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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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 ...
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Is it possible to rotate a very very long (almost infinite) and rigid pole such that its end reach the speed of light? [duplicate]
$v=\omega r$ relation shows that even with a fixed $\omega$ and large $r$, the end of the pole can be rotated at a high speed. So if I make pole sufficiently long such that $v=c$, will it be possible ...
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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 does implementing the annihilation operator $\hat a$ not allow action at a distance?
I was reading a paper (link) in which they implement action at a distance using the annihilation operator, and in it they say that "this observation does not imply superluminal signaling because ...
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Circumstances of a superluminal causality violation [on hold]
In the case of the Roman ring, a traveler is able to go through a wormhole mouth and emerge at some point in the past without violating causality, so long as the time traveled back is less than the ...
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Do superluminal worldlines constitute closed time-like curves under the right conditions?
A closed time-like curve is defined as a word-line that returns to its starting point, in the $x$, $y$, $z$, $t$ coordinates. So, for a chronology respecting observer, an object traversing a closed ...
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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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How an ultra-relativistic electron near the speed of light keeps its spin velocity without becoming partially superluminal?
If an electron has spin and volume than the point on the surface is rotating at constant speed according to Planck constant defined angular momentum.If this electron accelerates then this point on the ...
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Why not double speed of light? [duplicate]
Well, the speed of light seems to be constant for some reason, but what if in a void, just what if, a light beam is shot out of a light beam before it hits a medium, why the hell doesn't the second ...
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Images traveling faster than light
Please help me understand my mistake(s) in this reasoning. I will write as if I knew exactly what I'm talking about for the sake of clarity, but I of course don't.
Consider observer A and its ...
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Why can't gravity force an object past the speed of light? [duplicate]
I hope this question is not a duplicate (it doesn't seem to be) and that it is appropriate for this site.
If we had a universe with only two bodies. One is ultra massive, and the other is very small. ...
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Instantaneous quantum features
Two of the most striking quantum oddities are entanglement and the wave-function collapse or state vector reduction.
Firstly, quantum entanglement is the quantum phenomena involving states of ...
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Why does FTL not leave behind a motion blur? [closed]
I once thought anything traveling faster than light would leave behind a motion blur that on one end recedes at the speed of light and at the other increases at the velocity of the object. If an ...
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“High-Frequency Gravitational Wave Generator” patent from U.S. Navy, among other things [closed]
A scientist going by the name Salvatore Cezar Pais, employed by the U.S. navy, was recently granted the following eyebrow-raising patents:
-High frequency gravitational wave generator (10322827)
-...
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1answer
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Relative speed when getting close to the speed of light
I was thinking about the relative speed of an observation reference frame and an object which has been accelerated to a speed close to the speed of light. I'm by no mean an expert and the last physics ...
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How can I show that the speed of light in vacuum is the same in all reference frames?
I have regularly heard that the Michelson-Morley experiment demonstrates that the speed of light is constant in all reference frames.
By doing some research I have found that it actually demonstrated ...
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Is it possible that the universe is not expanding faster than the speed of light? [closed]
What if the speed of light increases proportionately to the expansion of space? Is it possible that light traveling in the medium of space gets to travel faster if the medium is expanding? An analogy ...
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Would possibility of instant communication break physics? [duplicate]
I recently read a sci-fi book, where some (very few) people can communicate telepathically, which happens to be instantaneous.
So, every spaceship has a crew member who telepathically communicates ...
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Can something travel faster than the speed of light? [duplicate]
I understand this is a very complicated question to answer as no one really knows. However if gravity exerts an infinite force in the singularity of a black hole, then can't it travel faster than 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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Would close to light speed travel be possible if all atoms in the system were instantly given “forward motion”?
I have heard people say that based on our current understanding and ideas for possible/current technology no person would ever be able to even travel at a solid (70-80%) the speed of light because ...
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Illusion that $v > c$?
I am currently studying length contraction in special relativity (and having the hardest time getting the harder exercises in my book right) and there is the following exercise in my book is driving ...
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Speed of at expansion at the start of the big bang [duplicate]
If I understand the basics of the big bang correctly it starts with a very small dense point. At the moment of the big bang, less then microseconds after, the universe is already the size of our solar ...
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Would an observer going faster than the speed of light in a vacuum be able to observe photons that they emit? [closed]
If I could exceed the speed of light in a vacuum, would I be able to see photons that I previously emitted?
Would this be theoretically possible?
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Can Quantum Entangled particles convey information faster than speed of light? [duplicate]
Can Quantum Entangled particles convey information faster than speed of light. If they don't what was wrong with John Bells experiment?
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Does light travel faster in between Casimir plates?
Speed of light is in general $c/n$ where $n$ is a refractive index. But for example introducing two parallel plates with very small spatial separation will perturb the energy density of vacuum ...
