Could a huge pole that's moved back and forth be a method of FTL communication?
Here's the plan for the proposed system of FTL communication.
A huge pole made of the strongest solid in existence (or whatever solid would work best for this scenario, if no solid exists that would allow for it then assume the pole is made of indestructible Unobtanium) stretches between two space stations on the endpoints of the pole.
The two endpoints are 54.6 million kilometers away from each other (the distance from Earth to Mars), so communication is on a large delay (13 minutes and 48 seconds).
Here's how we get around this:
At Endpoint Two, the end of the pole is suspended in front of a button. The pole is pushed by the station of Endpoint One back and forth to telegraph out a message.
The theory goes that by pushing the pole, the movement of the pole affects the whole pole simultaneously, allowing information to be transferred faster than the speed of light.
Is this in any way plausible as a method of FTL communication? Assume whatever resources and means required are available, and that if need be the pole can be made of indestructible materials.
This post was sourced from https://worldbuilding.stackexchange.com/q/111817. It is licensed under CC BY-SA 4.0.
1 answer
The answer to your question, regrettably, is no, and the counterargument is a classic one.
- The pole is composed of atoms and molecules and particles; it isn't one giant indivisible object.
- Those atoms and molecules and particles can move about, to some extent, even if the pole isn't easily deformable.
- When you push one end of a pole - any pole - you're only directly pushing on some of the constituent molecules. Those molecules then push on other molecules in the pole via intermolecular forces, including electromagnetic interactions.
- Those forces take time to propagate - and they propagate slower than the speed of light. The change in density, in fact, shouldn't propagate faster than the speed of sound in the pole - much less than the speed of light in a vacuum.
Therefore, the pole will be moved at a speed slower than the speed of light.
For more reading, see questions on Physics Stack Exchange (1, 2, 3 and links therein) that talk about the same subject. See also the Ehrenfest paradox, another problem in special relativity about rigid bodies, albeit one with a different resolution.
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