National Aeronautics and Space Administration

Movie (54 MB)

AUDIO:
Narrator:Astronomers now believe that the mysterious dark energy makes up 70% of the composition of our universe, while dark matter makes up another 25%. Robert Kirshner, Kluse Professor of Astronomy at Harvard University, is an astronomer at the Harvard Smithsonian Center for Astrophysics. Evidence that his team gathered has revealed that our universe is expanding at an ever increasing rate.

Dr. Robert Kirshner: Well, I'm an observational astronomer. I make measurements of things, usually using telescopes - I do pretty much what you think an astronomer does do. I go to a telescope and make measuremenst of things. In this case it's exploding stars and the purpose of those measurements is to find out the history of how the universe has been expanding.

I got interested in astronomy pretty early, There was a neigbhor who had a telescope and he was kind of having trouble setting it up. I thought "How hard can this be?" So we figured out which way the North Star was and got the axles pointed the right way. But I do remember just being impressed with the mystery of it, and with the visual experience too.

Well, we've gotten a really big surprise, which is that the universe seems to be expanding outward faster over time, not slowing down the way we expected. And so we thinkg there must be something that has this kind of anti-gravity quality to it, which we call the dark energy. So finding out what is making the universe expand is something which is actually within our grasp. And the technique for doing it that I have been working on is to use these exploding stars - these supernovae - to try to measure the history of cosmic expansion.

It turns out that a certain kind of supernova is pretty much the same from one galaxy to the next - they have the same brightness. So that means we can judge their distance from their apparent brightness. Now that's one part of the story, how far away are they. The other part is really how fast is the universe expanding.

VIDEO:
This video opens with an image of distant galaxies, while the narrator talks about dark energy and dark matter. Then Dr. Robert Kirshner explaining his interest in astronomy. While he talks about his neighbor, there is an older picture of a young boy with a telescope. Then there is an image of the night time sky full of stars. We see Dr. Kirshner talking, and the final image is of a supernova on the edge of a galaxy.