All Questions
Tagged with faster-than-light causality
134
questions
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126
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If the speed of causality changes, could you go FTL?
In the middle of some research, I reached a sort of confusion that I’d like to sort out. In flat space FTL is impossible, because in a Minkowski metric,
$$\mathrm{d}s^2=c^2 \mathrm{d}t^2-\mathrm{d}x^2-...
- 689
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2
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129
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Can a non-local theory be consistent with special relativity?
If there was a non-local theory that explained quantum entanglement correlations, does it follow that it would violate special relativity?
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68
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About information transmission speed [duplicate]
Einstein says information cannot be transmitted faster than light.
Say I set an alarm that ring at 9:00 am. I go to school, and wait until 9:00 am. Then I tell my friends that my alarm rang. If the ...
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25
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Communication via entanglement [duplicate]
For years now i have in my haed a thought experiment for information exchange via quantum entanglement. And i am aware that something must be wrong with it but i can't figure out what it is.
The ...
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5
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1
answer
361
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Stuck on thought experiment about light [duplicate]
Say we have a very long fluid pipe with the width of a few astronomical units, and that this pipe is perfectly resistant to sustain the stress of a perfectly incompressible fluid going through it ...
- 87
1
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1
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849
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Why Going Faster-Than-Light (FTL) Leads to Time Paradoxes? [duplicate]
In this video: https://www.youtube.com/watch?v=an0M-wcHw5A&lc=UgxqC71gefTRIuVubGt4AaABAg.9jI6ltMIeu59jx2P8cpn_z
In the video the following events happen:
A supernova goes off.
Earth sees the ...
- 2,706
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2
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126
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How to show that a if $v > c$ there is a frame which breaks causality in special relativity?
I'm reading about special relativity and looking at the Lorentz transformations.
I'm reading that:
If $v > c$, we can find a frame in which $t_2' < t_1'$, i.e. a signal arrived before being ...
- 937
1
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3
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352
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A simple counter-example to the no-communication theorem? [duplicate]
Let's say Alice and Bob would like to communicate through entangled qubits. They have a machine that generates qubits in the state
$$
| \psi \rangle = \alpha | 0 0 \rangle + \beta | 1 1 \rangle .
$$
...
- 841
7
votes
4
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1k
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Could the speed of causality be (significantly) faster than $c$?
The other day my son (13) asked me whether it was possible that light went very slightly slower than our best measured $c$, and at the same time had a very tiny mass, but we aren't able to measure ...
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Why does an Alcubierre drive, travelling FTL, violate causality, if the universe expanding FTL doesn't?
An Alcubierre drive seems to be plausible as a means to travel faster than light, because
it doesn't move the object itself, but the space around it.
it's said that matter and information can't move ...
- 151
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0
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100
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Can quantum field excitations propagate faster than light?
(Let's assume we are in the Klein-Gordon free field theory)
If we had e.g. a localised field configuration (i.e. field state which is a field configuration eigenstate) at $t=0$. (By localised field ...
- 2,604
-3
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161
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Does "Superluminal travel of non-information" means we already "achieved" superluminal speeds?
From what I understood of Vsauce video talking about "Superluminal travel of non-information," the absence of information seems to travel faster than the speed of light, since we perceive ...
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53
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If gravity can catch up a light photon (speed=$c$) and change its wavelength is it faster than light?
Why can gravity catch up a light photon (speed=$c$) and change its wavelength? How can that be logic although nature shows somehow it is... Maybe gravity has different speed than gravitational waves ...
- 2,255
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1
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95
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How does a scalar potential $V$ that follows $\rho$ momentarily lead to infinite propagation velocity?
$$\nabla^2V(\mathbf r,t)=-\frac{\rho(\mathbf r,t)}{\epsilon_0}\implies V(\mathbf r,t)=\frac1{4\pi\epsilon_0}\int\frac{\rho(\mathbf r',t)}R\mathrm d\tau'$$
I am trying to understand how this equation $...
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15
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Contradictions caused by moving faster than light
There was a Joe Rogan episode with Brian Greene where Joe thinks aliens are watching us because the universe is infinite and there are an infinite number of them. So some of them must be watching.
...
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