The impossibility of FTL information

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    Ftl Information
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Discussion Overview

The discussion revolves around the impossibility of faster-than-light (FTL) transmission of classical information, exploring various theories, hypotheses, and principles that support this notion. The scope includes theoretical aspects, implications from relativity, and connections to quantum mechanics.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant seeks a comprehensive index of theories and principles against FTL transmission, mentioning Eberhard's theorem, Special Relativity, and Shannon's information theory.
  • Another participant notes that entanglement requires a classical channel for information extraction, which presents a limitation on FTL communication.
  • It is argued that relativity is the primary reason for the belief that information cannot propagate faster than light, with no independent derivation of an upper bound on information speed in quantum mechanics.
  • A participant highlights that Maxwell's laws predict a specific speed for electromagnetic radiation, asserting that all massless particles travel at the speed of light.
  • There is a confirmation of the claim that all massless particles travel at 'c', indicating agreement on this point.

Areas of Agreement / Disagreement

Participants express differing views on the foundations of the belief in the impossibility of FTL communication, with some emphasizing the role of relativity while others point to the implications of quantum mechanics. There is no consensus on all aspects discussed.

Contextual Notes

The discussion includes assumptions about the relationship between relativity and quantum mechanics, as well as the implications of Maxwell's laws, which remain unresolved. The dependence on definitions of information and speed is also noted.

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I want to make an index over all things against FTL transmission of classical information. All theories, hypotheses, theorems, axioms and rules... you name it.

I'm not looking for explanations or references, only the headlines such as Eberhard's theorem, Special Relativity, and Shanon's information theory.

Of course you can say that it is sufficient to know that to extract the encoded information in entanglement, you need a classical channel to access the correlation between Alice's and Bob's measurements. That's one broken link in the chain, but I want to know all the other links.

I'm not a physicist, but I want to increase my knowledge of quantum mechanics to test the "hidden" hypothesis in my signature.
 
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Relativity is the only reason we believe information can propagate no faster than light. Anything else is just a statement that this or that theory is consistent with relativity. For instance, you can't derive an upper bound to information's speed of propagation in quantum mechanics. However, you can show, as you noted, that entanglement doesn't allow the transmission of quantum information without exchanging signals (which, as we know from SR, can only propagate at or slower than the speed of light) and so quantum mechanics is consistent with relativity. If relativity were falsified, there would be no other independent reasons to believe the speed of light is the maximum speed of information. Of course, relativity theory is the foundation for all of modern physics and one of the most well-established experimental facts in scientific history—so when I say it's the "only" reason for disbelieving FTL communication, that is rather understating the situation a little.
 
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It should be noted that Maxwell's laws of electromagnetism predict a VERY specific velocity for electromagnetic radiation (light). More specifically the "speed of light" is really the "speed of massless particles". To my knowledge (and please correct me if I am wrong - anyone), ALL massless particles travel at 'c'.
 
snatchingthepi said:
To my knowledge (and please correct me if I am wrong - anyone), ALL massless particles travel at 'c'.

You're correct.
 

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