Friday 26 December 2008


Galaxy Zoo is often described as "like a game": not knowing what the next galaxy will be is one of its addictive features. Well, now Universe Today reports that scientific gaming has gone a step further.

The game is aimed to study mathematical models of gravitational waves. Albert Einstein described the Universe as being like a rubber sheet, which was bent by any object with mass. Imagine a marble being rolled along this rubber sheet. It dents the sheet itself, of course; but its path would be bent by the hollows made by other massive objects. If it comes too close to one, it will end up going round it in circles; any closer and they'll collide and end up in one hollow, all the deeper through both their masses.

Russell Stannard describes this as a much better model for the way gravity works than thinking of gravity as a force. A large object and a small object, such as the Moon and an astronaut, will end up circling the Earth in the same path at the same speed - which means the Earth's force, gravity, has to pull much harder on the Moon. How does it know how much harder to pull, and why would it choose to do that? Thinking of gravity as simply being the shape of space, and not a force at all, makes things far simpler.

Anyway, Einstein also predicted that, sometimes, ripples would travel through the fabric of spacetime, much as they do across the water - or across a sheet if you stretch it and start bouncing it around. A case of this would be two black holes colliding. I can't make out from the article exactly what the game involves, but it looks like lots of exciting simulations of this scenario which can be run and the data gathered gradually.

(Image from the BBC website.)

The book that changed my life, "BANG!", stated the following two years ago:

"to detect the effort . . . formidable precision is required - equivalent to measuring the length of a mile-long rod to an accuracy of less than the size of a single atomic nucleus. Perhaps the best hope lies in using satellites, and various projects are being planned. Detecting gravitational waves would enable us to probe a whole new set of situations and objects, including some of the rarest phenomena in the Universe.

. . . Although we have not yet detected gravitational waves, there is compelling evidence for their existence in the form of a system, unique in our experience and known as the double pulsar, in which two compact neutron stars orbit each other . . . these two pulsars are spiralling in towards each other, which means that energy must be being lost from the ssystem; the amount being lost corresponds quite well to the predicted energy that would go into gravitational waves - but until we detect the waves themsevlves, we cannot be sure that we have the answer."

People seem to have a fascination with black holes from an early age - as I discovered when I gave a talk to a class of year 6 pupils, intended to last 10 minutes, and ended up being nearly an hour, largely because they had so many excellent questions about these intriguing objects. Perhaps it's their mystery - that they give nothing up - that fascinates people. Or perhaps it's their terrifying power and invincibility. Whatever it is, they really spark people's imagination. "Black Holes and Uncle Albert" has a brilliant passage describing a girl's near-death when she allows her imaginary spacecraft to go too near one, and "Empire of the Stars" begins with a thrilling description of spaghettification. In any case, I wish I had a PlayStation 3 for the mere fun of the game, as well as the science, and I bet this will be a real hit even in the middle of this recession.

(Update: Some pretty amusing comments here!)

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