Someone has said that you transformed relativity from a discipline of mathematics to a discipline of engineering. How do you react to that description? I'm very proud if somebody says that, because I confess that in the beginning general relativity seemed to be a paradise for advancing mathematics, and now you go and look at one of these detectors being built and you feel "My, that's really impressive. These things must be real, these gravitational waves, even if we haven't got the direct evidence." We have wonderful indirect evidence. My Princeton colleague, Joe Taylor, and his younger associate, Hulse, have found that in a double star going round the loss of energy causes the two components to spiral together, and they measure the rate at which they're spiraling together and find that it corresponds to the loss of energy by gravitational radiation the Einstein's theory predicts. So indirectly we have proof, but that's one thing to have the proof that energy is taken away, but that's not quite the same thing as seeing the radiation really move something in front of your eyes.