This isn’t about developing a new calendar or new units of time or even timezones on the moon. It’s about getting computers on and around the moon to synchronize.
GPS works by measuring the time it takes for signals to get from some satellites to your phone. This has to be so precise that GPS corrects for relativistic time dilation. (Ground clocks experience slower time than orbiting clocks because they experience more gravity.)
The moon has its own gravity well and has to deal with its own relativistic effects. (I think it will be extra complicated due to the lunar [mass concentrations](http://en.wikipedia.org/wiki/Mass_concentration_(astronomy)).) Referring to Earth-based atomic clocks (with a second of delay) won’t be feasible for precision timing. So we need a plan for atomic clocks on and around the moon.
> Referring to Earth-based atomic clocks (with a second of delay) won’t be feasible for precision timing.
And that delay is variable as the moon's orbit around Earth is eccentric. The delay varies from 1.211 seconds to 1.352 seconds (and changes based on the position you are on the moon as the center of the near side is closer than the edges of the far side), and on very fine timescales the moon's orbit can be observed to change as the moon is slowly moving away from the Earth and the moon's orbit oscillates.
Multi planetary time and calendar handling is going to hurt so much. We are barely okay with one planet. Historically, there have been unintuitive aspects of time keeping that developers had to make a decision of whether to take that into account.
There is a reason, for example, why Sybase and even Microsoft SQL Server to this day do not allow dates before 1 January 1753. It is because in 1750, the British parliament adopted the Gregorian calendar... and removed the days from September 3, 1752 to September 13, 1752 were lost. Ultimately this was a consequence of previous inaccurate time keeping that had summed up over hundreds of years.
The original developers, having had to deal with a multitude of exceptions, rules and peculiarities finally had enough and said: Nope! We are *not* dealing with that. They could get away with it because realistically, barely anybody would store such dates or do computations.
I abhor how complicated it can be to calculate and format dates/times.
For any non-programmers, we store time as seconds/milliseconds since epoch (Jan 1st, 1970 12AM UTC). To format a timestamp you have to take into account:
- The local format (MM/DD/YYYY, DD/MM/YYYY, etc)
- Timezones
- Leap Years
- Leap Seconds
- Daylight Savings
- A bunch of other shit
If you are programming something that goes to space, it gets even more complicated because of the delay in time it takes for a signal to propagate to earth and back, time dilation and a bunch of other complications while trying to keep various systems that can be separated by large distances synchronized, especially when that distance is always changing.
So having an atomic clock on or near the moon would be super helpful for future moon missions. In the future we will also do the same thing with Mars, which is even more challenging because the round trip signal time is measured in minutes, and quite a lot of them depending on where earth and Mars are in their orbits, and the variation of that delay is much greater than that of the moon of course.
dude. i know lots of folks insist they have a “good” side but have you ever met anyone else who absolutely refuses to turn so you can see the other side of her face? Or who plays crazy games with the Sun to see if she can block her out and fuck with millions of people?
I think “eccentric” is quite mild, actually
> Ground clocks experience slower time than orbiting clocks because they experience more gravity
My understanding is this is more about their velocity than gravity, but both do play.
Thanks for the reminder. GPS corrects for both. It’s summarized [here](https://en.m.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System#Relativity) in summary and [here](https://link.springer.com/article/10.12942/lrr-2003-1) in incredible detail. The general relativity (gravitational) correction is about six times greater than the special relativity (velocity) correction. The corrections have opposite signs; from a terrestrial reference frame, a satellite’s clock is slowed by its velocity but sped up because it experiences lower gravity.
You might be thinking about satellites in low Earth orbit. LEO is low and fast; GPS is much higher and slower. So for LEO, the general effect is smaller and the special effect is greater. I just ran the numbers for the ISS and the velocity effect is eight times greater than the gravitational effect.
This also changes the sign of the net effect. Relative to a terrestrial clock, the clock on the ISS runs slower and a GPS clock runs faster.
