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John Kierein
2002-Jan-14, 04:22 PM
We see stars in our galaxy that are at least 12 billion years old. We also see galaxies that look just like our galaxy that are at least 8 billion light years away. We know these galaxies contain old stars because when hubble first made the images of them we thought there was a dearth of spiral galxies. But then Hubble added a new instrument, NICMOS, that imaged these galaxies in the near IR. NICMOS showed up the older stars in these distant galaxies that had been redshifted out of the visible and lo and behold, they are spirals after all! so presumably these distant galaxies also contain stars that were at least 12 billion years old when the light was emitted! If they are 8 to 10 billion years away their light is from stars that are much older than any estimate of the big bang. How can the big bang possibly explain this?

The Bad Astronomer
2002-Jan-14, 04:27 PM
You are assuming that the stars in those galaxies are 12 billion years old. There is no evidence of that; getting the ages of stars is difficult, involving (as I recall) high resolution spectroscopy which is not possible on faint sources like those distant galaxies.

It is possible that spirals look like ours shortly after they form. If that's true, then you can get distant, young spirals which look just like the Milky Way. You would need to get an age measurement of the distant galaxies to know for sure.

John Kierein
2002-Jan-14, 05:11 PM
The reason given for the lack of spirals in the visible Hubble deep field and their presence in the NICMOS was that the visible didn't show the old stars while the NICMOS showed the old stars. Admittedly, there is no direct spectral line evidence as to how old is old, but there is no reason to believe the old stars are different from the old stars in our galaxy or nearby ones. If the old stars show up in NICMOS and the distant galaxy's look no different from nearby ones, why would they be any different in composition from the nearby ones? I think the burden is on the big bang to show why they are different. The evidence is that they are the same.

The Bad Astronomer
2002-Jan-14, 06:20 PM
As I recall, the lack of spirals in the visible versus the IR images is due secondarily to age, but more from obscuration. The visible image is from stars emitting UV in their rest frame; these are usually younger more massive stars embedded in dust. The dust patchily obscures the UV so we see clumpy emission.

The IR image comes from visible light in the galaxy rest frame, which is from somewhat older stars which have broken through the birth-nebula.

However, the timescale for the change is not many billions of years, but tens of millions of years. So it's still possible that the difference in age between the stars represented in the two images is not large compared to the age of the Universe, or the galaxy itself.

I believe the implications and interpretations of the images are still being hotly debated by astronomers. I don't want anyone to think what I am saying is either the final word, or the correct explanation! I am simply giving my opinion of the images.

John Kierein
2002-Jan-14, 06:40 PM
Big bang proponents were quick to say the apparent lack of spirals in the visible was evidence for evolution in galaxy formation. Now that the spirals are there after all, they want to say that the stars in the spirals are not as old as the spirals in nearby spirals.
Some want to say that spirals require collisions with other galaxies to create the shape which is due to them being closer together shortly after the big bang; but there is no evidence that the early universe is more densely packed with galaxies than the nearby ones. The galaxies are supposedly flying away from each other so, it's hard to understand why they collide in an expanding universe.
Others claim that spirals are formed from the spin of the galaxies, but there isn't enough time for the number of rotations needed for this for those so close to the time of the big bang, unless they spin a lot faster in the early universe and have been slowing down ever since. (I know of no evidence for this slowdown.)

Russ
2002-Jan-15, 03:21 PM
Hey JK. I don't like the "Big Bang" concept either but have no scientifically supportable hypothisis to argue. It is my interpretation of the "Big Bang" cosmology that it results from our having tooooo local of an outlook. My "sense of the force" is that we can detect only about 0.0001% of the univese. It is many orders of magnitude bigger in all directions. What we see and interpret as the BB is just a small fraction of an event happening on a much larger scale.

I got going on this as a thought problem based on an article I read in Scientific American about 6 years ago. I don't remember the title but the thrust of it was enumerating the problems with BBC. This included the problem with having stars older than the universe, missing matter, expansion vs inflation, etc.

I wrote a hypothisis with some really ugly hand drawn graphics in an effort to get it clear for myself. It's too much to try to post here but the whole thing makes sense to me.

