Questions tagged [speed-of-light]
The speed of light is a fundamental universal constant that marks the maximum speed at which energy and information can propagate. Its value is $299792458\frac{\mathrm{m}}{\mathrm{s}}$.
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What would happen if $c$ wasn't constant, but the quotient of $c$ with the scale factor $a(t)$ was? [closed]
I'm supposing there are strong reasons to disregard this scenario but I can't understand exactly what would it imply, and why it is not at all considered in cosmology. What I'm talking about is: we ...
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What is a simple example that contradicts the theory that light (photons) could have a super small mass? [duplicate]
The obvious example is that, to bring something that has mass to the speed $c$ requires infinite energy due to special relativity. But what if a kid asked me "What if light/photos had a super ...
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Does aether not exist or is it simply superfluous?
My question is motivated from studying the null result of the Michelson Morley experiment.
Does the experiment prove that the aether does not exist? Wikipedia says that it was more broadly ...
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Since the speed of light is constant and also the speed limit; would you, in your reference frame, have no upper bound on your speed? [closed]
Let us imagine you are in a vacuum and after having maintained a speed of 0 km/s (standing still) you accelerate to 297,000 km/s (99%). You know this is now your speed because you have a speedometer ...
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Is a photon truly massless? [duplicate]
First of all, I am not a physicist or mathematician, not even a hobbyist but the following statements have always puzzled me:
$E=mc^2$
A photon is a desecrated particle of energy.
A photon is ...
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Why do sound waves travel faster in water than light waves?
If light waves travel faster in air than in water,
why do sound waves travel slower in air than in water?
Is there any difference in how light and sound waves refract when they enter the water?
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Physical meaning of $vx/c^2$ in Lorentz transformation
In Lorentz transformation, this is the formula of time dilation
$$ t' = \gamma \left( t - \frac{vx}{c^2} \right) $$
It can be derivated from the formula of length contraction and be proved ...
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Increasing the view of observable universe
I have read that the maximum observable universe is about 92 billion light years in diameter by measuring the microwave background waves emitted after some few million years ago from the big bang and ...
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Is there a good quantum explanation of refraction? [duplicate]
I'm aware of the classical explanation of refraction which deals with light being a wave that gets "slowed" down while passing from a medium to another. One problem that I have with this ...
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Deriving the Minkowski Metric from homogeneity of space-time and the isotropy of space
In this wikipedia page, it says that one can derive the spacetime interval between 2 arbitrary events from the second postulate of special relativity, together with the homogeneity of spacetime and ...
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What is the problem with this method to measure one-way speed of light? [closed]
I am having a hard time grasping the idea that one-way speed of light is immeasurable. I have watched several videos (including the Veritasium one), read the Wikipedia article, and read some questions ...
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Is this a valid experiment to measure the one-way speed of light?
Consider the following setup. Place a light source at point $A$ and three mirrors at point $B,C,D$ such that the light follows the path $ABCDA$ (refer diagram). Let the distance $AB=CD=2d$ and $BC=CD=...
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Can we get the values of $G$, $h$ and $c$ to be numerically equal if we use a convenient system of measurement?
The speed of light in vacuum is approximated to be $3×10^8\ ms^{-1}.$ But, if we change the units, we can get a different number. For example, it won't be $3×10^8$ if we used $ft\,s^{-1}$ instead of $...
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Velocity of light in different directions [duplicate]
From what I understand, we have not been able to measure unidirectional speed of light. It is said that theoretically it is possible for light to travel at $c/2$ in one direction and infinity speed in ...
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When 'speed of light' changes, is it because the pendulum moves slower or the transition of caesium-133 gets more sluggish or?
I am a layman thinking about the speed of light. Say we measure the speed of light as:
number of Bohr radii the light covers per pendulum swing
number of Bohr radii the light covers per 9192631770 ...
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