"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.

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Can photons travel faster than $c$? (Feynman Lectures)

I apologise for the very non-technical nature of this question. I am new to QED and perhaps am interpreting things in the wrong way, but I'll ask anyway, and hopefully someone can provide a ...
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Is quantum entanglement functionally equivalent to a measurement?

I saw the following talk the other day: http://www.youtube.com/watch?v=dEaecUuEqfc&feature=share In it, Dr. Ron Garret posits that entanglement isn't really that "special" of a property. He ...
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3answers
574 views

Why does nonlinearity in quantum mechanics lead to superluminal signaling?

I recently came across two nice papers on the foundations of quantum mechancis, Aaronson 2004 and Hardy 2001. Aaronson makes the statement, which was new to me, that nonlinearity in QM leads to ...
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How does faster than light travel violate causality?

Let's say I have two planets that are one hundred thousand lightyears away from each other. I and my immortal friend on the other planet want to communicate, with a strong laser and a tachyon ...
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How can we measure the speed of light in spacetime, and the rate of universe expansion, and come up with conflicting answers? [closed]

In spacetime, there should be no way to measure anything at the speed of light or passed it. The conclusion I make from here, is that we can't observe anything moving faster than the speed of light. ...
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184 views

Impulse travelling faster than light

There have been conducted many experiments in which light impulses traveled faster than light like the one in Princeton in 2000. This phenomenon has something to do with quantum entanglement. Does ...
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1answer
333 views

Theoretically if you passed the speed of light in a medium, would there be a sonic boom equivalent?

I know that it is technically impossible to reach the speed of light in vacuum since the mass of the object traveling would reach infinity. However in a medium, would there be some sort of theoretical ...
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36 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 ...
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Travelling faster than the speed of light

Let's say I fire a bus through space at (almost) the speed of light. If I'm inside the bus (sitting on the back seat) and I run up the aisle of the bus will I in fact be traveling faster than the ...
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What's going on along the “sides” of an Alcubierre warp bubble?

The models/depictions I've seen of warp bubbles show space compressed ahead of the bubble and expanded behind, so that the space inside the bubble moves with respect to the space outside. If that is ...
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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 ...
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Alcubierre warp bubble effect on gravity and space

I read the question Faster-than-light communication using Alcubierre warp drive metric around a single qubit?, and these questions came to mind: What kind of impact would an Alcubierre warp bubble ...
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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 ...
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52 views

Why doesn't this scheme allow for faster than light communication? [duplicate]

$\newcommand{\ket}[1]{\lvert #1 \rangle}$Consider the following experiment. Alice and Bob share $n$ entangled pairs of qubits in the state $\frac{\ket{00}+\ket{11}}{\sqrt{2}}$. Alice wishes to ...
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1answer
31 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?
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31 views

As the speed of sound varies in different mediums, what's the density of a theoretical material that allows it to go at the speed of light? [duplicate]

Viewing a list of the speeds of sound in various mediums, I note that none of them come even close to 300,000,000 m/s. It appears that as the speed of sound goes up, the object's density more or less ...
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248 views

Would warp bubbles emit gravitational Cerenkov radiation in general relativity?

Inspired by the gravtiomagnetic analogy, I would expect that just as a charged tachyon would emit normal (electromagetic) Cerenkov radiation, any mass-carrying warp drive would emit gravitational ...
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821 views

Do tachyons move faster than light?

I am trying to understand whether or not tachyons travel faster than light. The linked Wikipedia page shows some seemingly contradictory statements, and they are confusing. For instance, the first ...
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45 views

Was the expansion after the big bang faster than the speed of light? [duplicate]

I think it's called Planck time and it's the speed at which matter spread during the big bang. Was the big bang expansion faster than the speed of light?
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107 views

Speed of light paradox [duplicate]

If I send two rockets from the Earth in opposite directions, at, say, 60% of the speed of light relative to the Earth, then relative to each other they are travelling at 120% of the speed of light. ...
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60 views

Does EPR permit information to travel faster than light? [duplicate]

This question always throws me: Discuss if the EPR paradox violates special relativity? The information of the state of one particle is instantaneously transmitted to the other particle, but ...
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1answer
137 views

Navigating a Time Machine

Notes: The background for this question is working out details of a sci-fi story. Answers to the effect of "time travel isn't possible" or "FTL isn't possible" are therefore not helpful. I'm looking ...
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Is it possible to apply force to a light particle?

I know, the universal speed limit is the speed of light $c$. So, is it possible to apply more force to a light particle? What would happen to it if we could?
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53 views

Travelling at a relative speed greater than the speed of light [duplicate]

I've wondered about this since I was a kid. I've been told the speed of light is a constant ($c$), which would mean that light always travels at the same velocity. Now, here's what interests me: if ...
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4answers
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Can internet speed be faster than speed of light?

We send email in order to transfer information and, over time, the technology used to send email improves to send email at faster rate. Since we use the Internet to send information from one place to ...
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Superluminal speed?

