Photon frequency loss over time?

[rcgldr]

I remember reading an article many years ago that there was a theory that part of the red-shift we observe from far away galaxy's could be do to a time (or distance) related reduction in frequency of light, in addition to the "doppler" effect. Has this theory ever re-surfaced again (it may have been 10 or more years ago that I read this article)?

 

[neutrino]

Maybe you read about cosmological redshift.
http://curious.astro.cornell.edu/question.php?number=278

 

[Chronos]

Jeff, what do you imagine those photons give up their energy to? Eventually they must glow, don't you think?

 

[rcgldr]

Maybe you read about cosmological redshift.

Possibly, but I'm pretty sure that there was an inference that it was more than just space stretching or speed that contributed to red shift. Maybe it was related to dark matter or something similar between an observered galaxy and the earth.

It wasn't clear, but I assume the strecthing of the space in universe is due to the decrease in graviational fields as objects move away from each other?

 

[ratfink]

Do you mean the tired light theory as first proposed by fritz Zwicky (1927?).
Photons lose energy as they travel and since E = hf the frequency reduces and wavelength increasesd. They are redshifted.
He put it down to gravitational effects.

 

[rcgldr]

Do you mean the tired light theory as first proposed by fritz Zwicky (1927?).
Photons lose energy as they travel and since E = hf the frequency reduces and wavelength increasesd. They are redshifted.
He put it down to gravitational effects.

That's probably what I read, athough I'm not quite old enough to have remembered it went first published. Has this theory been abandonded now?

 

[ratfink]

It keeps rearing its ugly head. try
brynjolfsson
http://www.lyndonashmore.com
toivo
to name but a few

 

[SpaceTiger]

That's probably what I read, athough I'm not quite old enough to have remembered it went first published. Has this theory been abandonded now?

Tired light theory hasn't been taken seriously by the mainstream for quite some time. It was a viable alternative for several decades after it was proposed (20s), but the CMB and other cosmological tests have since put it very firmly to sleep.

 

[ratfink]

Let me put this another way! Instead of just quoting ‘cosmological tests’ it would help if you stated what they are.
As far as I know, we have the Tolman surface brightness test and supernovae time dilation. Any more?
The Tolman surface brightness test was always 'iffy' as it relied on models on how galaxies aged. On nearby galaxies it showed that expanding models were probably nearer the truth than static models. But this was on nearby galaxies (three in the same cluster?)
However the HUDF came along and now the tolman test comes out very firmly in favour of a static universe.
That leaves us with ‘time dilation.’ Supernovae light curves’ are stretched which agrees with the expanding theory whilst quasar light curves are not stretched – which agrees with the static universe. Since this is the same phenomenon, until such time as anyone can come with a theory that unifies these effects then the jury must remain out.
CMB? Didn’t you tell me that the axis of evil is still there on the latest data?
If the clumps are aligned about our solar system and galactic plane then even that has a problem. Furthermore, the horizon problem in the CMB is only solved by inflation and that has no experimental verification whatsoever!
So we can neglect cosmological tests and the CMB to rule out a static universe – unless you know of any other?

 

[SpaceTiger]

Let me put this another way! Instead of just quoting ‘cosmological tests’ it would help if you stated what they are.

The abundances of light elements, the cosmic microwave background, the formation of large scale structure, star formation rate vs. redshift, the Soltan argument, evolution of morphology with redshift, supernova time dilation, GRB time dilation, and much more, I'm sure. The CMB, abundances, and large scale structure all constitute multiple tests of BB predictions.

However the HUDF came along and now the tolman test comes out very firmly in favour of a static universe.

Eric Lerner is a well-known crank. Those results come about from one of the effects I mentioned above -- the evolution of star formation with redshift. High-z galaxies are nothing like low-z ones, so as you've suggested, the test is not very useful. It may have some value at low redshifts and where galaxies haven't evolved much, but it's still not a very strong test.

CMB? Didn’t you tell me that the axis of evil is still there on the latest data?

The "axis of evil" is a sign of possible contamination in the data at low multipoles. The vast majority of the information in the CMB lies at high multipoles, where the standard model fits the data to very high precision. The CMB is a very dramatic test of mainstream theory -- it comes as no surprise to me that most of the laymen advocating steady state models don't understand the WMAP results.

Furthermore, the horizon problem in the CMB is only solved by inflation and that has no experimental verification whatsoever!

Wrong again. Inflation is actually doing quite well lately. The universe has continued to be consistent with flat, now to a precision of a few percent. Furthermore, the fluctuations in both the CMB and large scale structure (see the "genus" test) have been shown to be gaussian, another prediction of inflation. Finally, the WMAP measurements indicate a spectral slope just slightly deviant from unity, just as predicted by inflation.