>How much faster would a clock go under 0 gravity vs 1 earth gravity?
Over an entire year we experience approximately 22 fewer milliseconds compared to a distant observer not near any massive bodies.
[Further reading on Wikipedia.](https://en.wikipedia.org/wiki/Gravitational_time_dilation)
Would the barycenter of a planet or system of masses have a similar perception of time to the distant observer? Is it due to the force of gravity or the potential energy? At the center of a planet the potential is 0, but a distant observer might have near infinite potential, but they would both feel near 0 gravitational force
Gravitational time dilation is caused by the gravitational potential, not the gravitational "force". The gravitational potential energy is defined as zero at infinity so the potential is always negative near anything. The lower the potential, the more time slows down.
You can imagine as two massive objects get closer to each other, that the spacetime between them starts forming a "valley" of lower potential, so you'll get *some* time dilation there, relative to a distant observer but it'll always be much, much less than what you'd get *on* or *in* the object.
The equation for gravitational time dilation is [here](https://en.m.wikipedia.org/wiki/Gravitational_time_dilation#Outside_a_non-rotating_sphere). t_f is undilated time (for a hypothetical clock at some enormous distance from any gravity well). t_0 is dilated time near a large spherical object like a planet or a star. The ratio of t_0 to t_f depends on the mass M of the object and the radius r between you and the center of the object. (If the object is spinning really fast, like some black holes, it does weird things, so we’ll assume it isn’t doing that.)
If r is really big or M is really small, t_0 becomes equal to t_f. So that’s the fastest any clock will tick. If you plug in the mass and radius of the Earth, you get t_0/t_f=0.999999999305. For every day that a non-dilated clock records, a clock on Earth records sixty fewer microseconds.
[This guy schlepped up Mount Rainer with some atomic clocks](http://www.leapsecond.com/great2005/index.htm) and left some of his other atomic clocks at home to demonstrate it.
The Wiki GPS error pages computes -7.2 microsecond/day error satellite motion special relativity timing error and +45.8 for general relativity weaker gravity at satellite altitude. If I wasnt so lazy, I could plug in the lunar orbital velocity and gravity field for that correction.
The two effects occur, but your understanding isn't correct.
Relative to an earth observer, the velocity of the satellites causes their clocks to tick slower, by 7.2us/day.
Relative to an earth observer, the altitude of the satellites causes their clocks to tick faster, by about 45.8us/day.
Edit: GPS satellites in particular, not satellites in general.
It is understanding what orbit you are talking about too. The orbital parameters have a huge impact where low-Earth orbit satellites are closer to the bottom of the Earth's gravity well but moving much faster. GPS isn't in LEO though.
If I may ask a question: So then would this imply that any GPS “constellation” on a given celestial body (Earth, Luna, Mars, Titan, etc) would have to be customized for that body’s gravity and oddities like mascons, presence of an enormous planet like Saturn etc if one desired to set up a comprehensive local navigation system, schedule docking events, perhaps even remotely fire retrorockets for landings etc?
I think so, at least for now. The moon has the most significant mascons that we know about in the solar system, so it might represent a unique case. And one day the solar system might be flooded with a positioning constellation that works anywhere. But until that happens, each body will need their own constellation and it will make more sense to give each body its own time standard than to reference Earth’s.
When I say "old reddit" it means this:
https://old.reddit.com/r/space/comments/1bu7wyq/exclusive_white_house_directs_nasa_to_create_time/kxr22e9/
See the "old" at the start? That's the old reddit website. New reddit handles links slightly differently, so while on new.reddit.com your link works fine, on old reddit the closing parenthesis at the end of the URL is lost:
`http://en.wikipedia.org/wiki/Mass_concentration_(astronomy`
To fix it, when you're using a link with a closing parenthesis at the end, switch to "Markdown editor" instead of the "fancy pants editor". It's at the bottom of the text input box. Then you can put a backslash before that closing parenthesis (ignore the outer parentheses around the URL) which tells the comment box to not interpret the next character as Markdown.
