Yesterday I talked about astrophysicists’ love for being perplexed. These days, a hot topic of wonder and perplexity is the accelerating speed of the universe.

I remember when I first heard the surprising news. It was a decade or so ago, and I was at a party with some friends in Oakland. Someone turned to a man in the group and asked, “So, Saul, is the universe going to keep expanding, or is it going to eventually contract again?”

I watched Saul’s face change, a look of wonder and excitement spreading across it. “Well,” he responded, “we’re actually just in the process of answering that question!” Turns out, this was Saul Perlmutter, an astrophysicist whose team was one of the two groups breaking the story in 1998 that the rate of expansion of the universe is increasing–a finding so unexpected that up until then it was considered a joking matter. No one would have taken it at all seriously except for the fact that two teams at UC Berkeley, working independently, came to the same conclusion.

Yesterday at the Conference on World Affairs in Boulder I heard the leader of the other team, Alex Filippenko, and physicist Michelle Thaller talk about this astrophysics surprise and what it says about us, the universe, and other related matters. The panel was titled “Dark Energy: Cosmic ‘Antigravity,'” and the lecture hall on the CU campus was packed to standing room only.

In elementary school we learned that the universe is expanding, right? What the two Berkeley teams established is that not only is it expanding, but the rate of expansion is increasing. Thaller and Filippenko emphasized that space is not empty, as we tend to imagine. Rather, they said, space is “something,” it exerts an active pressure, and that “something” is growing. Physicists call it dark energy, a pressure that is pushing every galaxay apart from every other galaxy. Space itself is repelling all objects as it speeds along.

We live, in other words, in a runaway universe. But it is not the galaxies running away with the train. Instead, the part of the universe we thought was empty–space itself–is full. And expanding.

Michelle Thaller summed it up:

We’re at this little cusp in history where scientists found something we were not looking for. And it’s revolutionizing science.