# 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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### Can an object with mass travel at the speed of light?

according to the Einstein, no object mass with can reach the speed of light. but in the electron gun the speed of electron can be calculated from $$E_k = \frac{1}{2}mv^2 = eV$$ and because $m$ and $e$ ...
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### Einstein's Cosmic Speed Limit $c$ challenged by Black Holes/Massive Objects [duplicate]

To even suggest the great Einstein is incorrect on anything he has written is inconceivably absurd. Being fully aware of this I do indeed dare to not only suggest he is wrong but I cannot believe ...
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### Is it possible to defy time using speed? [closed]

I have always wondered if we were to travel at past the speed of light (even beyond the current capability) would we be able to slow down time around us? I have asked my teacher at school and he has ...
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### Super luminal speed paradox? [duplicate]

Chosing a reference frame in which the Earth is at rest and doesn't rotate is related, but different. Here I'm asking if there is a paradox and if my attempt at resolution has merit, and if not ...
360 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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### Effects of travel greater than speed of light [closed]

What will happen if a person with say weight of 100 kilograms, starts to travel with, a) equal to speed of light? b) greater than speed of light?
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### How can I go and also not go faster than light?

Suppose I am in a spaceship. In this spaceship there is also my friend. So my friend and my relative velocity is zero. So no matter how fast my ship goes my friend's velocity relative to me is zero($0$...
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### What is the effect of gravitational field on an object moving at the speed of light? [closed]

If a body moving at the speed of light moves towards another stationary body having much greater mass then,this body makes the moving body to accelerate under its gravitational field in such a way ...
561 views

### The speed of light and electrons [duplicate]

In physics as we understand it today, can an electron be made to move faster than the speed of light in vacuum? Whether by natural causes, or man-made means?
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### This morning the speed of light is 60cm/hour. Is the following an accurate description of what I would see? [closed]

My alarm clock, 60 cm away from me, set for 7 am, rings*. I look at it and it reads 6 am ! Puzzled I “immediately” look at my wristwatch 20 cm away from me and it reads 6:40. As I get closer to it, ...
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### Can information be sent faster than speed of light [duplicate]

I just had this idea one day and I decided upon a thought experiment to verify it. Imagine 2 people A & B sitting on two sides of a pipe which is stretched to a length of 3x10^8 m. The pipe is ...
145 views

### Can you see back in time? [closed]

When you look at the stars, the light that you see is probably hundreds of years old. Which means that you don't know if they still exist. Does all this mean, that if you fly in a speed faster than ...
476 views

### Travelling at/over speed of light, I fire a laser in front of me. What happens to the light from the laser? [closed]

For a moment, assume that travel at/over the speed of light is possible, and we fire a laser in front of us, what happens to the light emitted from the laser? Would the photons scatter, or would the ...
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### Quantum Entanglement and Faster than light Communication

Suppose, Alice has a Billion of photons in random states, while Bob has their entangled pairs. Suppose, Alice can measure the spin of the photons in X axis, while Bob can measure their spin in an axis ...
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### Faster than light communication

Assuming the right equipment why won't this scenario work? Two source devices capable of producing entangled photon pairs at set intervals and two detectors capable of descriminating the state of the ...
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### Acting on an object at a distance faster than light, or making small cogs immovable [duplicate]

Here's my question; If we have a line of connected cogs, arranged in such a way that for any one cog to move each other cog would necessarily have to move also, and that line of cogs were of an ...
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### Theory on how to break the speed of light [closed]

I am 14 years old and I think I have a good grasp on physics but I have a question. Imagine you were to shrink everything in the universe (except for yourself) down to the size of an atom and it was ...
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### Aging while traveling faster than speed of light? [closed]

theoretically, if organic matter was able to travel faster than the speed of light, without becoming "pure energy", and since theoretically traveling faster then the speed of light would travel ...
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### Using entanglement for communication based on the double slit experiment [duplicate]

When we perform a double slit experiment we receive interference pattern. when we measure in a specific slit the exact location of the photon (or electron) the interference pattern disappears and we ...
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### My theory to travel near the speed of light. Why will this theory not work? [closed]

Why can't a spacecraft travel near the speed of light? Here's my theory. We assemble the spacecraft in the Earth's orbit just like the International Space Station, each time, equipping it with lots ...
37 views