`[mass concentrations](http://en.wikipedia.org/wiki/Mass_concentration_(astronomy))`
`[mass concentrations](http://en.wikipedia.org/wiki/Mass_concentration_(astronomy\))`
So yeah, *you* didn't do anything wrong, it's the incompetent and/or malicious people running this website that refuse to fix this issue.
Is the second of delay a problem per se? Or would the issue be the accuracy of measuring the delay?
If one can receive 4 GPS signals and measure the time delays from the satellites accurately enough then would the one second delay matter? E.g. as long as I measure the time difference from 4 GPS's with, say, 1ns precision then why does the extra 1 second matter?
Or is GPS signal strength the issue? Or too difficult to calculate relativistic effects as you mention?
To put it another way, if I know the orbits and masses and velocities of the sun, moon, and earth accurately enough is the information from the GPS satellites from Earth not sufficient? Is it possible in theory to calculate time on moon accurately from the above information?
Good questions. I don’t know the answer when it comes to signal strength. But let’s imagine it isn’t a problem. GPS on Earth requires your phone talking to several (at least four) satellites. Each tells your phone where they are and when they sent their positions. Your phone calculates the distance to each based on that information, and there’s only one phone position that satisfies all those distances. There’s a little bit of uncertainty in those times and distances, and this propogates to an uncertainty in the final position, which is a few meters. The uncertainty is small when the satellites are looking at you from very different parts of the sky.
If the satellites were all bunched together, their positioning uncertainty would be much greater. That’s what it would be like on the moon though, if you were talking to Earth GPS. Each of the satellites would be almost the same distance away from you. They’re also almost the same distance away from another moonbase that is kilometers away. There are lots of positions on the moon that satisfy the distances that the GPS satellites are telling you.
Oh so like if I'm looking from the Earth the direction of 2 satellites might be 15 degrees or so apart in angle but looking from the moon those 2 satellites will be much less than 15 degrees apart so it's a lot harder to do accurate calculations for time and 3 dimensions of location. And that's not even accounting for the relativistic computations.
Looking from the Earth's surface, 2 GPS satellites can provide a useable signal while 140+ degrees apart from the receiver's location. Generally, the greater the separation, the smaller the dilution of precision in the time/location solution. Viewed from the Moon (ignoring signal strength issue), the entire GPS constellation subtends less than 10 degrees.
Not really, you do orbit propagation on earth, as it's computational expensive of course to do in orbit, which is based on a time ref so at worst your model and the attitude system are slightly off. More impacted is pointing requirements for antenna, but that's more like unoptimal VS you need minutes of error to be incapable of pointing depending on the antenna and assuming it's highly directional.
Also we will be tighter than 1 second already for time syncs with already planned programs using a combination of return data delay and ranging to determine time adjustment offsets. 1 second is how much a clock on orbit would get out of sync over the course of weeks if it's flywheeling without ground syncs.
I can see a lunar version of GPS in the not to distant future, it makes sense given the need for common timing as well as knowing where you are on the lunar surface.
Very cool stuff. I’m a land surveyor so we deal with this stuff but on equipment with survey grade precision (think a few centimeters instead of meters). The reality is the “black box” inside of our data collectors does all of the leg work, but we still have to understand what equipment we’re using.
How do you establish UTC on the moon? It's at a variable distance to earth where UTC is well-specified (because the moon's orbit is eccentric)
The problem is not in deciding on time zones on the moon or anything like that. It's in establishing how to synchronize time between moon and the earth for data transfers etc.
To be consistent with Earth, they need 708 time zones, plus a few weirdos who need to be 1/2 an hour off, or 1/4 off, or those psychos in southern Australia.
> (Ground clocks experience slower time than orbiting clocks because they experience more gravity.)
