- #1
DaveC426913
Gold Member
- 22,762
- 6,438
- TL;DR Summary
- We sometimes talk about millions of years passing back on Earth during a relativistic journey but how is that possible without actually traveling 3 million light years?
The recent threads about relativity and the (ersatz) twin paradox got me flummoxed (again).
I referenced a story (A World Out of Time) where the man character came back to an Earth that was 3 million years older than when he left. The reason is that he journeyed to the galactic centre and back at very near light speed - the time dilation was such that only 150 years passed on board his ship - a factor of 20,000.
Question: The only way three million years could have passed on Earth is if he actually travelled 3 million light years (at 0.99999999875c), right? i.e. he would have had to loop around the core and back again, like, 57 times!
* there's mention of a trip around a black hole in the story but let's just ignore that for now and concentrate on a generic scenario
I referenced a story (A World Out of Time) where the man character came back to an Earth that was 3 million years older than when he left. The reason is that he journeyed to the galactic centre and back at very near light speed - the time dilation was such that only 150 years passed on board his ship - a factor of 20,000.
Question: The only way three million years could have passed on Earth is if he actually travelled 3 million light years (at 0.99999999875c), right? i.e. he would have had to loop around the core and back again, like, 57 times!
* there's mention of a trip around a black hole in the story but let's just ignore that for now and concentrate on a generic scenario