Instead of expanding forever,
the universe may only have
10 billion years until it collapses
Author: David Perlman, Chronicle Science Editor
(downloaded from http://sfgate.com/ cgi-bin/article.cgi?f= /c/a/2002/09/23/MN241327.DTL)
To Andrei Linde, the eminent Moscow-born cosmologist at Stanford University, the end of the universe is nigh.
In a startling new set of calculations, Linde and his physicist wife have just proposed that the entire universe, born in the Big Bang some 14 billion years ago, will collapse and end with a Big Crunch in the next 10 billion years or so.
And when the final collapse comes, even a single proton -- the heart of a hydrogen atom -- would be too big to contain the dead remains, Linde maintains.
Linde and his wife are among a worldwide band of physicists and astronomers who are trying to puzzle out the complexities of the cosmos from clues hidden in distant exploding stars, in the echoes of the universe's earliest instants, and in the tangled equations of relativity and space-time.
An art student and philosopher before he took to physics, Linde is one of the founders of the so-called "inflationary" universe scenario, a revolutionary concept that sees the early universe inflating in a sudden burst of speed after the Big Bang then settling into a more stable rate of expansion.
In the view of most cosmologists today, all the galaxies, stars and planets of the expanding universe are now speeding so far apart from each other that at some infinitely future time the universe will end up dark, forlorn and empty.
Now, however, Linde and Renata Kallosh, his wife who is also a Stanford physics professor, have proposed a new scenario:
Instead of expanding forever, they suggest, the universe is only in the middle-age of its expansion. Eventually it will slow down, pause and then start collapsing until -- some 10 to 20 billion years from now -- everything in it will end in one infinitely tiny point of mass and energy that cosmologists call a "singularity."
But should we care?
"This is for everyone," Linde says. "People must surely all want to know their ultimate fate, and isn't the fate of the universe the fate of us all? If I tell everybody that the universe is going to disappear, wouldn't people be interested to know?"
Linde and his wife have just published two dense and complex papers describing their new view of cosmology in an Internet publication sponsored by the National Science Foundation and called the "e-Print Archive."
They concede it is just one of many models of the universe that cosmologists are pondering, but Linde considers it the most interesting. "We tried our best to come up with a good theory that explains the acceleration of the universe," he said recently, "but ours is just a model. It's just part of the answer."
The "singularity" that Linde sees as the ultimate fate of the universe is a kind of absolute nothingness. It is something like what the fate of black holes is supposed to be, crunching together more and more tightly under the force of their own gravity until they, too, become singularities.
That kind of singularity is what many cosmologists consider to be the true origin of the universe at a time just before the Big Bang. Then, in a few billionths of a second, the universe began the extremely rapid phase of inflation that Linde and Alan Guth, now at MIT, proposed more than 20 years ago.
Soon after that, the universe expanded somewhat more sedately, until from its ripples of energy and gravity galaxies and clusters of galaxies formed within a few hundred thousand years. Later the stars gave birth to their circling planets, and ultimately life emerged -- at least on one.
One major problem facing scientists who try to puzzle out what happened after the Big Bang is that the structure of the universe seems too strange to be believed. Only about 5 percent of it is made up of ordinary matter -- the kind that makes up everything from our bodies to the Earth, the moon and the stars, scientists believe.
Another 25 percent is "dark matter," so called because although no one has ever seen it, it's needed to explain the powerful force of gravity that tugs at everything in the cosmos. It may be some sort of elementary particle like neutrinos, which have almost no mass, or perhaps some other particle as yet undiscovered.
And finally, the remaining 70 percent of the universe seems to be composed of a mysterious something the scientists call "dark energy," which Einstein termed the "cosmological constant" in an effort to support his early belief that the universe is actually static and neither expanding nor contracting.
Today cosmologists infer from their data that dark energy exists, but call it a mystery they can't explain.
But if that dark energy acts like a kind of anti-gravity -- "positive," astronomers call it -- then it would thrust everything in the universe apart. If it's "negative," as astrophysicist Alex Filippenko of UC Berkeley explains, then it would pull everything in the universe together, much the way gravity does.
In the dark energy concept, positive and negative bear no relation to electric charge, and according to the new Linde model dark energy would, of course, be negative.
The model has its detractors, however. And one alternative has recently been proposed by Paul Steinhardt of Princeton who with Neil Turok of Cambridge University has resurrected a new version of the old cyclic or "oscillating" universe. According to this theory, the universe may not have begun in a single Big Bang, but may be only part of an endless cycle of expansion and rebirth.
Last April, Steinhardt and Turok proposed that during each cycle, the universe fills with hot, dense matter and radiation, and then expands, accelerates and cools down. After trillions of years, the matter and radiation dissipate so much that expansion stalls, and an energy field fills the nearly empty universe. This energy creates new matter and radiation to start the cycle all over again, according to Steinhardt and Turok.
To that claim, however, Linde the theorist has two answers: Steinhardt's original calculations backing a cyclic universe were "full of significant mistakes," he said in an e-mail message last week. Furthermore, "only observations can tell us our future," he argued. "It is not up to us to make a decision about the future of the universe, it is up to the observers. And we will try to help them."
At the Lawrence Berkeley National Laboratory, astrophysicist Saul Perlmutter leads a project that is observing scores -- and soon thousands -- of extremely distant exploding stars called supernovae. His team, together with colleagues at Australia's Mount Stromlo Observatory, are using the supernovae as measuring beacons to gather more information on the rate of expansion of the universe, and perhaps on its true future.
Perlmutter believes the information so far indicates strongly that the universe is expanding so fast and so far that it will most probably continue forever.
"But at this point, however, we're still in the baby-step phase of cosmology," Perlmutter says. "Still, I'm hoping we'll eventually get to the 'Aha!' stage after we've really clobbered the supernovae for what they can tell us."
And these guys are
among the ones
telling us how
the universe began from
NOTHING !!
among the ones
telling us how
the universe began from
NOTHING !!
return to
SOMETHING from NOTHING?
SOMETHING from NOTHING?