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
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.
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.
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.
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.
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^
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.
“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.”
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).
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”.
Shouldn’t it have its own time system? And have its own time zones? You can’t give the moon its own single time zone (unless you’re into the idea of a single universal time zone).
That’s actually what they’re doing. The reporting said timezone when the actual order is more about time standards.
They’re creating coordinated lunar time, as a complement to coordinated universal time, so it’s a different time system with details about how it relates to UTC.
Timezones on the moon don’t serve as much function, because the day/night cycle is closer to a month long, and doesn’t map to human rhythms at all. In a hypothetical where we have moon colonies on opposite sides of the moon, there’s no reason for them to not still have synchronized day/night, since it already has no relation to the movement of the sun in the lunar sky.
Based on a completely superficial review there are three almost guaranteed ways to become unhinged; studying infinities, refactoring legacy code, and working with timezones.
I’ve been a proponent of this for ages. It makes no sense to cross some imaginary line and suddenly time shifts. Time should change constantly as you move east or west, up or down. Everyone has their own personal time, which is constantly updated.
That was kinda the situation in the past: Every town would have its own time, synced to the local noon every once in a while as the precision of the church or townhall clock demanded. That stuck around until railroad operators and passengers got sick and tired of dealing with the timetables that produces.
Lmao I love how he just gets more and more flabbergasted throughout the whole video. Truly an accurate depiction of dealing with timezones (which I’m unfortunately dealing with right now!)
In the military that’s all we used. It’s called Zulu time in the Army and it makes for coordinating events in multiple time zones fairly easy. I would assume the moon would be the same since there will 100% be a moon base with military.
I have response teams in a “follow the sun” model as well as having my US team spread coast to coast, plus all our clients set their servers to UTC. It makes the most sense to keep something set to UTC at a moment’s glance.
That sounds… iffy. Thing is that UTC lags more and more behind TAI as UTC takes the earth’s rotation into account, introducing leap seconds so that all the timezones don’t slowly drift across the globe. Moon people care preciously little about the earth’s rotation around its own axis, more relevant is its own day/night cycle which (because tidal lock) is an earth month. The system might just be stable enough so that UTC can simultaneously sync to that, you’d have to ask an astronomer.
Actually, no, forget it: The moon moves quite fast relatively to the earth’s surface, more than enough for relativistic effects to apply – they also apply to GPS satellites, stuff simply wouldn’t work if those things ran on Newtonian maths. Sooner or later it’s going to need adjustments due to that.
UTC doesn’t become wrong, you can either just accept a different pace of the clock, i.e. earth ppl will be ever so late to a meeting or it’s just a different kind of timezone conversion. Better would be to have a single time based on the reference frame of the center of the galaxy and everyone keep there time relative to that.
just use a time based on light?, like meter is based on the speed fo light in the vaccum, or use atomic based times?, like how long take for the hydrogen atom todo something bla bla bla
The second […] is defined by taking the fixed numerical value of the caesium frequency, ΔνCs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9192631770 when expressed in the unit Hz, which is equal to s−1.
Do not matter for relativity though, always same change.
So are you saying that a caesium-133 atom observed on both the Earth and the Moon to oscillate 9,192,631,770 times will not represent the same absolute span of time?
So, one observer will see those oscillations happen faster than the other?
Does this have to do with the specific gravity fields of both observers, in that those fields affect how the atom oscillates?
Or is there something else I’m missing?
If special relativity is the answer, all good. I’m an electrical engineer trained in classic physics, so I’ll rest knowing that I’d probably need to study that to understand the time differences.
So, one observer will see those oscillations happen faster than the other?
Not quite. In each observer’s frame of reference, time appears to pass the same; it’s only when you try to reconcile the between two objects that are not at rest with respect to each other does relativity show up.
Basically, when you bring someone back to Earth, the observers will find that their watches don’t match up even though both observers experience time passing the same way as normal (because the oberserver is by definition at rest with respect to their own frame of reference).
TL; DR: Relativity is a pain in the ass and makes no sense in everyday terms.
edit: disclaimer - I am not a physicist and have not taken physics classes in a decade plus, but I do teach science at a college. I’m going mostly on half-remembered lectures and some random one-off discussions I’ve had with my buddy in the physics department over the past few years.
It’s that relativity thing where each person will see the oscillations happening correctly, but when they look at what the other person did, the answer will seem wrong.
The difference is small enough that it really only matters if you’re NASA and building moon GPS. MPS?
That’s actually what’s different on the moon. Relativity and all that means that time itself actually flows differently on the moon than it does on earth.