Azpod
2002-Jan-15, 05:25 PM
On 2002-01-15 10:21, Russ wrote:
Hey JK. I don't like the "Big Bang" concept either but have no scientifically supportable hypothisis to argue. It is my interpretation of the "Big Bang" cosmology that it results from our having tooooo local of an outlook. My "sense of the force" is that we can detect only about 0.0001% of the univese. It is many orders of magnitude bigger in all directions. What we see and interpret as the BB is just a small fraction of an event happening on a much larger scale.

I got going on this as a thought problem based on an article I read in Scientific American about 6 years ago. I don't remember the title but the thrust of it was enumerating the problems with BBC. This included the problem with having stars older than the universe, missing matter, expansion vs inflation, etc.

I wrote a hypothisis with some really ugly hand drawn graphics in an effort to get it clear for myself. It's too much to try to post here but the whole thing makes sense to me.



Sounds like an interesting hypothesis. Do you happen to have the SA article that turned you onto this theory? If you can post which date the article was published in, we can probably find it. It sounds like it would make an interesting read.

As for me, I think the universe was created 30 seconds ago. All evidence that anything came before that (including our own memories) is simply just part of the starting state of the universe.

Of course, that is hardly a scientific theory, since it is non-falsifiable. /phpBB/images/smiles/icon_smile.gif

Hale_Bopp
2002-Jan-15, 05:52 PM
Well, six years is a long time in cosmology. I believe they have solved the stars older than the universe problem since then.

I think even the most adrdent proponent of BBC would admit the theory is not yet complete. After all, there is still a large amount of research being done.

With that said, in spite of its weaknesses, from everything I have read pro and con, it still seems to describe the current state of the universe better than any other theory I have studied. Just a few pieces of evidence are the cosmic background radiation and the prediction of abundances of the elements created by the big bang.

There are still plenty of myseteries, such as the seeming acceleration of the expansion of the universe and the dark matter puzzle.

I try to read some of the technical articles and find the math difficult to follow. However, if you read the technical articles, you will find that many of the most common objections to the theories were accounted for in their research. One of the trademarks of a good scientific paper is awknowledging what you took into account and what you didn't or couldn't for various reasons, and the possible effect it would have on your conclusions, if any. Unfortunately, the popular media stories that most people use to learn about these developments, cannot deliever this level of detail.

So, if you have a problem with BBC, that's great! There ARE still problems to be solved that may lead to new and interesting discoveries. However, try to look at the scientific papers to be sure that your issues have not already been addressed.

I am not directing this at anyone in particular (and I admit I haven't read all the papers to know if your concerns were addressed or not), but just making some observations about science in general.

Rob

Hale_Bopp
2002-Jan-15, 05:52 PM
Well, six years is a long time in cosmology. I believe they have solved the stars older than the universe problem since then.

I think even the most adrdent proponent of BBC would admit the theory is not yet complete. After all, there is still a large amount of research being done.

With that said, in spite of its weaknesses, from everything I have read pro and con, it still seems to describe the current state of the universe better than any other theory I have studied. Just a few pieces of evidence are the cosmic background radiation and the prediction of abundances of the elements created by the big bang.

There are still plenty of myseteries, such as the seeming acceleration of the expansion of the universe and the dark matter puzzle.

I try to read some of the technical articles and find the math difficult to follow. However, if you read the technical articles, you will find that many of the most common objections to the theories were accounted for in their research. One of the trademarks of a good scientific paper is awknowledging what you took into account and what you didn't or couldn't for various reasons, and the possible effect it would have on your conclusions, if any. Unfortunately, the popular media stories that most people use to learn about these developments, cannot deliever this level of detail.

So, if you have a problem with BBC, that's great! There ARE still problems to be solved that may lead to new and interesting discoveries. However, try to look at the scientific papers to be sure that your issues have not already been addressed.

I am not directing this at anyone in particular (and I admit I haven't read all the papers to know if your concerns were addressed or not), but just making some observations about science in general.

Rob

DStahl
2002-Jan-15, 07:15 PM
I had to take Principles of Physical Cosmology back to the local library (still can't afford to buy a copy *whine*) so I can't quote Peebles directly on this. But near the end of his chapter on alternative cosmologies he says something like--
-----------
Many cosmologists are unsatisfied with the big bang and expanding universe model and would happily welcome a viable alternative.
-----------

I think maybe the pros are more open to alternatives than half-educated (half-witted?) fellows like me!