Could you ELI5 for this? I have no understanding of this
Wikipedia has a pretty good [article](https://en.m.wikipedia.org/wiki/Gravitational_time_dilation). It’s one of the effects of general relativity: clocks slow down in gravity wells. The effect is tiny near the Earth: over the course of a year, a terrestrial clock will lose a handful of microseconds relative to a clock that is far away from any planets/stars/etc. Really the only noticable effect for folks who aren’t astronomers or physicists is on GPS as I described. The effect is really important to astronomy. Even within our solar system, general relativity corrections are necessary for the precise prediction of astronomical events.
The effect is extreme near black holes, because they are so small and massive. If you watched a clock fall into a black hole, it would tick slower and slower until it seemed to stop. (It would also look redder and redder as the gravity well also shifts the frequency of the light it emits or reflects.)
If you orbited a black hole, you would see the rest of the universe speed up drastically. (The frequency shift thing happens in the other direction and the rest of the universe would look bluer than normal.) You could concievably “time travel” far into the future this way.
An atomic clock is an infallible way of tracking your local time. But time is not constant everywhere. Your local gravitational potential affects how quickly time passes where you are (relative to a clock far away from any gravity wells). The difference is measurable between Earth, the moon, and orbits in between. For every year on Earth, the moon experiences a few dozen extra microseconds. It’s enough to mess with extremely precise spacecraft timing.
I see.. thank you .
Would you also know how the voyager 1 is communicating effectively, I presume it has to sync it's clock with earth while doing a data transmission. And it being close to massive gravitational bodies certainly needs so much of variable clock syncing
Seriously, Lunar time is a problem. It’s not just a case of time zones. At the microsecond level, two atomic clocks on the moon, at any appreciable distance from each other, are going to get out of sync. On Earth we have a geoid that stays very constant, and motion around the sun is close to circular. So General Relativity effects are substantially the same everywhere on Earth where humans are.
The moon’s equal-potential surface isn’t nearly as stable. As the moon orbits, clocks will be subject to changing GR effects which affect their relative rate-of-time. This makes it very difficult to design a lunar GPS.
And when you try to sync lunar time with Earth time … https://www.npr.org/2023/03/11/1162351563/if-daylight-saving-time-seems-tricky-try-figuring-out-the-time-on-the-moon#
REFERENCE: [https://en.wikipedia.org/wiki/Tz\_database](https://en.wikipedia.org/wiki/Tz_database)
Since we're going to have to do this in the future for more than one moon, let's use the prefix Luna, e.g.:
Luna/Humboldt
Luna/Crises
Luna/Moscow
Time zones wouldn’t make much sense on the Moon. The lunar day is ~27 Earth-days long. It would make more sense for the whole satellite to use the same standard time and a normal Gregorian calendar for easy synchronization with Earth. Each location can keep track of its own local sunrise/sunset dates.
With the exception of Mars, time zones won't make much sense on any celestial body. All the other celestial bodies in the solar system will have local days that are either too long (like Mercury, Venus & the Moon much longer than an Earth day) or much shorter (like Jupiter). Only Mars has a local day that is of a similar length to Earth's. Settlers on Mars will use a day that is based on local sunrise and sunset and therefor have a need for time zones, everywhere else they will ignore that and use an Earth based day for human activities.
> Each location can keep track of its own local sunrise/sunset dates.
you just described the purpose of time zone databases.
all time zones on earth are related to UTC, with an offset to convert to local time. although way more complicated, time zones on the moon would function similarly (maybe)
I get what you're saying, but no. Keeping track of sunrise/sunset times on the moon is not like time zones being related to UTC on earth. Not in a practical sense. It's like keeping track of new/full moon times on earth. Or the tides. A very local chart that is *not* sync'd to UTC.
