Speed of Light & Thought Exp: How to Send Info 186K Miles Instantly

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SUMMARY

This discussion centers on the theoretical implications of sending information over a 186,000-mile rod constructed from ultra-light, ultra-rigid material. The author demonstrates that while a light signal can travel to an observer in about one second, the mechanical signal through the rod cannot exceed the speed of sound in the material, which is significantly slower than the speed of light. The discussion emphasizes that the propagation of momentum through the rod is limited by the electromagnetic force at an atomic level, confirming that no rigid rod can transmit information faster than light.

PREREQUISITES
  • Understanding of the speed of light and its implications in physics
  • Familiarity with the concepts of mechanical wave propagation
  • Knowledge of atomic interactions and electromagnetic forces
  • Basic principles of relativity and information transfer
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  • Research the properties of ultra-light materials and their applications in physics
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Physicists, engineers, and students interested in the fundamental limits of information transfer and the properties of materials in theoretical physics.

Stig Ramone
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I've built a rod 186K miles long, of ultra-light, ultra-rigid material. I am on one end of the rod, and an observer is at the other end (we're both in the near vacuum of space). I want to send a signal to the observer on the other end of the rod signaling whether the Packers have won the superbowl - signal received, they won, no signal, they lost.

The packers win, so I bang my end of the rod with a fast and massive hammer (moving the rod quickly) and instantaneously / simultaneously on my end, there is a great flash of light sent towards the observer.

The light signal reaches the observer in about a second. What prevents the observer from seeing his / her end of the rod move in say 1/2 second? (No fair blaming compression of the rod or mass of the rod).
 
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The signal will propagate in the rod at the speed of sound. There is no way to make this speed faster than the speed of light: on an atomic level, it is the electromagnetic force that propagates the momentum from atom to atom.

This is the 35323. thread about a perfectly rigid rod, and you can find the same answer (and more details) in all of them, there is no point in repeating the discussion again.
 

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