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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What would happen if a space ship may travel as quickly as the speed of light? [on hold]

Ofcouse, it is impossible. Beacuse of need of infinite energy to accelarate infinite mass... Bur if it might be possible...??? I did a fictional study as an amateur. I shared it, but i need feedback ...
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2answers
102 views

Does the speed of light have a range of speeds due to medium-dependency?

An EM particle-wave propagates in a vacuum at a constant speed $c$, independent of the source/receiver but dependent on most mediums it moves through. Since the vacuum is a medium, and if logically ...
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175 views

How can light travel at a speed greater than the speed of light

I was reading John Rennie's answer here, Can light travel faster? I now know that the sentence ''the speed of light is always constant in vacuum'' is just an oversimplification, for example light ...
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1answer
38 views

Would we see the past if we look to a mirror 1 light year away? [duplicate]

What would we see if we place a mirror 1 light year away? Would we see the present or the past?
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3answers
108 views

How is it possible for the wavelength of light to change in a medium?

So my physics class has just finished a long unit on optics while at the same time I've been trying to teach myself relativity. I admit my understanding is probably rudimentary, but I figured all the ...
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Why doesn't light, which travels faster than sound, produce a sonic boom?

I know that when an object exceeds the speed of sound ($340$ m/s) a sonic boom is produced. Light which travels at $300,000,000$ m/s, much more than the speed of sound but doesn't produce a sonic ...
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3answers
45 views

Photon: speed and mass

Is it correct to think that the speed of light does not depend on the speed of light source because photons have no mass, so they have no the kind of inertia that is associated with mass, so they can ...
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0answers
29 views

What is the speed of gravity? [duplicate]

Hypothetically, let`s say that one day our Sun is suddenly removed from the galaxy. For us, on earth, would take up to 8.3 minutes to notice that the sun was removed, since the distance from the earth ...
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22 views

Relative speed and time [duplicate]

There is a notion that travelling at the speed of light is impossible for a matter. But what if the there are 2 objects that are coming towards each other with half the speed of light. Thus relatively ...
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0answers
31 views

Is there an area of the universe observable from earth that is newer than the rest [on hold]

If the big bang theory and expansion theory is correct, if we look from earth to the sky will we observe in a specific area newer galaxies than the galaxies we see in the rest of the observable sky? ...
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3answers
233 views

Why does red light travel faster than blue light?

I know that light of all frequencies travel at the same speed in vacuum. But I wonder why their speed differ in any other medium, why does red light travel faster if it has less energy than blue ...
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2answers
123 views

Special Relativity - Distance Not Increased?

I just watched the movie Interstellar and the question was asked of why/how high-speed travel would slow time within an area. Curious as I am, I watched several YouTube videos to quickly 'educate' ...
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2answers
53 views

Speed of light yes or no? [closed]

First off I am not a physics student: I am more of a science enthusiast. My question pertains to time and the speed of light: According to Einstein, no mass can travel at the speed of light. Now, ...
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29 views

Speed of light in a medium as superposition of dipole radiation

Studying electromagnetism I know that the speed of light in a medium is $v = c/\eta$ and that it's possible to derive this from the Maxwell equations in the medium. But I wanted to find a microscopic ...
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1answer
63 views

Is there a horizontal event horizon on a spinning black hole?

It seems that most of the information one reads about black holes theorises that they are not spinning. The theories then describe all matter approaching a black hole as being absorbed by it. Wouldn't ...
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1answer
59 views

Would light from the Sun necessarily reach Earth after 8 minutes if the Sun was switched off?

Would light from the Sun still reach Earth if there was a hypothetical event that shut off the Sun? The time taken by light to travel from the Sun to the Earth is 8 minutes. Couldn't a catastrophe in ...
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0answers
27 views

Would you be able to see yourself in a mirror in front of you as you two are in a room traveling at the speed of light? [duplicate]

Veritasium talked about this in one video. If you are in a room or a train, plane, car or whatever just a closed space traveling at the speed of light and you put a mirror in front of you, could you ...
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1answer
337 views

Speed of light and virtual particles

After becoming extremely bored while studying for an Afrikaans exam, I started thinking about virtual particles. So, can light (photons) interact with virtual particles (even though they only exist ...
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2answers
113 views

Propagation speed of photons when taking higher-order QFT corrections into account

In our group of experimental physicist who have nothing to do with and know very little about quantum field theory, we recently had a question concerning the propagation speed of photons in vacuum: ...
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3answers
731 views

Why don't quantum effects invalidate the speed of light barrier?

While proving that no matter can reach the speed of light (a fact which I call the kinetic energy barrier), Einstein uses the fact that he can calculate the velocity and position of an electron. ...
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4answers
2k views

Is the universe a quantum computer - is light speed barrier a computational constraint

There is currently a debate ongoing on leading maths blog Gödel’s Lost Letter, between Gil Kalai and Aram Harrow, with the former arguing that building a quantum computer may not be possible due to ...
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2answers
194 views

Is it really possible to “discover” the speed of light with a microwave oven?

I've seen a number of sites/videos online that describe a method for measuring the speed of light, using a microwave oven and a chocolate bar. For example, this video on youtube. The basic idea is to ...
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1answer
110 views

I want to know why light even moves at all.

Never mind in a vacuum, why and how does light even move at all? What propels it?
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99 views

Why are the proper time and the proper length not defined in the same frame of reference?

I've just read this interesting Wikipedia article about time dilation and length contraction in special relativity. . Derivation of time dilation Applying the above postulates, consider the ...
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1answer
35 views

How does the photon differentiate between events?

