The following Yahoo News Space.com excerpt is from an article titled Physicists Predict the Death of Cosmology. Astronomy is a hobby of mine, and I handled my high school and college physics pretty well. Additionally, I understand most of the major concepts that cosmology puts forth. However, this article borders on Taoist philosophy on steroids. Check it out and see if your brain hurts as bad as mine did after you are finished:
Physicists are now foretelling the death of cosmology, or the study of our universe, as we know it. Thankfully, cosmologists won't be jobless for a couple trillion years.
The universe is rapidly expanding--perhaps not rapidly enough to rip to shreds, but enough that distant galaxies will eventually be moving away faster than the speed of light. This much has been known for decades.
Once all these galaxies blink out of existence, scientists ask in an upcoming issue of The Journal of Relativity and Gravitation, how will future intelligent beings study space if the human race's knowledge is long gone? Will they be able to figure out if the Big Bang happened? Or rediscover relativity?
For the most part, said Lawrence Krauss, a theoretical physicist at Case Western Reserve University in Cleveland, Ohio, and co-author of the journal article, future observers will be out of luck. "They'll be stuck in an endless black void," Krauss said, noting that any galaxies outside of our own cluster will disappear in about 100 billion years. "They'll feel very special after that happens, because our tiny cluster of galaxies will be the observable universe to them."
Without a cosmological frame of reference, Krauss explained, future observers will be clueless that their universe is still expanding. "It will be a sort of twisted situation, where thinking returns to what it was at the turn of the 20th century," he said.
In other words, observers will think the universe is just a static--or non-expanding--cluster of galaxies just as scientists thought until the 1920s. "The static universe," as the journal article states, "will have returned with a vengeance."
An additional issue for future observers will be the disappearance of cosmic microwave background radiation--the fingerprint of the Big Bang's occurrence--in about 250 billion years. Without it, Krauss said, observers can't be certain about how the universe was created, not to mention when.
The problem relates to the Doppler effect: When a speeding train approaches, the sound waves from its whistle are squished together to make a higher pitch. As it passes, the sound waves are stretched out like a slinky and become lower in pitch and fainter. Similarly, as the universe expands outward, the "pitch" of light will lengthen and fade away. "The wavelength of light will be so large it will eventually reach the size of our galaxy," Krauss said. "It will just be absorbed."
Krauss, however, is confident that someone (presumably human in form) will be the next Einstein and rediscover general relativity. He's also hopeful that future observers will be able to explain the creation of the solar system by studying stars within the galaxy.
Can I get a WOW?!? Mr. Krauss is throwing some serious heat with these fastballs. I have three quick thoughts about this discussion:
One, yes, general relativity does stipulate that it is theoretically possible for expansion to proceed until some objects exceed the speed of light, but the proportion of mass per cubic parsec (mostly populated by dark matter) is supposed to help slow the expansion down. Recent observations show that this is happening, so Mr. Krauss's statement seems to be a bit of hyperbole.
Two, even if dark matter wasn't slowing expansion down, eventually everything in the universe would be moving faster than the speed of light. Under that scenario, Mr. Krauss's statement about future observers thinking that they would be alone in the local cluster of galaxies would not seem to work.
Three, even if the cluster of galaxies in which we reside manages to stay somewhat intact, that does not mean that future observers cannot glean the phenomenon of expansion. There are at least two dozen galaxies in the association of which our Milky Way is a member. Some are retreating, some are approaching. If the astronomers of the future have eyes like ours and instruments similar to ours, then it stands to reason that they will work out what a redshift or blueshift means as far as objects retreating or approaching is concerned.
I don't have advanced degrees in astrophysics or cosmology. Since I don't, I realize that there could easily be something I have overlooked. Still, this is a fascinating topic, and I hope that there are followup articles to expand on the ideas presented here.