"Faster-than-light", also known as superluminal velocities, refers to any sort of travel at a speed greater than the speed of light. Prohibited in mainstream physics due to the Special theory of relativity.

learn more… | top users | synonyms

23
votes
5answers
5k views

Could gravity accelerate light? [duplicate]

Gravity causes anything with energy to accelerate toward the source. Black holes, for example, have such strong gravity that they pull in light and don't let any escape. But can acceleration still ...
-1
votes
1answer
114 views

Take advantage of time dilation or create a warp drive? [closed]

It is my understanding that time dilation slows down perceived time relative to the outside of a given vessel as it approaches the speed of light. Does that not mean that the inhabitants of said ...
2
votes
2answers
108 views

Backwards in time?

A “Universe Today” article titled “Galaxies Are Moving Away From Us Faster than the Speed of Light” prompted the following question, which the author of the article was unable to answer: “Would such ...
1
vote
1answer
113 views

Can we prove absolutely that FTL = causality violation

I've been wondering about this for a long time. Given that special relativity is normally true, can we still prove that causality violation must occur if FTL is found? All proofs I can find, depend on ...
2
votes
2answers
152 views

Does the uncertainty principle imply the existence of particles that exceed the speed of light?

The uncertainty principle allows for the creation of virtual particles (with non-zero mass) that exist for very short durations. This allows empty space to have particle pairs that pop into existence ...
-1
votes
1answer
71 views

Speed of light, velocity limits and superluminal travel [closed]

I know that a massive object cannot reach the speed of light as it would require an infinite amount of energy to do so (though my knowledge of the reasons of this phenomenon is very limited). ...
0
votes
0answers
139 views

Is velocity of de broglie wave faster than light? [duplicate]

In one of the properties of matter waves is that it can travel faster than light. In my test I was asked to prove this. There are derivations of both can travel faster then $c$ cannot faster than ...
2
votes
2answers
130 views

Speed of light in zero-index material or similar

I've always thought that the maximum speed of light is achieved in vacuum. Now in some "popsci" news there are references as if there are mediums where light can go faster. Are these zero-index ...
1
vote
4answers
305 views

Why can't anything travel faster than light?

It is a well known fact, that nothing can travel faster than light. I have discussed that fun fact numerous times with my 8 year old son. One day he asked "why?", and I realized that I didn't know the ...
0
votes
1answer
105 views

Tomorrowland movie and tachyons? [duplicate]

Would be possible if tachyonic existed to send info to the past or see the future? since the tachyons according to special relativity could travel to the past? i have searched in wikipedia and the ...
0
votes
1answer
87 views

How can light cross $c$ in the given hypothetical experiment? Where I am wrong? [closed]

There is a concave mirror, which has somehow maintained the speed $\frac{c}{2}$ toward west ( for instance) , and there is a light wave or you can say a ray of light is moving in N-E direction. So we ...
0
votes
1answer
125 views

Quantum entanglement and information transfer

I know it was stated many times that information transfer using entanglement is not possible and I am most probably wrong but I would be glad if you can at least point me to where I am mistaken. If ...
19
votes
1answer
4k views

Physics behind this neutrino-related joke

In the comment section of a newspaper article reporting on the 2015 Nobel Prize for Physics, which was awarded for work on neutrino oscillation, I found the following joke: "I'm sorry, we do not ...
0
votes
2answers
69 views

Does my interstellar pole thought experiment violate casualty? [duplicate]

I have heard that it is impossible to send a signal faster than light. However, what if I had a long (4.5 light years) pole and placed one end on Earth and the another end around Proxima Centauri. If ...
0
votes
2answers
118 views

Can less gravity speed up time? [closed]

We know more gravity slows down time per Einsteins Theory of Relativity. However will a significantly less gravitational pull speed up time? Or is "our time" aka earth standard of time the fastest ...
0
votes
3answers
100 views

Equal and opposite reaction at light speed

My knowledge of physics is very limited. And this question is only really to help me put to rest a question i have had for some time. I would like the answer to be a simple one as i am not really in ...
-5
votes
2answers
140 views

How Energy can be real if C² isn't real? (E=MC²) [closed]

So, Nothing can go faster than speed of light. How come the Energy be real if C² isn't real? Is it even allowed to square C? How can we use C² as a constant as it has not representations in ...
1
vote
2answers
96 views

Would a tachyon be able to escape a black hole?

