Lord Martin Rees, University of Cambridge, Dr Andrew Pontzen, UCL
Gravitational waves made a big splash around the world but why has their detection revolutionised astronomy and physics? Chris Smith put this to Andrew Pontzen and Martin Rees...
Martin - These gravitational waves are predicted by Einsteinís theory and, in fact, they are the most distinctive and remarkable prediction of the theory and what is amazing is that the observations seem to fit extremely well with the calculations. So itís a really strong vindication of Einsteinís theory, about 100 years after he proposed the theory.
Chris - Are there any other things that we should do in order to validate, vindicate, and corroborate Einsteinís predictions?
Martin - Well we still donít know exactly what shape these black holes are and how fast they're spinning and, of course, as astrophysicists, weíd like to know how the black holes got there. What was the evolution that led to them so thereís a great deal for astrophysicists to do.
Chris - Weíve heard a lot of people saying these gravitational ripples arrived from a billion light years away. How do we know where those black holes were situated out in space?
Martin - The signal was detected in two detectors about 2,000 miles apart, and there was a slight time lag between the two detections and that tells you something about the direction because it tells you how much longer it took the waves to get from one to the other, going at the speed of light. And if we had three detectors, we could do a kind of triangulation, but I think we should realise what amazing technology this is. Weíre detecting this event, which happened millions of times further away than all the stars you see in the sky, and itís been detected by these instruments even though itís a tiny jitter in the mirrors that we heard about. A very tiny effect - itís amazing technology.
Chris - 1/10,000 the diameter of a proton is the catchphrase theyíre citing.
Martin - Thatís right. Another way they would present this is like measuring the diameter of a human hair at the distance of Alpha Centauri, the nearest star. So itís amazing precision so itís the engineers who need far more credit than the theorists.
Chris - And Andrew - is it true to say then that in the past weíve had some of our efforts at astronomy frustrated by light being interrupted on itís course to us by stuff like dust and other other materials, but these gravitational waves should pass straight through everything? So we should, in theory not get them occluded by anything in way...
Andrew - Well, thatís certainly true. But I think thereís an even bigger difference when you start observing the sky using gravitational waves, which is the kind of objects youíre picking up are simply things you would never see with a traditional telescopeÖ
Chris - So this really is a new vista?
Andrew - Oh yes. I mean, even now, weíre talking about two black holes about 30 times each the mass of our sun merging. If you just stop and think about what that actually means for a second, itís actually mind-blowing andÖ
Chris - I can tell youíre excited. So on a scale of one to ten where would you put this?
Andrew - WellÖ Itís sort ofÖ I mean itís a ten...
Chris - Heís lost for words!
Andrew - Look itís a ten in terms of scientific significance. In terms of my career, itís just a source of regret really because when I started, I had an opportunity actually to work on a PhD on gravitational waves. And, at the time, I thoughtÖ oh come on, I mean these tiny things, theyíre never really going to be detected are they? So I didnít and worked on something else and now I look like a bit of a fool.
Chris - Martin?
Martin - No, I would put it nine out of ten. In a way, the primordial gravitational waves, if we could detect them, would be even more exciting but theyíre very hard to detect. So that would have been ten out of then. I would give these nine out of ten but, because Iím an astrophysicist, I am not just interested in them as tests of Einsteinís theory but as part of the evolutionary story of how stars form, evolve, and die. This is telling us about a new way in which stars end their lives.