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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Speed of light in double-slit experiment

Given the fact that the photons arrive at different places on the screen, does the speed of each photon is different ?
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816 views

With respect to what can't we travel at the speed of light? [closed]

According to theory of relativity the speed of light in vacuum is ultimate. But since objects move relative to each other, with respect to what can't we travel at the speed of light?
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Would this ship travel faster than light

Im curious about using a geometric thruster system to break the speed of light barrier, Using a system of beams that rotate along alternating axis' from either end of themselves so as to travel a ...
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41 views

Can one shed light on the velocity of the photon through the fourth dimension x4 using limits? [duplicate]

THIS QUESTION IS COMPLETELY DIFFERENT!! IT DISCUSSES LIMITS!! To begin with, please study the mathematics from Brian Greene’s book An Elegant Universe. The upshot is that the faster an object moves ...
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42 views

Some perspective on two slits

I am not a physicist but i enjoyed the subject as a hobby and have my formal education in the field of computer science. If any of what follows is a big flaw in my understanding, I hope it will be ...
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1answer
68 views

How fast does matter grow more massive when accelerating? [on hold]

I am wondering since it is understood that mass of matter increases as its velocity increases, how fast does this process occur if it is a physical process? For instance, if a mass initially at rest, ...
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43 views

Minimum and Maximum Speeds of a Mass [on hold]

I understand that it is impossible for a object with rest mass to travel at $c$ (the speed of light) due to time limitations. I also understand that the speed of an object is calculated using a frame ...
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14 views

Kinetic Hysteresis [duplicate]

I have been wondering about this question for quite some time, but, until now, I was not sure how to phrase it without sounding naïve. Let's take Newton's Cradle (just three congruent balls will do). ...
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10answers
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How can a photon have no mass and still travel at the speed of light?

I've read a number of the helpful Q&As on photons that mention the mass/mass-less issue. Do I understand correctly that the idea of mass-less (a rest mass of 0) may be just a convention to make ...
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45 views

Action at a Distance [duplicate]

Since photons move at $c$, do they experience time or distance? If they don't, doesn't this explain action at a distance? From the point of view of the photons, there is no time, so the action at a ...
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Does the speed of light in vacuum define the universal speed limit?

Is light the thing causing the universal speed limit to be $299\,792\,458\,\mathrm{m/s}$? So the universal speed limit would be different if light travelled faster or slower? Or, is $299\,792\,458\,\...
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3answers
108 views

How the speed of light is constant with the particle horizon moving toward us?

I asked a question earlier with the same subject in mind. However, I was rather upset at the time and it didn't make much sense. I'm taking an astronomy course and seem to be misunderstanding ...
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132 views

Is it possible to slow down light?

Last I knew, light is the fastest thing in the universe but I could be wrong. Anyways, if the speed of light is 299,792,458 m/s (correct me if that is inaccurate) then is it possible to slow it down? ...
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2answers
89 views

As electron is accelerated nearly to the speed of light what would occur? [on hold]

What would occur if an electron at rest was accelerated nearly to the speed of light? Would the photons emitted by the electron approach a gamma wave photon as it approached the speed of light, or ...
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1answer
142 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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Constancy of the speed of light in the hypotenuse of the triangle in the Michelson and Morley experiment [on hold]

In Michelson and Morley experiment, Michelson calculated that the total time traveled by light with respect to the stationary observer standing at ether field was $2L/c$. Here, Michelson followed ...
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3answers
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The speed of light upon reflection [duplicate]

(NOTE: I am an 8th grader, so I may not be capable of perfectly elaborating my point by scientific measures. Also, English is not my first language) I have read that the speed of light is constant, ...
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5answers
920 views

Why Sun light can reach us if Time is dilating?

I understand that if something is moving with constant speed in respect to an observer, the time of the moving one runs slower, so the more your speed is, the more your time ticks slower. Which ...
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115 views

What is the velocity of the photon through the fourth dimension x4? [closed]

Photons are real, physical objects. The fourth dimension is a real, physical entity. Therefore, photons must have a relationship with the fourth dimension. They must have some velocity relative to ...
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1answer
144 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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If something is not moving in space, is it moving on the time axis at the speed of light? [duplicate]

I heard this theory yesterday: If something is not moving in space, then it is moving on the time axis at the speed of light. I realize that in essence there is no object which can be considered as "...
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75 views

What do we mean by speed of light dependent on direction?

I have a statement in textbook saying: When the speed of light is independent of direction, the secondary waves are spherical. When is it dependent on direction and how will the secondary ...
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Change in Speed of Light [duplicate]

Whenever light enters from air to glass its speed decreases but when it cross the glass and again come in air its speed increases. What is the reason behind this property? What is slowing it and what ...
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4answers
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To what extent can speed of light be reduced? [duplicate]

Light slows down upon entering different transparent objects, and the ratio is taken as refractive index of the object. If light can be slowed down, then is there a limit up to which it can be slowed ...
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Can the speed of light become complex inside a metamaterial?