 

[Nereid]

the Soltan argument,

I suspect this is not well known among PF readers; could anyone provide both a succinct summary of what it is? Also, when was it first published? And how widely has it been used (in cosmology)?

 

[setAI]

it would be nice if an actual physicist or student would have metioned that the question is scientifically invalid- since photons have no tau- thus they can't do anything 'over time' to begin with-

 

[Garth]

it would be nice if an actual physicist or student would have metioned that the question is scientifically invalid- since photons have no tau- thus they can't do anything 'over time' to begin with-

A good point.

Observed cosmological red shift is to do with the way the photon is being observed, compared with how it was emitted.

A photon is emitted by one atom and absorbed by another much later in the universe's history. Cosmological curvature results in a time dilation between the two, but should not that time dilation affect the mass of the atom as well as the frequency of the photon? i.e. if there is a de Broglie frequency associated with the atom's rest mass.

Just a thought.

Garth

 

[SpaceTiger]

it would be nice if an actual physicist or student would have metioned that the question is scientifically invalid- since photons have no tau- thus they can't do anything 'over time' to begin with-

They can certainly change as a function of coordinate time, which is usually what people mean by "time" in cosmology.

 

[ratfink]

Eh Up!
Space tiger tells us that

The universe has continued to be consistent with flat, now to a precision of a few percent.

Garth says

Cosmological curvature results in a time dilation between the two,

A contradiction I fear!
Which means that neither knows what they are talking about?

 

[Garth]

A contradiction I fear!

Not at all.

Cosmological curvatue is space-time curvature, the present mainstream model is concordant with a spatially flat, or near flat universe.

The isotropic and homogeneous space-like foliations appear to have a flat geometry even though they are embedded in a 4D space-time that has curvature.

This curvature is represented by the scale function R(t) as well as the (space) curvature constant k.

I hope this helps.

Which means that neither knows what they are talking about?

You might well be right - "cosmologists are often in error but never in doubt"

But I will let SpaceTiger speak for himself.

Garth

 

[SpaceTiger]

I suspect this is not well known among PF readers; could anyone provide both a succinct summary of what it is? Also, when was it first published? And how widely has it been used (in cosmology)?

The Soltan argument basically compares the present day mass density of black holes to the integrated luminosity density of quasars. The idea is that supermassive black holes are expected to grow by mass accretion -- a process that radiates energy that we see in the form of active galactic nuclei. If we add up the total radiated energy from AGN over the history of the universe, we can infer how much mass was accreted. If our ideas about AGNe and cosmology are correct, this inferred accreted mass density ought to be comparable to the mass density of black holes. In general, the luminosity and mass accretion rate are related by

L=\epsilon \dot{M}c^2

The efficiency, \epsilon, is not known in general, but has characteristic values of order 0.1 in most black hole accretion theories. The Soltan argument can be used in several ways -- for example, to infer the efficiency of accretion. In the present context, it can be used to support the expansion paradigm. Using a reasonable value for the efficiency, the present-day mass density of black holes is comparable (to within an OOM) to the inferred accreted mass density:

http://www.arxiv.org/abs/astro-ph/0203082"

 

[SpaceTiger]

A contradiction I fear!
Which means that neither knows what they are talking about?

To the contrary, Garth knows quite a bit about GR. I won't insult you and suggest that you didn't know that the universe had been measured to be flat, but when two ideas seem to contradict one another, it's always wise to consider the possibility that you might yourself be misunderstanding something about them.

 

[ratfink]

So, is it flat or is it curved?

 

[Garth]

So, is it flat or is it curved?

The consensus of opinion is the WMAP data is consistent with spatially flat universe. Such a spatially flat 3D hyper-surface would be embedded in a 4D curved space-time.

The curvature of space-time is revealed by working out all the components of the Riemannian tensor with the Robertson-Walker metric in which k = 0, they are not all zero. It is this 4D space-time curvature that describes the gravitational field.

The peculiar thing about the GR cosmological solution is when all the Riemannian components are zero, in the empty universe case, then the 3D space hyper-surface is not flat but hyperbolic and expanding linearly.

My caveat on that consensus opinion is, as the WMAP data is angular in nature and conformal transformations preserve angles, it is also consistent with a spatially conformally flat universe.

Garth

 

[ratfink]

Thanks garth,
Sorry for the delay, been stargazing - the alignment of the planets is brill at present!
So, what you are saying is that it has taken nearly one hundred years and several COBE type satellite results to show that in X,Y,Z coordinates space is flat - which is what they thought it looked like at the beginning?
Out of interest, what evidence is there that space is curved in 4D space time?
Thanks.