Or at least escape from a portion of the hole inside the photon horizon?
-1
votes
1answer
49 views

What do you see if you directly observe your destination while in warp? [closed]

Say you are traveling in a warp bubble towards Earth from 10,000 lightyears away with an ETA of 24 hours. On the front of your ship, you mount a high powered telescope pointed directly at Earth (your ...
0
votes
1answer
57 views

Speed of entangled particle changes [duplicate]

If two particles are entangled at a distance of light years, does changing one affect the other instantaneously, or does it take years to occur? What gives us the answer to this question?
-4
votes
2answers
73 views

Can light travel with a speed less than its speed at same time?

I know that the velocity of light with respect to anything is constant ($c$) . What, then, is velocity of light with respect to light?
8
votes
3answers
224 views

Alongside a light ray (in another medium)

It is a said fact that the speed of light is insurmountable. But can the validity of this fact be questioned in another medium? If I pass a beam of light in, say water (here the light speed is ...
3
votes
1answer
66 views

Observable Universe from two different perspectives

My layman understanding is that the universe is much bigger than that we can observe however due to the cosmological constant the observable universe is the matter etc. that is not moving away from us ...
2
votes
4answers
3k views

“FTL” Communication with Quantum Entanglement? [duplicate]

Can quantum entanglement make sending a message, whether audio, video, or even Morse code, instantaneous between two points (faster than it could travel normally at the speed of light)? Let me first ...
3
votes
4answers
200 views

Can FTL-Communication between two points in the same frame of reference break causality?

Hi I want to get to the bottom of some thaughts I have and for that I need an answer to a - I have to admit - highly constructed example. Lets assume - against all possibility - we find a strange ...
1
vote
0answers
37 views

What is special about quantum entanglement? [duplicate]

Get two pieces of paper. In secret write the same number on both papers. Transfer one paper to the Moon. Look to the paper which is left at the Earth. Voila! We know what is on the Moon paper. The ...
0
votes
1answer
179 views

Do wormholes violate causality [duplicate]

Does opening and closign a wormhole to send a message within seconds across the galaxy violate causality? Wouldn't different observers disagree about the order of events and what effected what? Is ...
2
votes
1answer
82 views

Can someone explain why this QM FTL communication setup is wrong?

So I thought I understood the double-slit experiment and EPR paradox until this setup occured to me. It combines EPR entanglement with "which-way" double slit setups. I know it must be wrong, but I ...
1
vote
2answers
76 views

Black Hole horizons and the Equivalence Principle?

In the reference frame of a freefalling observer, does crossing the event horizon not cause a contradiction between two classical principles that supposedly apply at the event horizon: the equivalence ...
5
votes
1answer
100 views

Since space expands (and can theoretically contract) faster than light, does that mean that in a big crunch information could travel FTL?

Layperson here. In a theoretical big crunch with space contracting faster than the speed of light, would information be travelling faster than speed of light? Because the points A and B themselves ...
5
votes
1answer
146 views

What would happen in this “close to the speed of light” scenario?

Say you had a really long pole made of a super strong material, and at the you turned it through an angle of (for example) 45 degrees. Turning the pole through a small angle at the bottom would ...
0
votes
1answer
55 views

What is the difference between the expansion of space and the Alcubierre drive?

The Alcubierre drive violates causality. As far as I know the expansion of space does not. The usual explanation for why space is allowed to go FTL is that the matter doesn't move. The Alcubierre ...
0
votes
0answers
24 views

How does a shadow appear to break the speed of light? [duplicate]

Take the image below for example: For the shadow to travel from point A to B would be extremly fast on the surface on the moon but probably not breaking the speed of light. But if the moon were 20 ...
-1
votes
2answers
344 views

Faster-Than-Light Communication using Entangled Photons

Based on my understanding of the “Double-Slit Quantum Eraser Experiment”, documented here: http://grad.physics.sunysb.edu/~amarch/, it seems that Faster-Than-Light communication is possible. Of ...
1
vote
2answers
224 views

Do Entangled Particles communicate through Wormholes? [closed]

If so, would this “spooky action at a distance” still be spooky if that “distance” is actually shorter than it appears? Sorry if this is a Noob question. Just trying to understand how Entangled ...
36
votes
6answers
7k views

Do all the conservation laws of Physics take no time to propagate?

