The speed of light is a fundamental universal constant that marks the maximum speed at which energy and information can propagate. Its value is $299792458\frac{\mathrm{m}}{\mathrm{s}}$.

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Meaning of constant $c$ [on hold]

I have a puzzlement over Einstein's expression $E = mc^2$. The constant expressed as $c$ is the measured speed at which Light crosses a vacuuum. BUT it is also used to denote the maximum possible ...
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47 views

Speed of light interpretation [on hold]

I was wondering if any theory interprets the speed of light such that light needs to stay and visit some small open set for each tick of time? Then it could be renamed law of the good guest or ...
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Deriving the speed of the propagation of a change in the Electromagnetic Field from Maxwell's Equations

I've been told that, from Maxwell's equations, one can find that the propagation of change in the Electromagnetic Field travels at a speed $\frac{1}{\sqrt{\mu_0 \epsilon_0}}$ (the values of which can ...
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3answers
668 views

What if a faster-than-light particle is found?

What will be the consequence (severe ones) on laws of physics if a particle that travels faster than light is discovered? I am looking for a more general answer so that a high school student would be ...
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1answer
25 views

How are the frequency and wavelength of electromagnetic waves affected within an event horizon?

I apologize if this has been asked previously or if my thinking is way off base, but I am inexperienced with relativity (and this is my first question on the site). I am wondering; as one (not ...
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2answers
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Does the constancy of the speed of light in vacuum hold for any observer in GR as well?

From SR, we know that the speed of light in a vacuum is the same for all observers, regardless of the motion of the light source. But in GR, does it still hold for all observers? I mean the constancy ...
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51 views

Relativity of time in regard to speed of light [closed]

Someone stated that if you go on a train for 1 year going 99.999999999% the speed of light 233 year would have passed to those outside the train due to time dilation. So what speed do we perceive time ...
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3answers
160 views

Relative velocity of light beams

Assume two light beams moving in the same direction i want to use the relativistic velocity transformation equation to find the relative velocity with each other, Note : i let $C$=1 ...
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0answers
47 views

If Black Holes Consume Space What Is The Space Traversing? [duplicate]

I've heard it stated by physicists that space moves into (Or through/down into if you like) black holes faster than the speed of light and that this is possible because the speed of light is a ...
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1answer
105 views

How far does a photon move in the 4th dimension when it travels one light second? [closed]

In one second a photon moves 3x10^8 meters through the three spatial dimensions. Light's velocity is 3x10^8 m/s. If the photon moved at all in the fourth dimension, it's velocity would no longer be ...
2
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2answers
369 views

Stanford: “Objects in spacetime all move at constant speed $c$.” Are they right? [duplicate]

In this Stanford University lecture on Relativity, it is stated: Likewise, objects in spacetime all move at constant speed c in spacetime but if you change its direction, say by moving at speed v in ...
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1answer
75 views

Can light break relativity's reference frame? [closed]

I have fairly little experience with relativity and physics in general, so I might just be missing something, but I do often ponder how the universe works. My understanding of relativity is that ...
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3answers
87 views
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1answer
77 views

At what speeds does time dilations start to occur?

My question is, is it possible for time dilation to occur at a speed less than that of speed of light?
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28 views

How much time will for the observer last sound of thunder? [closed]

We have height of the cloud 5 km. The observer stands 20 km away. The speed of sound depends only on the temperature. $C=a\times\sqrt T$ Temperature on 5 km is $-33^o C$ and on the ground $7^oC$. ...
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1answer
113 views

What would we see if a camera orbiting close to light speed beamed down images of us on earth?

If a camera was sent up in a satellite, put in orbit at close to light speed, and instructed to beam down images to earth, what would we see if we watched its video feed? (Ignoring the fact that ...
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1answer
578 views

Does a photon travel through space exactly at the speed of light?

In practice, given that in the vacuum of the universe is not perfectly empty, does the photon actually reach exactly c? Is it even possible? If it travels at exactly c, then from the photon ...
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2answers
140 views

Einstein wrote $x^4=ict$, where $c$ is the speed of light. Does this mean the fourth dimension is moving? [closed]

Saw this on a forum: Einstein wrote$x^4=ict$, where $c$ is the speed of light. Does this mean the fourth dimension is moving? We can write $x^4=ict$ as $dx^4/dt =ic$. The fourth dimensions is thus ...
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0answers
54 views

Cherenkov Luminescence Imaging, Cherenkov radiation,

Is it possible to see glowing from Thin Layer chromatography (TLC silica gel on Aluminium) when we image it by IVIS spectrum (no radioactive source)?
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3answers
479 views

How did we realize that light travels at a finite speed?

We all know that light travels at a finite speed of nearly $3\times10^8\mathrm{m\,s^{-1}}$. But how did we come to think that light has a finite speed? Why did the scientists try to calculate the ...
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2answers
3k views

Were Michelson-Morley results a surprise?

How unexpected were the Michelson-Morley experiment results? Did physicists have theoretical reasons to predict that the speed of light would result to be invariant?
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2answers
173 views

What's the max speed a man-made satellite can travel in space before its circuitry stopped working?

Assume it could withstand extreme temperatures in either direction. I'm mainly curious what would happen to its circuits as it approached the speed of light.
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3answers
294 views

Why does the Michelson-Morley experiment only contradict the aether?

This question is related to Validity of Maxwell's equations with no aether or relativity? (so please read this first). In this question, the answers seem to suggest that getting rid of the aether ...
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1answer
83 views

Why is the speed of light being invariant and finite in all inertial reference frames?

I understand the basics of Lorentz transformation and Riemann Geometry but I still cannot understand why the speed of light is the same in all inertial references. Has anyone ever researched about ...
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3answers
145 views

What's the problem with light traveling at speed higher than $c$?

