In that case, why did you even start this thread?

From Wiki:
Seems that your question is answered quite well.

That wiki quote is vague. Photons or other particles? That's everything! Why state photons when we are talking about all particles?

Inversely proportional to the square of velocity? This is not the end all answer.

It says "photons or other particles moving at relativistic speeds"

this means that it works for particles and photons. It works for anything moving at close to or at the speed of light.

Dividing an effect by 9*10^16 tends to make it a very small effect.

Interesting... it said it's "negligible"... which is not "zero"...

dcl: The acronym FLRW may be familiar to some viewers, but I suspect that they are in a very small minority. From the level of sophistication I perceive in most viewers, I doubt that many even know what a metric is, much less the names or properties of any specific metrics. Although I am a physicist, I have not had occasion to encounter the FLRW metric in my work or even in my leisure reading. I am a novice where the more advanced aspects of astrophysics are concerned.

You seem to be using the "<logon name>:" construction in two different ways. Here (and elsewhere) you've used it to indicate the person who is speaking. But here you use it to address another poster directly.
I wonder if you might consider using the quote facility (button at bottom right) to make this difference clearer, and your posts correspondingly easier to read.

Grant Hutchison

grant hutchison: I started to try your suggestion by clicking the "Quote" button but the response was something I wasn't sure how to interpret. I've been creating my posts in WORD, spell-checking them there, then copying them into the post box. Doing this seemed to work well for me. What is the problem you find in the way I've been doing it? I'm willing to change if I can understand how doing so would produce something that other contributors would find easier to deal with than with what I've been doing. I don't understand the problem you're pointing out with the way I've been doing it. How am I using the "logon name" in two different ways? The text you quoted in your quote box seems irrelevant to the problem you cited and puzzled me until I decided to ignore it because it seemed to be irrelevant.

I'm accustomed to clicking on quote when I am responding to a specific post. Feels natural and ensures that the quotation looks like someone else's text.

On the "Is the expansion of space constant?" thread you use the logon names and a colon to flag who's talking, using this sort of exchange:
In that case, you follow a quote from tommac with your own response.

But here, on the same thread, you address publius directly, using his logon name and colon:
And here, on this thread (in the text I quoted before), you simply preface a stand-alone remark with your own logon name:
It's a little awkward to track who's addressing who. Using the quote facility allows your text to contrast with the text you're quoting, and allows us to link back to the context of the quoted text via the little arrow buttons.

Grant Hutchison

I'm guessing that this last one was directed to me. If yes, then I'd like to explain what the real supposition is (so you don't need to guess):

The supposition is not that photons can lose energy without any contact with anything (I think that Einstein's theory, that I assume true, prevents them from this). However they should lose energy from point of view of Newtonian physics through so called "gravitational interaction" that in astronomy is known as dynamical friction. Since in Newtonian physics we have strict conservation of enrgy, it has to be reflected by the redshift of those photons (despite that the real mechanism of the redshift is different than what Newtonian physics assumes, since real physics is not Newtonian but Einsteinian).

Now, the amount of dynamical friction of photons is not known since (I assume) it was never calculated outside the Newtonian physics and the Newtonian physics doesn't apply to photons, but "gravitational interaction" obviously does apply to photons. So we have a small discrapancy in energy of photons from point of view of any physics (either Newtonian or Einsteinian), which is somehow swept under the carpet in saying that it is "negligible" so presumably we may forget about it.

I didn't forget about it and calculated the redshift being the relativistic counterpart of the loss of energy of photons myself, and it came very close to the Hubble redshift. So at least it is not "negligible" and if we treat physics seriously then the Huble constant should be adjusted for this value.

Unfortunately then the expansion would disappear and it may pose certain problem to the Big Bang Theorists. That's why I'd like to discuss with them this issue and also maybe that's why they try to avoid discussing it with me (for lack of time as they claim). For over 20 years by now. Since I don't believe in conspiracy theories where something may be adequately explained by stupidity I don't suspect a conspiracy (explanation for those who have a custom of jumping to conclusions).

In the meantime it turned out that the dynamical friction of photons is a purely relativistic effect and it is inversly proportional to the radius of curvature of space (in first approximation the redshift Z=r/R, where r is distance the light travels and R is radius of curvature of space, which makes Hubble constant H_o=c/R, where c is speed of light, a very convenient device for calculating the radius of curvature of space, and so also the space density, once one admits though that the big Bang was a mistake, which I doubt could happen).

