Science Questions

Sat, 5th Aug 2006

Part of the show Q&A and What Does Derek Look Like?

Question

David in Shetland asked:

If you have a star which is approximately 860 000 miles across and it explodes like a supernova, would the matter coming from it travel faster than the speed of light. Would a gamma ray burst also travel faster than the speed of light?

Answer

Just to reassure everyone at home, the sun is probably too small to become a supernova; it's more likely to become a red giant, which will kill us all anyway but slightly less violently. But fundamentally no. Nothing can go faster than the speed of light. In a supernova things would get very very close and be very energetic, but according to Einstein you just can't get faster than the speed of light. Things can give the impression of going faster than the speed of light, however. A lovely analogy is that if you were to shine a torch beam at the wall and then move your hand across at the speed of light, the end of the beam would sweep out at a distance greater than the speed of light would have travelled if it were just travelling from A to B. This is because it's on the end of a long beam of light. So you can fool someone into thinking something is going faster than the speed of light, but as far as we know, there's no way we can go faster. As for gamma ray bursts, gamma rays are just a form of light. It's electromagnetic radiation. Light that we can see is just one collection of frequencies or wavelengths of light. Gamma rays are another very short wavelength of radiation. X-rays are a little bit longer than that and then you go through ultraviolet and then visible light and then infrared, microwaves and radiowaves and so on.

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