Obviously theoretical but if I took a light year long stick and say pushed a button at the other end would that button be pushed at the same time for me as say someone standing at the button? How does the frame of reference work when physically moving something? And could that “work” as a method of instant communication?
In: Planetary Science
What you’re suggesting wouldn’t even require a super long stick. An ordinary stick would also work for instantaneous communication, if it worked that way.
But it doesn’t. Consider – when you exert your force on the atoms at one end of the stick, how do the atoms on the other side know?
The answer is, when you move the atoms, each one pushes or pulls on the next one. Once the next one has gotten sufficiently out of place, it pushes or pulls on the next one, and so on. Since the electromagnetic force (the force used by atoms to do this) is communicated at the speed of light, that’s the upper limit for how quickly this effect can cascade.
Though in practice, it’s way less. In fact, it’s always the speed of sound in whatever material the stick is made of. Meaning if you tap the stick at one end and someone at the other end waits to hear it, the delay will be the same as the delay for the other end of the stick to move.
The only reason we don’t notice this effect is because most sticks are way too short for a delay from that speed to be noticeable. It’s there, and you’d see it if you used one of those trillion frames per second cameras that some fancy labs have. But it’s beyond what your eyes can detect.
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