# How photons exceeds their velocity?

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## Main Question or Discussion Point

Is there a theory that explains the mechanism under which photons exceeds the speed of light?
It should refer to cases including photons generated in an oscillating charges, dipoles, inhalations, different kind of excitation, accelerated particles, scattering phenomenons etc.
Please note that I exclude explanation based on equation of state (energy balance or minimization). For example the energy reduction of an exited electron is the reason for energy formation in terms of electromagnetic radiation but it does not say nothing about the reason it should propagates in the speed of light.

In case there are non, then do you familiar with attempts to explain it.

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Drakkith
Staff Emeritus
Is there a theory that explains the mechanism under which photons exceeds the speed of light?
I'm not sure what you mean. Photons are light. They can't exceed their own speed limit.

No . I meant their own velocity.

russ_watters
Mentor
No . I meant their own velocity.
Still not following: light travels at the speed of light. it does not "exceed it's own velocity". Indeed, that's a logical self contradiction.

jtbell
Mentor
mechanism under which photons exceeds the speed of light?
Which specific phenomena or experiments are you thinking of? References or links would be helpful, so we can see if you are simply misinterpreting something.

I will give an example:
It is possible to understand how car gets its speed: the burning fuel expends and push pistons that arranged in a setup allows it to convert the pistons oscillations into rotation etc...
This gives the mechanism that eventually explain how the car gets its velocity.
I am looking for explanation to how the photons gets their velocity. The mechanism should includes the fact that no matter how, the velocity is all always 2.99*10^8 m/sec (In vacuum).

Sorry for not explaining my self properly. Maybe it is also my imperfect English.

Nugatory
Mentor
I am looking for explanation to how the photons gets their velocity. The mechanism should includes the fact that no matter how, the velocity is all always 2.99*10^8 m/sec (In vacuum).
Are you familiar with Maxwell's equations? These describe the behavior of time-varying electrical and magnetic fields and how electromagnetic waves (which is what light is) are formed and travel at speed $c$ in vacuum.

Photons are not what you're thinking they are - they aren't little tiny projectiles travelling through space with speed $c$, so there's no sensible way of talking about how they "get their velocity".

CWatters
Homework Helper
Gold Member
I have a similar question along these lines, Is it conceivable to imagine light as not existing in time as at c time is 0. And the universe observes light only because it is moving slower which allows time to pass so that it appears as if light has moved from one place to another when it hasn't moved at all but just always been there... (sorry i don't think this make sense)

Drakkith
Staff Emeritus
Is it conceivable to imagine light as not existing in time as at c time is 0.
Not true. When v = c the equations you're thinking of don't work due to a division by zero error and you cannot say that light experiences zero time.

And the universe observes light only because it is moving slower which allows time to pass so that it appears as if light has moved from one place to another when it hasn't moved at all but just always been there... (sorry i don't think this make sense)
Indeed, that does not make sense and doesn't match up with how science defines things like movement.

CWatters
Homework Helper
Gold Member
How would a light switch work if the light is "always there"?

That's not what I meant, It is difficult to explain. Light is travelling at c, therefore it doesn't experience time, time has stopped - from its creation to its end would be instantaneous. I am trying to imagine what it would be like to be a photon, time would not exist or is stopped. If it has stopped then it still would not experience time or take eternity to make its journey.

If you look at it the other way around from the speed of light and everything else in the universe is moving slower which then requires time to be perceived. Therefore light would always have been there in space time and would have a start and end without time..

I'm sorry this has not much to do with the original post except that light only has one velocity and doesn't change.

davenn
Gold Member
2019 Award
except that light only has one velocity and doesn't change.
ahhh but you can slow light aka an EM wave propagation speed down

you do understand that visible light is just a small section of the wide EM spectrum ?

Light is travelling at c, therefore it doesn't experience time, time has stopped
That is completely not true, you can't define 'time' for photons, because there is no rest frame of photons.

Yes sorry I know that I was referring to all of the EM spectrum as "light" to simplify it. Also all EM waves travel at c, the propagation of an em wave through a medium doesn't slow the wave down. It absorbs the wave and then re-emits it? It hasn't slowed down in a sense

That is completely not true, you can't define 'time' for photons, because there is no rest frame of photons.
Well that is what I was getting at, there is no time for photons, they are instantaneous in there own right, they do not use or create energy just transmit it. Therefore they do not exist in time from there POV.