Argos
2002-Jan-15, 07:22 PM
Until yesterday, the beginning of the world leaned on three pillars: the expansion of the universe, the record of residual microwave and the abundance of chemical elements in the cosmos. A hint of how the primeval structures of the universe formed was obtained upon the 300 million measures performed by the Cosmic Background Explorer (COBE). Some notable astronomers don't hesitate in refusing the Big Bang idea. One of them, Grote Reber, a radioastronomy pioneer, considers the model a doubtful hypothesis. To him, the spectral shift to the red is not due to the Doppler effect, but to gravitational interactions instead. The astronomer Alton Arp has specialized in searching for objects that can't be explained under the light of a classical Dopplerian interpretation. He has found galaxy pairs apparently unite by a "matter bridge", which present rather different recession speeds, in spite of being located roughly at the same distance. Edwin Hubble himself, when discovered the recession of the galaxies, considered the Doppler effect interpretation a mere hypothesis, suggesting that the light could be depleted of energy during its trajectory through space. The American astronomer Otto Struve questioned : "Are we really sure that nothing happens to a ray of light as it crosses 10 billion LY?". As we see, the Big Bang remains an open hypothesis.

Russ
2002-Jan-15, 09:47 PM
On 2002-01-15 12:25, Azpod wrote:
Sounds like an interesting hypothesis. Do you happen to have the SA article that turned you onto this theory? If you can post which date the article was published in, we can probably find it. It sounds like it would make an interesting read.

It WAS an interesting read. That's what got me going. /phpBB/images/smiles/icon_biggrin.gif Unfortunately all I can remember is that it was about 6 (give or take a couple) years ago. I'm too damn lazy to go digging through back issues to try to find it. I MAY have the printout of my hypothisis in foreground files but I wouldn't bet on it. As I recall I sited the article.


As for me, I think the universe was created 30 seconds ago. All evidence that anything came before that (including our own memories) is simply just part of the starting state of the universe.

/phpBB/images/smiles/icon_lol.gif /phpBB/images/smiles/icon_lol.gif You guys crack me up! /phpBB/images/smiles/icon_lol.gif /phpBB/images/smiles/icon_lol.gif


Of course, that is hardly a scientific theory, since it is non-falsifiable. /phpBB/images/smiles/icon_smile.gif

So you're going to let that stop you?! /phpBB/images/smiles/icon_wink.gif Publish man! Publish or parrish! /phpBB/images/smiles/icon_lol.gif

Sorry I don't have better responses for you. I'd really like a peer review of my ideas but, as luck would have it, I have to work for a living and kids, so spare time is at a premium. /phpBB/images/smiles/icon_razz.gif

Chip
2002-Jan-15, 10:51 PM
On 2002-01-15 14:22, Argos wrote:
"...Edwin Hubble himself, when discovered the recession of the galaxies, considered the Doppler effect interpretation a mere hypothesis, suggesting that the light could be depleted of energy during its trajectory through space. The American astronomer Otto Struve questioned : "Are we really sure that nothing happens to a ray of light as it crosses 10 billion LY?". As we see, the Big Bang remains an open hypothesis.


Yes, but -- Hubble (who was brilliant BTW,) nevertheless did not differentiate two types of Cepheid variables when measuring distances. Also "H II regions" were thought of only as bright stars within remote galaxies in his day. The value of the Hubble constant was thus lowered when these refinements were later made.

The "Big Bang" (a group of theories supporting cosmological models,) is not "proof" as it is a theory, but it is supported more consistently by observational data than all the alternative theories. This doesn't mean the alternatives are wrong. It simply means that the Big Bang theory is supported by more observational data, and that data also builds a more consistent-with-observation cosmological model than the others.

P.S. You can find a lot of this data all over the internet, and in a great many papers and books, including popular books in the science section of any large bookshop. (-;


<font size=-1>[ This Message was edited by: Chip on 2002-01-15 21:41 ]</font>

Spaceman Spiff
2002-Jan-16, 03:56 AM
On 2002-01-14 13:40, John Kierein wrote:
Big bang proponents were quick to say the apparent lack of spirals in the visible was evidence for evolution in galaxy formation. Now that the spirals are there after all, they want to say that the stars in the spirals are not as old as the spirals in nearby spirals.
Some want to say that spirals require collisions with other galaxies to create the shape which is due to them being closer together shortly after the big bang; but there is no evidence that the early universe is more densely packed with galaxies than the nearby ones. The galaxies are supposedly flying away from each other so, it's hard to understand why they collide in an expanding universe.
Others claim that spirals are formed from the spin of the galaxies, but there isn't enough time for the number of rotations needed for this for those so close to the time of the big bang, unless they spin a lot faster in the early universe and have been slowing down ever since. (I know of no evidence for this slowdown.)


