Speed of Light Thought Experiment

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Discussion Overview

The discussion revolves around a thought experiment concerning the implications of rotating a long object to a speed that could theoretically exceed the speed of light. Participants explore the physical limitations and consequences of such a scenario, including material properties and the transmission of motion through the object.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the outcome of rotating a lengthy object at speeds that could exceed light speed, prompting a discussion on the physical implications.
  • Another participant asserts that information about motion in the object is transmitted at the speed of sound in the material, suggesting that attempting to exceed this speed would result in deformation rather than actual motion at light speed.
  • It is noted that the torque required for rotation increases with speed, implying a barrier similar to the linear speed limit of light.
  • Concerns are raised about material stress, with one participant stating that it becomes infinite as speeds approach light speed.
  • A participant proposes that if the rod is not rigid, the far end will not move simultaneously with the near end, supporting the idea that information travels at the speed of sound in the material.
  • One participant expresses a desire to learn more and correct misconceptions, indicating an ongoing journey of understanding.

Areas of Agreement / Disagreement

Participants generally agree on the physical limitations imposed by the speed of sound in materials and the implications of material stress, but there is no consensus on the specifics of the thought experiment or the nature of the motion involved.

Contextual Notes

Limitations include assumptions about the rigidity of materials, the definitions of speed in different contexts, and the unresolved nature of the thought experiment's implications.

Who May Find This Useful

This discussion may be of interest to those exploring concepts in physics related to motion, material properties, and the theoretical limits of speed in physical systems.

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What would happen if you were to construct a massively lengthy object (Suppress your inner perv for a moment please) and rotated it so that the part of the object farthest away from you would theoretically move faster than light?
 
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This is a very common misconception frequently brought up here. Any information concerning the motion of end A is transmitted to end B at the speed of sound in the material. If you make an effort, say with a sledge hammer, to move the stick at a speed faster then sound in the material you will simply deform the end while the vibrations created will travel away at the speed of sound.

BTW, the speed of sound in materials is MUCH smaller then the speed of light.
 
...For rotating objects, you'll find that the torque required to get it to rotate keeps increasing as the rotational speed increases, and you'll never get to C. It's the rotational equivalent of the linear speed 'barrier'.
 
Also the material stress in the rod becomes infinite.
 
Ok, so we attempt to spin a long rod. If the rod is not rigid then if we push the short end to hard the longer end will not stay straight but will bend. This leads me to the conclusion that the far end of any rod will not move at the same time as the short end. I well bet (with no real proof) that the wave of information moving to the far end of the rod will travel at the speed of sound in the rod. If you attempt to accelerate the short end faster then some value determined by the material the rod will either deform or break.

example, http://www.physicscentral.com/experiment/physicsathome/images/towers-falling.jpg"
 
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Thanks for the answers. I'm not incredibly well read but am steadily learning and hopefully such misconceptions will be erased from my world view as I gather more knowledge. :)
 

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