 

[Garth]

Thanks garth,
Sorry for the delay, been stargazing - the alignment of the planets is brill at present!
So, what you are saying is that it has taken nearly one hundred years and several COBE type satellite results to show that in X,Y,Z coordinates space is flat - which is what they thought it looked like at the beginning?

At the beginning they also thought space was static.

Out of interest, what evidence is there that space is curved in 4D space time?
Thanks.

Gravitation.
It particular, the finer details of the orbits of planets such as Mercury and the trajectories of light rays passing close to the Sun follow the geodesics ('straight -lines') through a curved 4D space-time as predicted by GR.

Garth

 

[ratfink]

Well no, These are local perturbations and I am sure we are all happy with that. In this thread we are looking at the universe in total. When we look at the Universe as a whole, in 3d it is flat and in 4d it is supposedly curved? I was just wondering which way it curves in 4D space (do we know?) and what evidence do we have?
Ta

 

[Garth]

Well no, These are local perturbations and I am sure we are all happy with that. In this thread we are looking at the universe in total. When we look at the Universe as a whole, in 3d it is flat and in 4d it is supposedly curved? I was just wondering which way it curves in 4D space (do we know?) and what evidence do we have?
Ta

Sorry I misunderstood your question.

Astrophysics, and scientific cosmology, is the application of the physics 'down here' in the laboratory to observations of the universe 'out there'.

The 'down here' bit in GR are the solar system experiments that verify the predictions of the theory. These verify the understanding that "space is curved in 4D space time".

Once GR is accepted as an accurate description of gravitational fields the GR field equation is solved for the cosmological case, with a maximally symmetric space, which is homogeneous and isotropic.

This yielded the Friedmann models that are then verified by:
1. Hubble red shift.
2. BB nucleosynthesis predicting a 3/4 H and 1/4 He composition by mass of the primordial gas exiting the BB. This is concordant with the present day element relative abundance mix taking 10 Gyrs. worth of stellar nucleosynthesis into account.
3. The CMB.
4. The relative abundance of some rare isotopes that were produced in the BB, although these are often model dependent and do not constitute a hard prediction.

The standard model also requires, Inflation, non-baryonic DM and DE which have been able to be combined into a self consistent model. Although I have an issue with this as they have not been discovered in laboratory physics.

However, the veracity of the first three predictions are grounds for confidence in the basic GR understanding that ""space is curved in 4D space time".

Garth

 

[Garth]

Also there is large scale gravitational lensing of distant quasars by nearer galaxies. Although this is not quite on the cosmological scale.

I was just wondering which way it curves in 4D space (do we know?) and what evidence do we have?

As far as this question is concerned the curvature of space-time around the Sun has a definite direction, light rays are bent towards the Sun as they pass close by. However cosmological curvature has no such direction in space. Instead it is revealed as a time dilation.

The expression "space-time curvature" is a mathematical one that may be confusing. It may have a spatial component as well as a temporal one. The temporal 'curvature' though manifests itself as a time dilation - you cannot 'bend' time in the normal sense (http://www.tauworkshop.com/DaliWatch.JPG not withstanding!)

Garth

 

[SpaceTiger]

Out of interest, what evidence is there that space is curved in 4D space time?

A flat spacetime would just be Minkowski space. In a spatially flat FRW universe, the 4D curvature manifests itself as expansion or contraction. Therefore, for these purposes, we should be able to answer, "What is the evidence that the universe is curved in 4D?", in the same way as, "What is the evidence that the universe is expanding?". Ratfink can just refer to the responses I already gave in reference to the latter question.

 

[ratfink]

Thanks Garth,
You see my interest in 'curvature' is entwined with the question of "where does the energy go" in the BB theory.
Photons of light have a longer wavelength on arrival than when these same photons set off. Ergo, their frequency and hence energy is therefore less.
So in BB, where did this energy go and how did they lose it?
Now the standard BB answer is that it went into "curving space". BUT we know from this thread that space in the x,y,z coords is flat - so it must have gone into curving space time?
But if space time is a mathematical concept then how do photons curve it in becomng redshifted?

 

[ratfink]

To the contrary, Garth knows quite a bit about GR. I won't insult you and suggest that you didn't know that the universe had been measured to be flat, but when two ideas seem to contradict one another, it's always wise to consider the possibility that you might yourself be misunderstanding something about them.

Do you mean this one?

