universal expansion

[Greco]

I was thinking about cryogenics, superconductors, absolute zero and the thought occured to me that as the universe expands it looses heat and at some point it must get to zero. Once it reaches zero how does that effect the speed of light? Does light freeze and stop?What does frozen light look like? Will a frozen universe re-collapse or keep going? But is it possible to have absolute zero and still have motion?

I hope I havent caused brain freeze :D

I'm editing to add an additional thought. Does our body expand along with the universal expansion? It might explain why I'm overweight :D

[mathman]

The speed of light does not depend on temperature. The current temperature of the universe (as measured by the cosmic backround) is a little less than 3 deg. K.

[fadingCaptain]

Here's a question: after the stars all burn out what happens to the temperature? Does it decrease to a point? What is the point?

[Starthane Xyzth]

@Greco: only the distances between superclusters of galaxies is actually increasing. Gravitationally bound structures like clusters, individual galaxies, stars and planets themselves, do not share in the overall expansion of the Universe - not do smaller, electromagnetically-bound objects, such as our bodies, raindrops, or single atoms. Within a bound stucture, distances are often DECREASING: our galaxy is heading for a merger with M31, and our Local Group is falling towards the Virgo Custer.

@fadingCaptain: the cosmic background temperature is more dependent on the relic radiation from the Big Bang than on starlight. It will decline continually as the Universe expands, but never quite reach absolute zero; think of an asymptotic curve levelling off.

[John Connellan]

Does our body expand along with the universal expansion? It might explain why I'm overweight

No it will only explain why u are FAT, not overweight :D

[John Connellan]

Here's a question: after the stars all burn out what happens to the temperature? Does it decrease to a point? What is the point?

The universe is indeed getting cooler due to expansion. The stars themselves however are actually adding heat to the universe (turning nuclear potential energy into heat energy) and so it is cooling a little slower than it should be. I guess the final temperature of the universe depends on what model u want to take. With an infinitely expanding universe the final temp should tend towards absolute zero.

[Starthane Xyzth]

Even after all coherent matter has decayed, all black holes have evaporated and nothing is left in space but isolated photons and leptons, there will still be a background temperature; plus, occasional electron-positron annihilations will yield new gamma-ray photons which then begin to redshift as the Universe continues to expand. If time is infinite and the Universe open, it may never reach any absolutely final condition or temperature.