To take a specific example, at 90 per cent of the speed of light lengths are shrunk by more than half, and clocks run at less than half speed. These effects are, however, entirely relative to the observers concerned. A 'superwitch' travelling with the broom handle at such a speed relative to the ground would notice nothing unusual about either its length or the rate of passage of time. For such an observer it would be the objects that are fixed to the ground that are contracted, with clocks on the ground seeming to run slow compared with a clock attached to the flying broomstick. Thus when observers are in relative motion each sees the other's length contracted and the other's clock running slow.
Blogger Comments:
To be clear, travelling at 90 per cent of the clocks run at less than half speed relative to the clocks on the ground. For the fast-moving observer, the clock appears to run normally, but it is the clock on the ground that appears to run faster by comparison. This is why the twin travelling at high speed ages more slowly than the twin on the ground; see the twin paradox.
In other words, in this thought experiment, the fast-moving observer sees the other's clock running fast — not slow — and it is only the observer on the ground who sees the other's clock running slow. And, a faster clock here means contracted time intervals, whereas a slower clock means expanded time intervals (between each 'tick').
By the same token, the fast-moving observer sees the other's length expanded — not contracted — and it is only the observer on the ground who sees the other's length contracted.
No comments:
Post a Comment