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Cosmic Question

"The observations are not that definitive, so we have to build stories behind our observations," says Alan Guth, a pioneering MIT cosmologist.

The race to figure out the fate of the universe has grown more intense in recent years as a result of a startling discovery. In 1998, the Hubble Space Telescope obtained images of distant supernovae (exploding stars) that revealed that the universe not only is expanding but is doing so at an accelerating rate. A few years later, new observations showed that, many billions of years ago, the expansion was actually decelerating. So the cosmos apparently downshifts and upshifts. Second gear awhile back, fifth gear today.

There's a story there, written in starlight: The deepest portrait of the universe ever recorded, by a Hubble camera. (Nasa Via Reuters)

Something is causing the current acceleration, and this force, whatever it is, seems to account for about 70 percent of the total energy in the universe. Scientists call it "dark energy." That sounds better than "secret energy" or "invisible energy" or "we-got-no-clue energy."

Scientists had long thought that the universe might have just the right amount of stuff in it to allow gravity to slow the cosmic expansion to a nice, stable, steady cruising speed, such that the universe would always be around, always habitable. But what we see through telescopes doesn't support that happy scenario.

It looks for all the world as though dark energy will rip the universe apart. It might take a trillion years, but everything we see -- every star, planet, asteroid, comet, speck of dust and molecule of gas -- will decay and dissipate, and in the end there will be essentially nothing at all -- the universe ending with a whimper.

"The universe will go on expanding forever. And will get cold and dark and presumably ultimately lifeless," explains Guth, describing this scenario.

Scientists have to follow the data, but they'd also like to find a model for the future that's more interesting than an eternal wasteland. "I don't like it," Steinhardt says.

Perhaps, Steinhardt says, dark energy is not a constant force but something that can grow less dominant over time. If dark energy weakens, gravity could reassert itself as a shaper of the universe, and the whole business could contract again.

Unfortunately, none of this can be measured directly at the moment. There's no such thing as a dark energy detector. No one has figured out how to catch this particular kind of lightning in a bottle.

It could be that we're nowhere close to understanding what's happening in the universe. The place always turns out to be bigger and more complicated than we thought. In the 1920s we discovered that we live in but one of countless galaxies of stars, and that all these galaxies are moving away from one another. The universe is expanding. Hit rewind and we see that about 13.7 billion years ago, everything in the universe was compressed into an unimaginably hot, dense wad of energy. Something happened to transform that cosmic knot into a vast universe. It all went bang -- but why? How?

In the early 1980s, Guth, Linde, Steinhardt and others developed a provocative theory called "inflation," which suggests that the tiny embryonic universe went through an extremely brief (fraction of a second) inflationary epoch, increasing from something smaller than a pinhead to something cosmic in scale.

Steinhardt has more recently developed the hypothesis of colliding branes, an attempt to incorporate string theory into cosmology. Steinhardt's scenario has many moving parts and requires unseen dimensions of space. He admits it's still a maverick view, and perhaps it will always be hard to get converts to a new theory that is built on the assumption that we're going to collide with a hidden universe.

Steinhardt, however, has no monopoly on mind-bending theories. Linde has spent years talking about the possibility that a scientist might be able to create an entire universe in a laboratory.

You'd only need a speck of matter, Linde says. If you could get it to start inflating, it would eventually turn into a whole new gigantic galaxy-filled universe. For reasons that are pretty much lost in translation between scientist and journalist, the creation of this new universe somehow doesn't destroy the laboratory, or even break any beakers or flasks, but rather the new cosmos squirts off into unseen dimensions while continuing to look like a tiny little thing to the physicist.

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