Discovery that universe is expanding faster and faster earns physics Nobel
Three astronomers will share the Nobel prize in physics, for their finding that the universe's post-Big Bang expansion is neither slowing nor retreating, but is speeding up.
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If the universe held just the right density of matter and energy, the combined gravity of everything in the cosmos would allow the universe to expand forever, but at pace that would continually slow, though it would never reach zero. The other view posited that gravity ultimately would win out and throw the expansion into reverse. The universe would contract until everything collided in a cataclysmic "Big Crunch."Skip to next paragraph
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For a variety of reasons, most cosmologists tended to back the idea of an endless slowdown in the expansion rate. An accelerating universe was not on the cosmological radar screen.
Two teams tried to resolve the question by observing the light from exploding stars, known as supernovae, appearing at the farthest distances their telescopes would allow them to observe. Dr. Perlmutter led one team. Dr. Schmidt led the other, which included Dr. Riess.
One type of supernova in particular, known as a type 1A supernova, shows a common peak brightness wherever it pops up. By studying the spectra and the brightness of some 50 type 1A supernovae at enormous distances, the two teams independently found that the supernovae were dimmer than should be the case if the universe's expansion rate were slowing. After crunching the numbers, the data showed that the expansion was speeding up.
The teams published their results in astronomy journals in 1998 and 1999.
What is driving the expansion? That's the question astrophysicists are now trying to answer.
For many scientists, the new-found force harkens back to a concept called the cosmological constant. In essence, it was a fudge factor Albert Einstein used to make his preference for a steady-state universe hold up in the face of predictions from his general theory of relativity that the universe ultimately would contract, thanks to gravity.
The cosmological constant was a kind of antigravity that pushed out against gravity's inward tug. Later, when observations showed that the cosmos was expanding, he dubbed the cosmological constant his biggest mistake.
Detailed measurements of the background hiss from the Big Bang – itself a source for two Nobel-winning discoveries – show that what researchers dub "dark energy" represents roughly 75 percent of all the matter and energy in the universe. It pervades the universe, but its effects begin to show up only as the gravitational attraction between objects in an expanding universe weakens sufficiently.
"It's as if we found 700 new chemical elements that we didn't know about, but they were all around us all the time. It's that kind of revelation," Dr. Schewe says.
The discovery also is one more lesson in humility for humanity, he suggests. The particles that make up matter that physicists and astronomers can detect and measure account for only about 4 to 5 percent of all the matter and energy in the universe.
"The matter that we see, that we've studied so painstakingly all these years, it just a tiny, tiny fraction of the stuff that makes up the universe," Schewe says.
As for the future of the universe itself? Either the ultimate get-away-from-it-all experience, or a cold, dark, lonely one.
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