Sign up ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free.

Superman throws a light emitting object away from himself fast enough to notice a red-shift. The object passes through a region in which time runs more slowly. From Superman's perspective, does the red-shift change as the object slows or is the light's appearance unaffected?

share|cite|improve this question
Is there a common thought on this topic in the theoretical physics community? –  Brien Malone Nov 12 '11 at 5:38

1 Answer 1

up vote 3 down vote accepted

The object doesn't slow in this case, it speeds up. The redshift is increased. The clock-slowing-down factor is more traditionally called the gravitational potential, and where clocks are slow, this is close to a massive object. In the extreme limit that the light-emitting-object is approaching a black hole, time stops relative to Superman, so that Superman sees the object infinitely redshifted.

share|cite|improve this answer
Sorry to leave this hanging for ... gulp 3 years... I never received notification that this was answered! Weird. Oh well -- points for you. –  Brien Malone Sep 18 at 21:45

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.