Subject: Confusion over red shift

I went through the Mad Science archives and didn't see any answers that say that light leaks energy as it travels, but the archives are big and I might have missed them!

This idea, usually called `tired light'', has many predictable consequences, not one of which is seen. There are many things tired light cannot explain, too.

The biggest problem is that we see time dilation in distant supernovae. Exploding stars that are very far away appear to get brighter and dimmer slower than ones that are nearby. This dilation of time is exactly what we expect if the supernova is moving rapidly with respect to us; in other words, the supernova is so far away that the expansion of the universe is carrying it away from us at a healthy fraction of the speed of light. We know time appears to slow down for a clock moving relative to a stationary observer, and the amount of dilation seen in distant supernovae matches very well with the dilation predicted given their velocity.

For more about current thinking in cosmology and a discussion of why tired light doesn't work, check out Ned Wright's excellent Cosmology FAQ (tired light is listed under ``fads and fallacies'').