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 a few years.
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?
Island universe
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."
No
background material
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.
And, said
Krauss, there's a positive side to not knowing the universe's true history:
"There'll be almost no static on their TV screens," Krauss said, explaining
that if there are no distant galaxies around to emit cosmic rays, the airways
will be a lot cleaner.
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