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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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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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Why didn't Lorentz conclude that no object can go faster than light?
Based on Lorentz factor $\gamma = \frac{1}{\sqrt {1-\frac{v^2}{c^2}}}$ it is easy to see $v < c$ since otherwise $\gamma$ would be either undefined or a complex number, which is non-physical. Also, ...
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How Can the Universe Be Bigger Than It is Old? [duplicate]
My question is this: If we can look back to roughly 500m years after the big bang and have estimated the age of the universe at 13.7B years, why is the galaxy we are looking at not a part of the non-...
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1answer
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Traveling to another galaxy impossible for ever?
If galaxies are moving apart from each other faster than the speed of light, does that mean that it's impossible to travel to another galaxy, regardless of what technology get discovered? Because you ...
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1answer
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Can light in a medium travel faster than speed of light $c$ in vacuum?
Refractive index of medium $m$, $n_m$, is given by $$n_m = \sqrt{\mu_r\epsilon_r}$$where $\mu_r$ and $\epsilon_r$ are permittivity and permeability of the medium respectively.
And, velocity of light ...
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What is Cherenkov radiation? [duplicate]
What is Cherenkov radiation? I came across this concept when I was learning SR.
Why can't particles moving at speed of excess of speed of light in the medium. Why it does not violate the limitation ...
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So is quantum entanglement actually FTL “communication” or is it mundane pre-determination?
I have to say right off the bat, I'm a little frustrated that there seem to be very contradictory answers about this, at least to a layman like me. If two particles are entangled and you separate them ...
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Significance of the LIGO experiment with respect to length contraction
it might be best to first detail my (admittedly limited) understanding of the LIGO experiment. a beam of light is split along two 4Km evacuated pipes then reflected back where their interference ...
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Does gravity sometimes get transmitted faster than the speed of light?
Consider Earth moving around the Sun. Is the force of gravity exerted by Earth onto the Sun directed towards the point where Earth is "right now", or towards the point where Earth was 8 minutes ago (...
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Turning on headlights near light speed [duplicate]
If i turn headlights on in a car at v = 0.99*c, will the headlight speed be 0.01*c? I know speed of light is always the same but it really confuses me? My question is, does space contract so much at ...
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speed of freezing vs. moving [closed]
An idea came to my mind and like to discuss it.
We know that out there in the space the absolute zero (aka. -273 C) is almost reached where all the particles and atoms would freeze up and stop giving ...
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Are tachyons time travelers?
If tachyons are faster than light, that means they have passed a certain point before anyone or anything can “see” them. Theories have mentioned that if anything can go faster than light, then it can ...
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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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1answer
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Observing supraluminally receding galaxies – is the “swimmer against variable current” analogy valid? [closed]
Davis and Lineweaver in Superluminal Recession Velocities state that “galaxies with distances greater than $D=c/H$ are receding from us with velocities greater than the speed of light and superluminal ...
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1answer
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Delayed choice quantum eraser without randomization?
My understanding of delayed choice quantum eraser experiments roughly corresponds to the Wikipedia article about them, so please forgive if this question is stupid.
In all delayed choice experiments ...
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Apparent FTL speeds seen by observer
MY guestion is if I was in a ship orbiting a black hole (not very close to the event horizon) I am orbiting pretty far and I am experiencing that my time is slowing down realitive to people on earth. ...
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Why do two moving inertial frames of reference atribute the same velocity to each other?
In both relativity and Newtonian mechanics, it is a self-evident axiom according to which two inertial observers who move relative to each other measure the same velocity of, say, $v$. I want to know ...
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Gear Theory — Entanglement — Spooky action at a distance explained? [duplicate]
Nothing can travel faster than the speed of light. Not even an electrical signal. Entanglement seems to violate this. But, does it?
Imagine 100 gears lined up in sequence all the way across a ...
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1answer
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Faster than light speed transfer of certain event
I am CS/Math person I am not quite sure what it means in physics
information cannot be transferred faster than light (FTL). I tried to understand the proof of no transfer theorem but I lacked the ...
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How big is the universe 1 second after the Big Bang? [duplicate]
In his book Astrophysics for People in a Hurry, Neil de Grass Tyson starts of with the Big Bang and narrates on what (probably) happened within the first moments of our universe. He further states (p. ...
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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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Is the speed of light greater if traveling at an initial velocity greater than zero? [duplicate]
I'm reading "a brief history of time" and he states "the speed of light should be the same whatever the speed of the source, and this has been confirmed," (24). Why is it not increased if it has an ...
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Relative velocity greater than speed of light
Is it possible a relative velocity between 2 objects to be greater than the speed of light?
I know that it is impossible to reach the speed of light considering us to be immobile but is this ...
