objects but the bending of space-time as a property of mass." - Maybe the greater distance between massive stars, the stronger the property of gravity becomes.

Dark matter maybe the results of the expanding universe. Whereby the property of gravity is pushing dark matter faster to its conclusion. A total voild of everthing there is the universe.

trinitree88
2009-Jul-10, 09:09 PM
There's a little news here. Results from DAMA not confirmed with regards to dark matter. 6-8 standard deviations not. pete

see:http://arxiv.org/PS_cache/arxiv/pdf/0907/0907.1438v1.pdf

Jerry
2009-Jul-17, 08:06 PM
http://arxiv.org/PS_cache/arxiv/pdf/0907/0907.2731v2.pdf
IMPROVED CMB MAP FROM WMAP DATA

The cosmic microwave background (CMB) temperature maps published by the Wilkinson Microwave Anisotropy Probe (WMAP) team are found to be inconsistent with the differential time-ordered data (TOD), from which the maps are reconstructed. The inconsistency indicates that there is a serious problem in the map making routine of the WMAP team, and it is necessary to reprocess the WMAP data. We develop a self-consistent software package of map-making and power spectrum estimation independently of the WMAP team. Our software passes a variety of tests. New CMB maps are then reconstructed, which are significantly different with the official WMAP maps. In the new maps, the inconsistency disappeared, along with the hitherto unexplained high level alignment between the CMB quadrupole and octopole components detected in released WMAP maps. An improved CMB cross-power spectrum is then derived from the new maps which better agrees with that of BOOMRANG.

Two important results are hence obtained: the CMB quadrupole drops to nearly zero, and the power in multiple moment range between 200 and 675 decreases on average by about 13%, causing the best-fit cosmological parameters to change considerably, e.g., the total matter density increases from 0.26 up to 0.32 and the dark energy density decreases from 0.74 down to 0.68. These new parameters match with improved accuracy those of other independent experiments. Our results indicate that there is still room for significant revision in the cosmological model parameters.

Fluffing the data removes some rather quirky track marks, but gives us nothing absolute: If the baseline calabration errors were this bad, all bets are off. Hopefully, Planck will give us new, improved absolutes...possibly very different absolutes.

Jerry
2009-Jul-24, 05:22 AM
arXiv:0907.3940

Kai Schmidt-Hoberg, Martin Wolfgang Winkler

Abstract

We perform an extensive study of the DAMA annual modulation data in the context of inelastic dark matter. We find that inelastic dark matter with mass m > 15 GeV is excluded at the 95% confidence level by the combination of DAMA spectral information and results from other direct detection experiments. However, at smaller m, inelastic dark matter constitutes a possible solution to the DAMA puzzle.

borman
2009-Jul-24, 08:46 PM
Some Additional Constraints of the DAMA signal

Analysis of the low-energy electron-recoil spectrum of the CDMS experiment

http://arxiv.org/abs/0907.1438

DAMA/LIBRA and leptonically interacting Dark Matter

http://arxiv.org/abs/0907.3159

With the later paper, the question as to the lack of evidence from other Dark Matter Particle searches to support the DAMA/LIBRA signal might stem from the possibility that the DAMA/LIBRA signal might be due to lepton-Dark Matter interactions rather than hadron-Dark Matter interactions that are the foundation of most searches is considered. The arguments and conclusions are that this approach will not succeed in addressing the incompatible results between the DAMA/LIBRA interpretation of their discovered signal and the other negative CDM search results.

Jerry
2009-Oct-26, 04:53 PM
http://arxiv.org/abs/0910.4480v1


No excess over the expected atmospheric background has been observed. Upper limits have been obtained on the annihilation rate of captured lightest Kaluza-Klein particle (LKP) WIMPs in the Sun and converted to limits on the LKP-proton cross-sections for LKP masses in the range 250 -- 3000 GeV. These results are the most stringent limits to date on LKP annihilation in the Sun.
Dark Matter still remains the difference between what gravitational theories predict, and what we observe.

A place holder we do not understand.

borman
2009-Oct-30, 02:29 AM
Adler has written a paper stating that inelastic WIMP collisions with normal matter should produce noticeable calorimeter values compared to elastic collisions where the difference is around nine orders. It would be a test of the idea he persues regarding elasitc and inelastic Dark Matter Particles being responsible for the flyby anomaly. Some of the GPS craft with eccentric orbits should cross enough "flux" lines to heat up enough to test the hypothesis of "dual" Dark Matter Particles.

borman
2010-Jan-27, 10:44 PM
More constraints

Observations of Milky Way Dwarf Spheroidal galaxies with the Fermi-LAT detector and constraints on Dark Matter models
http://arxiv.org/abs/1001.4531

sabianq
2010-Jan-28, 12:19 AM
"Explanation of the whirlpool galaxy from constant space-time torsion:
the case against dark matter"

ECE unified field theory?

http://aias.us/documents/uft/a123rdpaper.pdf

Jerry
2010-Jan-28, 01:55 AM
http://arxiv.org/abs/1001.4836

[/quote=too many authors]
The limits on hvi (hvi Z) shown in Table I are about one or more orders of magnitude weaker than the cross-sections expected for a typical thermal WIMP. However, there are several models in the literature that predict larger cross-sections and are constrained by these results.[/quote]

... So WHIMPs are either non-existant or extremely WHIMPY.

