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Author Topic: If a photon is travelling at the speed of light, does time not exist for it?  (Read 23762 times)

Offline QuantumClue

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Photons do, and can decay. They just don't decay spontaneously in space. There is  a big difference there.
 

Offline QuantumClue

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Quote from: JP
in physics, there is no theory that defines the frame of reference of a photon

Quote from: JP
We don't know how to describe the reference frame of a photon scientifically, so any claims about it not experiencing time in it's own reference frame aren't scientific.

Looked at from a slightly different perspective; is there any scientific evidence suggesting that a photon's apparent experience of time exists other than in the F of R of an observer?

I'll answer this. The answer is no.

If a photon decayed spontaneously in space, there might be some indication that it experiences a time, but this is not the case. Relative to us however, as JP has noted, photons do experience time.
QC, it's the other way around as I see it. It's to our frame of reference the photons take time, to their 'own', if that one exist, time can't exist. At least not as we experience it, if it did we should observe a 'decay', just as JP describes it.
==

Saying that because they are 'massless' they do not apply to our 'reality'?
Is that science?

When I say relative to us, I mean it requires observers like us to attribute a time pass. JP and myself are talking about the same thing.
 

Offline JP

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The other issue is this: aren't electrons also stable?  They can certainly annihilate in collisions, but I don't think that one left alone would spontaneously decay into photons...  I'm not a particle physicist, so I could be wrong on this.

When an atom does emit an electron (beta decay), I don't think it travels quite at c, but I don't know if it decays or not.

You're right.  An electron can never travel at c since it has mass.  I didn't mean to imply that it did.  Because it has mass and can't move at c, it has a reference frame within relativity, unlike a photon, and so it experiences time in it's reference frame.  But I think it's also stable. 

I was making two points.  One of them is that stability of a particle isn't necessarily a good definition of the lack of passage of time.  If electrons are stable, they have a reference frame in special relativity in which time passes.  I'd be interested to know if they're stable or not and what characteristics of particles influences their stability, but that's probably a topic for another thread and we'd need some particle physicists!

The second point I was making is that if you insist on adding a reference frame for a photon, and you believe that SR is basically correct, that reference frame should depend only on the photon's speed.  (I've argued strongly against this, since there's no good science behind it!) Therefore anything of zero mass, moving at the speed of light should have the same "timelessness" property as a photon.  If you're assuming that instability of a particle is a sign that it experiences time passing in it's own reference frame, then gluons experience time they aren't stable!  But gluons are massless and move at c, so they should be in the same kind of "timeless" reference frame as a photon! 

I think there's two conclusions you can draw from this:

1) There's something fundamentally wrong with just tacking on a reference frame for things moving at light speed and calling it "timeless" (by basically setting v=c in the equations of SR).  You can (and I have) argued this from the derivation of SR, in which setting v=c is wrong because the equations of SR are invalid in that case.

2) It's probably wrong to define "timeless" reference frames as those held by particles which are stable.  That concept of time doesn't agree with the concept of time in special relativity, at any rate, so even if you did define it this way, I'm not sure how much use it would be.  You'd basically just be using the word "timeless" to replace "stable," and it wouldn't have any real relation to measurements time as used in other areas of physics.

But let's take a step back.  We need to agree on terms, since the definitions of time and "timeless" I'm arguing from are very precise. 

Proponents of a "timeless" photon, what does "timelessness" mean in precise technical terms?
 

Offline imatfaal

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Ok JP - super speculative question. 

i. In a superconductor the condensate of cooper pairs can act through the higgs mechanism to give a mass to the photon.

ii. If a photon has a mass - can it still be travelling at maximal velocity within that material?  i.e. this is not just a photon travelling slowly because of a refractive index greater than 1 - it's a Marks and Spencer's photon(sorry scrub that) - it's a photon travelling at less than the speed of light.

iii.  Would this change the decay characteristics?  Could this provide a difference between the timeless epithet and travelling at lightspeed? 


I agree with you, I think, that the example of the gluon already knocks that into the long grass; but perhaps evidence from the photon would be more conclusive.
 

Offline imatfaal

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Photons do, and can decay. They just don't decay spontaneously in space. There is  a big difference there.

You got more details on that - I would be interested
 

Offline Bill S

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As a non-scientist it would be presumptuous of me to describe myself as a proponent of a "timeless" photon, and I think we might need to be sure of some consensus on a definition of time before tackling timelessness.

I am probably agreeing with JP when I say I think terminology is an important factor.  I know I have another question, I know what it is, but it will take a little thought to frame it in words that will ensure that everyone else knows what it is, or is that just wishful thinking? :-\
 

Offline yor_on

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Yep Imatfaal, I'm curious to that statement too. QC, you have a link to that?

And JP. The frame existing for a photon is the one where we observe it.
The frame existent for a gluon is theory, no direct observations possible as far as I understands?

That we from indirect observations define something we call a gluon is true, as you pointed out before, but there's no direct observations possible. And as far as I understands it does not exist inside a observable time frame, which to my eyes place it outside Plank time. If you know different JP, link me up :) That's one of the really weird ones to me. That something outside Planck-time actually 'interacts' inside it.