So my question is not what happens to energy of photons, but how astronomers explain the mechanism that allows them to ignore the redshift being the relativistic counterpart of the Newtonian loss of energy of photons (however tiny it is). I was told that by assuming validity of only the conservation of 4-momentum and not energy and momentum separately. It creates a problem of conversion of momentum into energy that anyone who understands the issue should be able to answer. I just want straight answers to straight questions, nothing outragious.

This contribution responds to JimJast's 08 May 2008 08:46 PM contribution. Most of it is quotation of previous text. All new text starts iwth "| " at the left margin to make them it out.

dcl: As I understand it, you are asking through what mechanism energy is being created continuously to offset the energy lost by photons in traveling through empty space. I am not aware that any such energy loss has been either observed or predicted by theory. The cosmological red shift is explained by Doppler effect, not by loss of energy by light while traveling through space.

JimJast: I'm not asking about photons traveling through empty space but through space of certain non zero density (roughly 10^{-27}kg/m^3). Those photons must have certain redshift proportional to some function of this density (actually it is a square root of density) unless the energy is delivered to them or something else is happening. Since according to the Big Bang Theory those photons don't have any redshift (except Doppler) then either energy is delivered through some mechanism or something else is going on. In any case it should be understood by astronomers and astronomrs should be able to explain the phenomenon since astronomers invented the Big Bang Theory so they better understand it and know why there is no redshift due to the dynamical friction but only due to Doppler effect.

| dcl: You didn't say from where your figure for the density of matter in "free space" came. My guess
| is that it's estimated density of hydrogen atoms and ions in free space. If so, its effect would be to scatter
| and absorb light. That would indeed produce attenuation of received light from a given cosmological
| object, but there's no reason to expect that loss to be compensated by creation of energy.

dcl: Your argument seems to be based on the idea that photons lose energy through dissipation of rest mass, which implies that photons have rest mass greater than zero. Efforts to determine the rest mass of photons have been able thus far only to establish lower limits on the possible rest mass of a photon. They have not been able to show that the photon has precisely zero rest mass The fact that photons travel at a speed that special relativity says cannot be exceeded, much less attained by matter implies that photons have zero rest mass.

JimJast: That's right and that's why it is not the loss of energy through dissipation of rest mass but through another mechanism. Since the loss of energy is necessary and it can't be through the dissipation of zero mass the available option seems to be the redshift through slowing down of time rate at the source of the photons (a mechanism similar to the gravitational redshift but working independently of the direcion of movement of the photon and so having a tensoral character). This would be this other mechanism that astronomers should be aware of and being able to calculate how much of it there is. Do they know?

| dcl: As I stated above, the mechanism is simple scattering of photons out of the direct path toward our
| detectors by the hydrogen atoms and ions along the light path.

dcl: If you can document information to the contrary, please do so by citing references.

JimJast: I'm asking experts about actual knowledge in this matter which must exist if astronomers insist that the universe is expanding. If they don't have any knowledge nor any theory why do they insist that the Big Bang is a Theory? A theory is a possible explanation of physical facts. If you don't have explanation of elementaty stuff you don't have a theory just a vague hypothesis.

Who then is a right guy to ask? I asked aleady Ned Wright and he refused to talk to me when I turned his attention to the fact that in the real universe there are no gravitational forces acting at the distance (they are only in Newtonian gravitation, not in Einstein's). The gravity physicists like John Baez maintain that energy is not conserved in gravitation and only 4-momentum is but don't explain how momentum changes into energy (through what mechanism). Does it mean that nobody involved in astronomy knows anything?

| dcl: Momentum cannot change into energy; their dimensionalities are different. One varies with velocity,
| the other with the square of velocity.

JimJast: My astronomy professor said once that one nice thing about astronomy is that unlike in civil engineering one may be 100% wrong and nobody is hurt. Ain't astronomers exploiting this feature of astronomy excessively?

| dcl: I don't understand your saying, "if astronomers insist...". Are you denying that the Universe is not
| expanding? If so, on what basis? Why are you asking, "If they don't have any knowledge nor any theory
| why do they insist that the Big Bang is a Theory?" Your question seems to imply that they don't have any
| knowledge nor any theory." I think I must be misinterpreting your question. A theory is more than a
| possible explanation of physical facts. What you're describing is a hypothesis, not a theory. The special
| and general theories of relativity and the theory of evolution were hypotheses until supported by
| substantial bodies of data.

I'll try to respond to the new texts.

The density of space comes from galaxies since as I leaned in my astronomy courses there is practicly nothing else except them (otherwise the light would be scattered and we wouldn't see it). So the model is Einstein's dust universe with galaxies as particles of dust and nothing between them.

