Could the speed of light be variable?

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Discussion Overview

The discussion centers around the concept of whether the speed of light could be variable, exploring both theoretical implications and practical observations in different media. Participants examine the speed of light in various contexts, including its behavior in substances like water compared to a vacuum.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Some participants propose that the speed of light varies depending on the medium, as it travels slower in substances like water compared to a vacuum due to the refractive index.
  • Others argue that while the speed of light in a vacuum is considered constant according to current theory, there are hypotheses suggesting it may have varied over time, though evidence for this is limited.
  • A related question is raised about whether the speed of light through water could be exceeded by an object traveling through water, questioning if the constant 'C' changes for relativistic equations in non-vacuum conditions.
  • One participant references Cherenkov radiation as a phenomenon related to the speed of light in different media.

Areas of Agreement / Disagreement

Participants express differing views on the constancy of the speed of light, with some supporting the idea of variability in different media and others focusing on the theoretical constancy in a vacuum. The discussion remains unresolved regarding the implications of these perspectives.

Contextual Notes

Limitations include the dependence on definitions of speed in various media and the unresolved nature of the evidence regarding historical variability of the speed of light.

Dremmer
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Could the speed of light be variable? (not always travel at the same speed)
 
Science news on Phys.org
The speed of light (in current theory) in a vacuum is constant. However, some possibilities have been raised that it might have varied over time, but the evidence is at best scanty.
 
This is a related question...

Could the speed of light through water be exceeded by an object traveling through water. In other words does the C change for all of the relativistic equations if the experiment is conducted in a medium other then vacuum?
 

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