Kwalish Kid
2010-Jan-28, 02:36 AM
And the quotation continues;

However, there are several models in the literature that predict larger cross-sections and are constrained by these results. A WIMP produced non-thermally may have a much larger annihilation cross-section than a thermally produced WIMP and still produce the required DM relic density. An example is...
As usual, you have provided us with a paper that doesn't threaten the standard cosmological model.

Jerry
2010-Jan-28, 04:54 AM
Of course not. How would one disprove dark matter exists? The search for WHIMPS is not unlike the radio band searches a century ago for messages from angels, or the SETI searches of the last few decades. We can't prove there are not angels or aliens either.

But with each progressive constraint, the possibility that the 'dark matter' explanation for mass behavior is wrong increases. Nancy defined 'dark matter' as a 'place holder' for something we do not understand. It is good to keep searching, but more emphasis needs to be placed upon verifying that the fundamental assumptions are sound.

sabianq
2010-Jan-28, 04:57 AM
isnt that why we call it "Dark" Matter?
cause we dont understand it? not because we cant see it??

loglo
2010-Jan-28, 12:29 PM
"Explanation of the whirlpool galaxy from constant space-time torsion:
the case against dark matter"

ECE unified field theory?

http://aias.us/documents/uft/a123rdpaper.pdf


It is well known that the now obsolete Einsteinian general relativity omits consideration of space-time torsion, and in so doing uses an incorrect symmetric connection [1]- [10] with multiple sequential mathematical errors that render the theory meaningless in physics


Yeah , right. :rolleyes:

Nereid
2010-Jan-28, 02:18 PM
It gets better.

The document's authors are M. W. Evans and H. Eckhardt.

The authors of [1]-[10] are?

Well, M. W. Evans is the sole, or lead, author of [1], [4], [5], [6], [8], [9], and [10] (and H. Eckhardt the second author of [10]).

[2] is titled "The Evans Equations of Unified Field Theory", and [3] "The Life of Myron Evans".

[7] is "ECE Papers and Archives on www.aiais.us".

I guess M. W. Evans knows something well.

And what is aiais? Why it's the "Alpha Institute for Advanced Study", which its website describes as "among the leading theoretical physics institutes worldwide".

loglo
2010-Jan-28, 03:35 PM
I tried applying the Baez crackpot index (http://math.ucr.edu/home/baez/crackpot.html)to their webpage, I lost count. A comprehensive refutation to ECE is here. (http://www.mathematik.tu-darmstadt.de/~bruhn/GCUFT.html)

Jerry
2010-Jan-31, 04:43 AM
So by definition, if you reject the currently most poplular explainations for why Newtonian and Einsteining physics are failing, you get crackpot points for 1) Mentioning their names, 2) starting with the assumption that GR and QM cannot be reconciliated because they are both fundamentally flawed.

loglo
2010-Jan-31, 12:29 PM
So by definition, if you reject the currently most poplular explainations for why Newtonian and Einsteining physics are failing, you get crackpot points for 1) Mentioning their names, 2) starting with the assumption that GR and QM cannot be reconciliated because they are both fundamentally flawed.

No, but you do for calling GR redundant, every physicist who criticises your work wrong or on a personal crusade and are consistently ignored in the relevent literature but still persist in peddling a discriedited theory.

noncryptic
2010-Jan-31, 02:46 PM
This seems the right place to ask about an issue with Dark Matter that has been bothering me for a while:


A large enough cloud of (non-ionized) baryonic matter particles/atoms will gravitationally collapse into stars etc.

But apparently a similar size cloud (or even a much larger cloud) of Dark Matter, although it does "clump", it does not gravitationally collapse (into stars etc).

How does the Dark Matter working hypothesis explain that phenomena?

StupendousMan
2010-Jan-31, 03:23 PM
This seems the right place to ask about an issue with Dark Matter that has been bothering me for a while:


A large enough cloud of (non-ionized) baryonic matter particles/atoms will gravitationally collapse into stars etc.

But apparently a similar size cloud (or even a much larger cloud) of Dark Matter, although it does "clump", it does not gravitationally collapse (into stars etc).

How does the Dark Matter working hypothesis explain that phenomena?

