Red shift is the increase in the wavelength of an electromagnetic wave as it travels through space. If the wave travels for a time long enough can its wavelength increase so much that it becomes infinite?If possible, what would its consequences be? The red shift would alter the frequency of the wave, thus would the energy of the wave change?

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    $\begingroup$ Uh...what kind of consequences would you expect? $\endgroup$ – ACuriousMind Dec 1 '14 at 14:46
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    $\begingroup$ Nothing finite can produce an infinite thing, especially not in finite time. $\endgroup$ – Kyle Kanos Dec 1 '14 at 14:51
  • $\begingroup$ Red shift occurs because objects are moving away from us. For the wavelength to become 0, the object would be moving away at the speed of light, which is impossible according to currently accepted relativity theory. $\endgroup$ – barrycarter Dec 1 '14 at 17:10
  • $\begingroup$ @ACuriousMind I may be expecting the wave to vanish, its energy dissipated by the expansion of space-time. $\endgroup$ – Quantum Sphinx Dec 2 '14 at 2:16
  • $\begingroup$ @KyleKanos, if you squint your eyes the right way, an absorbed photon is one that has merely been redshifted to an infinite wavelength and a zero amplitude :) $\endgroup$ – Jerry Schirmer Dec 2 '14 at 2:19

There are different possible causes for Red Shift, e.g movement of the light source away from the detector (or vice versa), gravitational red shift, or the expansion of space.

For the expansion of space, have a look at the Wikipedia page on Cosmic Microwave Background, in particular...

The photons that existed at the time of photon decoupling have been propagating ever since, though growing fainter and less energetic, since the expansion of space causes their wavelength to increase over time (and wavelength is inversely proportional to energy according to Planck's relation).

So yes the electromagnetic waves will lose energy over time (and their wavelength will increase) but no I don't think it will ever reach zero energy (or infinite wavelength) as this would take infinite time.

  • $\begingroup$ Here, can we say that the energy of the wave is used up in expanding space-time? $\endgroup$ – Quantum Sphinx Dec 2 '14 at 3:33
  • $\begingroup$ If you move away from a light source so that it appears Red Shifted is the energy of the wave used up in expanding space-time? No. The energy measured is relative to your motion. I think this is the same answer for your question above, if space is expanding then we are moving relative to the photons which results in red shift. $\endgroup$ – Quantumplate Dec 2 '14 at 3:52

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