Yet we see the galaxies without any scattering, so your model is not observationally confirmed.

This is what I thought, and that's why we need an expert to explain how momentum changes into energy in the Big Bang Theory. There must be a way if the Big Bang theorists claim that energy is not conserved separately from momentum as it used to be in the pre-Big Bang physics and now only the 4-momentum is conserved. It means that if energy is not conserved and 4-momentum is then the non conserved part of energy must come from momentum to keep the total 4-momentum conserved, since in 4-momentum there is nothing else except energy and momentum.

The basis for my assumption that the universe is Einstein's (stationary) is my calculation that produces for a stationary universe the redshift that is observed as the Hubble redshift. This calculation is based on conservation of energy which the Big Bang theorists consider non existent in relativity. They say that only 4-momentum is conserved which I don't understand and that's why I ask how it can be conserved without energy and momentum being conserve separately (the problem mentioned above that also you don't believe possible but yet the Big Bang theorists insist it is how the universe works). Hopefully they will explain it how it is possible and it will be end of it. Before that I'll wait, having my doubts about the expansion.

JimJast: The paper by Jastrzebski that you cited is way beyond my level of comprehension. Although I'm a physicist and been through the derivation of the Einstein field equations of general relativity, my familiarity with general relativity remains that of an amateur. I'm certainly not about to suggest that the Jastrzebski paper is fraudulent, but I cannot dismiss that possibility. There is a book entitled "Fads and Fallacies in the Name of Science" that cites many exmples of fraudulent attacks on general relativity among other subjects. I once encountered an example myself of what appeared to me to be such a fraud. It was a manuscript that I was asked to evaluate by the Director of Research of the place where I was working at the time. It purported to prove that the steady-state theory was correct and to disprove the Big Bang theory. It contained. among other things, a reference to the Lee and Yang paper on parity con-conservation for no apparent reason. He worked for the same company I worked for and, after I reported my findings to the Director of Researched, he was invited to present his theory to the theoretical physicists in the company and didn't impress them, either. I also sent a copy to George Gamow, a principal participant in creation of the Big Bang theory and with whom I'd had previous contact, and asked him what he thought of it. He responded, as nearly as I recall, "I received a copy of it, too. A lot of arm waving with no significant substance. So down into the waste basket with it." The last sentence is a direct quote that I especially remember, a reflection of his less than perfect mastery of American idiom.

I am really referring to more than just this post.

JonJast, there is a massive flaw in your reasoning. In dynamical friction, the energy is transfered from the particle to the medium. If photons are experiancing dynamic friction, then the energy is going into the medium that is being scattered. There is no violation of conservation.

If the amount of energy lost is on the order of picoeV lost per eV of the photon per megaparsec travelled, then the difference is academic.

First, the paper has gone through peer review and no problem with it has been reported except that it does not confirm the expansion nor propose any new physics (obviously) so the editors (Phys. Rev. Lett.) decided not to publish it, as not interesting to their readers and to save the valuable journal space. So even if it is fraudulent neither me nor any referee (there was total of 6 referees and editors involved) noticed that.

Second, I wrote the paper with intention that it could be understood by a high school student interested in physics (such as I was once). Too bad, and I wonder why, it was "way beyond [your] level of comprehension". If you tell me what was "beyond" I'll try to present it in a different way, possibly easier to understand. It is useless to write papers that no one undrstands and therefore can't evaluate.

There are several problems with dynamical friction of photons and the resulting redshift:

(i) The effect must exist regarless of how small the amount of it there is. In the Big Bang theory it is assumed zero on a basis that it is "negligible" without calculating it, at least I didn't see published any results, beyond the Newtonian back-of-envelope calculation since it is so tiny (and then it is many orders of magnitude smaller than anything reasonable).

(ii) It can't be calculated directly with the Newtonian gravitation since the Newtonian gravitation does not apply to fast particles and besides after exact calculations are done it turns out that the effect depends on the curvature of space only (the effect turns out to be a purely relativistic effect) and in the Newtonian gravitation the space is assumed flat. Then there is no surprise that it turns out to be so tiny when calculated with Newtonian gravitation.

(iii) When the calculation is conducted rigorously applying the principle of conservation of energy the redshift comes out as approximately equal to the Hubble redshift.

The last problem is of course what has to be taken under consideration, and that's why the Big Bang theory has to assume no conservation of energy in relativity to satisfy astronomers who insist that the universe is expanding. Then the explanation of the mechanism how momentum is converted into energy in relativity (where 4-momentum is conserved) is job of astronomers who insist on expansion.