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WorseAstronomer
2003-Jun-02, 02:34 PM
I'm truely an amatuer astronomer. In fact, those of you that are amatuers, as well, I'm not in your league.

Pretty much, it's a hobby, and I read different books and articles when I get the chance.

Therefore, any idea I have is probably suspect.


Still, one of the things about astro-physics that has been bugging me is the concept of a graviton. I may be really naive', but I'm not sure I believe in it.

The way I see it, if Einstein is correct and mass curves space, is there a need for a messanger particle for gravity? Isn't gravity the warping of space? Doesn't General Relativity say that the moon orbits the Earth because the Earth warps the space around it and the moon, in trying to follow a straight path, can't since the space in which it is traveling is warped around the Earth? If that's the case, where is the need for a graviton?

Seriously, I know there are scientists much smarter than I, with much more knowledge on the subject who are still looking for the graviton. Which leads me to believe that there's a flaw somewhere in my reasoning. Can anyone out there point me in the right direction on the graviton?

Thanks!

Glom
2003-Jun-02, 02:50 PM
Relativity is classical. Since Einstein, the field of quantum physics has been discovered. The graviton comes into play in the quantum realm.

Hamlet
2003-Jun-02, 03:11 PM
Still, one of the things about astro-physics that has been bugging me is the concept of a graviton. I may be really naive', but I'm not sure I believe in it.

Well there is not, as yet, any direct evidence that the graviton exists. It is strongly suspected to exist because the other fundamental forces all have carrier particles associated with them. The strong nuclear force has gluons, the weak nuclear force has W and Z bosons and the electromagnetic force has photons. It would be odd that gravity is not mediated by a force particle, but we just don't know yet.

You're not being naive, simply skeptical, which is a good thing. Keep learning!

WorseAstronomer
2003-Jun-03, 03:15 PM
Thanks, guys!

I know the other 3 forces have their messanger particles. But, from my (extremely limited) understanding, I thought the concept of gravity was that every piece of matter had some gravitational attraction to every other piece of matter. Explaining gravity simply by warped space makes sense (at least to me) on why even a slight mass causes at least some level of warping, affecting, at least at a minute level, all other matter.

But if each piece of mass required a graviton or gravitons to attract to all other masses, that's a lot of gravitons to be flying around the universe constantly.

And Glom, I've read just a little bit on quantam mechanics (and understand it even less, I assure you!) but I had thought that in terms of gravity, quantam mechanics meant that even smooth space was warped and constantly changing at infinitesimally small regions.

Like I said, I've got a REALLY limited understanding of quantam mechanics; but, does quantam mechanics not require every piece of matter to be attracted to each other? Or does it accept that there will be quite a few gravitons?

DStahl
2003-Jun-03, 07:04 PM
Well, I'm no expert, just an armchair science enthusiast. But you might look at it this way: There's more than one or even two ways to skin a cat like gravity. As long as they are mathematically equivalent--as long as they yield the same predictions for the behavior of objects--then who's to say what the "ultimate reality" really is?

It's possible to think of gravity as spacetime curvature, and you are absolutely right that this was one of Einstein's great insights. But it's also possible to think of gravity as a field in flat spacetime, a field with the peculiar property of changing the dimensions of rulers and the speed of clocks. I understand that physicists often use this visualization when working on problems involving gravity waves, for instance.

So I suspect that a quantum theory of gravity, using gravitons, will be another tool in the toolbox--in the realm of macroscopic things it will be precisely equivalent to general relativity as far as its mathematical predictions go. In the realm of subatomic-sized objects it may avoid the problems general relativity has describing things like the center of a black hole.

For another example, Faraday's laws are perfectly good for describing electromagnetism but they take no account of quantum theory. The quantum description of electrodynamics agrees perfectly with Faraday's laws in the large, and gives us a good tool to use in predicting the behavior of charged particles at a subatomic level.

Just my opinion on this--I hope others will correct me if they think I'm full o' beans.

RickNZ
2003-Jun-03, 08:52 PM
Quick question or 3 regarding the standard model.

How do they know all this? Is it all theoretical or was it backed up in the lab>?

Color charge? How was that discovered?
Gluons/hadrons?
Are we sure W etc carry a force otherwise known as weak?

The Supreme Canuck
2003-Jun-03, 08:55 PM
WorseAstronomer:

If you want to know more about quantum mechanics, read "A Brief History of Time" by Stephen Hawking. It was written for amateurs like us. :wink:

RickNZ
2003-Jun-03, 09:19 PM
Is it any better than stephen hawkings universe? While i agree that theres laymen.
Theres also 'laymen' if u catch my meaning.

