Travelling at the speed of light, will this work?

sawcyy · Dec 19, 2013

Picture this: I have an extremely long pole and the end of this pole could touch the Moon, and I'm stood here on Earth holding the other end.

Starting from the left side of the Moon, I only need to turn the pole a tiny bit for the end of it to reach the right side of the Moon.

I hope someone understands what I'm trying to say, but surely that end of the pole touching the Moon would have traveled faster than the speed of light, right?

poldi · Dec 19, 2013

No, because the pole is not a solid object - it is composed of atoms in contact. So as you move your end, that motion must be transmitted from atom to atom along the length of the pole. 400,000 km is a lot of atoms to move like a line of dominos.

We are used to objects (like a broomstick) to move instantaneously because the length of the object is so small.

Thomas · Dec 19, 2013

No physical object can be perfectly rigid. As such, as you move the near end, the pole will bend and no part will ever exceed the speed of light. (That's if it doesn't break.) Indeed, the far end won't even start moving until a considerable time after you move the near end, the movement propagating at the speed of sound in the pole.

3e14159265358979323846 · Dec 22, 2013

<< I hope someone understands what I'm trying to say, but surely that end of the pole touching the Moon would have traveled faster than the speed of light, right? >>

-- No.
First of all, that is impossible for obvious practical reasons.
Secondly, in order to move that pole at the speed of light, you'd need an infinite amount of energy, as its moment of inertia would increase with speed as a consequence of increasing mass.

Travelling at the speed of light, will this work?

sawcyy

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