# Resolution of the EPR paradox using special relativity

Please refer to the question "Resolution of the EPR paradox using relativity of simultaneity" I hope that this question will be clearer.

EPR photon experiments are a paradox for scientists. Can someone tell me why?

Distances and traveling time of photons are always measured on the basis of light speed c (300.000 km/sec.). However, according to time dilation formulas of special relativity (T'=T/γ) these measured values are no real values, but only observed values, observed by any observer. An application of these formulas (and more precisely: of the factor reciprocal gamma) yields that the real speed of light is not defined (zero-by-zero division) and the distances and times are shrinking down to zero. As a result it seems clear that all events of photons are taking place simultaneously, and thus photons may be here and there simultaneously - thus no paradox at all!

I learned already that possibly relativity and time dilation do not apply to particles moving at light speed. But what is the sound reason for such an exception if on the other hand this is prohibiting a resolution of the EPR paradox?

• Your “solution” has many problem. The easiest to see is the fact that the EPR paradox is exactly the same with slow moving objects like neutrons and atoms. – Frédéric Grosshans Jan 23 '14 at 17:51
• What you say is correct but out of subject, I limited my question to photons – Moonraker Jan 23 '14 at 19:01
• The whole point of relativity is that there are no 'real' values, except the absolute speed of light, $c$ (ignoring space-time curvature). Every (inertial, if you want to stick to SR) frame of reference is equally good. – Danu Jan 23 '14 at 22:50

## 1 Answer

For one, the transformation you propose is not a valid change of reference frame. It is meaningless to talk about the rest frame of a photon. The "sound reason" for that is exactly that, as you note, the photon would see the universe contracted to a plane, which it crosses at the speed of light in a single instant. That means that the spatial and temporal coordinates become degenerate and it is not possible to do physics.

Regardless of that, if it were possible to perform such a transformation, and solve the problem there, then it must also be possible to solve it in the laboratory's frame, because all valid reference frames have an equal standing in relativity. Thus you must also be able to provide an explanation in the lab frame.

• The question is perhaps more difficult than you think - I received already similar answers on my question, very short: 1. Observers do not observe only reference frames. 2. Photons do not have any reference frame. 3. For no speed v reciprocal gamma yields c. - I would prefer this question to be answered by a specialist familiar with limits of application of SR. – Moonraker Jan 23 '14 at 19:02