DStahl
2003-Jun-03, 09:33 PM
RickNZ, there's an online summary of the standard model of particle physics at this site (http://www.kuro5hin.org/story/2002/5/1/3712/31700) written by Matthew Nobes. Here are some excerpts:

"The Z and W bosons were first directly observed in 1983 at the CERN complex in Switzerland. The experimental team was lead by Carlo Rubbia and Simon van der Meer. Indirect evidence for the Z boson had been seen many years earlier in another CERN experiment. "

"As of this writing the Higgs boson is the only particle in the standard model which has not been observed. There are strong reasons to believe that it will be found at the next big particle accelerator, the Large Hadron Collider , which is being built (at a multi billion dollar cost) at present."

----

A discussion of quarks by the same author is here (http://www.kuro5hin.org/story/2002/5/14/19363/8142).

nexus
2003-Jun-04, 01:26 AM
If there is no particle carrying gravitational force then why does gravity travel slower than the speed of light? (Sorry if this has been answered already, but I'm tired and not reading well.)

DStahl
2003-Jun-04, 01:37 AM
Hehe, no, the question of 'the speed of gravity' is a perplexing one. Gravitational waves, the spacetime disturbances emitted by close-orbiting neutron stars as they spiral together, do indeed propagate at the speed of light. (Or, if you like, gravitational waves are changes in the strength and vector of the gravitational field in flat spacetime...) And if the Sun were suddenly to vanish then the Earth would not notice it's disappearance for 8+ minutes because both the light from the Sun and its gravitational influence propagate at the speed of light.

Grand Vizier
2003-Jun-04, 01:45 AM
If there is no particle carrying gravitational force then why does gravity travel slower than the speed of light? (Sorry if this has been answered already, but I'm tired and not reading well.)

As I understand it, if gravity is seen either as warped space time (general relativity) or a field with curious properties, then it doesn't travel at all, it just sits there (just like space does - it would be like talking about the speed of space or, come to that, of the speed of a magnetic field). On the other hand, disturbances in the field or warp (gravity waves) should propagate at the speed of light. A recent experiment, which has been since hotly disputed, admittedly, claims to have proved this.

http://www.nature.com/nsu/030106/030106-8.html

The terminology gets confusing. But as far as I can make out (I'm no expert), what is being measured is the propagation of changes in space-time caused by the movement of a large object - namely Jupiter. A lot of reports describe this as the 'speed of gravity', but I'm not sure that's right.

RickNZ
2003-Jun-04, 03:24 AM
Glom u miss understood me. I know about the direct observations of said bosons. My question refered to the discovery of weak force.

CryoSkull
2003-Jun-04, 05:50 AM
Doesn't General Relativity say that the moon orbits the Earth because the Earth warps the space around it and the moon, in trying to follow a straight path, can't since the space in which it is traveling is warped around the Earth?

I really feel that is not correct (I am not talking about GR, but about the example), simply because -

Moon is travelling in a straight line since space around earth is curved. All moon is doing is following the straight Line with const velocity

But wait! what if the moon stops moving? According to the example, moon is moving in a straight line. So it should stop right in its tracks and stay there - suspended.

But that's not what happens, as soon as it stops, it will start hurling itself at earth.

I would really appreciate anyone, if a flaw is there in my argument. I feel there is something wrong in my explanation too ( esp the velocity part, it should be speed, But I felt if the Space around in curved, and path of moon is 'straight', velocity will be applicable)

John Kierein
2003-Jun-04, 11:30 AM
In my paper in the book "Pushing Gravity" I identify the graviton as being the absence of a photon in the very long wavelength cosmic background radiation. This is theoretical. But the long wavelength background has been measured, with dim spots at known massive places, so in a sense, if the theory is correct then this graviton has been observed. The maps showing this were first measured by Reber and published in the late 1960s.

Grand Vizier
2003-Jun-04, 05:43 PM
In my paper in the book "Pushing Gravity" I identify the graviton as being the absence of a photon in the very long wavelength cosmic background radiation. This is theoretical. But the long wavelength background has been measured, with dim spots at known massive places, so in a sense, if the theory is correct then this graviton has been observed. The maps showing this were first measured by Reber and published in the late 1960s.

