1 upvotes, 2 direct replies (showing 2)
View submission: Ask Anything Wednesday - Engineering, Mathematics, Computer Science
If I made a rod of a sufficiently strong material sufficiently long and then had a device that transmitted messages to the other side of it by moving it back and forth by tiny bits, what would prevent this system from being utilized for faster than light communication?
I assume SOMEthing wouldn't work, I've just been intermittently curious about exactly what for the last few years.
Comment by bluesbrother21 at 27/07/2023 at 00:19 UTC
5 upvotes, 0 direct replies
This is actually exactly the definition of the speed of sound in a medium! The speed of sound is really the speed of how long it takes each of those molecules to bump into the ones next to them and convey that information. The speed of sound is generally quite a bit slower than the speed of light, so physically moving a rod doesn't provide much benefit there unfortunately. For reference, the speed of sound in steel is on the order of 5000 m/s, as opposed to 3E8 m/s for light in a vacuum.
Comment by 01l1lll1l1l1l0OOll11 at 27/07/2023 at 00:00 UTC
3 upvotes, 1 direct replies
The rod only moves because each molecule is bumping into the next one down the line. The individual molecules cannot move faster than the speed of light.
You could imagine a compression wave traveling down the length of the rod at the speed of light as each molecule bumps into the next one.