LogFAQs > #932288111

Mr Hangman posted...

You can make it Earth-centric, that's not the problem. Say you're on Earth, keeping time, and I'm on Mars. I ask you what time is it. You send a reply with the exact time you sent the message. It will take between 3 and 22.5 minutes to reach me. The distance varies that much. If I set my time to that I'll be slow. So now I have to compensate for that time delay. To do that I need to know exactly what the delay was. To do that I need to measure the delay of a round-trip message bounce. Of course the distance is also changing a bit all that time.

Now I've synced my clock with you, but there's probably some error in all that process. Then even if our two clocks both keep perfect time, they will still drift apart something like half a second per year due to special and general relativity. Within the solar system these effects are not too significant, although they do matter for high precision systems like GPS. But when it comes to interstellar travel, then the question of what time is it gets complicated.

Cant you just estimate the time it would take light to travel to earth, account for that, then use earth time?