All Questions
Tagged with information causality
26 questions
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2
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123
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Is it possible to transmit information from within a black hole via the momentum of a rocket activated after passing the event horizon?
Imagine a simple, non-rotating black hole and a massive rocket that is free-falling past the event horizon of the black hole, linearly towards the singularity. The rocket is massive enough that it ...
- 671
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0
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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 ...
- 59
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0
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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 ...
- 1
7
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4
answers
2k
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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 ...
- 209
-3
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2
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164
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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 ...
- 275
16
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4
answers
3k
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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.
...
- 931
0
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1
answer
43
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When the Earth suddenly stops pulling [closed]
Let's say the Earth stops attracting objects to itself all of a sudden. So, I was wondering what would happen to a person standing on the surface of the Earth? (Neglect the effect of the rotation of ...
3
votes
2
answers
381
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Proof for impossibility of FTL Signals
Is there is formal proof for the fact that signals must always travel at a speed less than the speed of light in a vacuum?
I understand that special relativity dictates that for massive particles to ...
- 183
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1
answer
182
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Time-orderings for the time-like and light-like vectors cannot be altered
My question concerns the time-ordering for the time-like vector between two space-time points:
$$ (t_1,\vec{x_1}) \text{ and } (t_2,\vec{x_2})$$
Is it correct to claim that:
For a time-like vector, $(...
- 4,376
1
vote
2
answers
71
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Moving a 2x2 the length of the solar system [duplicate]
If we were able to push a 2x2 piece of wood that is the length of our solar system, how would it behave? My colleague says since its all part of the same molecular structure, the whole piece of wood ...
- 11
0
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0
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47
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Speed of light vs Tug of war [duplicate]
Suppose there's a "theoretical rope" that's 299 792 459 meters long in empty space.
The speed of light is 299 792 458 m/s.
Is it possible that if the rope is "tugged" on one end, ...
- 173
-1
votes
2
answers
213
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Exceeding the speed of light by means of a shadow, will we ever be able to transmit information faster than light? [closed]
I bumped into this:
Can a shadow move faster than the speed of light?
while trying to see if I could find out anything about what I'd been thinking for 2 years now.
Bear with me here, cause I'm only ...
- 9
0
votes
3
answers
73
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Information propagating at less than the speed of light
Which speed does information propagate at in a medium?
For example, if we live in a pool which is one light-year cube and somebody dewaters of the pool from an observer which is at 1 light-year ...
- 1
8
votes
4
answers
2k
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No FTL information implies no FTL travel?
The general consensus in the scientific community is that it is impossible to transmit information faster than light.
There is also speculation that it might be possible to open wormholes or travel ...
- 191
33
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9
answers
3k
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What precisely does it mean for "information to not travel faster than the speed of light"?
This is something that's been bothering me for a while. The way we usually first hear about causality is that "nothing travels faster than $c$". But then you learn that phase velocities can ...
- 3,733
0
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2
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287
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Causality (time travel) question
This bugs me, and I don't know if I would be able to understand reasoning in answers on this thought experiment.
Let say observer is on the earth in this example. Let him use quantum entangled pair of ...
1
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0
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60
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How come no information can travel faster than light when we can measure a black hole's mass? [duplicate]
So I learned about the Schwartzchild radius, which is the radius of an object's event horizon. But how we define an event horizon is that it's a region of space where the gravitational acceleration ...
4
votes
3
answers
944
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Why group speed can contain information but phase speed can't?
I was watching sixty symbol on YouTube about reflective index and learnt that it is the sum of all the speed of light or phase speed that appears slower than speed of light in the medium, and also the ...
- 13.1k
2
votes
2
answers
296
views
Superluminal clarification and FTL information transmission
Sixty Symbols recently released a video about superluminal motions (https://youtu.be/IsEDigUHsOQ).
This sparked a question I hadn’t considered before – although, I’m fairly sure it must be rather ...
- 209
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votes
3
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291
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Why cant information and forces travel faster than the speed of light when they aren't mass?
I understand why the speed of light is a constant in all reference frames, and the reason behind why the mass of an object increases as it approaches the speed of light.( Since the added energy has to ...
- 1,787
3
votes
2
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349
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Is entropy maximized or increasing?
Do different real processes involve different rates of change of entropy? (Is the rate of change of entropy constant with time throughout all regions of space, or perhaps in other words, constant with ...
- 455
4
votes
3
answers
2k
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The speed of information
Does this expression have any rigorous meaning?
Intuitively ,I feel that information about an event or a system in my environment propagates to me at a certain "speed".
Does this correspond to ...
- 117
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3
answers
2k
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Sending information faster than light
If I could ever send my friend any information faster than light it would violate causality. If he just guesses the information and acts on it before he could ever receive it, everything is fine. What ...
- 303
19
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5
answers
5k
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Why does the speed of light totally prevent instantaneous information exchange?
Based on the classical light-cone approach it's easy to see you can't transmit information faster than $c$ but why does the speed of light (as far as I know) treat information transmission in this way ...
- 1,006
1
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2
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160
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Does information paradox in the Many Worlds interpretation cause a problem? [closed]
I'm taking a philosophy of time travel class. In one of the lectures, the teacher was discussing problems with the Many Worlds interpretation. He talked about how since anything that can possibly ...
- 111
26
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2
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5k
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What do physicists mean by "information"?
On the question why certain velocities (i.e. phase velocity) can be greater than the speed of light, people will say something like:
since no matter or "information" is transferred, therefore the ...
- 1,754