All Questions
Tagged with spacetime speed-of-light
189
questions
2
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3
answers
444
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Why does $ds^2=0$ for a light signal's worldline in general relativity?
I know that in special relativity, the invariant interval $ds^2$ for a light signal's worldline is $$ds^2=\eta_{\mu\nu}dx^\mu dx^\nu=0$$ where the flat metric $\eta_{\mu\nu}=\text{diag}(-1,1,1,1)$.
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- 4,235
0
votes
2
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51
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Spacetime in photon frame [duplicate]
The time-axis and the space-axis overlap for a photon's world line. Does it mean that photon has no "past" or "future" but only "present" and no "there" but ...
- 199
0
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3
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Why are the coordinate axes of a moving frame $K'$ tilted in spacetime diagrams?
I am currently trying to self-teach special relativity (if relevant, I am still in school). I think that I already have a good intuitive understanding of, for example, time dilation and length ...
- 3,778
8
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6
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Does speed of light being constant make time a derived unit?
This is a paradox I'm trying to understand. I'm not tackling relativity yet. I'm still working through Walter Lewin's lectures on electro magnetism. However, I understand base and derived units pretty ...
- 197
-2
votes
1
answer
98
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What would it be like to go past the speed of light? [closed]
Question #1:
I'm actually surprised that nobody has asked this question before, but theoretically speaking, what would it be like to go past the speed of light? This is actually only one of a few ...
- 183
1
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0
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Which postulates did Einstein really use in his 1905 derivation of the Lorentz transformations? [closed]
Einstein explicitly states in "Zur Elektrodynamik bewegter Körper" that the only two postulates he requires for his derivation of the Lorentz transformations are 1) the principle of ...
- 111
2
votes
7
answers
2k
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Contradictions of explanations for the speed of light [closed]
I've recently started reading the book Biocentrism, by Robert Lanza and Bob Berman, which in its mind-blowing chapters, discusses the perceptions of reality, space, and time. Lanza states that:
If ...
0
votes
2
answers
404
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How the world changes from the point of view of a photon [duplicate]
Imagine a universe without time, or more specifically without the Flow of Time. Everything will be a 2D projection and nothing more. No movement, no interaction, and in other words no Change.
But our ...
- 129
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2
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604
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At what speed does mass warp spacetime?
It is well understood that Einstein’s General Theory of Relativity explains how gravitational effects appear to occur instantaneously at a distance. Mass warps spacetime and so objects simply follow ...
- 9
12
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3
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How quickly does spacetime that's been deformed return to "flat" after the deforming mass moves on?
I'm just curious. I've no physics eductation beyond GCSE. I've searched and searched for an answer but haven't been able to find one. I'm guessing it's at the speed of light??
To elaborate; I'm ...
2
votes
4
answers
180
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How do we know that experimental evidence of special relativity can't be attributed to other, unrelated effects? [closed]
While there are many experimental results that seem to align with the predictions of special relativity--some examples being muons from the upper atmosphere reaching the Earth's surface despite their ...
- 365
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1
answer
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If I use sound wave in Michelson Morley experimental set up will this wave interfare?
We know that light waves do not interfere in the Michelson Morley experiment, and this is where the concept of relativity came. But I can not admit it. We made this experiment on earth. For some brief ...
1
vote
2
answers
1k
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Is the magnitude of the four-velocity vector in spacetime arbitrary?
I know that the squared magnitude of the four-velocity vector is plus or minus $c^2$, but I’m a little confused on whether or not this vector has been normalised arbitrarily, since it is often claimed ...
- 2,123
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Transformation of space at almost the speed of light from different observers
I hear this a lot in documentary movies, where they claim that if you would be able to travel through space near the speed of light, then things would seem squished, the Earth would seem like a 70 ...
4
votes
2
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576
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How much of our universe is outside of our light cone today?
It seems to me that part of our universe is spacelike separated from us. So it's part of the same space as ours but it's outside of our light cone because of the expansion of space. So there could be ...
