# Speed of light travel

## Main Question or Discussion Point

Ok, I have come up with a new theory of traveling at the speed of light. This is totally theoretical and isn't phesable at any level. That aside, here it is.

Make a pole 1000 light years long. Now swing the pole like a bat. The tip of the pole should be traveling millions of times faster than the speed of light.

Again, this is theoretical. You can assume that the pole is strong enough to stand the length without snapping. Lets say the pole's total mass is 1 pound. Would this work? Please explain.

P.S.
Yes, I know about E=mc$$^{2}$$

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You can assume that the pole is strong enough to stand the length without snapping.
No, you can't, which is exactly why your theory doesn't work. Nothing is infinitely rigid.

If you would swing a pole of that length at that speed assuming it won't break, it would bend. It would bend just enough so that the tip would still not travel at the speed of light. You cannot assume that it doesn't bend, because that would imply it was infinitely rigid.
Simply speaking; if you imagine the pole as a large row of atoms/molecules gripping on to each other. If you swing your pole, the atoms nearest to you would swing nearly instantly. But the atoms at the end of the pole would not feel anything; that is, until the 'shockwave' of the sudden movement reaches them. This shockwave travels at the speed of sound in the pole, which is not faster than light.

Also, this isn't a new theory, it is probably one of the most thought up 'experiments' to have something move at the speed of light.

The pole consists of atoms that interact with each other via local interactions. So picture a lattice of atoms such that if you deform the lattice the atoms can move bumping into the neighboring atomes thereby propagating the deformation throughout the lattice.

If you push some supposedly rigid structure, then what really happens is that one side is squeezed and that compression wave propagates to the other end. This happens so fast (at the speed of sound), that it looks like it is intantaneous.

No, you can't, which is exactly why your theory doesn't work. Nothing is infinitely rigid.

If you would swing a pole of that length at that speed assuming it won't break, it would bend. It would bend just enough so that the tip would still not travel at the speed of light. You cannot assume that it doesn't bend, because that would imply it was infinitely rigid.
Simply speaking; if you imagine the pole as a large row of atoms/molecules gripping on to each other. If you swing your pole, the atoms nearest to you would swing nearly instantly. But the atoms at the end of the pole would not feel anything; that is, until the 'shockwave' of the sudden movement reaches them. This shockwave travels at the speed of sound in the pole, which is not faster than light.

Also, this isn't a new theory, it is probably one of the most thought up 'experiments' to have something move at the speed of light.
So the pole would bend so that nothing would be traveling at the speed of light? I also figured that this theory has already been thought of.

So the pole would bend so that nothing would be traveling at the speed of light?
Yes, and there is no way to avoid that without assuming infinite rigidity.

Ok. New question, what is rigidity?

russ_watters
Mentor
So the pole would bend so that nothing would be traveling at the speed of light?
Exactly. It would coil itself into a spiral as the force propagates along the rod at the speed of sound. You can simulate the effect by spraying a garden hose while spinning in place.

russ_watters
Mentor
Ok. New question, what is rigidity?
More commonly known as stiffness. Stiffness is a function of elasticity and moment of inertia (geometry): http://en.wikipedia.org/wiki/Stiffness

Stiffness is a static property. When you apply a quick force, the situation becomes dynamic and the mass factors in. Together, these factors determine the speed of wave propagation (sound) in the object.

interesting

If nothing is infinitely rigid , what if we used an electron positron pair that were entangled and separated them by 10 light years and then rotated that would that work .
or if we had the electron positron pair that were entangled and we rotated one of them counter clock wise and the other one rotated immediately that would be faster than light .
or the Path integral formulation of quantum mechanics where light takes all possible paths and it get there in a time faster than c for certain paths how do we explain this .

DaveC426913
Gold Member
If nothing is infinitely rigid , what if we used an electron positron pair that were entangled and separated them by 10 light years and then rotated that would that work .
You misunderstand what entanglement is. It does not mean they are locked together in any fixed way.

oh i see