4 ms·
Slightly off topic but I wonder how you handle time where dilation is present. For example if a spacecraft travels to mars and there is mars local time, plus ti
by setquk 8y ago
Slightly off topic but I wonder how you handle time where dilation is present. For example if a spacecraft travels to mars and there is mars local time, plus time dilation from the journey, when does a transmission start from a reference frame? Not UTC related for sure! Or is it? And then what happens if someone else goes there in a different orbital pattern and the dilation is different.
and then there is the question of how you would represent a recurring calendar entry between both places.
- deleted 8y ago[deleted]
- Retric 8y agoWith care you can calculate UTC independent of any time dilation. Local system is mostly irrelevant in terms of UTC and we already deal with systems with different clocks due to leap seconds. Now you might care about communication lag, but nothing makes earth unique so you need to handle lag with arbitrary endpoints anyway.
- oconnor663 8y agoIf two spacecraft start going fast enough in different directions, they can disagree about what order two different events happened in. At that point, it's not enough to give an event a single time coordinate in some reference frame; you also need to know its position in space.
- cryptonector 8y agoIf you can compute time dilation, then you can map back to Earth time (UTC) or whatever, and use that in your communications. Otherwise you give up and use only local time in your communications. And if ever our interpid travelers meet again they can compare their clocks and determine dilation (which will not change the fact that they'll have observed events in different orders, but they'll understand this, hopefully).
- dalore 8y agoSo you would need to know both the position and momentum? Good luck with that.
- thaumasiotes 8y agoAt the scale of a spaceship, it's easy.
- jetrink 8y agoThis is a very old problem and not limited to spacecraft. If you sail around the world eastward, each of your days is slightly shorter than the days of your countrymen and by the time you get home, you will have experienced a full additional day-night cycle. I think the solutions would be the same: separate timekeeping standards where it makes sense, like Mars, and frequent corrections to spaceships' clocks to keep in step with a universal standard like UTC as sailing ships used to do[1]. 1. https://en.wikipedia.org/wiki/Noon_Gun#Time_signalling https://en.wikipedia.org/wiki/Noon_Gun#Time_signalling
- cryptonector 8y agoThat was part of the plot of Around the World in 80 Days...
- phyzome 8y agoThat's not time dilation, that's... I guess you would call it clock dilation.
- mchahn 8y agoSpeaking of physics, I just read The Order of Time by Carlo Rovelli. The book is about time in physics and the title refers to the fact that is no real ordering of events. Good read.