Questions tagged [faster-than-light]

"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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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 ...
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Does quantum entanglement necessitate that two particles communicate their state with one another?

I often hear it said that quantum particles, like an electron-positron pair or two entangled photons, which are entangled with one another communicate or transfer information about their state ...
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Why can't quantum tunnelling carry energy or information faster than light?

A few experimenters have at one time or another claimed that quantum tunnelling allows the transfer of information or energy at superluminal speeds. One was the idea that music was carried across a ...
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Can information travel faster than speed of light in this situation?

I know the answer is no but I have a thought experiment that seem to be violating that. Imagine two persons living on two different planets namely A and C which are 10 light years apart. There is a ...
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Can we prove that things can't exceed the speed of light? [duplicate]

A is in a rocket with proper acceleration a0 = 3.00 × 108 m/s2 to the right. As far as I know speed of object is restricted by the speed of light but with dv=a.dt, the rocket will reach the speed of ...
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Has quantum collapse been ruled out?

This morning, a new arXiv paper 2105.13519 appeared providing detail of an EPR steering experiment showing that if it is assumed that the EPR steering requires quantum collapse, then more than one bit ...
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Speed due to gravity [duplicate]

Assuming a miraculous arrangement of a string of black holes for slingshot purpose, and a solid ball slinging by these black holes one after the other, gaining speed with each slingshot, is it ...
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Can the surface of a neutron star move faster than light? How length contraction manifests there?

It is known that any Kerr black hole is surrounded by ergosphere, inside which everything rotates around the black hole faster than light. Since ergosphere is greater than event horizon, one can ...
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What would happen if universe wouldn’t accelerate faster than speed of light? [closed]

Its quite stunning to assume that not only space-time is expanding but also the rate of expansion is greather that speed of light. But after the initial surprise, I ve been wondering if that fenomena ...
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Sabine Hossenfelder's argument to rule FTL paradoxes out

I have recently seen Sabine Hossenfelder's video on faster-than-light travel, in which she argues no paradoxes would arise if we had something like a FTL warp device, because the trajectories leading ...
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Richard Feynman Nobel Lecture, typo error?

In the Richard P. Feynman Nobel Lecture, I think I saw a typo in his explanation of the retarded waves. I post it there because I did not saw anywhere on the web someone who noticed it. It is an old ...
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What would happen if a black hole disappeared? [closed]

Imagine if a black hole disappeared. Would spacetime act like a rubber band and propel objects that used to be caught in its gravitational field outwards - i.e. some kind of space time explosion? How ...
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Since the speed of light is constant and also the speed limit; would you, in your reference frame, have no upper bound on your speed? [closed]

Let us imagine you are in a vacuum and after having maintained a speed of 0 km/s (standing still) you accelerate to 297,000 km/s (99%). You know this is now your speed because you have a speedometer ...
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What exactly is the motion in Warp drive?

I know that there exists something like the Alcubierre warp bubble, and there are many threads here about it, but unfortunately the answers didn't help me to understand what the basic principle is... ...
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Does this research paper prove that warp drives are impossible?

Does this preprint prove that warp drives are impossible? J. Santiago, S. Schuster and M. Visser, "Generic warp drives violate the null energy condition" It states that the NEC (Null Energy ...
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If EP=EPR is discovered to be equal then would this allow a basis for FTL communication?

If EP=EPR is discovered to be equal then would this allow a basis for FTL communication as microscopic wormholes of Planck length act as a bridge for entangled particles. This would only hold true if ...
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Warp drive small scale experiments “proof of concept” [duplicate]

Possible small scale warp drive experiments, or small scale experiments with quantum mechanics to model space-time warping? Why is it so difficult to engineer a small scale warp drive even though ...
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Erik Lentz's faster-than-light soliton

It's well known that, in relativity, if you can go faster than light, you can go backwards in time and create a paradox. Also, attempts to create "warp-drive" space-times in which something ...
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Why is a relativistic observer required to show that FTL communication breaks causality?

Physics Matt has a blog on the issues with FTL communication. At one point they use an example of a relativistic observer seeing a FTL message arrive before it is sent, to show how causality is broken....
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What is observed by Astronauts traveling from M at just under $c$, but proper distance increases at greater than $c$ due to spacetime expansion?

A rocket is traveling at a reasonable speed directly away from planet M at a large distance D. M is shaped like a coin and to the astronaut looking through a telescope directly out the back of the ...
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Does entanglement mean that information travels faster than light? [duplicate]

Every time in physics (in popsci) I hear that it is not possible to travel faster than light, as this would cause many problems that I do not understand. On the other side, in Quantum Computing (in ...
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Testing space-time warp on a smaller scale, “Breaking the Warp Barrier: Hyper-Fast Solitons in Einstein-Maxwell-Plasma Theory” [duplicate]

So according to this paper it creates a warp drive without the need of negative energy to operate which many think does not exist in reality. So my question is what would you do to experimentally ...
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Why the Warp-drive uses a 3D shape to distort space instead of a 4D shape?

I know that warp-drives are just a theory and that they would require exotic mass (that is also a theoretical material), but, as said in this video, after some re-calculations, it was theorised that ...
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Does non-local interepretations of quantum mechanics imply FTL communication? [closed]

For example the pilot wave theory... And if this is the case then does FTL commuincation imply time travel (i.e: information going back in time).
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Indirectly breaking the speed of light through inflationary phase

How do you define velocity? Rate of change of "space" between two objects-and that will give relative velocity between them. Now in inflationary phase the universe expanded faster than light ...
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Does the collapse of the wave function happen immediately everywhere?

