Q:

Given Einstein's Relativity considers all frames of reference to be equally valid, then a photon's frame of reference is equally valid to ours even though the photon travels at the speed of light. So imagine a photon emitted from a star in the early universe 13 billion years ago which is absorbed by the Hubble Space Telescope today. According to our perspective, that quantum of light traveled across the universe for 13 billion years before it was absorbed. However, from the photon's frame of reference, no time passed between the moment it was emitted from the star and the instant it was absorbed. In addition, at the speed of light, the length contraction (or Lorentz contraction) shrinks distance to zero. But herein lies the apparent paradox in two parts: 1) Given that time measures change, in the early universe 13 billion years ago when the star first emitted the photon, there was no Hubble Telescope for the photon to instantaneously collide with from its (the photon's) frame of reference. 2) Given the complete length contraction of all points in space to zero at the speed of light, how can a single photon ever be absorbed at any one particular point when, if all distance between points in the universe is zero from the photon's frame of reference, the photon will hit each and every point throughout the universe simultaneously, not just one? In layman's terms, please help me understand how this apparent paradox can be resolved.

- Tom (age 50)

Aurora, CO

- Tom (age 50)

Aurora, CO

A:

Deep question! Although Einstein got into this business hoping to see how things looked from a photons point of view, that wasn't one of the viewpoints that relativity describes. The rues for translating coordinates from one frame to another only work for frames moving at less than c with respect to each other. We have no descriptions from the photon;s point of view.

Sorry!

Mike W.

*(published on 02/28/2016)*