Out with a bang
The December issue was my favourite for some months, because it contained more physics than usual. However, I had a question regarding the Big Bang. In any explosion, all the exploding material, mass and energy, travels outwards from the origin, leaving a continuously expanding vacuum at the centre, which by now would add up to a mind-bogglingly enormous empty volume in interstellar space. So where is it? Unlike the Higgs boson, it shouldn’t be hard to spot, surely?
Mark Farren
The Big Bang is often likened to an explosion, in the sense that a lot of stuff moved apart quickly. But it wasn’t literally an explosion, and the metaphor rapidly falls apart. In an explosion, you have a centre where the combustion happens, and things move away from that centre at high speeds. But with the Big Bang, there is no literal ‘bang’, and there’s also no centre: the Big Bang happened everywhere at once. It’s hard for us to picture, but a metaphor that cosmologist
Marcus Chown uses is raisins in a fruit cake. As the cake rises in the oven, all the raisins move away from all the other raisins – they don’t radiate out from the centre of the cake. Sara Rigby, online assistant