Question: Does light wave disintegrates(i.e. its crest and troughs vanishes leaving a straight line) when it travels unhindered and stretched too far due to expansion of universe? Though it can’t be observed, is it theoretically possible? — Vinod
Answer: The apparent stretching of light waves caused by the expansion of the universe is in fact not due to the actual stretching-out of the light waves. One sees a “redshift” of the light from an object that is moving away due to the recessional motion causing the illusion of a lower frequency. The lower frequency is measured by the observer because each successive crest of the light wave emitted by the moving object is emitted from a position further away from the observer than the previous wave. This appears to the observer as a lowering of the frequency of the light coming from the moving object. The light wave itself is, in fact, not changed or stretched.