For instance, conservation of momentum, does it take time to propagate between two or more objects? If it does, then there would be some moment that the momentum is not conserved. If it doesn't take ...
1
vote
1answer
110 views

How does a world line of an Alcubierre drive look like?

In my recent question ”Speed of light and warp drives in general relativity” I asked exactly how an Alcubierre drive worked and exactly what "FTL travel" meant. One of the comments I got stated that: ...
0
votes
1answer
125 views

Faster than speed of light [duplicate]

I was watching a Physics TV show, When someone called Alex Filippenko said that when there was the Big Bang, the Space extended at a speed faster than speed of light. He said that it wasn't against ...
1
vote
1answer
176 views

Klein-Gordon equation and wave velocity

It looks like solutions of the KG eqn travel faster than light, because if $$\omega^2 - k^2 = m^2$$ then $$\mid\ \omega\mid \ > \ \mid k\ \mid$$ and I thought the wave velocity was $\omega / k$. ...
5
votes
1answer
227 views

Speed of light and current dimensions of the universe [duplicate]

I've seen several documentaries explaining that the diameter of the universe is currently estimated at over 90 billion light-years. And which that - in the face of the age of the universe being about ...
3
votes
2answers
214 views

Speed of light and warp drives in general relativity

Velocities can be a tricky thing in general relativity. A cool concept seemly consistent with the Einstein field equations) is an Alcubierre drive, described by the Alcubierre metric. However, I ...
0
votes
1answer
163 views

How does measurement affect multi-particle entangled particles?

It is my understanding that you can have two entangled particles, A and B, and measure their spins from two different angles, X and Y, such that: If you measure A using one angle (e.g. X), there's ...
7
votes
3answers
359 views

Pendulum moving faster than speed of light

In classical mechanics, the period $T$ of a pendulum is given by $$ T = 2\pi\sqrt{\frac{l}{g}},$$ where $g$ is the gravitational field and $l$ the length of the rope attaching the bob to the pivot. ...
0
votes
1answer
72 views

Light travels in a medium

According to Snell's law : $${n_1 \over n_2} = {v_2 \over v_1}$$ $v_2 = v_1 n_1 / n_2$ Assuming that $n_1$ is vacuum , we will find the following equation: $$v = c / n$$ (We may find the same ...
0
votes
2answers
73 views

Relative Velocity Problem: Light? [duplicate]

Assume 2 rockets coming towards each other at each other at 99% of speed of light, and so as they pass each other the relative velocity between 2 rockets would be 198% of Speed of Light and so what ...
0
votes
0answers
37 views

Don't photons pass photons move away at speeds faster than light? [duplicate]

I understand there is a longstanding rule that nothing travels faster than the speed of light... but if you had two flashlight aimed at each other and turned them on inside a vacuum the photons from ...
1
vote
1answer
142 views

On the no-faster-than-light in special relativity

In the special relativity it is well established that, in the vacuum no one can ever travel faster than light, due to the relativistic velocity addition formula. Recently I saw some silly statement ...
-1
votes
2answers
173 views

Nothing can travel faster than the speed of the light, but could this be an exception? [duplicate]

I often show off by asking people how fast electrons flow through wires. Then I tell them it's actually only a few millimeters per second. To clear the disbelief off their faces and boost my ego, I ...
-1
votes
1answer
57 views

Is it possible to travel forward and backward along with time? [closed]

Is it possible to travel along through time if we found a thing that is more speeder than light?
0
votes
0answers
53 views

Is there any explanation for these objects apparently traveling faster than light? [duplicate]

This is from a documentary on the science channel: https://www.youtube.com/watch?v=RaELad94KZs