4 ms·

It’s a fun question to ponder but the answer is pretty obvious: UTC. As the clocks very, very slowly drift apart due to relativity, the moon could add a leap b

It’s a fun question to ponder but the answer is pretty obvious: UTC. As the clocks very, very slowly drift apart due to relativity, the moon could add a leap back 2 seconds every century to reconcile with Earth. Or add a leap back hour in 200,000 years.

JumpCrisscross 4y ago
> the moon could add a leap back 2 seconds every century to reconcile with Earth This seems like a system built to catastrophically break the moment it has to scale even a little bit. Why not start with a solid foundation? A native lunar time based on facts on its ground. One would also reference UTC, the same way many people have multiple clocks. But there's no need to be doing major relativistic correction between two internally-consistent blobs on the fly over the entire edge.
- nostromo 4y ago
  This is a step back to the bad old days when every town had its own definition of noon. Communication and anything that required scheduling was a mess because there were too many local definitions of time.
  - dredmorbius 4y ago
    Specifically: telegraph and railroads killed local time. Until then, things happened far enough apart, and sufficiently loosely coupled (shipping or riders on horseback being the principle means of long-distance travel) that coordination at a finer grain than a few minutes (and quite often hours or days) was unnecessary. Financial transactions are now precise to the microsecond, amongst other processes. Scientific / measurement precision can be far higher still.
  - JumpCrisscross 4y ago
    > step back to the bad old days when every town had its own definition of noon It worked until there were tens of thousands of towns. Even then, we didn’t port Greenwich time to Alabama; we aggregated the commonsense approach. We could inhabit every planet and solid moon in the system and not come close to they breaking point.
    - dredmorbius 4y ago
      Far less the number of towns than the amount and precision of interactions amongst them.
- roydivision 4y ago
  Or take a step back and look at the larger picture - devise a universe time that we can all adhere to where ever we are. Why remain earth centric when we're making more and more steps away from earth?
  - omnicognate 4y ago
    Unfortunately, Einstein threw a very large spanner into the works as far as that idea is concerned: https://en.m.wikipedia.org/wiki/Relativity_of_simultaneity https://en.m.wikipedia.org/wiki/Relativity_of_simultaneity.
    - dotancohen 4y ago
      Then how about using the pulses of a distant pulsar to measure time? That should get us through to the next few centuries at least. The fine article mentions that Lunar atomic clocks could be placed in Lunar orbit. However, there are very few stable lunar orbits due to the numerous mascons near the surface. And station-keeping would affect the clocks' accuracy - not to mention that the tidal variations on the Earth side and far side will affect the clocks as well. And any Lunar-specific solution would be unlikely to scale to Mars, Mars' moons, asteroids, and interplanetary spacecraft. Thus reinforcing the distant pulsars' signal as the optimum solution for the time being that humans remain in the solar system.
      - helsinkiandrew 4y ago
        But aren't the pulses of pulsars affected by black holes and wouldn't the pulses arrive at Mars, Moon, Earth at different times anyway?
  - midoridensha 4y ago
    Because it's impossible. There's no such thing as a universal time; it's all relative to wherever you are at that moment. Earth is small enough that relativistic effects between any two points are insignificant, but the Moon is far enough away that it'll be noticeable, though not that much. Anything farther, however, and it all breaks down. Within the system, it'll probably be "close enough" to have an offset between different places. If we expand to different star systems, though, it'll be impossible because they're moving in different directions.
- parsimo2010 4y ago
  You don't have to worry about scaling- Earth has one moon. And there are just eight planets in the solar system. It seems obvious that any off-earth colony governed by humans on Earth will have at least one time system that attempts to reference Earth time. There may also be a local time scale in sync with the rising or the setting of the sun. But that probably won't be the case on the moon, because a "day" is weeks long. So the humans will use a clock that references UTC. Perhaps a fixed offset from UTC if the Moon base is governed by a single country. The hard science part is dealing with gravity wells and keeping stuff in sync. But the top level answer will be that clocks will follow UTC, and any communications systems between the Earth and the Moon will be built to tolerate 2.5 seconds of lag.
classified 4y ago
What, no Daylight Saving Time?
zokier 4y ago
Making the timescale just utc would mean that moon-seconds would not match si-seconds, which sounds very problematic.

