Can Light Travel Faster Than Its Speed in a Vacuum?

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Discussion Overview

The discussion centers around the speed of light, particularly whether it can travel faster than its established speed in a vacuum, and how various media, including dark matter, may influence this speed. Participants explore theoretical implications, experimental considerations, and the nature of light's interaction with different substances.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants note that the speed of light in a vacuum is 299,792,458 m/s and is slower in denser media like glass or water, questioning the effects of dark matter on this speed.
  • Others assert that nothing can exceed the universal speed limit, which is currently understood to be the speed of light in a vacuum.
  • A participant mentions that the invariance of the speed of light under General Relativity assumes no media, suggesting that a slightly slower speed of light in nearly empty space would be significant.
  • One participant argues that while space is not empty, its low density has minimal effect on light speed, citing the dispersion of light in denser media as evidence.
  • Another participant claims that if a particle like a photon travels at the speed of light, it must have zero mass, questioning the existence of particles with negative mass.
  • Concerns are raised about the interaction between light and dark matter, with one participant suggesting that if dark matter were dense enough to affect light speed, it would have been detected by now.
  • Another participant asserts that dark matter does not affect light propagation, emphasizing that if it did, it would not be classified as "dark."

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the influence of dark matter on the speed of light and the implications of light's behavior in various media. The discussion remains unresolved with no consensus reached.

Contextual Notes

Participants reference various assumptions about dark matter's properties and its interactions with light, as well as the implications of light speed in different contexts. There are unresolved questions regarding the nature of dark matter and its potential effects on light propagation.

goldust
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Speed of light through vacuum is 299 792 458 m / s, but is slower through a denser medium like glass or water. We now know vacuum is not empty as previously thought, but has all kinds of new material in them like dark matter. Has any experiments been done to determine how fast light can be thorough a medium that has no dark matter in it? Would it be intuitively faster than the currently measured speed of light through vacuum?
 
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Nothing is faster than universal speed limit, which as far as is currently known is also the speed of light in a vacuum
 
The speed of light is invariant under GR, which assumes no media whatsoever. What would be remarkable is detection of a slightly slower speed of light through nearly empty space.
 
Although space is not empty, the density is very low, and has little effect on the speed of light. How do we know this? For one thing, media don't just slow down light, they disperse light, causing different colors to separate. If space were fairly dense, then we would see that the images of faraway galaxies were temporally and spatially shifted by color.
 
Nope.The Speed Of Light Now Known Is The Fastest.Because,
If A Particle ( Eg.Photon) Moves At The Speed Of Light ( i.e The Speed Of Light In Vaccum(299 792 458 m/s), Its Mass Would Be Zero . So Is There Anything With A Mass Of Value With A Negative Sign (eg.-12kg)?So The Speed Of Light Now Known Is The Fastest Speed That A Matter Can Attain At Its Peak.

S.I.S ;)
 
goldust said:
Speed of light through vacuum is 299 792 458 m / s, but is slower through a denser medium like glass or water. We now know vacuum is not empty as previously thought, but has all kinds of new material in them like dark matter. Has any experiments been done to determine how fast light can be thorough a medium that has no dark matter in it? Would it be intuitively faster than the currently measured speed of light through vacuum?

This about this: if dark matter is dense enough that it affects the speed of light, we would have discovered dark matter already by now!.

Secondly, your description of light interaction with dark matter implies that there is an electromagnetic interaction between light and dark matter. Most of the models for dark matter candidates based on what we know about dark matter has no such interaction. Dark matter's main channel of interaction is via its gravitational presence. So "your dark matter" here will be very different than what we know about dark matter.

Zz.
 
Dark matter does not affect light propagation. If it did, it wouldn't be dark.
 

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