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 to the human body if we went almost at the speed of light? [duplicate]

If we were to travel almost at $299\,792\,458~m/s$, or the speed of light, what would happen to the human body? Would we be fine or would there be consequences? Would our body shut down? I've been ...
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49 views

Is it possible for someone traveling at the speed of light to see at all? [on hold]

I know that the speed of light is the same for all observers regardless of your speed, But this question is really worth thinking about. If someone let's say managed to reach the speed of light, ...
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70 views

Is speed of light is impossible, even for light in nature? [closed]

im not a student, teacher, researcher in fact I've never even taken a physics class. But I Love to argue!, i spent a day proving (in my mind anyway) that, 1. a photon does have mass. 2. its ...
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45 views

Camera on the ground vs camera in a train

A couple days ago my history teacher was explaining special relativity with the train example, where you are in a train close to light speed and you see a clock on the train terminal and the clock ...
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54 views

Light speed time distortion

From my understanding objects moving close to the speed of light experience a time distortion in that time moves slower and slower as they get closer to the speed of light. If that is the case ...
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Traveling near the speed of light

If I travel near the speed of light, form a stationary observer perspectives, I will take 1 year plus to travel 1 light year, but in my perspective, would I take less than 1 year to travel to that ...
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56 views

Is Lorentz transformation applicable of light itself?

I've just studied Einstein's Special Theory of Relativity and have followed most part of it. I was just wondering that whether the equations of Lorentz transformation are applicable on light? i.e. can ...
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30 views

Filming light in slo mo

So I was thinking of a cool video I could make when I thought of filming a video of me turning on a light. I thought that if you film yourself turning on a light and slo mo that video enough times ...
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3answers
58 views

Our speed and direction by comparing the speed of light?

If the speed of light is constant no matter the speed of the source, shouldn't we be able to know the direction and exact speed we are going relative to the absolute 0 in speed? If a photon is sent in ...
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23 views

Do the mediums decrease or increase the speed of light? (source to target) [duplicate]

If sun is the source of light then is it possible that the speed of light might increase depending on the mediums its going through or its not possible.
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When light changes medium, does it decelerate, or instantaneously change speed? [duplicate]

The velocity of light changes between mediums, but does light specifically decelerate when it enters a denser medium, or is the change is speed instantaneous?
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Light coming from distant stars

As we know, light travels with a constant speed and the Universe is ever-expanding and endless. Considering this fact, is it possible that the sky we see should change everyday? Let's say today we see ...
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The speed of light sets a lower limit to the rate at which a reference frame can pass through time. Is there anything that sets an upper limit? [duplicate]

Is there any "slowest" velocity that sets a cap on how fast a reference frame passes through time, or can you pass through time infinitely fast given a "slow" enough velocity?
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Will the Velocity of an object change if it moves fast,close to speed of light?

If an rocket moves with a speed of 0.5c. So, the speedometer in that rocket will show 0.5c. But there will be time dilation when someone sees it from the earth. Then it's Time dilation will be So, ...
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2answers
40 views

What would we see back on Earth if we shot a camera off into space and watched a live-stream?

I'm curious as to what we would see if we shot a camera off into space at, say, 50,000 mph and watched a live stream. Clearly in the beginning we'd be seeing things in more or less real time. But by ...
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1answer
41 views

Relative motion at almost the speed of light

My title might not be precise but I didn't know how to decribe it better. I've been reading about the special and general theories of relativity for a short while and I started wondering. First, ...
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88 views

Speed of light and perception

So I'm reading a book called "The Elegant Universe" and here is a part of it Imagine two countries that have been at war are sitting down to sign a treaty ending hostilities while traveling aboard a ...
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3answers
85 views

Which is more fundamental,''constancy of speed of light'' or ''space-time''? [closed]

My friend asked me,''which is more basic or fundamental? constancy of speed of light which makes space-time behave dynamically OR dynamical behavior of space-time that makes light to travel with ...
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128 views

Is it true that all particles that have a speed less than the speed of light must also have mass?

I've previously learned that massive particles cannot achieve the speed of light. But recently I read that, concerning the gels that refract and bounce light within around enough that it can travel ...
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156 views

If you shine a light away from the center of a Schwarzchild black hole, will it stay still?

$$ A $$ Light is travelling away from the absolute center of the Schwarzchild black hole (i.e. none of that spinning/stretching field) at $\ C $, and so shouldn't $\ \Delta C$ need to be greater than ...
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46 views

How fast would you have to go to claim you saw the red light as green due to the Doppler Effect?

Driving toward it, I suspect you would have to be going at relativistic speeds. Calculating this, it appears to be around 1/6 the speed of light when driving directly at it, but since you are on the ...
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2answers
42 views

What--is the Ultimate Limit of heat based off c? [duplicate]

As heat goes up, molecules start moving at a faster rate. A gas molecule, if unhindered, could speed across the United States in three hours. I don't even want to know about plasma. But if heat ...
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47 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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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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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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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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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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131 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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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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190 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
76 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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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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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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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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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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149 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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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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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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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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Could gravitational waves and electromagnetic waves/light be the same thing? [duplicate]

They travel at the same speed, why? Maybe they are the same thing, but seen from different perspectives.
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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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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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60 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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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 ...
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92 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
27 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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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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69 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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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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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 ...