JumpCrisscross 4y ago

> the moon could add a leap back 2 seconds every century to reconcile with Earth This seems like a system built to catastrophically break the moment it has to scale even a little bit. Why not start with a solid foundation? A native lunar time based on facts on its ground. One would also reference UTC, the same way many people have multiple clocks. But there's no need to be doing major relativistic correction between two internally-consistent blobs on the fly over the entire edge.

nostromo 4y ago
This is a step back to the bad old days when every town had its own definition of noon. Communication and anything that required scheduling was a mess because there were too many local definitions of time.
- dredmorbius 4y ago
  Specifically: telegraph and railroads killed local time. Until then, things happened far enough apart, and sufficiently loosely coupled (shipping or riders on horseback being the principle means of long-distance travel) that coordination at a finer grain than a few minutes (and quite often hours or days) was unnecessary. Financial transactions are now precise to the microsecond, amongst other processes. Scientific / measurement precision can be far higher still.
- JumpCrisscross 4y ago
  > step back to the bad old days when every town had its own definition of noon It worked until there were tens of thousands of towns. Even then, we didn’t port Greenwich time to Alabama; we aggregated the commonsense approach. We could inhabit every planet and solid moon in the system and not come close to they breaking point.
  - dredmorbius 4y ago
    Far less the number of towns than the amount and precision of interactions amongst them.
roydivision 4y ago
Or take a step back and look at the larger picture - devise a universe time that we can all adhere to where ever we are. Why remain earth centric when we're making more and more steps away from earth?
- omnicognate 4y ago
  Unfortunately, Einstein threw a very large spanner into the works as far as that idea is concerned: https://en.m.wikipedia.org/wiki/Relativity_of_simultaneity https://en.m.wikipedia.org/wiki/Relativity_of_simultaneity.
  - dotancohen 4y ago
    Then how about using the pulses of a distant pulsar to measure time? That should get us through to the next few centuries at least. The fine article mentions that Lunar atomic clocks could be placed in Lunar orbit. However, there are very few stable lunar orbits due to the numerous mascons near the surface. And station-keeping would affect the clocks' accuracy - not to mention that the tidal variations on the Earth side and far side will affect the clocks as well. And any Lunar-specific solution would be unlikely to scale to Mars, Mars' moons, asteroids, and interplanetary spacecraft. Thus reinforcing the distant pulsars' signal as the optimum solution for the time being that humans remain in the solar system.
    - helsinkiandrew 4y ago
      But aren't the pulses of pulsars affected by black holes and wouldn't the pulses arrive at Mars, Moon, Earth at different times anyway?
- midoridensha 4y ago
  Because it's impossible. There's no such thing as a universal time; it's all relative to wherever you are at that moment. Earth is small enough that relativistic effects between any two points are insignificant, but the Moon is far enough away that it'll be noticeable, though not that much. Anything farther, however, and it all breaks down. Within the system, it'll probably be "close enough" to have an offset between different places. If we expand to different star systems, though, it'll be impossible because they're moving in different directions.
parsimo2010 4y ago
You don't have to worry about scaling- Earth has one moon. And there are just eight planets in the solar system. It seems obvious that any off-earth colony governed by humans on Earth will have at least one time system that attempts to reference Earth time. There may also be a local time scale in sync with the rising or the setting of the sun. But that probably won't be the case on the moon, because a "day" is weeks long. So the humans will use a clock that references UTC. Perhaps a fixed offset from UTC if the Moon base is governed by a single country. The hard science part is dealing with gravity wells and keeping stuff in sync. But the top level answer will be that clocks will follow UTC, and any communications systems between the Earth and the Moon will be built to tolerate 2.5 seconds of lag.

classified 4y ago

What, no Daylight Saving Time?

zokier 4y ago

Making the timescale just utc would mean that moon-seconds would not match si-seconds, which sounds very problematic.