JK you're taking things way too far. Sure,
some astronomers jumped the gun with the
original "analysis" of the HDF, by not
taking into account morphological differences that are due to the observed
REST wavelengths of light (i.e., nearby spiral galaxies look "chunky" at UV wavelengths and almost smooth at IR wavelengths).

However, the general conclusion still stands
that the galaxies that WE DO OBSERVE in the
HDF and other deep fields do show evidence
for galaxy evolution with redshift. See, for
example,

http://xxx.lanl.gov/abs/astro-ph/0109358
http://xxx.lanl.gov/abs/astro-ph/0012192
(the above study takes into account the results from NICMOS: observed frame infrared wavelengths = restframe optical wavelengths, softly contradicting your statement.)
http://xxx.lanl.gov/abs/astro-ph/0112547

and this sure looks interesting (gravitationally lensed proto-galaxy?):
http://antwrp.gsfc.nasa.gov/apod/ap011007.html

but see also
http://xxx.lanl.gov/abs/astro-ph/0012167

for a discussion of the effects (biases) of "missing galaxies" from small surveys such as the HDF (Malmquist and Disney biases regarding luminosity and surface brightness).

Next, THERE IS evidence for more galaxy interactions with increased redshift, z (or
lookback time). Here is a place to start:

http://antwrp.gsfc.nasa.gov/apod/ap990722.html

Next, why are the vast majority of quasars at significant redshift? Indeed why do their
numbers and luminosities evolve so strongly
with redshift.

Ditto radio galaxies?

Why does the Lyman alpha "forest" of
absorption lines
(due to gas lying within the intergalactic
medium)
become denser with increasing redshift? The
highest redshift quasars have almost no light squeeking through shortward of their
emitted Lyman alpha emission line.

Why does the star formation rate evolve
strongly with redshift? (>10 greater in
the distant past)

Where are all of the blue compact galaxies
today (visible at moderate redshifts)?

Next: SHOW me a grand design spiral galaxy at redshifts of 2, 3, or 6 with rest frame colors that look like the Andromeda galaxy or M81. I sure don't know of one. Heck, show me
ANY spiral galaxy with a lookback time of
13 billion years. 12 billion years? Even if
we found one, as the BADASTROMER says, that
doesn't mean the stars in its disk are as old
as the oldest stars in the Milky Way's disk. Now as to whether the disk can form in 2-3 billion years time - that's another question.
Nobody is yet tearing their hair out. But
you can bet your buttons that we will be
testing these very issues over the next few
years.

I could go on, but I won't. The point is
that nobody is saying we have all of the answers. What we have are observational data
and a theory that currently best explains them. Nothing that you have presented is
compelling to the contrary.

The data are yet relatively few, in regards
to universal evolution, but that's why we
are doing these galaxy surveys, why we're installing the ACS on Hubble in Feb/March,
and hopefully putting the NGST in orbit in
2007 or so: to gather data. And astronomers
will go will the data/evidence lead them. Nothing is sacred.


<font size=-1>[ This Message was edited by: Spaceman Spiff on 2002-01-15 22:59 ]</font>

<font size=-1>[ This Message was edited by: Spaceman Spiff on 2002-01-16 07:53 ]</font>

John Kierein
2002-Jan-16, 12:41 PM
The reason radio galaxies and quasars (bright in the radio) have discrepantly big red shifts is because these red shifts are not related to their distance, but instead are "intrinsic'. These objects have an exceedingly large number of electrons associated with them and radiate in the radio due to synchrotron radiation. Light which interacts with these electrons is red shifted by the Compton effect to produce the red shift. They are more local than their red shift would indicate which explains their discrepant brightness and in the case of Hercules A, their apparent size. (Hercules A would be the largest sinsingle object in the sky if it were as far away as it's red indicates, but is not so unusual if it is nearby.)
see http://www.angelfire.com/az/BIGBANGisWRONG/index.html and link to "where are the quasars?"

