Imagine that we had discovered an habitable planet, Planet X, located 10 light years away from Earth, and that we had managed to establish a small colony there. Now imagine that because of a much stronger gravity than on Earth, time on Planet X would run 5 times slower than on Earth: 1 year on Planet X = 5 years on Earth Someone sending a radio signal from Earth to Planet X would have to wait 20 years (10 + 10) to receive an answer. But what about the other way round? How much time would elapse for someone located on Planet X? More generally, does gravity and thus the flow of time affect the way time/distances are perceived in light years?