The Elephant in the Universe by Govert Schilling

Author:Govert Schilling
Language: eng
Format: epub, pdf
Publisher: Harvard University Press

15

The Runaway Universe

On January 8, 1998, scientists announced that the universe will never stop expanding, but for some silly reason I missed the press conference. Yes, I was one of the journalists attending the 191st meeting of the American Astronomical Society in Washington, DC. But it was my first AAS, and I had a hard time figuring out what was happening at what time and in which of the many rooms at the Washington Hilton Convention Center. So when Saul Perlmutter and Peter Garnavich presented their exciting results on the never-ending growth of the cosmos, I was probably listening to some dull talk elsewhere in the building.

Ever since the big bang, empty space has been expanding. But scientists have not always been sure if this expansion will continue indefinitely. That’s because cosmic expansion is slowed down by the collective gravity of all the matter in the universe. For decades, astronomers wondered whether there is enough gravitating matter—luminous and dark—to not just slow the expansion but bring it to a halt and ultimately reverse it. The result would be contraction, leading to what has been called a big crunch. Just how much matter is there, then? As we have seen in previous chapters, it’s not easy to “weigh” the universe and find out. So two teams of researchers, Perlmutter’s and Garnavich’s, independently came up with another way to assess the matter content, and therefore the future, of the universe: they measured the expansion’s history, by looking at distant supernova explosions.

The supernova message was loud and clear: there’s not enough slowing down going on to ever stop cosmic expansion. Apparently the universe’s biography is a never-ending story. As Perlmutter said at the AAS press briefing, “For the first time, we’re going to actually have data, so that you will go to an experimentalist to find out what the cosmology of the universe is, not to a philosopher.” At least, that’s what I read from other reporters. The next day, the New York Times had the news on its front page. “New Data Suggest Universe Will Expand Forever,” the headline read.

But there was more. The supernova measurements indicated not only that the expansion of the universe was endless but that it wasn’t even slowing down. The rate of expansion was in fact accelerating. That result wasn’t announced at the press conference. The discovery was so surprising, so weird, and so far-reaching that it took another six-and-a-half weeks before one of the competing research groups felt confident enough to announce it in public.

We live in an accelerating cosmos, a runaway universe. Empty space is being pushed apart by some uncanny force that cosmologists have christened dark energy, for lack of any better name. As if dark matter wasn’t mystery enough—curiouser and curiouser, to quote Lewis Carroll’s Alice. In December 1998, Science hailed the discovery of the universe’s accelerating expansion as the scientific breakthrough of the year; in 2011, three key scientists behind the revolutionary find, including Perlmutter, shared the Nobel Prize in Physics. And

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