Tag Info

Could the speed of causality be (significantly) faster than $c$?

The speed of light is routinely slowed in dielectric material and also in high gravitational fields. This is changing the dielectric constants of space increasing the capacitance per distance, which ...
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1 vote

The speed of light in vacuum (but which speed?)

Einstein used the constant $c$ that occurs in Maxwell's equations for electricity and magnetism, the idea being that Maxwell's equations should remain true under any change of inertial coordinate ...
• 279

The speed of light in vacuum (but which speed?)

In a vacuum an electromagnetic wave has the same phase and group velocities, so the speed of light in a vacuum is unambiguous. If the light is propagating through some medium this is generally not ...
• 357k
Accepted

The speed of light in vacuum (but which speed?)

Calling the constant $c$ the "speed of light" is something of a misnomer. In special relativity, time and space are taken on equal footing. To achieve this in a physical sense, one needs a &...
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The speed of light in vacuum (but which speed?)

For light in a vacuum, those speeds are experimentally as close to the same as can be measured. Based on this, and other experimental results, the theory assumes they are the same.
• 21.2k

Inconvenience of speed of light in optic fiber

This is really engineering more than physics. Vast resources have been expended developing methods of purifying glass to make optical fibers with very low loss. This allows us to have fibers that lose ...
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Superluminous scissors with a twist

There are actually 4 possibilities. (I think #3 and #4 are most likely) The scissors at the far end moves faster than light. The scissors bend. The scissors break because you cannot defy the laws ...

Is the meter relative to time?

I was reading a physics book and I found that the meter is the length that light travels for an amount of time, so since time is relative near the speed of light, does it mean that the meter will be ...
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Is the meter relative to time?

The short answer is that a meter is always a meter by definition. The modern definition of the meter in terms of the speed of light doesn't change that. A longer answer: One of the lessons from ...
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Is the meter relative to time?

It depends. Suppose you are carrying a meter stick with you. When you are at rest with respect to this meter stick, its size is always the same. It doesn't matter if you're near a black hole, near the ...
• 21.4k
Accepted

Understanding the math of the Michelson-Morley experiment

Say that light relative to the aether at rest moves at speed $c$, and say that the ether is moving in the $x$ direction at speed $v_E$. Let's consider a simplified version of the Michelson Morley ...
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Why is the speed limit of special relativity $C$ equal to the speed of light $c$ and why must there be only one?

(I wanted to write this as a comment but it became too long and I would consider my post as an attempt at an answer.) First, it's not clear what you're willing to accept as an acceptable starting ...
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Why is the speed limit of special relativity $C$ equal to the speed of light $c$ and why must there be only one?
There is no a priori reason that the invariant speed (your $C$) must equal the speed of light (your $c$). In fact, it is still possible that these two speeds will eventually be found to be unequal. ...