I can't see how this makes any sense, sorry. A photon is the carrier particle for EM radiation, the graviton, if it exists, for gravity. They are two different fundamental forces and have not been successfully unified as yet. Plus I cannot see how cosmic background radiation has anything to do with the attraction between two arbitrary bodies in space. And finally, as far as I know there is no 'very long wavelength cosmic background radiation' - there is a Cosmic Microwave Background, though.

Have you a link to the overall theory behind this?

John Kierein
2003-Jun-04, 07:04 PM
Here's a link to Pushing Gravity. The theory that gravity is a push of long wavelength radiation was first suggested by Charles Brush in 1910. The idea that radiation shadowing is "Mock Gravity" and the cause of galaxy formation was published by Hogan and White. The same idea was used by Whipple and others for planetary formation. You can do a google search on Brush and find his "Kinetic Theory of Gravitation" paper from Rex Research. This was published by both Science and Nature. You are right; this theory does provide a unification of EM & gravity. Pretty cool, huh.

Tobin Dax
2003-Jun-05, 06:18 PM
WorseAstronomer wrote:

Doesn't General Relativity say that the moon orbits the Earth because the Earth warps the space around it and the moon, in trying to follow a straight path, can't since the space in which it is traveling is warped around the Earth?

CryoSkull wrote:


I really feel that is not correct (I am not talking about GR, but about the example), simply because -

Moon is travelling in a straight line since space around earth is curved. All moon is doing is following the straight Line with const velocity

But wait! what if the moon stops moving? According to the example, moon is moving in a straight line. So it should stop right in its tracks and stay there - suspended.

But that's not what happens, as soon as it stops, it will start hurling itself at earth.

I would really appreciate anyone, if a flaw is there in my argument. I feel there is something wrong in my explanation too ( esp the velocity part, it should be speed, But I felt if the Space around in curved, and path of moon is 'straight', velocity will be applicable)

I can address the classical theory here. Cryoskull is correct when he says that the moon is travelling in a straight line in a warped space. However, this straight line is on an incline. If you are rolling a ball along a hill perpendicular to the slope, and you stop it, does it stop or does it roll down the hill? In your situation, the moon would "roll down the hill" just like the ball.

This can also be described as an energy argument where the Moon is travelling on an equipotential curve (which is elliptical in this case) at the appropriate speed so that the kinetic energy of the Moon matches the gravitational potential energy from Earth. If energy is conserved in the system, then the Moon would get farther out as it slowed down. (Tides are actually causing this to happen.) If energy was slowly drained from the system (i.e. via friction), the moon would spiral in as it would be in a stable orbit only when the two energies are again equal. At zero speed in this case, the moon would hit the earth. If the moon suddenly had zero speed, it would again be like dropping a ball. The moon would fall to the earth.

Does that help?

Dax

WorseAstronomer
2003-Jun-05, 06:35 PM
WorseAstronomer:

If you want to know more about quantum mechanics, read "A Brief History of Time" by Stephen Hawking. It was written for amateurs like us. :wink:

Thanks, but I already own it. Everything (what little there is!) I know of quantam mechanics, I own to Hawking, and a little to Brian Greene and a few others.

The funny thing is, I remember we had to do an interferrence pattern experiment in middle school (8th grade) science class. Never quite understood it until I started reading on my own.



And thanks, Dax, and CryoSkull. I think I really MEANT to say that the moon can't follow what a stationary observer might consider a straight line, since the Earth's mass warps the space in which it was travelling. But you guys are right, I definitely misspoke when I said it, "can't" follow a straight path, since according to the theory it IS.

You guys put it much better than I. Which is why I'm here!:D

Stonecut
2005-Dec-01, 03:00 AM
A note about those gravitons. It was my understanding that not only are gravitons plentiful, they are not bound to our dimension (brane.) They are able to pass through the possible 10 dimensions freely whereas every other particle of matter/string is bound to this dimension. Hairy stuff... but does offer a viable theory. (see www.pbs.org on Elegant Universe)

Tacitus
2005-Dec-01, 05:30 AM
Since this thread's been resurrected :), here's a link to a highly respected BBC Radio discussion series "In Our Time" which just had a programme all about the Graviton:

http://www.bbc.co.uk/radio4/history/inourtime/inourtime_20051124.shtml

I haven't listened to it yet, but these shows are usually very good. Have a look through the archives for other science related subjects.


THE GRAVITON

Albert Einstein said "I know why there are so many people who love chopping wood. In this activity one immediately sees the results". Einstein spent the last thirty years of his life trying to find a theory that would unify electromagnetism with gravity, but success eluded him.

