Pat, Lowestoft asked:
If they test atomic bombs again could it throw the Earth off its axis?
Dave - It shouldn't do anything particularly big to the Earth's axis. Although a nuclear bomb is very big, very powerful. It can release power equivalent to millions of tonnes of TNT. Compared to the weight of the Earth that's not very much energy. The amount of energy you'd need to flip the Earth over would be absolutely immense. It's just not enough energy there and also in order to do that sort of thing you'd have to build a rocket. You'd have to build a huge nuclear-powered rocket, throw a load of stuff into space and produce enough momentum to actually give a kick to the Earth which a nuclear bomb doesn't do. When a nuclear bomb goes off nothing actually leaves the Earth. It just lifts things up and lets them fall back down again.
Chris - I think probably the best evidence is that if you look at the power unleashed in the boxing day tsunami which was an enormous amount of energy – on par with something nuclear, I would say. This did make the planet jitter a tiny amount. It didn't actually destabilise the orbit.