Quote:
Originally Posted by Paddy
Bear with me as someone with little formal training in physics. If photons do not age or have any time effect due to their existence at light speed, how can they lose energy unless they encounter something to which impart that energy (presumably stopping in the process)? And why would they lose energy traveling in space?
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I touched on this on page 1. The universe is expanding - space itself is expanding. The further away an object is from us, the more it appears redshifted. Now you can attribute this redshifting to having it moving away from us - like a doppler effect to soundwaves as an ambulance drives past, but it is not that simple. It
appears to be moving away from us because the space between us and it is expanding (which in effect, causes it to move away from us). Imagine a rubber band with a series of lines drawn on it, and stretch that rubber band. Lines close together are seperated by a little bit, but lines far away become seperated by large amounts. It is the same with space expanding, which is why things more distant appear more redshifted.
Because of this redshifting, the wavelength, and hence energy, is decreasing the further it travels. Consider it this way, the photon hasn't changed, just the universe around it has, & hence the way it is perceived