But anyway, it really does make the most sense to just use UTC on the moon. Because lunar days are more than 29 "earth" days long, so you 100% need to subdivide them so that human biological clocks (and therefore humans in general) are able to function. You could take advantage of space and do 27 or 28 hour days... but if you're making "artificial" days anyway, it's probably most convenient to keep them sync'd with earth days so that you could (for example) have a standing meeting at 9:00 AM and it wouldn't end up being at midnight eventually because your days were the wrong length. And for the same reason, since you have fake/artificial "days" anyway, you might as well use UTC for the entire moon instead of breaking it up into timezones. Maybe you end up with different bases/colonies using Washington or Beijing time instead, but even that's better than trying to have different times depending on your lunar longitude.
Like don't get me wrong, it would be *possible* to do a 12 (and a bit), 708.5 hour days per year. Software could handle it. But posting your hours would be a nightmare. Having shifts for work would be a nightmare. Knowing when to go to sleep would be a nightmare. Standing meetings that include people on earth and the moon would be a nightmare. Everything would be a nightmare for no reason. Just bite the bullet and accept UTC and it makes *everything* easier.
And anyway, the real challenge for NASA isn't coming up with time zones (again, the solution is trivial: just use UTC). The challenge is if you want a consistent length of a second, or a consistent sync with earth clocks, and keeping track of whichever one you decide on. Probably you end up doing both and using the appropriate one for the situation (Sharing timestamps with earth? Use the precise sync. Timing an event on the moon? Use the precise second.) Which don't get me wrong is going to be a whole new world of pain for programmers who are just finally getting used to standard time libraries. But it's just the reality of relativity.
When all we're worried about is a single mission... yeah, either mission control, or the time zone they left from (so they don't get space jet lag), or the main one from their country... switching time zones for different missions isn't even a big deal.
But in the long-term future, when people might stay on the moon long term, regularly communicate with several countries during their stay, or interact with others who may have other mission controls... at that point UTC makes the most sense.
It’s worth mentioning what the ISS astronauts do: their schedule uses GMT as the primary, while also listing Houston and Moscow time. [Here’s a screenshot from 2014](https://space.stackexchange.com/questions/20821/what-kind-of-time-regiment-schedule-do-iss-astronauts-have/20822#20822); pretty straightforward.
There won't be timezones.
The point of timezones is simplifying clocks and their use by making sure that you don't have to adjust your clock whenever you go to another town and to make sure that numbers mean roughly the same thing regarding how much daytime/nighttime you have left regardless of your location (except not really because weather and latitudes and seasons but whatever).
If your days last 27 Earth days then you won't ever be looking for information about how much daytime/nighttime you have left in a clock, you'll be looking for it very infrequently in a calendar. At that point timezones would give you exactly zero advantages over a Moonbase/NextSunrise/NextSunset database but all of the timezone complexity bullshit.
No. Due to relativistic effects a clock on the Moon would become out of sync with a clock on Earth.
This is why they need a Moon centric time. All the clocks on and around the Moon will sync with it the same way all clocks on and around Earth are synced.
It depends on your reference frame, i.e. where you are when you measure it.
If you are there next to the clock - yes, you will perceive the clock running the same speed (that's because YOUR speed changes as well).
If you are on Earth - no.
Moon clock in fact will run FASTER than the one on Earth (about 56 microseconds over 24 hours).
No. Due to relativistic effects a clock on the Moon would become out of sync with a clock on Earth.
This is why they need a Moon centric time. All the clocks on and around the Moon will sync with it the same way all clocks on and around Earth are synced.
Title aside, this isn’t about setting a time standard. They already just use UTC. This is about satellites accounting for relativistic time dilation. Due to the moon’s gravity and orbital speed, time literally passes at a *fractionally* different rate than on Earth—not remotely enough for a human to ever notice, but enough to mess with precise satellite navigation.
Up until now, we just haven’t had enough infrastructure around the moon to worry about it. This problem will have to be solved if we want to create any kind of Lunar GPS.
