Scientists Find Cosmic Expansion Rate Faster
At their telescopes in the last few years, astronomers have been searching the heavens for evidence that the expansion of the universe is slowing down. The mutual gravitational attraction of all matter in stars, planets, and everything else known or hypothesized should be putting a gradual brake on the outward rush of space since the explosive moment of cosmic creation in the theorized Big Bang.
The preliminary results of the search are now in, and they are stunning. The expansion of the universe appears to be accelerating, instead of decelerating.
“Our observations show that the universe is expanding faster today than yesterday,” Dr. Adam Riess, a young astronomer at the University of California, at Berkeley, said in an interview last week. An analysis by him and an international team of scientists indicated that the cosmic expansion rate is about 15 percent greater now than when the universe was half its current age, about 7 billion years ago.
The group including Riess and another one, led by Dr. Saul Perlmutter of Lawrence Berkeley National Laboratory, used similar techniques of measuring the cosmic expansion rates over time by studying distant exploding stars, called supernovas. At first, the astronomers were not sure they could believe what they were seeing. But as they examined more supernovas and explored sources of possible error or alternative explanations, they have grown bold in describing the implications of their research at recent meetings.
“Try as we might, we have not found any errors,” Dr. Alexei V. Filippenko, a University of California astronomer who has worked on both teams, told colleagues recently at a meeting in Marina del Rey, Calif. “We get a nonzero cosmological constant.”
Translated, that means the astronomers are increasingly confident that they have detected the first strong evidence that the universe is permeated by a repulsive force, the opposite of gravity. The simplest explanation, other astrophysicists agree, is that the force is something called the cosmological constant. As conceived by theorists, this force is a property of the vacuum of space itself, an energy that acts on a large scale to stretch space and thus counteract gravity’s restraining power.
If the observations are correct, this is one more case of astronomers handing cosmologists a new piece to a jigsaw puzzle, which is always maddeningly incomplete, and asking them to find a way to fit it into a satisfying theoretical whole. Knowledge of an accelerating expansion could lead to a revised recipe of just what the universe is made of. It could resolve a paradox raised by previous controversial suggestions that the universe appears to be younger than its oldest stars. It could also change thinking about cosmic evolution and the ultimate fate of the universe.