The speed of light in a material is defined as $c = \frac{1}{\sqrt{\epsilon \mu}}$. There are metamaterials with negative permittivity $\epsilon < 0$ and permeability $\mu < 0$ at the same time. ...
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Information, entanglement and EPR

I'm currently trying to understand why superluminal information transport is not possible. Therefore, I would like to get some help concerning the definition of information or the general setting. ...
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678 views

How can we show that the speed of light is really constant in all reference frames?

I had a debate with a friend who cannot believe that the speed of light is constant. He said something like: so what if in the Michelson-experiment the moving apparatus simply added a constant ...
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Can an object appear to travel faster than the speed of light?

An object cannot travel faster than the speed of light. But given a video of an object travelling at $0.5c$, could one speed the video up so that the object appeared to be travelling at $1c$, $2c$ or ...
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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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Why is c=299792458m/s? [duplicate]

In my high school physics book, SI unit of length,ie metre is defined as -" the distance covered by light in 1/299792458 seconds". If we take a metre as distance travelled by light in 1/300000000 ...
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299 views

How is time not a constant?

I am a visual person, so it's hard to imagine the information I keep getting, but shouldn't time be a constant? If you were traveling at the speed of light and your able to cover $299{,}792{,}458$ ...
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Isn't the “constant speed of light” postulate valid also for sound waves?

The second postulate of Special Relativity says: As measured in any inertial frame of reference, light is always propagated in empty space with a definite velocity c that is independent of the ...
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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. Is ...
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Relation between intensity of light and refractive index

The intensity of light (as calculated from time average of the poynting vector) is given by $I = (1/2) \epsilon v E_0^2$. Here the intensity is dependent on the velocity of light in the medium. The ...
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628 views

Is special relativity axiomatic?

Can special relativity be somewhat described by the following statement? If the speed of light is a universal constant, and if light can be placed in separate frames of motion, then time must be ...
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What axiomatizations exist for special relativity?

Einstein 1905 gives the following axiomatization of special relativity (Perrett and Jeffery's translation): The laws by which the states of physical systems undergo change are not affected, whether ...
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What is the irreducible set of fundamental principles of Special Relativity? [duplicate]

This is something that I have been pondering for some time. The fundamental principles of special relativity are usually presented as forming a twofold: There is no absolute reference frame of ...
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Why speed of light is constant with respect to any inertial frame of reference? [duplicate]

Its getting too difficult to think.if we travel at the speed of light then will light will cross us at same speed or travel with us adjacent (special theory of relativity)
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Is there a fundamental picture for 'the speed of light'?

I am curious about the profound reason for the concept of 'the speed of light'. My considerations are: (1) It's related with the structure of spacetime (for example in Penrose's twistor plan),so ...
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If a photon has no mass why doesn't it have infinite speed? [duplicate]

Please help a naïve layperson understand -- if a photon has no mass, why is its velocity limited at all? Shouldn't a particle with no mass be able to travel at an infinite speed?
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Measuring the speed of light and defining the metre - absolute or relative?

If the metre is now defined as the distance light travels in vacuum in 1⁄299,792,458th of a second and the speed of light is accepted to be ...
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Is mass relative? [duplicate]

This question has to do with the relativistic mass of an object. I have been reading that as energy increases, so does mass to a much lesser extent, and that this applies to kinetic energy as well. ...
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32 views

Is measuring the speed of light using energy and wavelength cyclical?

I would like to measure the speed of light by directly measuring the frequency and wavelength of a light source. In order to determine the wavelength, I wanted to use a diffraction grating and the ...
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2answers
932 views

Is Earth's orbit around the Sun affected by the ~8 minutes light delay?

Gravitational change occurs at the speed of light. As a consequence, we experience on Earth the gravitational attraction of the Sun based on its position relative to us ~8 minutes ago. How does this ...
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Reflection At Speed of Light

I have looked online to no avail. There is two competing answers and I am curious to know which one is right. Someone asked me this question. If you are traveling at the speed of light can you see ...
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Why must $v$ be $< c$ in the Lorentz transformations? Do these equations not apply to light? [duplicate]

I was trying to understand how things look from the perspective of light. Looking at the Lorentz transformations, it seems that the universe would contract along the direction of movement into a plane,...
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Can orbiting a black hole 99.99% speed of light make other object with relatively fast clock travel faster than light, relative to me?

If i orbit a black hole, 99.9% speed of light, time for me is moving slowly, relative to me, planet earth is aging fast, and i have traveled 10 years into the future(relatively) in 1 second, suppose ...
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Imagine I'm on a spacecraft that was accelerated to 1.0$c$ could I only move backwards? [duplicate]

Imagine I'm in a sapcecraft1 that is moving with 1.0$c$ or at least is so close to that speed that a few miles per hour would just be left to reach $c$. So when I'm traveling now in the direction ...
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Did Einstein know about Michelson-Morley experiment?

The second postulate of special relativity deals with constancy of light in inertial reference frames. But, how did Einstein came to this conclusion? Did he knew about the Michelson-Morley experiment?