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Author Topic: If a photon is travelling at the speed of light, does time not exist for it?  (Read 23680 times)

Offline CPT ArkAngel

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it is 8 minutes for matter at no relative speed from the earth and the sun, certainly not for the photons...

I think what QC meant is that you cannot separate time and space. But it is theoretical.

According to Kaluza-Klein Theory, the charge is a fifth dimension. If the photons are made of charges (but having a total of zero), time and gravity could be an effect of the charges going at a slower speed than the speed of light... And it would generate relativity... Because all particles have charges, even the neutron. So all particles would have its own referential clock associated to its charge.
« Last Edit: 27/01/2011 00:51:37 by CPT ArkAngel »
 

Offline Geezer

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Well, during my extensive intergalactic travels, I've yet to see a photon transmogrify itself into something else. They don't seem to decay or nuthin, whereas, AFAIK, everything else does.

Ergo (that's Alienspeak for therefore) photons (if they exist at all) seem to be exempt from the ravages of time.
 

Offline JP

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True, Geezer.  Not decaying is a specific requirement as opposed to "not experiencing" time.  Photons clearly still move through time in all Einsteinian reference frames. 

By the way, the usual argument goes that photons are massless, so they move at the speed of light, and therefore they don't experience time.  To complicate matters, gluons are theoretically massless, but they lack the stability of photons: they hate existing in isolation.  Does this mean they don't experience time?

I think this is another case, as happens so often in science, where precise language is important, as is being very precise about what claims science can make about photons and what claims are philosophy.  (Thinking about the way a photon sees the universe from it's point of view is an exercise in imagination, not science!)
 

Offline Geezer

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It's probably more philosophical that anything else, but I think energy does seem to "leak out" of everything over time, so one way to explain why that does not seem to happen in the case of photons is to exempt them from time.

Surely it's only important in the photon's frame of reference? How we perceive that "time" is not relevant.

We know that time "slows down" for things that travel fast. Why is it unreasonable to think that, at the extreme limit of speed, time essentially stops, or does not even exist.
 

Offline CPT ArkAngel

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JP the Guardian of the Standard Model, you are very hard to convince but i must say you are often my first source of motivation to work and think harder about all this...

There is absolutely no proof that photons experience the passage of time. In fact, the mathematical equations of the Standard Model imply that photons have no timerate. In the contrary, Relativity as a whole would be crushed... I understand it is quite difficult to manage but it has to be this way if you look at the photons behaviour.

Geezer's arguments seem right to me.
« Last Edit: 27/01/2011 02:27:00 by CPT ArkAngel »
 

Offline CPT ArkAngel

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General Relativity equations are not valid for sizes smaller than the Planck Length and it doesn't explain what happen to the electromagnetic and nuclear forces beyond that in a black hole... It just supposed to vanish... Because it is not tied up with Quantum Theory...
 

Offline JP

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In fact, the mathematical equations of the Standard Model imply that photons have no timerate.

Really?  Can you give me an equation?
 

Offline JP

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It's probably more philosophical that anything else, but I think energy does seem to "leak out" of everything over time, so one way to explain why that does not seem to happen in the case of photons is to exempt them from time.

But clearly that can't be true.  The fact that photons are absorbed and emitted shows that they aren't exempt from time.  They have to move through it! 

I do get the point about a photon's non-decay possibly being related to it's internal clock, but without a scientific model to describe that internal clock (and relativity ain't the way to do it!), is this a scientific question?  Would it be better to say "It doesn't decay" and be done with it?
 

Offline Geezer

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It's probably more philosophical that anything else, but I think energy does seem to "leak out" of everything over time, so one way to explain why that does not seem to happen in the case of photons is to exempt them from time.

But clearly that can't be true.  The fact that photons are absorbed and emitted shows that they aren't exempt from time.  They have to move through it! 

I do get the point about a photon's non-decay possibly being related to it's internal clock, but without a scientific model to describe that internal clock (and relativity ain't the way to do it!), is this a scientific question?  Would it be better to say "It doesn't decay" and be done with it?

Yes. The process of creating and destroying them does involve time. I just think it's a reasonable extrapolation from the observed fact that they don't decay, and the fact that they travel at c to assume that time is meaningless in their frame.

I certainly can't prove it, but I don't think you can prove my hypothesis is invalid either  ;D
 

Offline JPC

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Hi I have no qualification in science, so please correct me. Also this is my first post here on this forum.

I have been taught in school about an equation for calculating time dilation.
T= factor by which the moving object has it's time shortened
t= time experienced by some stationary object
v= velocity of moving object
c= speed of light

T = t/sqrt(1-v^2/c^2)

The important part here is the bit in the square root, which if equal to zero makes the whole thing undefined.

For a photon, v = c

So sqrt(1-c^2/c^2) is the denominator

This simplifies to sqrt(1-1) = sqrt(0) = 0, which means the amount of time experienced is undefined, because t/0 is undefined.

Long story short, the amount of time experienced by a photon during one second of real time is 1/0, undefined (according to my understanding of this equation).

Below is a graph showing how time dilation varies over speed, units on the x axis are c.(source: Wikipedia)



The value on the y axis becomes infinitely large as it approaches 1, but it never reaches 1 (similar to the way y=1/x approaches, but never touches the y or x axis).

I am concerned, as there may be some other equation or consideration I am not aware of that can work around the "undefined" result to the equation above. I am also concerned I have made an error, as I thought someone else would have pulled the numbers out earlier, perhaps they are irrelevant to the question somehow?
 