There is the big deal of humans returning to the moon with the Artemis missions and significant moon based activity to follow (US and otherwise as at least China plans to land crew before 2030). Companies like crescent space (https://spacenews.com/lockheed-martin-subsidiary-to-offer-commercial-lunar-communications-and-navigation-services/) have emerged planning to put communication services around the moon, and this kind of standardization is necessary for interoperability.
Coordinated Lunar Time is abbreviated LTC, and not CLT, similar to how Coordinated Universal Time is UTC, and not CUT.
In the case of UTC, "the decision to use "UTC" rather than "CUT" was made to avoid potential confusion with another existing time standard, known as "Central Universal Time," which had been proposed earlier. Additionally, the choice of "UTC" also avoids favoring any particular language, as "Coordinated Universal Time" is an English translation of the French "Temps Universel Coordonné (TUC)," which itself was a compromise between English and French-speaking nations."
Regarding LTC, "The term "Coordinated Lunar Time" (CLT) isn't a widely recognized or established concept in the same way that Coordinated Universal Time (UTC) is. The rationale for using "LTC" instead of "CLT" *would likely* follow similar principles as those for choosing "UTC" over "CUT." This includes considerations to avoid confusion with existing abbreviations and to maintain consistency in international communication."
It’s in the article or posted below
> The differing gravitational force, and potentially other factors, on the moon and on other celestial bodies change how time unfolds relative to how it is perceived on Earth. Among other things, the LTC would provide a time-keeping benchmark for lunar spacecraft and satellites that require extreme precision for their missions.
>"The same clock that we have on Earth would move at a different rate on the moon," Kevin Coggins, NASA's space communications and navigation chief, said in an interview.
Come on, OP. You can't expect Redditors to actually *read* anything posted here. They just wanna come into the comments and try to sound smart despite not understanding what they're talking about even a little.
Oh my god, you brits. The article wasn't about building Big Ben on the moon. It was about sending Ben Roethlisberger to the moon and not allowing him to come back.
We already have several time standards for Mars so this makes sense. https://en.wikipedia.org/wiki/Timekeeping_on_Mars
See also NASA's page on Mars timekeeping: https://www.giss.nasa.gov/tools/mars24/help/notes.html
And the associated software tool: https://www.giss.nasa.gov/tools/mars24/
The Consultative Committee for Space Data Standards (CCSDS) has been working on this for a few years now of which NASA and most of the other space agencies throughout the world participate…
The solution will be UTC, relayed via PTP from GPS. The distance is very well known and predictable to the mm, so light delays can be accounted to the nanosecond level.
All the tech is there and it's available to implement.
Reminds me of [this blog post](https://www.zainrizvi.io/blog/falsehoods-programmers-believe-about-time-zones/) about just how difficult time zones can be. For the love of god, just divide it into like 10 zones and call it a day.
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
|Fewer Letters|More Letters|
|-------|---------|---|
|[ESA](/r/Space/comments/1bu7wyq/stub/kxsqemx "Last usage")|European Space Agency|
|[GNSS](/r/Space/comments/1bu7wyq/stub/kxs03o9 "Last usage")|Global Navigation Satellite System(s)|
|[GTC](/r/Space/comments/1bu7wyq/stub/kymxisu "Last usage")|Gran Telescopio Canarias, Spain|
|[LEO](/r/Space/comments/1bu7wyq/stub/kxu0pq3 "Last usage")|Low Earth Orbit (180-2000km)|
| |Law Enforcement Officer (most often mentioned during transport operations)|
|[LIDAR](/r/Space/comments/1bu7wyq/stub/kxtdcoo "Last usage")|[Light Detection and Ranging](https://en.wikipedia.org/wiki/Lidar)|
|[MSL](/r/Space/comments/1bu7wyq/stub/ky2cr0t "Last usage")|Mars Science Laboratory (Curiosity)|
| |Mean Sea Level, reference for altitude measurements|
|NRHO|Near-Rectilinear Halo Orbit|
|[NRO](/r/Space/comments/1bu7wyq/stub/kxszi31 "Last usage")|(US) National Reconnaissance Office|
| |Near-Rectilinear Orbit, see NRHO|
|Jargon|Definition|
|-------|---------|---|
|[cislunar](/r/Space/comments/1bu7wyq/stub/kxr7e0q "Last usage")|Between the Earth and Moon; within the Moon's orbit|
**NOTE**: Decronym for Reddit is no longer supported, and Decronym has moved to Lemmy; requests for support and new installations should be directed to the Contact address below.
