# Photon time

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If a rocket is traveling with almost the speed of light, the static observer "can" see that the time in that rocket is dilated, i.e. things are happening in a slower rate. Very very close to c, time dilation gets bigger and, from the static observer, nothing appear to happen in the rocket. It's like everything freezes.

Well, photons are travelling with the speed c but they appear to exhibit/produce rapid oscillations/variations: a change in the electric field creates a changing magnetic field that in turn creates another electric field and so on. How is this possible? At that speed it should be no change at all, according to special relativity.

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If a rocket is traveling with almost the speed of light, the static observer "can" see that the time in that rocket is dilated, i.e. things are happening in a slower rate. Very very close to c, time dilation gets bigger and, from the static observer, nothing appear to happen in the rocket. It's like everything freezes.

Well, photons are travelling with the speed c but they appear to exhibit/produce rapid oscillations/variations: a change in the electric field creates a changing magnetic field that in turn creates another electric field and so on. How is this possible? At that speed it should be no change at all, according to special relativity.

"according to special relativity" - you say this but it is not true.

SR says all inertial frames of reference are equivalent but that light speed is invariant for all inertial frames - together these mean that there is no inertial frame of reference for the photon; as such we understand that the theory is outside its bounds of application for the frame of reference of massless objects moving at the speed of light. You cannot do the normal sums, boosts, contractions etc based on a frame moving at the speed of light because it cannot be an inertial frame of reference.

As massive objects approach the speed of light (no matter how close) then you can make very exact predictions based on SR which are borne out by observation - but you cannot cross over to using the same maths for massless objects traveling at the speed of light

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Well, photons are travelling with the speed c but they appear to exhibit/produce rapid oscillations/variations: a change in the electric field creates a changing magnetic field that in turn creates another electric field and so on. How is this possible? At that speed it should be no change at all, according to special relativity.

The electromagnetic wave behavior is dictated by the Maxwell equations.

The Maxwell equations are invariant wrt the Lorentz transforms.

Therefore, your above claim is false.

BTW: you have already been told that massive objects (like the rocket) cannot travel at c.

Edited by zztop
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SR ...... is outside its bounds of application for the frame of reference of massless objects moving at the speed of light. You cannot do the normal sums, boosts, contractions etc based on a frame moving at the speed of light because it cannot be an inertial frame of reference.

Right, so it is outside SR bounds.

Ok, but then what theory can be applied in order to compare the time of the photon with our time? I remember reading that for a photon there is no time, no past, no future ... but if there is change, it should also be time.

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Right, so it is outside SR bounds.

Ok, but then what theory can be applied in order to compare the time of the photon with our time? I remember reading that for a photon there is no time, no past, no future ... but if there is change, it should also be time.

There is no such thing as "photon time". Photons do not experience time.

Edited by zztop
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Right, so it is outside SR bounds.

Ok, but then what theory can be applied in order to compare the time of the photon with our time? I remember reading that for a photon there is no time, no past, no future ... but if there is change, it should also be time.

"...for a photon there is no time, no past, no future ..." that is normally connected to the above misunderstanding of SR - I don't think we have any reason to say it otherwise. Photons move, change (red-/blue-shift for example), they are emitted, they are absorbed - they obviously exist within time.

I am not sure we have a valid concept of what time is for a massless particle - but then I am not sure we have a particularly valid concept of what time is for a hairless ape. We must not anthropomorphise light; photons hate that (they are shy as well as being massless quantum mechanical objects) - what sort of notion of the passing of time would such a thing like that have?

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"...for a photon there is no time, no past, no future ..." that is normally connected to the above misunderstanding of SR - I don't think we have any reason to say it otherwise. Photons move, change (red-/blue-shift for example), they are emitted, they are absorbed - they obviously exist within time.

I am not sure we have a valid concept of what time is for a massless particle - but then I am not sure we have a particularly valid concept of what time is for a hairless ape.

Ok, thank you

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How is this possible?

It turns out that time and length are relative to the frame in which they are measured, rather than being absolutes. They differ in such a way that c is invariant.

At that speed it should be no change at all, according to special relativity.

Special relativity applies to inertial frames, where you can treat objects in them as being at rest. Photons do not exist within inertial frames, so you can't draw any valid conclusions about how photons should look in their own frame. All we can do is say what photons look like in our frames of reference.

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Ok, but then what theory can be applied in order to compare the time of the photon with our time?

Why should there be any such comparison. Photons don't change or decay and so there is no meaning of "time" for a photon, anyway.

I remember reading that for a photon there is no time, no past, no future ... but if there is change, it should also be time.

That is a popular science version. It sounds more interesting than saying that the maths can't be applied because you get a divide by zero.

Well, photons are travelling with the speed c but they appear to exhibit/produce rapid oscillations/variations: a change in the electric field creates a changing magnetic field that in turn creates another electric field and so on. How is this possible? At that speed it should be no change at all, according to special relativity.

The changes are measured in our frame of reference, not the photon's (which doesn't exist anyway).

Also, the changing electric/magnetic field is a classical view. A photon doesn't directly correspond to that.

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The changes are measured in our frame of reference, not the photon's (which doesn't exist anyway).

Yes, and we see/measure the slowing of time in a very rapid moving rocket from our frame of reference also. In the rocket's frame time is running normal.

Also, the changing electric/magnetic field is a classical view. A photon doesn't directly correspond to that.

So, in a modern view how we explain the propagation of light / photon travel in vacuum?

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Yes, and we see/measure the slowing of time in a very rapid moving rocket from our frame of reference also. In the rocket's frame time is running normal.

You can't apply special relativity to a photon, so it is irrelevant.

So, in a modern view how we explain the propagation of light / photon travel in vacuum?

Quantum field theory. And, more specifically, quantum electrodynamics (QED) - there are some good videos by Feynman explaining this.

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Quantum field theory. And, more specifically, quantum electrodynamics (QED) - there are some good videos by Feynman explaining this.

Please post a link to one of them.

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At that speed it should be no change at all, according to special relativity.

I think for me, that confuses change, with time. If you designate the change involved in light as 1 unit, then change tends towards 1, not zero, as you approach the speed of light. Time on the other hand tends towards zero.

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On top of all that: a wave doesn't go up and down relative to the wave.

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