### Double Relativistic Speed of light [duplicate]

If two light photons are emitted from a point source and moving in opposite directions in space, how can global speed limit $c$ be maintained, as speed of one photon relative to other can be easily ...
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### Matter beyond the event horizon should time travel? [duplicate]

when anything passes the event horizon of a blackhole, it must be moving faster than light as even light cannot escape. So then, shoundnt it time travel?
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### If you fall for a long enough period of time, would you eventually hit or break the speed of light? [duplicate]

If you theoretically fall through an infinite hole, and since the longer or higher you fall, the faster you would progressively go, would you eventually hit or even surpass the speed of light, and if ...
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### A quantum entanglement experiment

Suppose we have an entangled electron-positron pair, such that total spin is zero. Separate them, and let Alice measure the spin (along $z$) of the electron, obtaining, say, $+\frac{1}{2}$. All the ...
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### What's the fuss over quantum entanglement about? Is it because people have misunderstood? [closed]

The first video I've seen about quantum entanglement claimed that changing A's spin will immediately take effect on B's spin as well. The more I read into this topic the less it seems that this is ...
1k views

### Can the Large Hadron Collider break the speed of light? [closed]

Can Large Hadron Collider experiments break the speed of light at some point in the future?
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### Newton's cradle faster than light?

If we have a Newton's cradle toy where the balls actually touch each other. Can energy be transferred from the first ball to the last one faster than the speed of light? And what factors control the ...
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### Why do physicists say information can't travel faster than light speed?

I often hear in physics videos light speed is the ultimate speedlimit two parts of the universe can communicate at, or even that speed of light is actual speed of causality. Where does that notion ...
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### 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?
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### Exceeding the speed of light [closed]

I understand that the speed of light c is derived from the self-interaction between elections/photons, and is thus the maximum speed of anything composed of electrons/photons. Suppose that there is a ...
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### Travelling at a speed faster than light [closed]

Imagine yourself to be bat. You cant see anything. You don't have eyes. All you can do is echolocate, using ultrasound. Now imagine something is moving away from you faster than the speed of sound. ...
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### How is traveling back in time different from traveling at a negative velocity? [closed]

A simplified explanation of why you can't travel through space faster than the speed of light is that you are already traveling at the speed of light, through spacetime. If you are stationary in ...
135 views

### Can someone explain in a simple manner that How can we use Quantum entanglement to transfer data instantly when we seperate photons? [duplicate]

So I'm an IT engineer and i just watched a video about Quantum entanglement, that somehow when we split the entangled photons, any change happening to one of them will be reflected to the other one ...
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### Entanglement question

If photons A and B are entangled and A shows, say, spin up, then B will show spin down. My question is, can a researcher change the spin of A, say by putting it through some kind of filter? If so, ...
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### Looking back in past [closed]

Can faster than light communication give us the ability to see in the past, that is to say, if we can imagine a ultra huge highly advance telescope 60 light minutes away from earth and we want to look ...
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### Can we accelerate photons to travel at speed of $1.5c$? Or any $xc$ when $x > 1$? [closed]

Can we move photons to travel at speed greater than speed of light in vacuum? If no then why? For example: I want to send some photons at 1.5c. Is that possible? How a photon of light can go from 0 to ...
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### If a person travelled faster than the speed of light would he be everywhere at once and if so why? [on hold]

An astrophysicist from Palomar or Berkeley said on public radio that if you were to reach the speed of light you would be everywhere at once. He didn't say why. Is that the case and why? Does ...
86 views

### Distance change per time and velocity not the same is Special relativity? [duplicate]

Many formulas in Special relativity have v - velocity. And theory says there is no absolute velocity only relative and it cannot be greater than speed of light. Consider this thought experiment: ...
199 views

### Communication via teleportation/entanglement (FTL communication)

I know this has been asked many times, but I have a hard time "crystallising" it in my mind. First: let's say we teleport a DVD (with quantum teleportation). Isn't this FTL communication? Second: ...
34k views

### Do radio waves go faster than the speed of light? [closed]

My science teacher used to say a lot of weird stuff, but I'm just making sure on this one.
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### If a car is travelling faster than the speed of light, do the headlights still work? [closed]

If a car is travelling faster than the speed of light, do the headlights still work? If you can help because i really need to know i am going on a trip with my car tomorrow!
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### 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 nature?...