[mikeh. (OP)]

I'm responding to a previous question but the last response seems to have been in 2009. 

Time does stop for photons - travelling at the speed of light, but if it does then the very idea of 'distance' must too.  If 'distance' were a 'real' quantity, it would always take time to traverse it.  No time, no distance.  For a photon then, and in a Kantian spirit, existence itself must be devoid of time and space.  This suggests that from a photon's 'point of view' existence is a featureless singularity of an infinitesimally short duration. 

These conditions hold within only the frame of reference of movement at the velocity of light. But if photons, - which move at the velocity of light, exist in a timeless and dimensionless frame of reference, by definition velocity or movement of any kind cannot exist.  How can velocity decrease as it increases?

[imatfaal]

Hi Mikeh (is that Mike H or Mikeh - just curious) - SR which is the basis of these thoughts does not allow for the frame of reference of photon.  Good question - but very complex and difficult, if not impossible to answer.

Not sure about why you mention Kant - I think of Kant in terms of necessity of experience; all of our physics states that nothing capable of experience or even of change (ie massive / non fundamental) can ever travel at the speed of light.  we can experience and experiment and through logic move from subjective senses to objective theories - nothing that is able to travel at c can do this and to criticise the theory from this angle seems unjust

[Nizzle]

Everything moves at the speed of light through the spacetime continuum, but the faster it moves through space, the slower it moves through time (and vice versa).

So time only stands still for photons moving through a vacuum, where their speed through space equals c (the speed of light in vacuum) and thus their speed through time equals 0. As soon as a photon travels through another medium, ie air or water or glass, it's speed through space will be a very small amount lower than c and that very small amount will be converted to "speed through time", so a photon, in my opinion, does age whenever it's not traveling through vacuum. Therefore, from the point of view of a photon, existence is not a featureless singularity of an infinitesimally short duration, but more like: "The big bang? Oh, wasn't that the day before yesterday?"

[imatfaal]

Everything moves at the speed of light through the spacetime continuum, but the faster it moves through space, the slower it moves through time (and vice versa).

So time only stands still for photons moving through a vacuum, where their speed through space equals c (the speed of light in vacuum) and thus their speed through time equals 0. As soon as a photon travels through another medium, ie air or water or glass, it's speed through space will be a very small amount lower than c and that very small amount will be converted to "speed through time", so a photon, in my opinion, does age whenever it's not traveling through vacuum. Therefore, from the point of view of a photon, existence is not a featureless singularity of an infinitesimally short duration, but more like: "The big bang? Oh, wasn't that the day before yesterday?"

hmmm - not sure about that Nizzle. Whilst the propagation of a signal will be slower through a medium - at no point will you be able to catch a photon doing anything apart from c.  Heuristically the signal delay is down to absorption and re-emission of quanta by the atoms of the medium - but the travelling of individual photons is always at c between interactions.  there is no bit of the spacetime metric to put the time spent in interaction to calculate the spacetime interval.  and if this was the case you would have the problem of photons accelerating and decelerating and the concomitant forces etc. 

[flr]

These conditions hold within only the frame of reference of movement at the velocity of light. But if photons, - which move at the velocity of light, exist in a timeless and dimensionless frame of reference, by definition velocity or movement of any kind cannot exist. 

If space length and time duration cannot be defined for photon, how then a frame of reference for photon (i.e. a frame of reference moving at speed of light) would work?

[Silver]

If time stops for photons, how do they red or blue shift?

Photons like electrons are unchanging so essentially ageless. You could as easily say time does not exist for electrons.

[imatfaal]

Time stopping for photons is a popular misreading of special relativity.  SR determines time dilation for massive particles travelling at below c - to extend the equations of time dilation to photons which are masslss and travelling at c is just not correct; ie there is no such thing as the local frame of a photon.

[Geezer]

Time stopping for photons is a popular misreading of special relativity.  SR determines time dilation for massive particles travelling at below c - to extend the equations of time dilation to photons which are masslss and travelling at c is just not correct; ie there is no such thing as the local frame of a photon.

Isn't that just a way of saying the math breaks down so SR can't provide an answer?

There is some empirical evidence that photons are "immune" to time. While everything else seems to decay, it seems that photons don't.

[imatfaal]

Time stopping for photons is a popular misreading of special relativity.  SR determines time dilation for massive particles travelling at below c - to extend the equations of time dilation to photons which are masslss and travelling at c is just not correct; ie there is no such thing as the local frame of a photon.

Isn't that just a way of saying the math breaks down so SR can't provide an answer?

There is some empirical evidence that photons are "immune" to time. While everything else seems to decay, it seems that photons don't.

It's not just that the maths breaks down - although no one ever likes trying to divide by zero; but the theory has limits - it deals in flat space and massive, thus, sub luminal particles.  photons might not decay because of a time thing, or because they are truly elementary, or because we just haven't noticed it happening. 

[Geezer]

or because we just haven't noticed it happening. 

Oh, I think we would. They would be redshifted, so everything would look like it was retreating from us

(thinking)
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[yor_on]

Mike, as far as I know 'photons' know where to go. And if they do, then they 'navigate' inside our time, as observed by us. To ask what a 'photon' sees is another thing. According to main stream definitions they propagate at 'c', which is a unchanging constant no matter from where you measure it, or how fast.

