Comment by manv1
3 years ago
Talk to any developer who's been around for any period of time, and they'll tell you that dealing with time is a PITA.
What's bad is that there's no real thought given to interplanetary time. It's alluded to occasionally in SF, but there are no RFCs etc about it.
Earth has UTC. Mars will presumably have MTC. What about things wandering about? How will that be mapped?
More importantly, what happens to timestamps, GUIDs, etc?
> Earth has UTC. Mars will presumably have MTC.
If UTC doesn't work on Mars, it's false advertising, and we should really change the name.
UTC kind of works on Mars, but doesn’t really make much sense there, because it includes the leap second hack to make sunrises on Earth happen within a second of where they would have been with constant-length 24-hour days while keeping constant-length seconds. If you don’t care about that, use TAI, which is the simple monotonic counter UTC is based off of, or a trivial transform such as GPS time. (If you need so much precision that differences in the “constant-length” second due to motion and gravity matter, you shouldn’t be listening to me.)
I think it’s important to realize that the precisions we use for everyday time measurement are absolutely ludicrous. If you tell a physicist you can get seven significant figures of a value on a common household device, you’ll be laughed out of the room, and yet you know when a new year starts down to the second (1 : 3 × 10⁷) and don’t think much about it. Hell, you can have that to the millisecond (ten figures) if you care to, although it starts to get mildly tricky to actually use the result. This is the kind of precision that usually requires tens of thousands (in the former case) to millions (in the latter one) of dollars in equipment, knowledge of all kinds of tricky physical effects, and a trip to your country’s metrology institute for calibration. At best.
It’s a marvel that time measurement allows us to get away with a small collection of historical and convenience hacks here.
He's joking about the "universal" in the UTC acronym. If UTC doesn't work on Mars, it's hardly "universal".
I mean, it would work in the sense that you could use it to count time, but the units wouldn't have any practical relation to the planet's rotation.
TAI wouldn't work on Mars either. Mars is higher up the Sun's gravity well. To keep Mars on TAI would require adding a leap second every 5-6 years as the divergence is ~0.18 seconds every year.
There is a time standard that theoretically covers both Earth and Mars, along with the rest of the solar system: Barycentric Coordinate Time (TCB): https://en.wikipedia.org/wiki/Barycentric_Coordinate_Time But to achieve a singular, shared reference clock you have to give up everything else TAI advocates believe is important in a time standard.
wait until you hear about the World Series.
Real thought has indeed been given to interplanetary time (even by the subject of TFA). You may find this of interest:
https://webcache.googleusercontent.com/search?q=cache:pyKjMo... (forgive the cache but a postscript file is more easily viewed this way in the browser).
Few other relevant pointers: https://en.wikipedia.org/wiki/Deep_Space_Atomic_Clock and https://en.wikipedia.org/wiki/Barycentric_Coordinate_Time
UTC-style time should never be used as unique identifiers by itself, and computer clocks telling such time should generally not be assumed to always have monotonically increasing output. Most systems are sufficiently sane that they don’t critically rely on such assumptions.
The most interesting issue regarding Mars is that time elapses slightly faster on Mars than on Earth due to relativistic time dilation (according to https://space.stackexchange.com/a/33592, by 0.17 seconds per year). Conversion between Mars and Earth calendars will eventually have to take that into account, possibly with some kind of leap second mechanism.
Overall, I don’t think it will be too much different than what we already do on earth with regard to different calendars and timezones. The one novel aspect will be the difference in length of day.
Regarding a common solar system time, there is BCT and BDT [0][1]. Astronomers already have to deal with that. Another interesting webpage about time scales is [2][3].
[0] https://en.wikipedia.org/wiki/Barycentric_Coordinate_Time
[1] https://en.wikipedia.org/wiki/Barycentric_Dynamical_Time
[2] https://www.ucolick.org/~sla/leapsecs/timescales.html
[3] https://www.ucolick.org/~sla/leapsecs/deltat.html
There is an implementation: Martian Time in Hare[0], which is based on the Martian Business Calendar[1]
[0] https://harelang.org/blog/2022-08-01-martian-time-in-hare/
[1] http://www.bdm.id.au/calendar/mars_calendar.html