I came by the quotation below. I'm confused: does it mean that it's actually possible for light and even material objects to move faster than light? Gravitational fields are present the velocities ...
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211 views

Thought experiment about no-cloning theorem and FTL information

The quantum no-cloning theorem states that one cannot "build" a perfect cloning device for arbitrary quantum systems. There also exists a famous thought experiment where Alice transmits information ...
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359 views

Faster than light signals and the price to be paid if we accept them : a very simple protocol

Most physicists currently understand entanglement as transferring information instantaneously, yet not violating causality. Is this really a satisfactory explanation, or should be look for something ...
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Time Reversal in a Black Hole

I had a lively discussion with a person about black holes recently, and was making the point about gravitational acceleration in GR being paralleled by speed in SR. One thing that I know people talk ...
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Is it possible for information to be transmitted faster than light by using a rigid pole?

Is it possible for information (like 1 and 0s) to be transmitted faster than light? For instance, take a rigid pole of several AU in length. Now say you have a person on each end, and one of them ...
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29 views

Is a Super-luminal Laser spot possible? [duplicate]

Note:This is not the same as Is the "How to break the speed of light" minute physics video wrong? because a larger distance is used in a different direction so that the time of flight of the ...
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55 views

Can we make a particle travel faster than $c$ in this way? [duplicate]

In my sixth grade science class our teacher asked us, for homework, if it was possible to have anything travel faster than light. Thinking about this, I came up with a rough idea of a way to make ...
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Would one-way FTL travel be safe from a causality standpoint?

Any demonstration I've seen of using FTL signals to violate causality seemed to involve an exchange of FTL signals. Would FTL travel be consistent with causality if it always involved motion in one ...
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Is there serious research on superluminal travel? [closed]

I was wondering if there are any serious attempts, or any ideas for loopholes in the current theories, that would enable us humans to travel with a speed greater than the speed of light?
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In superluminal phase velocities, what is it that is traveling faster than light?

I understand that information cannot be transmitted at a velocity greater than speed of light. I think of this in terms of the radio broadcast: the station sends out carrier frequencies $\omega_c$ but ...
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61 views

Can we travel faster than the speed of light? [duplicate]

So my question is completely a theoritical question. For example i have a stick made of the strongest material and lightest material and its lenght is as long as the solar system's diameter. The end ...
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1answer
50 views

Tachyons and the light barrier

I read somewhere that if something breaks the light barrier, i.e. a tachyon, that it will take infinite energy to make it go slower than the speed of light. So, does that mean that the object will ...
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4answers
138 views

Exceeding the speed of light using gravity? [duplicate]

From what I have learned, objects must accelerate as they approach a heavy mass. But I also know that they cannot travel faster than the speed of light. What if you had a proton travelling at ...
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3answers
199 views

How can light travel at a speed greater than the speed of light

I was reading John Rennie's answer here, Can light travel faster? I now know that the sentence ''the speed of light is always constant in vacuum'' is just an oversimplification, for example light ...
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What is the speed of gravity? [duplicate]

Hypothetically, let`s say that one day our Sun is suddenly removed from the galaxy. For us, on earth, would take up to 8.3 minutes to notice that the sun was removed, since the distance from the earth ...
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134 views

Special Relativity - Distance Not Increased?

I just watched the movie Interstellar and the question was asked of why/how high-speed travel would slow time within an area. Curious as I am, I watched several YouTube videos to quickly 'educate' ...
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102 views

Is dark matter moving faster than light? [closed]

My way of thinking is as follows: Consider a balloon. Let this be blown into a nearly elliptical sphere. Now, the temperature inside the balloon is increased by some means; this leads to the ...
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2answers
301 views

Energy transfer using quantum entanglement

Can we transfer energy from one place to another separated by arbitrarily large distances without any time lag? For instance, if Alice and Bob are two observers making measurements having a singlet ...
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58 views

Expanding universe and speed of light [duplicate]

Galaxies are moving away from us proportional to the distance between us and them , but nothing can travel faster than light, so even the farmost galaxies should be travelling away from us along with ...
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190 views

Acceleration due to Gravity: Free Fall [duplicate]

If we are in a free fall which implies we are accelerating at 9.8 m/sec every sec. And let's say that we are falling into a pit that has enormous depth. So isn't this be possible that we may ...
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Does entanglement not immediately contradict the theory of special relativity?

Does entanglement not immediately contradict the theory of special relativity? Why are people still so convinced nothing can travel faster than light when we are perfectly aware of something that ...
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1answer
161 views

Thought experiment on graviton breaking the speed of light [closed]

The effect of gravity travels at the speed of light. Suppose we can entangle a pair of gravitons (which are only theoretical, but who knows for sure?) and separate them over a vast distance. Hold on - ...
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If I move in a bus moving at the speed of light wouldn't I be disproving the laws of physics? [duplicate]

I'm just in 10 grade , so please bear with me. Just imagine If a bus was travelling at the speed of light , and I was was running inside it, wouldn't I be moving faster than light?
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Will an object always fall at an infinite speed in a black hole?

Most of you if not everybody will agree that the stronger the gravitational pull, the faster an object will fall. For example, on a planet with 50 times the gravity of Earth, any object will hit the ...