Short answer: dark matter interacts only weakly with itself and with normal matter

Longer answer: Suppose a cloud of ordinary hydrogen gas begins to collapse due to its own self-gravity. Molecules of hydrogen will bump into other molecules of hydrogen -- meaning the electric forces between their components (electrons and protons) become large enough to alter the motions of the molecules, and also cause the atoms to jump to higher energy states. Some of the atoms which have been excited will radiate the energy away as electromagnetic radiation. Some of the initial kinetic energy of the molecules escapes the cloud as radiation. Since the gas in the cloud now has less kinetic energy, and the molecules are moving more slowly, they cannot move as far away from the gravitational potential well at the center of the cloud, and the cloud shrinks.

(Warning: very simplified version of physics in above explanation. I don't have time to write a full chapter on the processes)

Now, suppose that there's a cloud of dark matter particles. Physicists assume that dark matter particles do NOT interact via the electromagnetic force with ordinary matter or with each other -- but only by the gravitational force. That means that when two dark matter particles happen to fly past each other, they do not exert strong forces on each other. The particles cannot easily radiate away any of their energy, either. The result is that the cloud does not shrink, since the particles cannot rid themselves of their initial kinetic energy.

(Warning: again, simplified physics)

noncryptic
2010-Jan-31, 05:00 PM
Thanks for explaining, mr Stupendous.
I now realize that i underestimated the importance of E/M / atomic forces in the condensation of normal matter.

borman
2010-Jan-31, 07:25 PM
Strain for Universal Theory

Dark Matter is invoked to allow GR to explain the motions of stars in galaxies and motions of galaxies in clusters. This requires large halo distributions of unseen non-baryonic matter that observes the same gravitational laws that baryonic matter observes. This permits GR to explain all over this large realm.

To remain universal over the same realm, but not invoke Dark Matter, would otherwise require modifications of the Newtonian gravity or GR. This would augment GR with a combination of Tensors, Vectors, and Scalars or put a transition limit on how gravity behaves at threshold accelerations. There is a further requirement to restore to GR at the proper limit to remain consistent with observations at the solar system level. At some point there must be some deviation from classical GR. Some of these theories will likely be falsified when GR accuracy is pressed to 16 decimals with upcoming tests such as STEP.

A possible third option is to not insist on one universal theory to cover the entire realm but there are additional theories for different aspects of the entire realm. From this perspective, GR is a rather precisely correct theory for its subrealm and is in no need of modification nor Dark Matter for it to work completely well within its domain without the Lambda term. To explain the other inertial phenomena observed that appear anomalous with respect to GR, such as Dark Matter, Dark Energy, and Large Scale Structures, would require additional theories rather than modified theories or unknown energy densities to be added to GR.

Jerry
2010-Feb-01, 05:18 AM
http://www.ligo.caltech.edu/LIGO_web/about/factsheet.html



More specifically, LIGO has the possibility to:

•Verify directly general relativity's prediction that gravitational waves exist.
•Test general relativity's prediction that these waves propagate at the same speed as light, and that the graviton (the fundamental particle that accompanies these waves) has zero rest mass.
•Test general relativity's prediction that the forces the waves exert on matter are perpendicular to the waves' direction of travel, and stretch matter along one perpendicular direction while squeezing it along the other; and also, thereby, test general relativity's prediction that the graviton has twice the rate of spin as the photon.
•Firmly verify that black holes exist, and test general relativity's predictions for the violently pulsating space-time curvature accompanying the collision of two black holes. This will be the most stringent test ever of Einstein's general relativity theory...

Last modified October 2, 2001


The fact is, LIGO found nothing. GR is failing it's most stringent test. I know everyone has a but: But Advanced LIGO will see so much further -ten times further. It has been more than a year since the LIGO Collaboration has updated the blog or issued a new release. You have to have a password to even look at the program for the March 2010 LIGO consortium meeting. More mips have flopped searching for gravity waves than for every other cosmic phenomenon combined. Optimism is waning.

http://ligonews.blogspot.com/

http://www.ligo.org/conferences/lv0310/program.shtml

Kwalish Kid
2010-Feb-01, 01:40 PM
What does your standard rant against GR have to do with this thread?

Jerry
2010-Feb-02, 12:16 AM
What does your standard rant against GR have to do with this thread?

Read the prior post:

"Dark Matter is invoked to allow GR to explain the motions of stars in galaxies and motions of galaxies in clusters."

But now, we need an additional explanation, for why we can't observe the gravitational perturbations predicted by GR. Perhaps the Dark Matter envelope dampens gravitational waves. As long as you are happy with a place-holder that only reacts gravitationally, you might as well give it some padding.

Kwalish Kid
2010-Feb-02, 04:21 AM
That's an interesting couple of straw-men you have there.

borman
2010-Feb-03, 02:17 AM
But now, we need an additional explanation, for why we can't observe the gravitational perturbations predicted by GR. Perhaps the Dark Matter envelope dampens gravitational waves. As long as you are happy with a place-holder that only reacts gravitationally, you might as well give it some padding.

If one were to assume that spacetime had microstructure, the energy from binary decay could be going into heating the horizon.

Thermodynamical Aspects of Gravity: New insights

http://arxiv.org/abs/0911.5004