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Subject: Re: Photons

Date: Thu Oct 22 22:08:07 1998
Posted by Ricky J. Sethi
Position: PhD

Supposedly, time slows down as you approach the speed of light. Therefore, does time exist for a photon? When a photon leaves a transitioning electron, does time not pass for the photon until it is absorbed by another electron (maybe Billions of our years later) at which point it ceases to exist.
Sorry - entered all my questions in the wrong area of science....


Hello Dr. Frankart,

Yes, it is very much as you suppose... time, the way we conceive of it, at least, does not pass for the photon. To the photon, the universe "appears" infinitely tiny. However, there is a trap in thinking of a photon's "existence" in terms of our own macroscopic existence (which is, after all, a necessary bias on our part). This is a very good question but, despite it's undeniable fascination, is also, in a way, unanswerable because the photon cannot be subjected to our experiences. I'm basically reiterating what others have articulated better, so I'll defer to them now. I'm including two of the online sources below (a previous madsci answer and a link to the Relativity FAQ). In addition, there are numerous books available on this subject that address this very idea... a few good ones are, in order of increasing detail:


Here is an excerpt from a previous MadSci answer that can be found here :
II. A photon does not experience its own existence. To a photon the moment of its creation is the moment of its annihilation and all distances in the universe are equal to zero from every point to every other point - hence, to a photon, the universe is still infinitely small... Like it was when it was created. Remember: everything in the universe is ultimately made of waveforms of some sort.
And here is an excerpt from the Relativity FAQ:
Sometimes people persist: What would the world look like in the reference frame of a photon? What does a photon experience? Does space contract to two dimensions at the speed of light? Does time stop for a photon? .... It is really not possible to make sense of such questions and any attempt to do so is bound to lead to paradoxes. There are no inertial reference frames in which the photon is at rest so it is hopeless to try to imagine what it would be like in one. Photons do not have experiences. There is no sense in saying that time stops when you go at the speed of light. This is not a failing of the theory of relativity. There are no inconsistencies revealed by these questions. They just don't make sense.
Despite these empty answers, nobody should feel too put down for asking such questions. They are exactly the kind of question that Einstein often asked himself from the age of 16 until he discovered special relativity ten years later.

Well, I hope this helps... if you have any further questions or would like any clarifications, please drop me a line at science@zentropy.com and I'll be more than happy to go into this in more detail.

Best regards,


Rick.


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