I'm trying to understand how Einstein concluded that time is relative based on thought experiments such as a torch attached to the end of a rocket. Based on answers to questions like this one, this ...
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1answer
59 views

Do Gravitational Waves disprove superluminal Alcubierre drive?

I am not a physicist. But... does the rate at which gravitational waves travel set an upper limit to the "speed" of a ship propelled with Alcubierre drive? Or does it present a relativistic trick ...
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2answers
58 views

How time and speed of light are related? [closed]

I want to know how speed and light and time are related? How will motion with highspeed effect time? I am not a physics student. I want an answer which is free of mathematical relations. I want an ...
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Demonstrating quantum non-locality by two consecutive measurements [on hold]

Entangled state measurements says that Bob's measurement polarizes the Alice's observations. Bell has invented that we need a third property (axis) of measurement is needed in order to demonstrate ...
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1answer
28 views

Multiple Objects at Constant Speed

Imagine 1 million objects travelling in space, at a constant speed, along an imaginary line. They don't deviate from that line for the sake of this argument. Now, object 1 has a velocity of $v_{1}=1$ ...
0
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1answer
49 views

Can something go faster than the speed of light in a medium? [duplicate]

Since some mediums have an index of refraction more than 1, light goes slower than in a vacuum. Does this mean it is possible for particles to go faster than the speed of light in these mediums? If ...
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1answer
94 views

Does massive particle really move at speed of light? [closed]

According to this answer I understood that particles with mass also move at speed of light but interaction with higgs field make this movement zigzag. So average speed is below speed of light. But I ...
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3answers
151 views

Why did Einstein took speed of light unit or constant in his equation of relativity?

We can find that no object can have speed more than light from Einstein's equation of relativity because if anything have speed more than light then we get -ve value within square root. But why did ...
0
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2answers
370 views

How to achieve speeds faster than light? [duplicate]

So, I heard that all speed is relative. And that nothing can travel faster than light. Then I guess it is OK for a spaceship to leave Earth at 0.6c constant speed. And what if an other spaceship were ...
42
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6answers
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If I run along the aisle of a bus traveling at (almost) the speed of light, can I travel faster than the speed of light?

Let's say I fire a bus through space at (almost) the speed of light in vacuum. If I'm inside the bus (sitting on the back seat) and I run up the aisle of the bus toward the front, does that mean I'm ...
0
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1answer
75 views

Does a black hole really slow down time?

When an object gets pulled into a black hole it seems to slow and stop, but could it be possibly be because the speed of light that hit the object and came back was slowing down as the object got ...
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1answer
61 views

What would happen if space were considered a medium?

Space is not empty they say, is it a new idea or has it always been like that? Can you explain what is the (current) real meaning of vacuum, which is just the Latin for empty Can you also explain ...
0
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1answer
112 views

Fermi velocity $v_F$ and speed of light

Can Fermi velocity $v_F$ be equal to speed of light, $c$, for ultra-relativistic electron plasma waves, in plasma physics, by using Fermi-Dirac distribution function?
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1answer
39 views

Speed of light in vacuum in special relativity

In special relativity, the speed of visible light is defined as a constant. But visible light is only a small part of the electromagnetism field. So why?
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1answer
56 views

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 ...
4
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2answers
208 views

Is there a limit to how hot an object can get?

If heat is the measure of how fast the atoms are moving in an object, than isn't there a limit to how hot that object can get as nothing can go as faster than the speed of light. So because the atoms ...
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1answer
52 views

Stacked motors thought experiment

first of all, I'm not a mathematician, just curious about something that came up to my mind and maybe you can help me out. Scenario: I have a motor that spins let's say at 20K revolutions per ...
42
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7answers
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Why is there no absolute maximum temperature?

If temperature makes particles vibrate faster, and movement is limited by the speed of light, then temperature must be limited as well I would assume. Why there is no limits?
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1answer
69 views

Maximum wavelength of a photon/electromagnetic radiation?

This asked; What is the minimum wavelength of electromagnetic radiation? And also this; What is the maximum possible frequency and wavelength? The second question is contradictory; maximum ...
3
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0answers
74 views

Experiment measuring vacuum permittivity and permeability in high speed

Suppose that we do NOT know anything of constancy of speed of light, to say nothing of special relativity. It is that we acquired a constant speed of light from Maxwell's Equations that we finally ...
0
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1answer
31 views

Incomprehensible substance: information traveling faster than light? [duplicate]

Say I'm holding a rod composed of an incomprehensible solid, and this solid rod is 1 light second long. Then say I poke you with the rod and at the same time I flash a light on you. If light is the ...
3
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7answers
855 views

Is there a universal rest frame of reference?

I am still struggling with C being a constant and what that implies. So can an experiment be done to find the resting state for the universe? Take a device with an observer and a light source and two ...
21
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3answers
5k views

How can muons travel faster than light through ice?

When a neutrino traveling through ice hits and interacts with an oxygen atom, muons are created. Cherenkov radiation can be created when muons travel through ice faster than light and create a ...
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1answer
50 views

Does slowing light violate relativity?

Last year Scottish scientists managed to slow down photons in vacuum by changing their shape. Does this violate the special theory of relativity?
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4answers
193 views

Could the Heisenberg uncertainty principle be derived from the speed of light limit? [closed]

Background: As I was thinking about an alternative approach to the question: "why is there a finite speed of light, and why its magnitude corresponds to c?" –ultimately, I was trying to understand ...
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1answer
63 views

how long will take for an astronal travel in near lightspeed in his point of view

I always had a question about relativity. Suppose an astronaut in orbit Saturn just must reach earth fast as possible. Your ship can travel at any speed between 0 and the speed of light. the distance ...