Tuesday, 2 February 2010

Time

Last night we watched a programme about time which we'd recorded, though I can't actually remember when it was transmitted. It was the second of a series by Professor Michio Kaku and was fascinating generally, but unexpectedly satisfying in one particular respect.

I don't remember being taught any Einsteinian relativity when I was at school, but I do know that not long after that I was aware that time was said to slow down as you approached the speed of light. Which is to say that if you were in a space ship travelling that fast, time would appear to proceed normally, but a hypothetical viewer from outside would see time inside your spaceship proceeding more slowly. And I'd heard about space shuttle experiments where time on the shuttle had trailed behind our time by a few seconds, but it wasn't all that impressive.

However, last night we saw Michio Kaku at the top of a mountain in the alps, talking about a really impressive demonstration of the effect.

Muons are sub-atomic particles produced when cosmic rays hit molecules of air in the upper atmosphere. They travel at close to the speed of light, but are very unstable and decay in a very short time, so you should not expect to see them more than a few hundred metres from the point at which they were created.

At the top of this alpine mountain was a sensor counting muons, and it was counting loads of them, despite the fact that it was several kilometres from the layer in the atmosphere where the muons were being created. It seems strange that we are able to count muons much further away from their point of origin than it's possible for them to travel before decaying.

Then to the rescue leaps Einsteinian relativity! The muons are travelling at close to the speed of light, so they experience time much more slowly than we do, and this is what allows them to travel so far.

And I think that is soooooooo neat, where neat in this context implies an intersection between smart and cool and cute!

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