As for if a photon have an 'internal frame'? I don't think so myself which in a way makes the discussion meaningless as it works from another principle, as I guess, than our arrow of time. But it does not makes it meaningless to call it 'time less' from our perspective, as we only have that proposition to work from. That is three dimensions (possibly more:) and 'time'.
« Last Edit: 28/01/2011 18:38:40 by yor_on »
 

Offline JP

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Matthew, I'm not entirely sure what happens to a photon in matter.  Is the slow down in a superconductor sufficiently different to, say, glass?  The way I usually understand a photon moving in matter is that it is propagating at the speed of light in between the bits of matter, but interactions with the matter essentially cause it to take longer to get through.  I don't think this should change its decay properties, or the fact that it moves at the speed of light in between those interactions.
 

Offline yor_on

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"When the temperature was lower than the Planck scale, the universe was an expanding gas of relativistic particles. These particles include quarks and leptons, the gauge bosons such as photons, gluons, and W and Z bosons, and perhaps more exotic particles like the supersymmetric partners of the standard model particles, heavy right-handed neutrinos, gauge bosons related to grand unification theories, etc. As the temperature cooled below the masses of certain particles (such as the W and Z bosons) they “freeze out” and decay, i.e., they are not longer created by inverse reactions of their decay products due to the lower temperature. Some of these particles with a short life time had disappeared long ago, and some with a long life time may still be with us today in the form of dark matter." From Quark-Gluon Plasma and the Early Universe

This description seems to agree with my assumption JP?
That Gluon's are under Planck scale. And if they are then you might want to question the idea of them being 'particles' too. Any particle making 'sense' to us will show a gravitational 'potential'. Do virtual particles do that? If they do, then one might consider finding the 'missing mass' in their 'interactions' with all 'thingies' over Planck scale

But if they don't they are something outside of 'SpaceTime' to my eyes.
 

Offline Bill S

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The more I try to think, the more questions I seem to find, so here goes with some thoughts and a question arising out of them.


If we assume that frame of reference = inertial frame = rest frame, then it makes perfect sense to argue that a photon cannot be assigned a frame of reference because in the rest frame of any object, the velocity of that object itself is zero.  

Relativity says that photons always move at the speed of light, so we might reason that, according to relativity, a photon would have to travel at the speed of light in its own frame of reference, which doesn’t seem to make a lot of sense.
 
However, relativity does not define a frame of reference for a photon; all it does is state that a photon must travel at c in the frame of reference of everyone and everything else.  

Bearing in mind that in relativity all motion, or lack of it, is relative, are we saying that a photon has no frame of reference in which it is stationary relative to itself?  
 

Offline imatfaal

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Matthew, I'm not entirely sure what happens to a photon in matter.  Is the slow down in a superconductor sufficiently different to, say, glass?  The way I usually understand a photon moving in matter is that it is propagating at the speed of light in between the bits of matter, but interactions with the matter essentially cause it to take longer to get through.  I don't think this should change its decay properties, or the fact that it moves at the speed of light in between those interactions.

I am trying to split two phenomena - you rightly describe how a photon moves through material via interactions; this is the case within glass.  The photon moves at light speed between interactions but overall at a slower speed- I think that's the best explanation I have read, not sure if it isnt a bit hand-wavy though.

But within a superconductor, electron pairs (cooper pairs) form a condensate.  It is thought that this condensate can act like a bosonic field and emulate the higg's field.  But in a superconductor (as opposed to everywhere else) this higgs-like field will provide mass (very very small) for the photon.  I would imagine a photon with mass would be forced to travel slower than a photon without mass.  A subluminal photon (and I still don't think it really works) would be free from any argument that time is meaningless for it as it is moving in a normal frame of reference.

I will dig out references for the cooper pair condensate field - I hope.
 

Offline Bill S

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Does the mass of the photon in this scenario exist other than in the F of R of an observer?
 

Offline yor_on

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That one doesn't make sense imatfaal?

If you consider the 'Higgs field' it exists everywhere according to the idea?
And then the difference would be that space isn't superconducting?
And that a photon acquire a mass inside a condensate?

Sounds very much like a theory without any foundation in experiments to me?
 

Offline JP

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This description seems to agree with my assumption JP?
That Gluon's are under Planck scale. And if they are then you might want to question the idea of them being 'particles' too. Any particle making 'sense' to us will show a gravitational 'potential'. Do virtual particles do that? If they do, then one might consider finding the 'missing mass' in their 'interactions' with all 'thingies' over Planck scale

But if they don't they are something outside of 'SpaceTime' to my eyes.

I don't think that gluons are under the planck scale any more than photons are.  Every fundamental particle in the standard model is a point particle, but their wave functions are smeared out over larger areas.  I assume gluons do cause gravity, but just like a photon causing gravity, you can't really measure it since they're so tiny.
 

Offline JP

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Bearing in mind that in relativity all motion, or lack of it, is relative, are we saying that a photon has no frame of reference in which it is stationary relative to itself?  