If you think of it then that is a very strange property. As far as I know nobody can answer why radiation behaves that way. You might refer it to 'time' possibly, which is another weird property according to the theory of relativity. Both time and 'c' stays the same for you, as measured locally. And your relative motion doesn't matter for that, neither does what mass you are on, as a neutron star.

It's the rules of the game. And trying to see why those rules exist, and what one would see when at that 'edge' of reality is very difficult. We know what we expect mass to see, when gaining a relativistic velocity, near lights speed. But that is mass, not bosons.

[imatfaal]

or because we just haven't noticed it happening. 

Oh, I think we would. They would be redshifted, so everything would look like it was retreating from us

(thinking)
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protons are expected to decay, are certainly not travelling at such a speed that "they are frozen in time" (hateful concept), and we have never noticed one of them decaying

[Geezer]

or because we just haven't noticed it happening. 

Oh, I think we would. They would be redshifted, so everything would look like it was retreating from us

(thinking)
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- wait a minute!

protons are expected to decay, are certainly not travelling at such a speed that "they are frozen in time" (hateful concept), and we have never noticed one of them decaying

Yes - protons are difficult to observe, but photons seem to be able to travel trough all of time without any difficulty at all.

[JP]

Of course, gluons (the only other massless particle we know about) decay so quickly that none have ever been observed.  We detect them through their decay products.

So half the massless particles we know about seem "immune" to time, while the other half seem to grow old and die very quickly. 

[hubble_bubble]

Photons maintain information over billions of light years, such as red or blue shift and luminosity. Which is why we have information from type 1A supernova. If this information was not 'frozen' then the expansion of the universe would be undetectable.

[Emc2]

"time" does not "stop" per se, for photons.   Time is an observation of progression or expansion.

 A photon leaves a distant star, say 1 million light years distance from observer, 1 million years later Photon arrives at observer.
 
  progression of said photon, never stopped.  Hence "time" per se, never stopped for the Photon.

  If a photon experienced "time stop", then basically it stops moving, instantly....of course this is not observed....

  Time is a funny thing, and may not even be anything at all, but an observation...

  Of course all of this, make no sense at all..........but it is reality......ha ha


  if you think about "time stopping" hence progression or expansion stopping, then at a "time stop", then time stops.....nothing moves, electrons stop orbiting protons n neutrons, elements stop spinning, energy ceases to exist, all particles stop moving, spinning, etc.etc.....


  if "time" ever did stop, per se......existence stops at that point also............end of all progression and expansion

[hubble_bubble]

What we cannot tell is if the photon is actually flat-lining until we detect it. It may only express its wavelength and other properties at the point it is absorbed. Like schrodinger's cat we may have to open the box to see it's state. The fact that matter undergoes time dilation until, if it was ever possible to reach light speed, it goes into a state of infinite dilation where time has no meaning, points to a frame where time does actually stop in THAT frame of reference.

[Emc2]

The fact that matter undergoes time dilation until, if it was ever possible to reach light speed, it goes into a state of infinite dilation where time has no meaning, points to a frame where time does actually stop in THAT frame of reference.

  If time actually "stopped" for that frame of reference, then inside of that frame of reference, movement is not possible, nor is energy, nor is mass, nor is gravity, nor is any force operating in a frame of reference that time has "stopped" inside of.

  I do not believe it possible for "time" ( progression, expansion/decay, etc )to stop and then have all these things and others to "stop" all at once.

  In a state of time stop.....time stops.....you can not escape from no time, into time,
  if you are in time stop.....
  then for you.............................. time stops,
  and you break down into elementary particles, and you cease to exist......as all stop spinning and orbiting, etc.....

  time stop is infinite.....................for the frame of reference that it happened in...hence not possible for a photon to have  "time" stop ( per se ) for it......mainly because time is not a thing, but an observation,

  and the main, and key point...

   a photon can not observe, so in essence "it" has no frame of reference....

   and nothing that observes can travel at the speed of light to observe the effects anyways....


 

 

[hubble_bubble]

I believe that the statement you made about breaking up into elementary particles at light speed is very interesting. Simply because the elementary particles would be unable to travel at this speed. They are not photons and have mass. Length contraction is of interest in this case though, as a particle seen as infinitely contracted (there's that infinity again) would not exhibit mass. It may well be expressed simply as energy where this has swapped places with mass. I know that is a bizarre concept but aren't quantum physics and relativity bizarre?

In the mass of a photon topic you posted the relationship p = E/c. Maybe it is momentum that has interchanged with mass. Interestingly this equation would give c=E/p showing that how fast the object travels affects the energy and shows a direct proportionality.

[hubble_bubble]

By the way the relationship p=E/c indicates that a rest frame is impossible just like light speed travel is as nothing can ever truly be at rest with respect to the rest of the universe. This relationship also appears to show the impossibility of reaching absolute zero. As photons reach light speed, which is impossible for other particles, could another undiscovered particle only exist at absolute zero?