Spaceman Spiff
2002-Jan-16, 01:06 PM
On 2002-01-16 07:41, John Kierein wrote:
The reason radio galaxies and quasars (bright in the radio) have discrepantly big red shifts is because these red shifts are not related to their distance, but instead are "intrinsic'. These objects have an exceedingly large number of electrons associated with them and radiate in the radio due to synchrotron radiation. Light which interacts with these electrons is red shifted by the Compton effect to produce the red shift. They are more local than their red shift would indicate which explains their discrepant brightness and in the case of Hercules A, their apparent size. (Hercules A would be the largest sinsingle object in the sky if it were as far away as it's red indicates, but is not so unusual if it is nearby.)
see http://www.angelfire.com/az/BIGBANGisWRONG/index.html and link to "where are the quasars?"


Quasars and radio galaxies don't have discrepently large redshifts. We find "inactive" galaxies at similar redshifts and often in the same cluster. And the radio quiet quasars? and the starlight of the galaxies that surround them?

I don't even want to go down the road of discussing "Kierein scattering" (IT IS NOT COMPTON scattering), whose existence has never been demonstrated and in fact has been shown to be non-sense (i.e. contradictory to physical evidence). Though, (apparently) no one will ever convince you otherwise.

Granted - we may yet find something about redshift that we don't yet understand, but it will not be Kierein scattering.

John Kierein
2002-Jan-16, 05:43 PM
Radio quiet quasars just don't have magnetic fields. You need electrons AND magnetic fields to get synchrotron radiation. The so-called remnants of galaxies are just the viewpoint that the fuzz has to be galactic; actually it could just be stellar like the planetary dust clouds, etc.; except they are rich in ions & electrons. Stars look just like quasars. Look at this picture - one is a star and one is a quasar. You can't tell em apart except for their red shift.http://oposite.stsci.edu/pubinfo/pr/96/25.html

Karl
2002-Jan-16, 06:31 PM
On 2002-01-16 12:43, John Kierein wrote:
Radio quiet quasars just don't have magnetic fields. You need electrons AND magnetic fields to get synchrotron radiation.

And our galaxy has both, wouldn't you agree? This results in the production of the galactic background radiation as a local phenomena not by extra-galactic sources as Reber suggests.

Chip
2002-Jan-16, 06:35 PM
On 2002-01-16 12:43, John Kierein wrote:
Radio quiet quasars just don't have magnetic fields. You need electrons AND magnetic fields to get synchrotron radiation. The so-called remnants of galaxies are just the viewpoint that the fuzz has to be galactic; actually it could just be stellar like the planetary dust clouds, etc.; except they are rich in ions & electrons. Stars look just like quasars. Look at this picture - one is a star and one is a quasar. You can't tell em apart except for their red shift.http://oposite.stsci.edu/pubinfo/pr/96/25.html


Hi John,

Are you saying that proto-galactic fragments as seen in the Hubble Deep Field are closer dust clouds? With all due respect, that seems kind of far-fetched because the fragments can be seen well enough to be differentiated from one another, faint as they are.

Concerning quasars looking the same as stars, I remember reading somewhere within the last year that recent observation has revealed that quasars are in fact within galaxies and/or surrounded by material. I'm sorry I don't have the source, maybe someone else does. The point is, they don't always look like stars. They're so bright, they mask the galaxy they're in. The newer photos often look like this picture (http://www.eso.org/outreach/press-rel/pr-2001/phot-20a-01-preview.jpg) from the European Southern Observatory.

The Bad Astronomer
2002-Jan-16, 06:37 PM
The so-called remnants of galaxies are just the viewpoint that the fuzz has to be galactic

Actually, it's far more than "just a viewpoint". There is copious evidence that the fuzz is indeed an underlying galaxy. See, for example, this paper from astronomers using NICMOS onboard Hubble (http://www.stecf.org/instruments/nicmos/sardinia/node34.html), who show that the fuzz is entirely consistent with known galactic properties.

The Bad Astronomer
2002-Jan-16, 06:39 PM
Here's another presentation (http://www.roe.ac.uk/ifa/research/public/qhost/sld001.htm) that has spectral matching as well. You can find plenty more by doing a search on google using the words "quasar host galaxies".

