Why does light travel at light speed?

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Discussion Overview

The discussion revolves around the nature of light and why photons travel at the speed of light (c). Participants explore various aspects of this phenomenon, including the properties of photons, the implications of relativity, and the fundamental principles governing the speed of light. The conversation touches on theoretical, conceptual, and mathematical reasoning.

Discussion Character

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

Main Points Raised

  • Some participants wonder if there is a force that pushes photons or if their speed is an inherent property of light.
  • One participant asserts that photons interact with the sun regardless of their origin, suggesting that their speed is simply a characteristic of light.
  • Another participant questions why photons are unique in traveling at c, proposing that their lack of rest mass might be a contributing factor.
  • There is a claim that massless particles, not just photons, can travel at c, although the status of neutrinos is debated.
  • One participant discusses the relativistic energy equation and its implications for massless particles, stating that the speed of a massless particle is c.
  • Another participant expresses confusion about the constancy of light speed relative to observers moving towards or away from a light source, suggesting that logic implies light speed should vary with the observer's velocity.
  • Some participants explore the idea that the universe may have multiple invariant scales, questioning what other physical quantities might be invariant alongside speed.
  • There is a discussion about the need for a conversion factor to relate time and space components in four-vectors, leading to the conclusion that this factor must be a speed.
  • One participant suggests that it is impossible to accelerate a massive particle beyond c if it starts below that speed, raising further questions about the nature of speed in the universe.

Areas of Agreement / Disagreement

Participants express a range of views on the nature of light and the implications of relativity, with no clear consensus reached. Disagreements exist regarding the properties of photons, the implications of masslessness, and the interpretation of light speed in relation to observers.

Contextual Notes

Some claims rely on specific interpretations of relativistic physics and the definitions of mass and speed, which may not be universally accepted. The discussion includes unresolved questions about the nature of light and the implications of various physical theories.

  • #61
Clarification for bob: if c had an infinite velocity in our reference frame, the universe we observe would instantly collapse. That is what the Maxwell equations demand, and what Einstein realized when he made 'the biggest mistake of his career' by adding the cosmological constant. That Einstein dude turned out to be pretty smart.
 
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  • #62
I am a bit wary of a cosmological constant. First of all Einstein introduced it because he did not want an expanding universe, then he took it out, now its back again.
Could the electromagnetic force travel at any speed faster than light speed, say 200,000 mps and still keep within the parameters of the energy fluctuations allowed without destroying the balance of the universe?
 
  • #63
Blueplanetbob said:
I am a bit wary of a cosmological constant. First of all Einstein introduced it because he did not want an expanding universe, then he took it out, now its back again.
Ah, but look at why it's now back! Because there are good observations which are consistent with cosmological models with this constant in them (OK, it's the other way round, but the observations are what triggered the renewed interest). Also note that it's only one proposed means of accounting for the observations ... you could make a case that it gets more attention than other means because of its pedigree (and you'd've been right in the first few years; now it's possible to argue that it does fit the data better than the alternatives ... stay tuned for another decade or three!)
 

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