 It's almost a hundred years ago that Einstein developed his general theory of relativity. And this led to some predictions that have already been tested, such as the bending of light when it goes around massive objects like the sun, the gravitational redshift effect which is used every day in our GPS tracking systems, and black holes. But there's one prediction that hasn't been directly tested yet, and this is gravitational waves. These are ripples in the fabric of space and time that move through space at the speed of light. And what they actually do is stretch and shrink the dimensions of space ever so slightly. This year is the International Year of Light, 150 years since James Clark Maxwell came up with the Maxwell equations. This was built upon by a lot of theorists and then finally the culmination was Einstein's theory of general relativity. So it would be wonderful to detect gravitational waves this year. I'm mostly focused on looking at the data that comes out of very large detectors to pick out the elusive signal of a gravitational wave. The field has evolved from small groups in single universities to a large global collaboration. So I'm here today in Glasgow to talk with Jim Huff who's been working in gravitational wave physics now for 40 years. His expertise is the design, development and building of gravitational wave detectors. So before we go to see the more modern experimental apparatus, I thought I'd like to show you what I started out by building here. This is an aluminum bar gravitational wave detector. And of course the effect of the gravitational wave should be to squeeze the bar and let it go again. And that should produce voltage from the transducers which we've put into electronics. So you were actually involved in this from the very beginning of it? Oh, from 1971. Many of us wanted to be part of showing that Einstein was in fact correct. Sometimes as more of a theorist I forget how important experimental tests are. The first piece of the puzzle of testing general relativity actually clicked into place only a couple of years after Einstein developed his theory. And that was of course Eddington and Dyson going to observe the total eclipse and watch the light bending by the nearby stars as they passed by the sun. One of the problems of course with gravitational waves where that wasn't in fact till the late 1950s that Joseph Weber and John Wheeler began to think that they were detectable. So Joseph Weber actually did set up a number of these aluminum bars and began to see signals that he claimed were gravitational waves. A number of us thought it would be a very good idea to test to see where the Weber was seeing anything. And we did not see the signals that he was seeing. And it's not really surprising of course with an apparatus like this you're limited by the fact that the two halves are really rather close together. The ideal thing to do is to put the kilometers apart and to do that you have to use lasers. In the clean room you're going to see a prototype for developing the laser interferometry for such detectors. So welcome to the experimental lab Stephen. Now the laser is not on so we can safely take off our goggles and speak to each other properly. Excellent that's a bit more comfortable. So over here we've got the laser which drives the whole apparatus. You first of all stabilize the wavelength of the laser to the length of this long cavity. Then you'd split it two ways comparing the phase of the light that comes out from the two arms. Can you explain how we went from lab based prototypes to large scale international collaborations. How did that come about? Of course we started with independent groups all competing with each other all hoping to see gravitational waves first. But then as the experiments had to get bigger to get more sensitive very few countries really can afford to do that themselves. So what has happened is there's been a number of international collaborations set up the LIGO collaboration in the US and the Virgo collaboration in Italy. These big interferometers with arm lengths up to four kilometers long do need to be international and countries do need to work together and to jointly fund them. So LIGO and Virgo of course are the leading edge of international collaborations but international collaboration is not new. Even back in the late 1700s there was a collaboration between France and Britain to measure the distance between the Greenwich Observatory and the equivalent observatory in France. Genovo William Roy was commissioned by the British government to do this particular measurement. That was one of the most accurate determinations makeable at that time. So some of the earliest examples of collaboration we're trying to map the globe and you talked about William Roy. Now what we're trying to do is map the solar system, the galaxy and the universe. One example of this is the Gaia satellite which is a European collaboration that is already mapping in great detail the positions of millions of stars. And of course collaboration is very important in all fields I mean CERN is a very good example of that for particle physics. So it's probably fair to say that we're in the era of big science and more and more we're going to see these multinational projects both for reasons of multidisciplinary challenges but also obviously financial. It is amazing that when collaborations like this are formed just how much they can do and how important they are.