The search is still on for a unifying theory of gravitational force and hopes are pinned on the location of the graviton - a hypothetical elementary particle that transmits the force of gravity. But the graviton is proving hard to find. Indeed, the next big research project which involves the largest earth-based laboratory in the world - a circular ring which goes underground for about twenty-seven miles and spans Switzerland, France and Germany - still won't allow us to detect gravitons per se, but might be able to prove their existence in other ways.

The idea of the graviton particle first emerged in the middle of the twentieth century, when the notion that particles as mediators of force was taken seriously. Physicists believed that it could be applicable to gravity and by the late 20th century the hunt was truly on for the ultimate theory, a theory of quantum gravity.

So why is the search for the graviton the major goal of theoretical physics? How will the measurement of gravitation waves help prove its existence? And how might the graviton unite the seemingly incompatible theories of general relativity and quantum mechanics?

Contributors

Roger Cashmore, Former Research Director at CERN and Principal of Brasenose College, Oxford

Jim Al-Khalili, Professor of Physics at the University of Surrey

Sheila Rowan, Reader in Physics in the Department of Physics and Astronomy at the University of Glasgow


BTW: I think if you hurry, and go to the "In Our Time" home page, you can download an mp3 for the show (may be gone by the end of tomorrow).

Carlos2006
2005-Dec-02, 01:53 AM
Elegant universe doc is indeed very intresting. So CERN (completed 2007) http://public.web.cern.ch/Public/Welcome.html could actually detect gravitons and sparticles, giving proof to string theory, which predicts them. http://www.pbs.org/wgbh/nova/elegant/program.html

Blob
2005-Dec-02, 03:25 AM
Hum,
The big problem with the CERN approach is that they are looking for gravitons (or their super symmetric partners) on the grounds that they are similar to the other bosons.
Ie, particles exchange bosons with other particles.

IMHO, the graviton may exist (as has already been said) as an inter dimensional closed string.

The `exchange` would occur in dimensions that are beyond the range of the CERN or LHC.

And mass may not be an intrinsic property of matter. It may only come about because of an underlying `graviton field` seeping from compactified dimensions.

turbo-1
2005-Dec-02, 04:04 AM
If you will read Einstein's essay "On the Ether", Chapter 1 of Saunder and Brown's book "The Philosopy of Vacuum" you will see that Einstein rejected all action-at-a-distance explanations for inertia and gravitational attraction, and insisted that these phenomena arise from matter's interaction in the local vacuum in which it is embedded. If he was right (and I'm not going to bet against him), there is no gravitational field or graviton, and there is no Higgs field or Higgs boson.

The most compelling proof of this is our observations of the universe. If mass is conveyed by matter's interaction with the Higgs field, and if gravitational attraction is mediated by a separate gravitational field, why does matter in the visible universe seem to obey the same rules everywhere? If we have two fundamental properties of matter mediated by two separate fields, and those two fields are not exquisitely congruent everywhere and everywhen, the universe would be a pretty quirky place.

John Kierein
2005-Dec-02, 02:03 PM
I have some ideas on the graviton which can be found here. On this forum it is considered "Against the mainstream".
http://tinyurl.com/bhzph

Wolverine
2005-Dec-02, 11:16 PM
I have some ideas on the graviton which can be found here. On this forum it is considered "Against the mainstream".
http://tinyurl.com/bhzph

In that case (http://www.bautforum.com/showthread.php?p=564845#post564845) you need to heed the following:


13. Alternative Concepts

If you have some idea which goes against commonly-held astronomical theory, then you are welcome to argue it here. Before you do, though READ THIS THREAD FIRST (http://www.bautforum.com/showthread.php?t=16242). This is very important. Then, if you still want to post your idea, you will do so politely, you will not call people names, and you will defend your arguments. Direct questions must be answered in a timely manner.

People will attack your arguments with glee and fervor here; that's what science and scientists do. If you cannot handle that sort of attack, then maybe you need to rethink your theory, too. Remember: you came here. It's our job to attack new theories. Those that are strong will survive, and may become part of mainstream science.

Additionally, keep promotion of your theories and ideas to only those Against the Mainstream (http://www.bautforum.com/forumdisplay.php?f=17) threads which discuss them. Hijacking other discussions to draw attention to your ideas will not be allowed.

If you wish to discuss your ATM ideas, please do so in ATM.

Nereid
2005-Dec-03, 12:03 AM
From the observational perspective, as several folk back in 2003 noted, there is no good results, whatsoever, that scream 'graviton'.

