The Dark Side Of The Universe | World Science Festival

Thank you.

And this program is also being livestreamed, so I also want to extend a warm welcome to the tens of millions of online viewers tonight. You know, a little more than a decade ago I went to a lecture by Saul Perlmutter—you'll meet him later tonight. The lecture was both amazing and disturbing. Saul was telling us about evidence he and his team had found

that the universe is filled with some invisible energy. Some dark energy that permeates all of space. Now I had already heard about these results, but I had dismissed them. I didn't think that they were right, but Saul's talk was so convincing, the evidence was so strong, that you had to think that there was really something to what he was saying.

Now, the reason why the talk was disturbing is that, basically, most of us—all of us—had concluded that there wasn't any of this dark energy in space. And, you know, I probably shouldn't say all of us. There were a few people in the community who did suspect that there might be this dark energy

and one of them, Michael Turner—you'll also meet him as well in just a little while— he was, they'll tell you about, he thought there might be this dark energy in space. But most of us thought that there wasn't any of this dark energy. So when Saul and his team convinced us that there was,

It sent many of us, theorists around the world, scurrying to try to figure out what this dark energy was, how it could fit into our theories, and at first, in fact, it was very hard to fit it into string theory, the theory that I focus upon. So I was calculating day and night,