 

[Garth]

Thanks Garth,
You see my interest in 'curvature' is entwined with the question of "where does the energy go" in the BB theory.
Photons of light have a longer wavelength on arrival than when these same photons set off. Ergo, their frequency and hence energy is therefore less.
So in BB, where did this energy go and how did they lose it?
Now the standard BB answer is that it went into "curving space". BUT we know from this thread that space in the x,y,z coords is flat - so it must have gone into curving space time?
But if space time is a mathematical concept then how do photons curve it in becomng redshifted?

The standard BB GR answer is actually the energy did not go anywhere, because energy is not conserved, and not to be expected to be conserved, in an "improper energy theorem" such as GR.

This question vexed Einstein, Hilbert and Klein and others until it was resolved by Emmy Noether (great name for a relativist! ) who coined the phrase "improper energy theorem".

You can read more about Noether's work in Nina Byers paper E. Noether's Discovery of the Deep Connection Between Symmetries and Conservation Laws.

If you are interested in an alternative published theory that tries a different approach you might be interested in http://en.wikipedia.org/wiki/Self_creation_cosmology . (You can find links to the published articles from that Wikipedia page)

Garth

 

[SpaceTiger]

Do you mean this one?

Do I mean what one?

 

[ratfink]

Nah,
energy is conserved.
if a photon has enough energy to expose a photographic plate on galaxy x, then surely it cannot expose it on galaxy y? It must have lost energy on the way.
Are you saying that whilst a photon exposes a photo of their hols on their plates it also exposes a photo on our photographicplates even though it 'lost energy' on the way? No way!

 

[ratfink]

Do I mean what one?

Ratfink can just refer to the responses I already gave in reference to the latter question.

The only previous response that I can find remotely relevant is

it's always wise to consider the possibility that you might yourself be misunderstanding something about them.

 

[SpaceTiger]

The only previous response that I can find remotely relevant...

This post is what I was referring to:

https://www.physicsforums.com/showpost.php?p=1002766&postcount=10"

Evidence for an expanding universe is also evidence for a curved spacetime.

 

[SpaceTiger]

Nah,
energy is conserved.

No, Garth is correct, energy is not always conserved in GR. If you've done research you believe contradicts this, please don't post it here, submit it to the Independent Research forum.

 

[ratfink]

No, Garth is correct, energy is not always conserved in GR. If you've done research you believe contradicts this, please don't post it here, submit it to the Independent Research forum.

This is incorrect. Energy conservation in GR is in dispute. Some say that energy is not conserved others say it is due to 'curvature'. I hope that this is not a 'warning' because you wish to avoid answering valid questions.

 

[ratfink]

So, would the photographic plate be exposed on both galaxies or only one?
This is what energy conservation is about (and forums for that matter too!)

 

[SpaceTiger]

This is incorrect. Energy conservation in GR is in dispute. Some say that energy is not conserved others say it is due to 'curvature'. I hope that this is not a 'warning' because you wish to avoid answering valid questions.

The only dispute is in appropriate definitions of energy in GR. See here:

http://math.ucr.edu/home/baez/physics/Relativity/GR/energy_gr.html"

Unless I'm to interpret your previous post as advocating a particular pseudotensor definition of energy, then it belongs in IR.

 

[ratfink]

This is not peer reviewed and who are they?

 

[ratfink]

OK,
Let me spell this out.
B/W paper is not sensitive to red light. That is why we have red safelights in photographic darkrooms.
Light from a distant galaxy is redshifted.
I say that there must be a point where the paper is not exposed anymore.
You and Garth say "Oh the pricinciple of conservation of energy does not apply".
I say B**-t either the paper is exposed or it is not. It is all to do with the photoelectric effect.
Nothing to do with reference frame - we all see the same result.
So I will ask again. If the photon has enough energy to excite and expose a photographic plate on galaxy X, will it once it has been redshifted, be able to expose it on galaxy y?

 

[Garth]

No need to be rude.

Energy is not generally conserved in GR because of the time dilation caused by space-time curvature. The energy of a system can only be consistently defined at null infinity where curvature effects and gravitational waves become insignificant.

The reason this is so is energy is a frame dependent concept, moving frames, or frames at different gravitational potential, measure energy differently from one another. We do not all see the same result - that is the whole point of relativity, certain measurements are relative.

In GR it is energy-momentum, or particle rest mass, that is conserved.

Your photographic plate question is irrelevant. The exposed plates X & Y both record the photon, but at a later cosmological time, after more cosmic expansion, the plate Y records a redder image. That is what Hubble red shift is all about.

Garth

 

[SpaceTiger]

That's enough, the OP's questions have long since been answered. I'm locking this.