My Beef with Gravity Waves

Yesterday there was brief moment when I thought that they had announced the first detection of a gravitational wave by LIGO. Needless to say, this turned out to not be the case. If it were then you would have heard about it – most likely from a newsreader doing their very best.

The paper that caused this trouble describes how LIGO has been used to place a low-limit on some properties of the Crab Nebula pulsar (you can read it here if you like). The way this paper was announced at the AAS meeting in St. Louis made it sound like they had a detection. But they didn’t and don’t (yet). Interestingly, I wasn’t all that excited though. For a few moments I was quite convinced they had finally made a detection and although it would have been historic I could only think of one thing: so what now?

The scientific community has been thinking about gravity waves for a very long time. They are a part of general relativity – although they were conceived of before that. To the non-astronomer, they basically answer the question, ‘what would happen if the Sun suddenly vanished?’. Would the Earth instantly fall out of orbit or wold it take time? Would we see it happened before or after we felt it happen?

The answer is that gravity is ‘transmitted’ via waves and that it travels at the speed of light – so we’d see and feel it at the same time. Gravity is thought to propagate through spacetime, much as light propogates through the electromagnetic field. The ripples it creates in spacetime are very tiny though and so they are extremely hard to detect.

So if you could ‘see’ gravitationally energetic events, then what would you do? Well it would allow you to perform a new kind of astronomy. It would open a new spectrum of analysis and viewing on the universe. This new spectrum would range from highly energetic events (e.g. coalescing black holes) to lower energy events (e.g. accretion disks). Mainly it it interesting in the way it would let us look into the physics of black holes.

Huge amounts of money have been ploughed into gravity wave physics. Interestingly the gravity waves groups around the UK always seem to have a lot of money! They use it to meet up and discuss theoretical results. They create lavish PR campaigns and recruit PhD students. They take data with LIGO and its contemporaries. What they do not do, and have not yet ever done, is detect a single gravity wave!

I realise this is political, but it always irks me slightly. Gravity waves have lots of money but no results. ESA is potentially going to bump another project in favour of contributing to LISA, a gravitational wave detector in space.

So I am asking for anyone that knows something about gravity waves to give me some reasons to like the idea of studying them again. I used to when I was a kid. They are very cool, they are high-tech, but they are  – for now – undetected and very, very expensive.

So any general relativity enthusiasts/experts out there who can offer me something to work with? Anyone?


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