Azpod
2002-Jan-16, 06:43 PM
On 2002-01-15 16:47, Russ wrote:



Of course, that is hardly a scientific theory, since it is non-falsifiable. /phpBB/images/smiles/icon_smile.gif

So you're going to let that stop you?! /phpBB/images/smiles/icon_wink.gif Publish man! Publish or parrish! /phpBB/images/smiles/icon_lol.gif


Hey, that hasn't stopped many people from publishing non-verifiable theories and calling it scientific because it happens to fit all the known observations. Publishing non-falsifiable theories doesn't bug me (because they very well could be correct), but doing so and calling them scientific bugs me. By definition, anything scientific can be tested and verified.

My 30 second universe fits all known observations perfectly, and not only that, it will also fit all new observations, until the end of time! /phpBB/images/smiles/icon_smile.gif Actually, that is one of the creation theories-- that the universe could have been created 30 seconds ago, 20 billion years ago or anytime in between, and we'd have no way of knowing. I happen to like it, since it could explain the creation of the universe by an intelligent God without throwing the rest of science out on its ear.

Of course it can only do that because it is a non-falsifiable theory, and therefore isn't a scientific one.

Spaceman Spiff
2002-Jan-16, 07:46 PM
On 2002-01-16 12:43, John Kierein wrote:
Radio quiet quasars just don't have magnetic fields. You need electrons AND magnetic fields to get synchrotron radiation.


You're telling ME that synchrotron radiation
consists of electrons spriraling around magnetic field lines? Sheesh. John, sometimes
WE LOOK STRAIGHT DOWN THE NARROW RELATIVISTIC SYNCHROTRON JET AND WE SEE NOTHING PECULIAR WITH THE REDSHIFTS IN THESE SOURCES AS COMPARED TO THE CASES WHEN THE JETS ARE ORIENTED AT ARBITRARY ANGLES.



The so-called remnants of galaxies are just the viewpoint that the fuzz has to be galactic; actually it could just be stellar like the planetary dust clouds, etc.; except they are rich in ions & electrons. Stars look just like quasars. Look at this picture - one is a star and one is a quasar. You can't tell em apart except for their red shift.http://oposite.stsci.edu/pubinfo/pr/96/25.html


As the BADASTROman says, this not just somebody's viewpoint. They are based upon evidence. We can see (images, colors, spectroscopy) the stars and elliptical and spiral galaxy structures surrounding an ultraluminous source of light in the galaxy's nucleus. We see those galaxies in clusters with normal galaxies. Yes, the most distant ones still look like points of light, but every year we are able to look at more distant quasars and find their galactic light.

And besides the spectrum of a quasar or active galaxy (so-called Seyfert type 1 seen more nearby) doesn't look anything like ANY star.



<font size=-1>[ This Message was edited by: Spaceman Spiff on 2002-01-16 15:44 ]</font>

Gsquare
2002-Jan-22, 07:38 PM
On 2002-01-14 13:40, John Kierein wrote: But then Hubble added a new instrument, NICMOS, that imaged these and lo and behold, they are spirals after all!
.....
Big bang proponents were quick to say the apparent lack of spirals in the visible was evidence for evolution in galaxy formation. Now that the spirals are there after all, they want to say that the stars in the spirals are not as old as the spirals in nearby spirals.
....
Others claim that spirals are formed from the spin of the galaxies, but there isn't enough time for the number of rotations needed for this for those so close to the time of the big bang, unless they spin a lot faster in the early universe and have been slowing down ever since. (I know of no evidence for this slowdown.)


Good points John !
I ought to add, (just to show how deficient astronomy is in current cosmological knowledge):
Is it not true that it has been determined that the stars on the periphery of spirals actually are measured at a higher tangental velocity than those toward the center showing total disregard for the usual eqns. of gravitational mechanics ? Was this not the origin of the speculation for 'missing mass' and 'dark matter', etc. No?

Well, instead of looking for the invisible (and possibly the unfalsifiable) maybe we ought to start readjusting our equations to take into account variablity in G and the like. [:)]
G^2

<font size=-1>[ This Message was edited by: Gsquare on 2002-01-22 14:41 ]</font>

<font size=-1>[ This Message was edited by: Gsquare on 2002-01-22 20:57 ]</font>

Kaptain K
2002-Jan-23, 10:49 AM
...Is it not true that it has been determined that the stars on the periphery of spirals actually are measured at a higher tangental velocity than those toward the center...
No. The rotational velocity at the perimeter is less than the velocity farther in. But not as much as would be expected IF the visible matter is the only mass in the galaxy.

