# How to reconcile photon not experiencing time with it's travel time?

1. Mar 16, 2013

### San K

If a photon does not experience space-time does that mean it cannot "degrade/fray"?

Is there a way to reconcile the, say, eight minutes, time
the photon (approx) took to travel from sun to earth
with
the zero time that passed in the (frame of reference of) photon?

Where was the photon, in a sense, during those 8 minutes?

2. Mar 16, 2013

### Mentz114

What does this mean ? Split ends ?

There's nothing to reconcile. Photons ( if they exist at all in free space ) do not have clocks and don't care about time.
Where do you think it was ?

You can resolve all these questions using Maxwell's equations and if necessary, GR.

3. Mar 16, 2013

### Bill_K

To describe the world line of a photon, just use the coordinate time in some handy reference frame. That's all you need to know. A photon does not have a rest frame. (Is there an echo in here?)

4. Mar 16, 2013

### San K

thanks Mentz114

a photon is a quanta of energy, within that quanta, i guess, there could be perturbations.

i guess, those perturbations would be created/initiated/caused during the prior interaction of the photon with matter-energy.

however would these perturbations (within the photon) freeze in time-space, when the photon is, say, moving in a vacuum (and not interacting with anything)?

Last edited: Mar 16, 2013
5. Mar 16, 2013

### San K

Don't photons need to exist (in free space) so as to, say, reach from the sun to earth (while traversing the free space between the sun and earth)?

6. Mar 17, 2013

### Mentz114

This is quantum mechanics but photons have wavelength and possibly a polarization state - but no other properties. And the wavelength is frame dependent. It is not useful to think that photons can be treated as small lumps of matter. When you've seen one photon you've seen them all.

It is possible that photons only appear when light interacts with matter. In this case we can't say anything except that light goes from A to B. Maybe while it is in transit it is an em wave. But it is not crucial because we can't detect light unless it interacts with matter.

Last edited: Mar 17, 2013
7. Mar 17, 2013

### Staff: Mentor

I think that conservation principles are more important for this. For a photon to decay into other particles those other particles would have to conserve energy, momentum, spin, charge, etc. It cannot decay into an electron because then it would violate conservation of charge. It cannot decay into an electron and a positron because then it would violate conservation of momentum. It cannot decay into a pair of photons because then it would violate conservation of spin. Etc.

We have had a rash of this question recently, and frankly I am getting tired of scratching. Here is the FAQ, please read through all of the other posts on the topic before continuing it here.