Drakkith
Staff Emeritus
Light is travelling at c, therefore it doesn't experience time, time has stopped - from its creation to its end would be instantaneous.
No, you cannot conclude this, partly for reasons I stated above. In relativity, which is where all this is from, in order to find out how much time has passed for an object we need to associate a frame of reference to that object. However, we run into a problem in that light always travels at c for any inertial reference frame. Attempting to assign a frame of reference to a beam of light results in a nonsensical answer where you're trying to give light a reference frame where it is moving with respect to its own reference frame. Which can't happen.

The fact of the matter is that we cannot say anything about how much time passes for light. We can't say that it does or doesn't experience time, for either claim requires us to violate basic logic and gives us nonsense as an answer. As @weirdoguy put it, you cannot define time for light.

If you look at it the other way around from the speed of light and everything else in the universe is moving slower which then requires time to be perceived.
This doesn't follow from your own argument. You've simply stated it, not provided any reason why this should happen. And because time cannot be defined for light, it doesn't work anyways.

from there POV
But the whole point is that photons have no POV!

But the whole point is that photons have no POV!
How about you as an observer, travelling at the speed of light? What happens to your frame of reference?

I can't travel at the speed of light because I have mass, laws of physics forbid this. POV of something=refrence frame of that 'something'. Photons have no frame of reference connected with them (because they are massless and move at c)=they have no POV.

Isaac0427
Gold Member
How about you as an observer, travelling at the speed of light? What happens to your frame of reference?
I guess the best way to say this is that if you could possibly travel at the speed of light, you would "break" relativity. Special relativity only works given two conditions; only light travels at c and light has no reference frame. In fact, if you could describe something from the POV of light, you couldn't use SR, because just by describing it you are breaking the foundation of relativity.

In other words, the math of SR (and graphing Lorentz transformations) shows that something traveling at c, even theoretically, has no frame of reference. Thus, an observer can't travel at c, if that were to happen, it would violate physics. I hope this clears things up. If it doesn't, I'll give it another shot. I know that this is a very confusing part of physics.

davenn
Gold Member
2019 Award
Also all EM waves travel at c, the propagation of an em wave through a medium doesn't slow the wave down. It absorbs the wave and then re-emits it? It hasn't slowed down in a sense
that is one theory, if going through a medium say a chunk of glass

but if you have a EM wave propagating along the outside of a wire transmission line ( in an air medium), it will only be about .95c
if it is travelling through insulation that is on the wire, depending on the insulation type, it can be as low as 0.66c

Dave

phinds
Gold Member
2019 Award
How about you as an observer, travelling at the speed of light? What happens to your frame of reference?
You are not listening. There IS NO such thing as a "frame of reference" at the speed of light because the speed of light is the same in all inertial frames and therefore it can't HAVE a frame. There is, of course, also the fact that only massless objects can travel at c.

phinds
Gold Member
2019 Award
I guess the best way to say this is that if you could possibly travel at the speed of light, you would "break" relativity. Special relativity only works given two conditions; only light travels at c and light has no reference frame. In fact, if you could describe something from the POV of light, you couldn't use SR, because just by describing it you are breaking the foundation of relativity.

In other words, the math of SR (and graphing Lorentz transformations) shows that something traveling at c, even theoretically, has no frame of reference. Thus, an observer can't travel at c, if that were to happen, it would violate physics. I hope this clears things up. If it doesn't, I'll give it another shot. I know that this is a very confusing part of physics.
No, gravitational waves are a ripple in space-time geometry and they travel at c.

In fact, when physicists say "the speed of light" they don't really mean a speed that is defined by light, they mean the universal speed limit which, as it turns out, light, gravity waves, and any massless object, obey. If it turned out that photons have a tiny tiny mass after all, the value of "c" would not change. It would STILL be the universal speed limit, we'd just have to stop calling it "the speed of light".

Isaac0427
Gold Member
No, gravitational waves are a ripple in space-time geometry and they travel at c.
Yes, I will revise that. I forgot about other massless particles. But, you get the point.