Speeds greater than the speed of light

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Discussion Overview

The discussion centers around the concept of speeds greater than the speed of light, exploring theoretical implications, potential communication methods, and the consequences for established physical laws. Participants examine whether such speeds can be reconciled with relativity and the implications for causality and free will.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants question if speeds greater than the speed of light exist and whether they could replace the speed of light as a universal constant in relativity.
  • One participant presents a fictional dialogue about superluminal communication, suggesting it leads to paradoxes regarding free will and causality.
  • Another participant argues that while calculations can yield superluminal speeds, they are not achievable by objects with mass, emphasizing the importance of the speed of light as a constant.
  • Some participants mention examples of phenomena that appear to exceed the speed of light but assert that none can transmit information, thus preserving causality.
  • There are discussions about the implications of superluminal signaling, including the potential for signaling backwards in time, which raises questions about the consistency of physical laws across reference frames.
  • One participant suggests that accepting superluminal communication would require rejecting fundamental principles such as causality and the uniformity of physical laws in all inertial frames.
  • Another participant notes that theories exist where Lorentz invariance is violated, hinting at alternative frameworks for understanding these concepts.

Areas of Agreement / Disagreement

Participants express a range of views, with no consensus on the existence or implications of superluminal speeds. Some argue against the feasibility of such speeds, while others explore hypothetical scenarios where they might exist.

Contextual Notes

The discussion includes speculative scenarios and hypothetical frameworks that challenge established physics, but the assumptions and definitions underlying these ideas remain unresolved.

  • #91
I'm not sure if my answer would fall under this category. I want to introduce an idea of transmitting information at a speed faster than the speed of light. I am sure somebody has already thought of this...? Basically all you need is a rod which would exceed the distance of the speed that the light travels, say in an hour (just for practical applications). Pushing that rod at one end will result in the rod being moved at the other end instantly, with zero delay. A principal of a Morse code can be applied - a rod can be pushing a button on the other end, thus transmitting information at a speed faster than the speed of light. Obviously there can be a number of problems with this - the rod can simply be pulled by a gravity of a passing planet, or be hit by a meteorite, etc... But the fact of the matter is that, information can be transmitted at a speed greater than the speed of light.
 
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  • #92
No, it can't. Pushing on a rod transmits information at the speed of sound in that material, which is always much less than the speed of light. And yes, your idea has been thought of many many many times on this forum already.
 
  • #93
escogido said:
I'm not sure if my answer would fall under this category. I want to introduce an idea of transmitting information at a speed faster than the speed of light. I am sure somebody has already thought of this...? Basically all you need is a rod which would exceed the distance of the speed that the light travels, say in an hour (just for practical applications). Pushing that rod at one end will result in the rod being moved at the other end instantly, with zero delay. A principal of a Morse code can be applied - a rod can be pushing a button on the other end, thus transmitting information at a speed faster than the speed of light. Obviously there can be a number of problems with this - the rod can simply be pulled by a gravity of a passing planet, or be hit by a meteorite, etc... But the fact of the matter is that, information can be transmitted at a speed greater than the speed of light.
Turns out this idea doesn't work because there are no perfectly rigid objects in relativity (solid objects are just collections of atoms held together be the electromagnetic force, and electromagnetic interactions travel at light speed). If you push one end, it creates a compression wave that travels along the rod at the speed of sound in the material, the other end doesn't move until the wave reaches it. See here for more info:

http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/FTL.html#4
 

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