It is usually taught that when we measure some measurable value the wave function collapses immediately everywhere. This idea sounds like a simplification of some more complicated mechanism. Are ...
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Will an Alcubierre Drive arrive before a beam of light, if sent between two stationary observers?

First, I'm not a physicist, just an engineer, and my first language is not English, so forgive any strange wording. I have a simple thought experiment about Alcubierre Drives: Imagine two stationary ...
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Indirectly breaking the speed of light

Imagine a system of two objects: a supermassive black hole mass of approximately $10^{36}$ kg and another $1$ kg object revolving around the black hole with an average mean distance of about $1.5×10^{...
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Can electrons travel faster than light in quantum field theory?

How does quantum field theory account for the movement of an electron orbiting a proton from one place to another place in the next instant of time - at a distance that even light couldn't reach in ...
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1answer
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Faster than light morse code v2 [duplicate]

Imagine a theoretical superhard steel cylinder pointed towards the moon , 1 cm in radius and 380,000 km long, traveling at 1km per hour towards the moon. Parallel to this cylinder, 1 meter away we ...
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What's the speed of force? [duplicate]

Brain storm: Suppose we have a perfect lever, which has 0 quality, and perfect rigidity. It is long enough that can reach Proxima Centauri from the earth. Someone push one side of lever from Proxima ...
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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, ...
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Is this solution for interstellar travel viable?

I have in mind a way to enable FTL travel. Is this way viable? In the paper: "Weighing the vacuum with the Archimedes experiment" we can see the dependency of the gravitational repulsion ...
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Faster than light communication protocol via GHZ-state

I had a chat with a guy recently who claimed that multipartite entanglement might actually be used for superluminal communication, and his argument is very simple. Suppose that 2 observers (Alice and ...
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1answer
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Cone-Light events

The events Q that occur within the cone of the light cone of an event P, are seen by all observers in the same order. But how can I be mathematically sure that in effect it happen?
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Do holonomic physical systems really exist?

According to Wikipedia on ‘Holonomic Constraints’: “In classical mechanics a system may be defined as holonomic if all constraints of the system are holonomic. (...) a holonomic constraint depends ...
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How fast can an object be made to vibrate?

Can an object (or system) be made to vibrate so fast, that the vibrational transit speed approaches the speed of light therefor slowing time down significantly for the object or system relative to ...
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Special relativity: Two moving objects from different reference frames [duplicate]

Imagine a inertial frame of reference, in which two objects are moving with constant velocity in opposite directions. Object one is moving at $50$% the speed of light and object two has a velocity of $...
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1answer
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Velocity of point of intersection of 2 rods [closed]

I'm not getting how are we getting u greater than c for part b by using formula for part a. Plz explain
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What, if anything, is wrong with this proposal for faster-than-light communication using entanglement swapping? [closed]

What, if anything, is wrong with this proposed mechanism for faster-than-light communication? Here are pastes from the proposal: Spooky Communication at a Distance Faster-Than-Light Communication via ...
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Speed of a train plus speed of light [duplicate]

Einstein postulates that the light travels at the same speed $c$ in every inertial frame of reference. Now, if I'm within a train which goes right with velocity $V$ and throw a ball to the right with ...
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Matter moved faster than photons at big bang? [duplicate]

The observable universe is 90 billion light years across. But the age of universe is 13.8 billion years. Light would take 90 billion years to cross this distance, how could matter move that far in ...
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1answer
150 views

How can information be communicated with entanglement? [closed]

Forgive my overly simplistic view of this. But I have been wondering this for years. Any insight would be greatly appreciated. So imagine you have two entangled particles, and they are separated and ...
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Is High-Fidelity Quantum-Entanglement Data-Transfer Real?

I was discussing quantum entanglement with a friend and explaining that faster than the speed of light data transfer isn't a reality with our current understanding of physics. He brought up quantum ...
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Does faster than light lead to closed timelike curves?

If some signal can be sent to a spacelike interval then is it possible in some reference frame to have a close timelike curve? Novikov claims so in this paper. The argument lies below eq$7$ but ...
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How did we beat the light?

We observe that the universe is 13.8 billion years old, give or take a little. We can say this because we observe and measure the fact that distant galaxies and the CMB are that far away from us, ...
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Why is my contrived superluminal thought experiment wrong?

An astronaut is on an odd mission. Each day, the spacecraft is accelerated by 10% of the speed of light, and at night the astronaut sleeps and will loose all memories of the previous day. Each day ...
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Observed Behavior of Light When Relative Motion $> c$

I am trying to wrap my head around some of the implications of relativity. Hopefully somebody can help enlighten me with a specific example I am wondering about: We have 2 objects, A and B, that are ...
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Is there a force that a body experiences as it approaches light speed?

My question can be boiled down to a thought experiment. Assume you have a space ship in an empty universe. This space ship is capable of a constant $1 m/s^2$ acceleration. As it approaches light ...
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Does the effect of field travels faster than light? [duplicate]

As I was going through some work of my college level courses of fundamental physics, the formula caught my attention $F={G}\frac{Mm}{r^s}$. "r" seems can be any value; there would still be ...

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