Exactly what I'm saying.  Until we can experimentally access that reference frame to make tests on it, it's not a scientific theory.  That's why all the discussion on such a frame is basically philosophy or personal opinion, not science. 
 

Offline JP

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Matthew, I'm not entirely sure what happens to a photon in matter.  Is the slow down in a superconductor sufficiently different to, say, glass?  The way I usually understand a photon moving in matter is that it is propagating at the speed of light in between the bits of matter, but interactions with the matter essentially cause it to take longer to get through.  I don't think this should change its decay properties, or the fact that it moves at the speed of light in between those interactions.

I am trying to split two phenomena - you rightly describe how a photon moves through material via interactions; this is the case within glass.  The photon moves at light speed between interactions but overall at a slower speed- I think that's the best explanation I have read, not sure if it isnt a bit hand-wavy though.

But within a superconductor, electron pairs (cooper pairs) form a condensate.  It is thought that this condensate can act like a bosonic field and emulate the higg's field.  But in a superconductor (as opposed to everywhere else) this higgs-like field will provide mass (very very small) for the photon.  I would imagine a photon with mass would be forced to travel slower than a photon without mass.  A subluminal photon (and I still don't think it really works) would be free from any argument that time is meaningless for it as it is moving in a normal frame of reference.

I will dig out references for the cooper pair condensate field - I hope.


Interesting.  It sounds like what's going on is that the superconductor is behaving mathematically similar to the Higgs field, but physically it isn't.  In that case, the photon won't physically have mass, but will slow down like it has gained mass via the Higgs mechanism.  I don't think it would decay... that would be very odd.  It would be interesting to see the paper, though!
 

Offline Bill S

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Quote from: Bill S
are we saying that a photon has no frame of reference in which it is stationary relative to itself?

Quote from: JP
Exactly what I'm saying

OK, but how can a photon be in motion relative to itself?  ???
 

Offline JP

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Just because it has no frame in which it's stationary does not mean that is has a frame in which it's in motion with respect to itself. 
 

Offline Geezer

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At the risk of over simplifying things (a common failure among aliens) I would speculate that the only way to avoid becoming a decadent imperialist lackey is to zip along at c. Now, photons of one sort or another do seem to be able to do that, presumably because they have no rest mass. (Because they are not resting like a bunch of decadent imp......)

So, if particles that have a rest mass (and therefore are not able to zip along at c) don't seem to decay, or lose energy, or alter in some way or another over time, my "theory" kind of falls apart.
 

Offline yor_on

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Heh, JP that one was lovely :)

"Just because it has no frame in which it's stationary does not mean that is has a frame in which it's in motion with respect to itself." I'm sure the way you thought of it will make a ultimate sense but reading it is soo sweet :) You will have to explain your thinking there.

And yes, assuming that gluons are 'inside Planck size', also assuming that there goes the border between what is 'reasonable' from the physics we know? you will have a point. But to me all of those emergences are exactly 'emergences' getting new properties as they scales up. That means that to me a gluon is an expression of interactions observed inside our macroscopic 'reality' leading us to define them as existing. But on their own 'scale', as I see it outside Plank size, they are nothing like it, just as I expect 'times arrow' to be an emergence needed for our macroscopic universe.
 

Offline JP

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Heh, JP that one was lovely :)

"Just because it has no frame in which it's stationary does not mean that is has a frame in which it's in motion with respect to itself." I'm sure the way you thought of it will make a ultimate sense but reading it is soo sweet :) You will have to explain your thinking there.

It seemed like Bill was assuming that you only have two options:
1) the photon has a reference frame in which it's at rest with respect to itself,
2) the photon has a reference frame in which it's moving with respect to itself,
and obviously (2) is a bit nonsensical.  There is a third option.  The photon has no reference frame (at least not one we know how to describe in terms of it's motion).  That's the one that's true since the above options are not allowed in relativity.
 

Offline JP

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So, if particles that have a rest mass (and therefore are not able to zip along at c) don't seem to decay, or lose energy, or alter in some way or another over time, my "theory" kind of falls apart.

That was my point with the electrons.  Also, gluons do zip along at c and do spontaneously decay.

Maybe we can save a lot of this for another thread, but I believe the reason why things that move at c tend to be stable is that being massless is a requirement for forces to act over long range (which is probably the same as saying that being massless is a requirement for force-carrying bosons to be stable).  However, gluons have an additional property that determines how they behave: color charge.  The color charge changes how they interact with the force and makes them short-lived.

So I guess the conclusion is that masslessness is a necessary requirement for force-carrying Bosons to be stable, but it isn't sufficient.
 

Offline yor_on

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What makes it so remarkable is how few types of interactions there are needed for creating a SpaceTime, as the color-force tells us. One might expect it to be more complex. And yeah, I knew it would make sense :)
 

Offline simplified

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Let's look on some sense of photon travel :D
The water pillar is history of events. The water level constantly increases. Movement of a wave on a surface  is movement of a photon. Event of movement of a photon does not plunge in the past. :)
 

Offline JP

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Movement of a wave on a surface  is movement of a photon.

No it isn't.  The idea that a photon is a wave in matter was discredited with the aether theory.
 

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