From the theoretical perspective, you have the 'unification' challenge - both QFT (quantum field theory, in its instantiation as the Standard Model of particle physics, and more) and GR (General Relativity, considerably advanced from what Einstein wrote, despite the desire of some to elevate his writings to gospel) have passed vast, vast numbers of experimental and observational tests (there is a small number of anomalies, at the very far reaches of experimental and observational capability). Yet QFT and GR are deeply, deeply incompatible.

While the EM and weak forces have been unified (the electro-weak theory that several folk shared Nobels for), and unification with the strong force seems within grasp, a QFT/GR unification remains highly elusive.

Not for lack of trying! The most exciting developments, now over a decade old (their theoretical roots stretch back to the early parts of the 20th century), are sting/M-Theory; other 'quantum gravity' theories, with lesser scope, are also under development (e.g. Loop Quantum Gravity).

So, if you are a hard-bitten 'it doesn't exist until there's solid observational/experimental evidence', then there are no gravitons. If you're a starry-eyed dreamer, with a 'without the math, it don't mean a thing' lifeline, then somehow or other there's just gotta be 'gravitons'.

But no matter your personal bent, ain't it a wonderful to be alive?! :clap:

trinitree88
2005-Dec-03, 03:04 AM
There remains of course the successful prediction in April of 1982 of the sextuple coincidences between the Rome, and Maryland gravity-wave detectors, and the Baksan,IMB, Mont Blanc, and Kamioka neutrino detectors during supernova 1987A, some five + years later by the unified field theory based on the SU (5) symmetry of Howard Georgi (Sci. American), and the work of George Gamow, that I constructed during the fall/winter of 1981-2. It is covered in other threads in ATM. But to say that there is no quantum theory of gravitation, or to say that the graviton has not been identified, or to say that no prediction of physical effects to be seen by any such theory has been validated ,or published, in a peer-reviewed journal,(Il Nuovo Cimento)....would not be the truth. :naughty: I believe speaking the truth will eventually win out. Supersymmetry with it's 17 particles and also never-to-be-seen-in-a-detector 17 antiparticles has faded like bioluminescence in the wake of an ocean liner. Lorentz invariance disappears along with our physical laws at the event horizon of a BH. Inflationary cosmologies break a number of conservation laws. My theory breaks no conservation law, breaks no precept of SR, maintains Lorentz invariance, and makes predictions that have been verified. Ken G wanted another. Here it is: every time a supernova goes off at the distance to the LMC or less, a coincidence will be seen not only in the the LIGO detectors, but in the worldwide neutrino detectors, and bar gravity wave detectors simultaneously...just as it was in 1987. Pete.

A third rate theory forbids.......................
A second rate theory explains after the fact.
A first rate theory predicts. A. Lomonosov

turbo-1
2005-Dec-03, 03:58 AM
From the observational perspective, as several folk back in 2003 noted, there is no good results, whatsoever, that scream 'graviton'.

From the theoretical perspective, you have the 'unification' challenge - both QFT (quantum field theory, in its instantiation as the Standard Model of particle physics, and more) and GR (General Relativity, considerably advanced from what Einstein wrote, despite the desire of some to elevate his writings to gospel) have passed vast, vast numbers of experimental and observational tests (there is a small number of anomalies, at the very far reaches of experimental and observational capability). Yet QFT and GR are deeply, deeply incompatible.

While the EM and weak forces have been unified (the electro-weak theory that several folk shared Nobels for), and unification with the strong force seems within grasp, a QFT/GR unification remains highly elusive.

Not for lack of trying! The most exciting developments, now over a decade old (their theoretical roots stretch back to the early parts of the 20th century), are sting/M-Theory; other 'quantum gravity' theories, with lesser scope, are also under development (e.g. Loop Quantum Gravity).

So, if you are a hard-bitten 'it doesn't exist until there's solid observational/experimental evidence', then there are no gravitons. If you're a starry-eyed dreamer, with a 'without the math, it don't mean a thing' lifeline, then somehow or other there's just gotta be 'gravitons'.

But no matter your personal bent, ain't it a wonderful to be alive?! :clap:Hi, helpful sea lady. If all gravitational and inertial effects are purely local, as demanded by Einstein (Uber den Ather, 1924) we not only do not need to search for the graviton, we can also stop looking for the Higgs boson. Mass, inertia, gravitation, and centrifugal effects are the result of matter's interaction with the local vacuum in which it is imbedded.