I came across this really interesting, and famous, paradox the other day while reading Wheeler’s Spacetime Physics; it’s called the pole-barn paradox. What it basically says is this: You have a 20 metre long (true length) pole in your hand, running into a 10 metre long (true length) barn, at such a speed that your friend standing just outside the barn sees the pole contracted to 10 metres. So it seems to him that you, along with the pole, can be entirely contained within the barn. But, to you, the barn seems contracted to 5 metres, and so, there would be no way you, along with the pole, could be contained within the barn. Puzzling, eh?
To make the question more clear, let us look at it this way: If someone standing outside the barn closes the back door (the one on the right), just at the moment the pole’s front end merges with the back door, the entire pole seems to be contained within the barn momentarily (before you crash! :P). Our question is, how is it that to you (running with the pole) it seems completely impossible?
I’ll keep you guys thinking about it ;)
Will be back with a detailed discussion about the resolution of this intriguing paradox… till then, Ta-Ta!