DoctorDon
2002-Jan-23, 01:05 PM
No. The rotational velocity at the perimeter is less than the velocity farther in. But not as much as would be expected IF the visible matter is the only mass in the galaxy.


Um, sorry, that's backwards. Here's the rotation curve for NGC3198 (Begeman 1989).




http://aether.lbl.gov/www/science/rotation.gif



If there were no dark matter, you would expect the curve to start falling again after it peaks, as the visible density decreases with r at large r. However, the observed velocity is greater than you would expect, implying either there is more matter there we can't see, or our theories of gravity need adjustment.

Yours,

Don Smith

Russ
2002-Jan-23, 01:09 PM
On 2002-01-16 13:43, Azpod wrote:
Hey, that hasn't stopped many people from publishing non-verifiable theories and calling it scientific because it happens to fit all the known observations. Publishing non-falsifiable theories doesn't bug me (because they very well could be correct), but doing so and calling them scientific bugs me. By definition, anything scientific can be tested and verified.

My 30 second universe fits all known observations perfectly, and not only that, it will also fit all new observations, until the end of time! /phpBB/images/smiles/icon_smile.gif Actually, that is one of the creation theories-- that the universe could have been created 30 seconds ago, 20 billion years ago or anytime in between, and we'd have no way of knowing. I happen to like it, since it could explain the creation of the universe by an intelligent God without throwing the rest of science out on its ear.

Of course it can only do that because it is a non-falsifiable theory, and therefore isn't a scientific one.

AAAAH, the age old problem of "How do you tell if you are being fooled or fooling yourself?" I deal with that in my business alot. If you have more than one oxygen analyzer how do you know which one is reading correctly? The old "A man with one watch always knows what time it is, a man with two is never sure." trick.

Does anybody know if there is a way to tell how old light is other than red shift?

Kaptain K
2002-Jan-23, 04:31 PM
Dr. Don,
Not so much backward as very poorly worded. Thanks for the clarification. I knew that the rotational velocity should taper off after the peak and that the post peak velocity was higher than it should be (if visible matter was all there is), but I was not aware of how linear the curve was "post peak". Thanks for the graphic.

Spaceman Spiff
2002-Jan-24, 12:00 AM
On 2002-01-23 08:09, Russ wrote:
AAAAH, the age old problem of "How do you tell if you are being fooled or fooling yourself?" I deal with that in my business alot. If you have more than one oxygen analyzer how do you know which one is reading correctly? The old "A man with one watch always knows what time it is, a man with two is never sure." trick.

Does anybody know if there is a way to tell how old light is other than red shift?



Try here for starters:
http://www.astro.ucla.edu/~wright/age.html

(the second and third methods apply to cosmic or extraterrestrial ages)

littled
2002-Jan-24, 04:19 AM
OK,
The big bang, if so why have we not been able to isolate the center of this cosmic occurrence? like throwing a rock in a pond. If all the galaxies are expanding it should be relatively easy to discerne the center of this cosmic event, where is it? spiral galaxies, obviiously there is a gravitional force creating these structures. Just like water going down the bathtub drain. Do all spirals rotate the same direction? What cosmic force determines the direction of rotation of these jewels?
later,
little d

Peter B
2002-Jan-24, 09:07 AM
G'day little d and welcome to the forum.

You said that if the galaxies are moving away from each other we should be able to discern a centre, like the expanding rings on the surface of a pool.

Unfortunately, it's not as simple as that. Every galaxy is moving away from every other galaxy (except where gravity is strong enough locally to overcome the expansion).

So while we see galaxies moving away from us, an observer in any other galaxy would see the same effect.

The best analogy is the balloon analogy. Take a balloon, and blow it up about half way. Take a texta and draw dots on the balloon's surface. These represent galaxies. Now start blowing the balloon up. All the dots will get further away from each other. But it's impossible to point to a centre of the balloon's surface.

Gsquare
2002-Jan-28, 02:39 AM
On 2002-01-23 08:09, Russ wrote:

Does anybody know if there is a way to tell how old light is other than red shift?


Uh... measure the distance to the source and divide by the speed of light?

SeanF
2002-Jan-28, 04:32 PM
On 2002-01-27 21:39, Gsquare wrote:


On 2002-01-23 08:09, Russ wrote:

Does anybody know if there is a way to tell how old light is other than red shift?


Uh... measure the distance to the source and divide by the speed of light?


What if the source has moved and is no longer in the same position it was when the light was emitted?