Kris
Guest
5/21/2006
23:59:08
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 Subject: A short question about SR
IP: Logged
Message:
I set up this 'thought experiment' whose conclusion I still cannot find. Imagine a 'skateboard' of proper length L travelling at a high velocity on a fjord, and there is an approaching crevasse of proper width less than L.
Since the skateboard is travelling at a relativistic velocity the crevasse looks even narrower. Now here is the 'catch'. The skateboard is fitted with some device that senses orientation and will not allow it to fall EXCEPT if the skateboard is level (In its own frame of reference. You could imagine some complicated system of gyroscopes or accelerometers connected to a few small rockets that will reorient the skateboard horizontally immediately.)
Hence, in the skateboard's travelling frame it will surely not fall through the crevasse. So far so good. In the crevasse's frame of reference, however, the skateboard's length will appear significantly contracted to less than the crevasse width. Furthermore, there is enough space for the skateboard to fall through horizontally, so the rocket system will not be required, and the skateboard should appear to fall.
How would you reconcile the two views? I suspect that it might have to do with the notion of 'horizontality' in each respective frame. Or perhaps simultaneity, as usual...
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