Could Light Energy Loss Explain the Expansion of Space?

[whatdofisheat]

could the lost energy from light cause the expansion of space?
i know we have no evidence that light can lose energy but over a long distance and i mean like a Mpc or more. TO me this almost seems like a chicken and and egg question.

 

[Garth]

could the lost energy from light cause the expansion of space?

No, in the Friedmann GR dust model, i.e. one with no pressure, the universe expands perfectly well without any light or CMB within it. In fact, as the present density of the CMB is so low compared with the density of matter in the universe, the present universe is a pretty good approximation to that dust model.

Garth

 

[SpaceTiger]

Not to mention the fact that the presence of radiation slows the expansion.

 

[whatdofisheat]

how does the pressence of radiation slow the expansion?
or what papers of expeiments have showen this?

 

[whatdofisheat]

i guess i also ment the acceleration of the expansion. the light energy is the force pushing the universe.

 

[misskitty]

Is the light energy really the pushing force of the universe? Does anyone have any evidence to show radiation slows the expansion of space?

 

[ohwilleke]

The mainstream answer to all of the above is presented at the link below with pretty pictures to boot:

http://astronomy.swin.edu.au/staff/gmackie/BigBang/universe.htm

 

[misskitty]

Evidence enough for me. I don't know about the rest of you, but the source looked pretty credible to me.

 

[Garth]

Is the light energy really the pushing force of the universe? Does anyone have any evidence to show radiation slows the expansion of space?

Radiation is a form of energy. Energy has a mass equivalent that generates a gravitational field. The gravitational field slows the expansion of the universe. Apparent acceleration of that expansion requires negative energy, hence Dark Energy, if you can stomach it!

Garth

 

[whatdofisheat]

no i think dark energy is a very bad idea it is made up just to satisfiy one condition if this energy was so dominent then it would affect every aspect of the universe yet thie expansion is only seen were gravity is not abundtant. if you show me dark energy ill belive
it
fish

 

[SpaceTiger]

no i think dark energy is a very bad idea it is made up just to satisfiy one condition if this energy was so dominent then it would affect every aspect of the universe yet thie expansion is only seen were gravity is not abundtant. if you show me dark energy ill belive
it

That was what many people thought when dark matter was proposed, but now all observations seem to support its existence (despite the lack of a direct detection). I agree that dark energy is fairly ad hoc and I think very few scientists would disregard intelligent discourse on alternative explanations for the acceleration (in fact, they have been entertaining such notions of late).

Also, keep in mind that "dark energy" is a fairly vague description and there are many vastly different theoretical phenomena that could be said to fall into that category. I'd say it's currently little more than a parameterization for our ignorance.

 

[Starship]

Since the main evidence for dark matter comes from the shape of galactic rotation curves, other explanations could be that gravity does not work as we think or that gravity is not the only force determining the dynamics of the galaxy.

Axions and neutralinos are the most promising but magnetic fields and filamentation cannot be ruled out.

 

[SpaceTiger]

Since the main evidence for dark matter comes from the shape of galactic rotation curves...

No, that was the first evidence for dark matter. Your information is about 20 years out of date. Since then, the CDM paradigm has been able to explain large scale structure, the power spectrum, lensing results, and the CMB. These things are all explained naturally with dark matter, while MOND has been struggling to restructure itself with each new observation. Until dark matter is directly detected, we won't be sure, but the case is getting stronger and stronger with time.

 

[misskitty]

So basically what you are saying, Tiger, is that there is credible evidence to support the theory of dark matter. Right?

 

[Starship]

No, that was the first evidence for dark matter. Your information is about 20 years out of date. Since then, the CDM paradigm has been able to explain large scale structure, the power spectrum, lensing results, and the CMB. These things are all explained naturally with dark matter, while MOND has been struggling to restructure itself with each new observation. Until dark matter is directly detected, we won't be sure, but the case is getting stronger and stronger with time.

The evidence is indeed gravitational. The most promising present candidates are axions, though there's a probability that gravity does not work as we think it does.

Here's one great http://arxiv.org/PS_cache/hep-ph/pdf/0404/0404175.pdf about the topic.

 

[misskitty]

Can I ask what axions are?

 

[Starship]

Can I ask what axions are?

Axions are hypothetical elementary particles proposed to explain the absence of an electrical dipole moment for the neutron. Axions has no electric charge, no spin, and interact with ordinary matter (electrons, photons, quarks, etc.) only very weakly.

 

[SpaceTiger]

The evidence is indeed gravitational.

The evidence is gravitational, but that doesn't mean that it's consistent with another gravitational law. That's an important distinction. MOND can be tweaked to explain the observations, but it's very ad hoc.

 

[SpaceTiger]

So basically what you are saying, Tiger, is that there is credible evidence to support the theory of dark matter. Right?

That's right.