As far as I know for a photon that's moving at the speed of light (obviously) time comes to a halt and space contracts to a point, making all travels instant from its perspective. Now this is the part ...
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1answer
56 views
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5answers
307 views

Detecting absolute motion inside a box

This is not a contradiction and I know it is impossible but still consider a thought experiment by me and point out if something is wrong. See the following picture and then the explanation follows. ...
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How is it possible the universe expanded faster than the speed of light during inflation?

In a documentary written in collaboration with Stephen Hawking, the narrator (supposedly Stephen Hawkings) says that by the time the cosmos was 10 minutes old, it had already expanded thousands of ...
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Given the quantum Zeno effect, won't continual observations of a photon stop/slow down light?

The quantum Zeno effect states that continual observations will prevent motion. Therefore, won't continual observations of a photon(s) reduce the speed of light? Is my reasoning flawed?
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4answers
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Is there a formula that gives the position of an object depending on the time, but which doesn't allow the object to surpass the speed of light?

I have found these two formulas: $v = at + v_0$ $x = \frac{1}{2}at^2 + v_0t + x_0$ a is the acceleration v is the velocity x is the position t is the time $v_0$ is the initial velocity $x_0$ is ...
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1answer
45 views

Top speed for a human

What is the fastest that a human being of average weight could possibly travel, and what is the most widely held theory for how this might be achieved (assuming this person is impervious to all forms ...
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2answers
59 views

Velocity of light

Velocity of light decreases as it enters a more optically denser medium. So how far can the velocity of light be reduced? Which object has the highest refractive index?
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2answers
77 views

Acceleration to lightspeed using gravity

Suppose we have a very advanced spaceship that (aside from colliding with planets or entering a blackhole) is indestructable, and can go very fast, but is incapable of moving at lightspeed on it's ...
3
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1answer
88 views

Doppler effect and light

Approaching the speed of sound in an aircraft is relatively difficult, because the closer you get to Mach 1, the denser the pressure is around you (sound accumulates causing vibrations). Is there a ...
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2answers
87 views

How to visualize the world while travelling near the speed of light? [closed]

I have been having some trouble with this for a while. I think in terms of vivid , moving images and i haven't been able to visualize this completely. I wondered if a person, like the Flash from the ...
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1answer
25 views

Unit definition concerning light and metre [closed]

A stupid question. I see metre is officially defined based on the speed of light: The meter is the length of the path travelled by light in vacuum during a time interval of 1 / 299 792 458 of ...
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4answers
2k views

Will an object always fall at an infinite speed in a black hole?

Most of you if not everybody will agree that the stronger the gravitational pull, the faster an object will fall. For example, on a planet with 50 times the gravity of Earth, any object will hit the ...
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6answers
4k views

Do photons have acceleration?

Photons travel at the fastest speed in our universe, the speed of light. Do photons have acceleration?
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4answers
176 views

Expected result of vertical Michelson-Morley Experiment [duplicate]

What would the result of a vertical variation of the Michelson-Morley experiment be? I.e., if one were to compare light traveling along a horizontal arm with light traveling along a vertical arm ...
5
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3answers
87 views

Has anyone tried Michaelson-Morley in an accelerated frame?

After doing much more digging than I thought I had to do, I found out that the speed of light is NOT invariant in an accelerated reference frame. Has anyone done any experiments to confirm this? In ...
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2answers
67 views

Can a point in empty space be motionless with respect to light?

Being that the speed of light is constant throughout the universe, can a point in empty space be motionless with respect to light?
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1answer
71 views

Is gravity instantaneous? [duplicate]

I want to know if (hypothetically) a star appears out of nowhere at a certain distance (say 20 light seconds) away from me, how long will it take for me to get the feel of it's gravity? Will I know it ...
11
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4answers
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Do all massless particles (e.g. photon, graviton, gluon) necessarily have the same speed $c$?

I suppose there was a discussion already on speed-of-gravity-and-speed-of-light. But I silly wonder whether all the massless mediators of four fundamental forces, i.e. Graviton: $g_{\mu\nu}$ ...
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2answers
122 views

Speed of light constant for all observers [duplicate]

General relativity has been proven many times over to be correct. In my meager understanding of things, they are all premised on the fact that the speed of light is constant to all observers. I would ...
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2answers
44 views

Is the influence of gravity greater than light? [duplicate]

As the influence of gravity is infinite throughout the universe.is the influence of its force on a body very far away faster than the speed of light.suppose a star dies...is the influence of its ...
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2answers
59 views

Gravity and the Speed of Light

Let's assume that I am on an airplane that is at about 4,000 altitude and now let's also assume that I am standing on one of the wings with a light torch, if I point the light torch below to the ...
0
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1answer
34 views

Travelling at the speed of light [closed]

more of a philosophical questions normally if you are travelling at some speed and you bump into some object, you generally would get slowed down and the force from your acceleration would be ...
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2answers
85 views

Does matter become energy at the speed of light? [closed]

According to modern physics, we can't push matter to the speed of light. It would slow down (relative to its environment). But theoretically, if matter were to travel the speed of light, would it ...
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2answers
254 views

What is the relationship between the speed of light and virtual particle production

What is the actual basis of the speed of light? Why is the transfer of information limited to it? Virtual particles that arise and disappear within a certain timeframe, is There a relationship ...
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1answer
123 views

Slower than light photons in vacuum?

This report on the BBC site suggests that optical photons have been prepared that travel slower than c in vacuum. How is this possible?