Wednesday, October 27, 2004

Searching, forever searching

I think it's about time I let the good readers know what it is I actually do. Well from my profile you should be able to gather the information that I am doing a PhD in gravitational wave astronomy. "What's it all about?", you might be asking. Well a gravitational wave is a prediction of Einstein's (you'll have heard of him, famous Austrian scientist guy, E=mc^2 and all that) General Theory of Relativity. This theory says that masses, like the Earth, cause space-time to curve, and this curved space-time is felt by us as gravity. "Gravity, wasn't that invented by Newton, when the apple dropped on his head." I hear you all cry. Newton did come up with a theory of gravitation, which works very well in nearly all scenarios. There were a few problem with it though, and some phenomenon which it couldn't explain (i.e. the precession of the perihelion of Mercury .) One problem with Newton's equation was that they said that gravity was felt instantaneously at any distance from the mass causing it. This didn't fit well with Einstein's new view whereby any information couldn't travel faster than the speed of light, so how could something know instantaneuosly what the gravitational field of a distant body was doing. Einstein's new theory included the fact that the gravitational field was time dependent and stuck to the maximum speed limit it could have. In case you're thinking that this relativity is all just theory and hasn't been challenged or tested then you'd be wrong. Relativity has been tested on many occasions most famously by Sir Arthur Eddington who travelled to Antarctica to observe a solar eclipse. This doesn't mean that relativity is the theory to end all theories, indeed there are things which it can't explain in the quantum world, but it is a very good approximation to the true nature of space-time. So how does this lead to gravitational waves? Well, the fact than masses curve space-time and that this curvature (gravity) propagates at the speed of light, means that you can get ripples (waves) on the surface of this space-time. These ripples are produced by masses that are accelerating. The problem is that these ripples are tiny and very hard to detect. I think that enough to get on with for now. I'll go into a bit more detail about what I do in trying to detect these gravitational waves and their sources on another day.

As for the news of the day from the world of astronomy, Cassini, a probe sent to Saturn to analyse it and its moons, has sent back the first images of the surface of Titan. Titan is Saturns largest moons and is the only moon to be shrouded in a thick atmosphere. The nature of this atmosphere makes in exciting for many reasons, but you'll have to go to this link to find out.

Keep your eyes on the skies.


  1. Nice. But the questions being asked by all right thinking people are: (i) Is Clarkson [last Sunday's Times] correct that the earths gravitational field is fading fast, which will lead to the earth falling over, and find a new axis, transforming Glasgow into a tropical paradise, and making Washington DC somewhat like Rwanda? (ii) What is the most suitable punishment for feminists who claim that E=MC^2 is invalid since it is a product of gender-specific power relations?

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  3. Clarkson was partially right, but slightly misinformed. Every few tens of thousands of years the Earth's magnetic field starts to weaken and then reverses, so the north magnetic pole becomes the south. This doesn't effect the actual spin axis of the Earth, so the Earth wont be falling over with Glasgow gaining new equatorial status. It's true that the climate of the Earth has fluctuated wildly over its history and I for one don't believe current climate change can be conclusively pinned on man-made pollution - it seems more likely that the sun which is going through a rather active period could possibly account for it. The main reason that Britain has had such a varied climate though is the fact that it's moved about the Earth's surface a lot over it's history - continental drift and all that have meant that Britain has resided around the equator in the past.

    A suitable punishment for said feminists is to have there constituant mass turn into energy by being flung into the sun.

  4. You were right, Matt, Titan is bloody interesting. I had never wasted a moments thought wondering about the similarities/differences between planets and other astral bodies. It makes learning about the "nine planets" seem a bit arbitrary when you think Titan would be a perfectly good planet if it was orbiting the sun on its own.