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The range of electromagnetic radiation is indefinite.

When was that established? Doesn't Hubble's limit have an effect?

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    $\begingroup$ Even if light lost energy, at what point would it have zero energy? It would asymptotically approach zero but never reach it. $\endgroup$ Jan 7, 2014 at 8:53
  • $\begingroup$ Why do you say that? Hubbles Limit is d = c / H_0 $\endgroup$ Jan 7, 2014 at 20:19

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It hasn't been "determined". It has been determined that photons have a range of at least 46 billion light years. Given that that is the maximum distance we can ever hope to see (or interact with at all), that sphere effectively is the universe, so the range for EM waves is "infinite", at least for all realistic intents and purposes.

Some known mechanisms that have an effect on the range of EM radiation are:

  • absorption by (partially) opaque medium
  • matter creation
  • intensity drop to below theoretical minimum detection thresholds

But, in an "idealized" universe where there is no matter at all and an infinite amount of space, AFAIK, there is no known or predicted limit on the maximum range of a photon that does not have enough energy to create matter.

The classical or relativistic Maxwell's equations (from which the existence of EM waves was first predicted) make no statement on any range limit, neither does anything in quantum mechanics I know of (except for matter creation, but I'm not counting that).

In fact, if you believe in conservation of energy, it's implausible there is a hard limit for general EM waves: into what form would a kHz photon for example convert its energy?

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  • $\begingroup$ For a photon to make a trip of 46 Bly are we assuming multiple hops from electron to electron count? Or are we assuming a single photon can be exchanged by two electrons separated by 46 Bly? $\endgroup$ Jan 8, 2014 at 22:22

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