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.