8mo ago

It's time to mentally prepare yourselves for this

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Shouldn't the moon have… 24 time zones as well, depending where on the moon you currently are?
- No, the moon's rotation isn't on a 24-hour cycle. I'm not an astronomer, but I pretty sure since it's tidally locked to earth and on a 28-day cycle around the earth, a lunar day is actually 28 Earth days, but I'm not actually sure how that would factor into the number of time zones (I'm pretty sure it would be more complicated than just 24 time zones to match 24 time zones on earth, though).
  Plus, I think the speed of the moon relative to the sun is different enough from Earth that you need to take relativity into effect, which is the real headache here.
  
  It's pretty simple, actually. The time zones are on average 1 hour apart. So there should be about 24*28=672 time zones on the Moon. SIMPLE.
  
  Or we invent 24 lunar hours and then we're back to 24 timezones.
  However I don't think keeping the sun overhead at noon is the goal here. That stuff is only important to humans. The real issue is figuring out how to count time on the moon in such a way that it doesn't run out of sync with how we count time on earth because of relativistic effects.
  
  The relativistic effects would be so small in human terms that the clock could just be synchronized with Earth time once daily and nobody would ever notice.
  
  Pretty sure it's both pointless and impossible to have an earth-like timezone system in an object that has coordinated rotation and translocation cycles. Meaning this mess we call "timezones" shouldn't exist in the moon.
  
  Shouldn't exist anywhere
  
  “An atomic clock on the moon will tick at a different rate than a clock on Earth,” said Kevin Coggins, Nasa’s top communications and navigation official. “It makes sense that when you go to another body, like the moon or Mars, that each one gets its own heartbeat.”
  article
  It's possible that they don't end up putting atomic clocks on the moon, but it's on the table, they haven't worked out the details yet.
  
  24 time zones on earth, though
  Even if you just count UTC offsets, there's 38 time zones: https://en.m.wikipedia.org/wiki/Time_zone
  There's more than that though, due to Daylight Saving Time. The rules for DST are part of the definition of the time zone. For example, in Australia, Queensland and Victoria are both UTC+10. However, Victoria observes DST while Queensland doesn't, so technically they're two separate timezones (in the Olsen database, they're Australia/Melbourne and Australia/Brisbane respectively).
  
  Yep, relativity accounts for a difference of like 50ms drift per earth day. I would assume that it's forward drifting if you're on earth but backwards if you're on the moon.
  Take that, timezone whiners!
  
  It's been a long time since I took modern physics, so I'm not positive, but I think you're right that the moon would have time moving slower, and if your 50ms/day is right (edit: I based this on the moon traveling faster than the earth, but I don't know anything about gravitational relativity, so that's probably wrong) then you'd need to do something like skip a second every 20th day on the moon to keep pace with Earth. We could call it an "anti-leap-second"
  Programmers, that seems pretty simple; what's the big deal? ^/s
  
  anti-leap-second
  HORROR
  
  We're close to skipping a second too here on earth since the Earth had actually sped up a bit the past decade.
  
  i heard, can't wait for satellites to fall out of the sky because of this one second
- The moon's day length is so long that it wouldn't make any sense for any crewed mission to use it, they're going to need their own lights on an arbitrary 24 hour cycle anyway, so there's no reason not to have every future crewed mission there use the same one
  
  I mean, this is the real answer here, but you can't just put them on UTC because of the relativity like we were discussing elsewhere, so it would still have to be a separate time zone for programming and timekeeping purposes, even if humans won't be able to tell the difference
  
  So, just plonk an atomic clock on the moon and call that moon time. Ocasionally synchronize moon time with UTC.
  
  That's pretty close to what they're doing. The tricky bit is detailing how you convert a lunar timestamp to a terrestrial timestamp.
  Jostling clocks with things like leap seconds turns out to be more trouble than it's really worth. Better to just let them get out of sync but be able to precisely define what the drift is.
- Because the moon is tidally locked to the Earth, some things are quite different up there.
  The day/night cycle is a lot longer, from sunrise to sunrise is ~28 Earth days. 14 straight days of sunlight, 14 straight days of darkness. Depending on where you are on the surface, you may never be able to see Earth at all, or if you can it remains more or less fixed in the sky; if you really pay attention it slightly wobbles. The waxing and waning of the Earth's disc are in sync with the sun as well, but not necessarily in phase. For example, if you're on the Moon's meridian, New Earth occurs at noon, but if you're to the East or West it will lag or lead. You can just barely make out major surface features of the Earth enough to tell that the Earth rotates, but at a period that has nothing to do with your local conditions.
  There wouldn't really be any utility to dividing the Moon into 24 time zones, it wouldn't line up with anything meaningful on Earth or to human circadian rhythms, so for expeditions like the Apollo program or upcoming Artemis flights, you'd just keep an onboard mission clock for the benefit of the crew and rely on artificial lighting and shades to maintain an Earth-like day/night cycle.
  It feels to me like this is a problem that doesn't need to be solved yet if ever; I would wait until there are actual people living on the Moon and let them solve the problem in a way that fits their needs, which we cannot fully anticipate from down here on Earth.
  I will note that time zones make more sense on Mars than the Moon. Mars has a rapid day/night cycle fairly similar to Earths, a Martian sol is about a half hour longer than an Earth day, fairly easy for humans to adapt to and live la vida loca. Some humans already have; NASA crews working on our various rovers adjust their working days to their rover's local solar conditions. They wear watches calibrated for Martian sols and the wake up and go to bed at a different Earth time every day so that they can work from the rover's sunrise to sunset, when they have light to see and when Spirit and Opportunity had power to move. And because the rovers are scattered across the surface of Mars, their local sunrises and sunsets happen at different times, so we already have de facto time zones on Mars.
  
  So, there is an actual utility for it, it's just not people centric.
  Having a framework for how you convert the clock measurements from the lunar reference frame to terrestrial reference frame is helpful for orbital maneuvering and navigation, as well as communication coordination.
  They're not building a "UTC+5” style timezone, but a "given the moons mass and orbit, here's how we define the time ratio between the earth and moon so we can consistently calibrate our clocks".

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