Offline simplified

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Photon has a limited energy,therefore can not touch "1" too. ;)
 

Offline CPT ArkAngel

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Light is not matter, it has no mass. Special Relativity is a special solution and therefore, you cannot conclude anything beyond its limits with it. Alone it is paradoxical...
 

Offline JP

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T = t/sqrt(1-v^2/c^2)

That is indeed the equation for time dilation, but it only applies for objects with mass, whereas photons are massless.  You can't just use it for photons, even though it makes it look like you'll divide by zero getting "undefined" time.  The derivation of that equation requires assuming that you're not dealing with massless photons in the first place.
 

Offline JP

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Light is not matter, it has no mass. Special Relativity is a special solution and therefore, you cannot conclude anything beyond its limits with it.

Exactly my point.  Special relativity doesn't apply to describe the point of view of photons, and therefore using it to conclude how they "experience" time (or anything else) is flawed.
 

Offline simplified

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A photon drags potential mass.Momentum has not Lorentz's factor for speed of photon.And energy has not Lorentz's factor for speed of photon.Without Lorentz's factor:
                         Kinetic Energy = mv²
                Momentum = mv
Momentum and energy of objects have Lorent's factors for speed.
With Lorentz's factor:
Speed of recoil of objects for momentum = L*v
Speed of recoil of objects for energy = L*v/√(L+1)
Then : Kinetic Energy = mv²L²/(L+1)
       Momentum = mvL  
 

Offline Bill S

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Quote from: JP
The word "experience" brings with it a lot of connotations that muddies the picture a bit,

Bad choice of word.  [:I] How better to express it?  What about: Is it only in the F of R of an observer that a photon appears to travel through time?

Quote
A photon is emitted by the sun at time t=0 and is absorbed by your eye at time t=8 minutes.  Is this "experiencing time"?

As you rightly point out, this would be experiencing time only if the photon were able to experience anything.

Another requirement would be that what the photon was experiencing was 8 minutes travel.

Would this not be faster than light travel?  ;D  
 

Offline Bill S

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Quote from: Geezer
The process of creating and destroying them does involve time.

Does a photon exist before it is created? - No.
Does a photon exist after it is destroyed? - No.
When is a photon created? - In the present.
When is a photon destroyed? - In the present.
Can we establish that any time is involved between creation and destruction, other than that which is perceived by an observer? - So far I see no evidence of this, so are we just airing our personal beliefs?
 

Offline Bill S

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Hi, JPC, welcome. Good to see someone who posts some maths I can understand.  :) That's rare.  Keep it up. 
 

Offline JP

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Quote from: JP
The word "experience" brings with it a lot of connotations that muddies the picture a bit,

Bad choice of word.  [:I] How better to express it?  What about: Is it only in the F of R of an observer that a photon appears to travel through time?

That's true, but it also describes all cases.  Since there is no F of R of a photon, all frames from which it is observed belong to non-photon observers, and all observers observe the photon moving forward in time.

Quote from: Bill S
Can we establish that any time is involved between creation and destruction, other than that which is perceived by an observer? - So far I see no evidence of this, so are we just airing our personal beliefs?
Exactly my point!  All observers known to science (the observers of SR and GR who can't be moving at the speed of light) see the photon moving through time.  There are no other scientifically viable observers in our current models, so talking about time passing or not passing for them (i.e. from a photon's perspective) is opinion without basis in science.  I think it's proper to say that time from a photon's point of view isn't well-defined, so that the question of time passing for them from their point of view isn't well-posed within our current models.
« Last Edit: 27/01/2011 22:53:55 by JP »
 

Offline Geezer

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Quote from: Geezer
The process of creating and destroying them does involve time.

Does a photon exist before it is created? - No.
Does a photon exist after it is destroyed? - No.
When is a photon created? - In the present.
When is a photon destroyed? - In the present.
Can we establish that any time is involved between creation and destruction, other than that which is perceived by an observer? - So far I see no evidence of this, so are we just airing our personal beliefs?

How do you explain the observation that photons do not decay over time when everything else does? Seems like pretty good evidence to me  :D
 

Offline yor_on

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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?
« Last Edit: 28/01/2011 02:10:21 by yor_on »
 

Offline JP

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Maybe we should start up a thread about what makes particles decay.  I've been thinking about it, and it seems like a pretty deep topic.

Let's say for the sake of argument that we take relativity and tack on an additional set of reference frames for objects moving at the speed of light.  We define time as not existing in these reference frames which means that particles moving at the speed of light don't decay.  The problem is that gluons, which are massless, would be in these reference frames too.  But gluons do decay!  Therefore, these reference frames can't be purely a function of velocity, which would be odd...  Then you'd have one type of reference frame for photons moving at light speed in which time didn't pass and a completely different type for gluons moving at light speed in which time passed.

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.
 

Offline yor_on

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Nope JP, 'time' is a macroscopic property as I see it. You're lifting up indirect evidence for something not measurable in themselves and theoretically described as 'decaying' as a macroscopic 'truth'. That's not correct.
==

On the other tentacle, that's just what I do when I discuss photons as 'time less' :)
« Last Edit: 28/01/2011 02:56:21 by yor_on »
 

Offline yor_on

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So yes JP, in a way you're perfectly correct.
But there is a difference, we don't see gluons.

But we do see photons.
 

Offline Geezer

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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.
 

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