The actual problem they’re working to solve is around timekeeping and GPS applications in different reference frames, but it’s hard to make a short headline about.
When I first saw the news I was thinking “there’s no way atoms vibrate differently on the moon” but you’re right it’s about perspective and I’ve realized there’s no way I’m smart enough to handle timezones on an interplanetary scale. I can only hope that the difference between earth seconds and moon seconds can be expressed as a consistent ratio.
I will gladly use some programming library invented in the basement of a university powered by coffee, and rage.
It’s well understood math, but it’s “only” relativistic orbital mechanics.
It boils down to a pretty consistent number, but how you get there is related to the weight of the moon, how far it is from earth, and how fast it’s going.
Since the moon is going different speeds at different places in it’s orbit, the number actually changes slightly over the month.
They’re just using the average though, since it makes life far easier. We use the average for earth too, since clocks move differently at different altitudes or distances from the equator.
It’s not too bad. Relativity says that no frame of reference is special.
On earth, a second looks like a second, but a second on the moon looks too quick.
On the moon, the second looks like a second, but a second on earth looks too slow.
Both are actually correct. The simplest solution is to declare 1 to be the base reference. In this case, the earth second. Any lunar colonies will just have to accept that their second is slightly longer than they think it should be.
If it helps, the difference is tiny. A second is 6.5x10^-10 seconds longer. This works out to 56 microseconds per 24 hours. It won’t affect much for a long time. About the only thing affected would be a lunar GPS.
Unfortunately, it’s not a useful one. While we know approximately where it is, we don’t know how deep the gravity well is. That gravity well slows the passage of time, just like the earth does. Without an exact mass, and mass density, we can’t calculate the correction factor.
No the second is still 9192631770 hyperfine transitions of Cs-133 on the moon and that’s the same length of time at least unless you want to severely annoy physicists by implying that the laws of nature aren’t constant throughout the universe. It’s just that from our perspective it looks like time is flowing differently there.
You are correct that if you are on thee moon and have a cs-133 atom with you is second will take that many transitions. And if you do the same thing on Earth, a second will take the same number of transitions.
But things get weird when you are on earth and observe a cs-133 atom that is on the moon. Because you are in different reference frames, you are traveling at different speeds and are in different gravity wells time is moving at different rates. This means that a cs atom locally will transition a different number of times in a second from your point of view on Earth vs one you are observing on the moon.
And it would all be reversed if you were on the Moon observing a clock back on the Earth.
They already have to account for this with GPS satellites. They all have atomic clocks on them but they don’t run at the same speed as clocks that are on the ground. The satellites are moving at a great speed and are further from the center of the earth than us, so the software that calculates the distance from your phone to the satellite have to use Einstein’s equations to account for the change in the rate of time.
I suspect that won't help. The reason the Moon needs a time zone is because of gravitational time dilation, time literally runs slower down here on Earth's surface relative to the Moon's surface. A computer on the Moon gains an extra 58.7 microseconds each Earth day, so if you're programming something that'll be running on Lunar time you'll need to account for that.
The point of the lunar time zone is not to have a specific UTC offset like other timezones. The moon would have its own set of atomic clocks, and time could be coordinated with earth based on ratio instead of offset.
They're not going to be maintaining literal atomic clocks on the Moon for this. They'll apply a mathematical adjustment to UTC based on what the physics calculations say is happening. The details of that adjustment are what NASA has yet to develop. It could involve subtracting a "leap second" from lunar time at intervals, leap seconds are already used for keeping UTC in sync with the solar time so it's an established process. Or maybe they'll just let Lunar time continue drifting relative to Earth, in which case there'll be a different "epoch" on each.
They probably actually will end up with atomic clocks on the moon, or at least in close lunar orbit. If the plan is to have something like gps on the moon, that’s a first step.
So, in this case a moon timezone, and more generally a “space timekeeping framework” makes sense because time actually moves at a different speed on the moon, so epoch times wouldn’t actually stay in sync.
If the goal of “time” is to make it easier to reason about simultaneous things, then space makes that way more complicated.
It’s just tricky to condense that into a headline that conveys the point.
Yup. So building a system for “how we build time systems in different reference frames” and “define how we relate those to earth” isn’t irrational, just makes for headlines that are either difficult or very misleading.
Unix is for commies. We’ll run our clocks the way Britain ran its coinage! 32 shillings to the third hour, four hours in a pound, 4.3 in a guinea. And of course 10 shekels in a pound, 7 to the guinea. To account for relativity of course.
Because the world is seen and directed by layers upon layers of abstractions that get divorced from reality but do give monetary benefits when manipulated in some way.
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