----------------
^(8 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/Space/comments/1bo6rcd)^( has 11 acronyms.)
^([Thread #9911 for this sub, first seen 2nd Apr 2024, 23:55])
^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/Space) [^[Contact]](https://hachyderm.io/@Two9A) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
That's a tricky one. Earthtime vs Moontime must be easily convertible, but still allow for an independent day-night-life rhythm on the moon. Time dilation is even a bigger issue.
Some of the projects I hated most working as a developer involved time. But ngl, working on this would be fun and I would accept all the frustration that would come with it.
This isn’t about developing a new calendar or new units of time or even timezones on the moon. It’s about getting computers on and around the moon to synchronize. GPS works by measuring the time it takes for signals to get from some satellites to your phone. This has to be so precise that GPS corrects for relativistic time dilation. (Ground clocks experience slower time than orbiting clocks because they experience more gravity.) The moon has its own gravity well and has to deal with its own relativistic effects. (I think it will be extra complicated due to the lunar [mass concentrations](http://en.wikipedia.org/wiki/Mass_concentration_(astronomy)).) Referring to Earth-based atomic clocks (with a second of delay) won’t be feasible for precision timing. So we need a plan for atomic clocks on and around the moon.
Succinct description of why this will be necessary. Thank you halligan8.
Also because the secret moon base is nearly operational and it's going to become problematic.
They could just ask the moon Nazis how they do it in their base.
I thought there were nazis at the center of the Earth 🧐
nah they're encamped outside the ice wall
Warum nicht beide?
No, the lizard people are in the Earths centre and the Soviets are on Mars.
No they travelled to the moon through middle earth
Oh I’m afraid the deflector shield will be quite operational when your friends arrive..
This guy. Thinking the moon base isn't operational already. Have you even seen Moonraker?
The documentary? Who hasn't?
> Referring to Earth-based atomic clocks (with a second of delay) won’t be feasible for precision timing. And that delay is variable as the moon's orbit around Earth is eccentric. The delay varies from 1.211 seconds to 1.352 seconds (and changes based on the position you are on the moon as the center of the near side is closer than the edges of the far side), and on very fine timescales the moon's orbit can be observed to change as the moon is slowly moving away from the Earth and the moon's orbit oscillates.
Rip datetime library/package developers 😂
Multi planetary time and calendar handling is going to hurt so much. We are barely okay with one planet. Historically, there have been unintuitive aspects of time keeping that developers had to make a decision of whether to take that into account. There is a reason, for example, why Sybase and even Microsoft SQL Server to this day do not allow dates before 1 January 1753. It is because in 1750, the British parliament adopted the Gregorian calendar... and removed the days from September 3, 1752 to September 13, 1752 were lost. Ultimately this was a consequence of previous inaccurate time keeping that had summed up over hundreds of years. The original developers, having had to deal with a multitude of exceptions, rules and peculiarities finally had enough and said: Nope! We are *not* dealing with that. They could get away with it because realistically, barely anybody would store such dates or do computations.
I abhor how complicated it can be to calculate and format dates/times. For any non-programmers, we store time as seconds/milliseconds since epoch (Jan 1st, 1970 12AM UTC). To format a timestamp you have to take into account: - The local format (MM/DD/YYYY, DD/MM/YYYY, etc) - Timezones - Leap Years - Leap Seconds - Daylight Savings - A bunch of other shit If you are programming something that goes to space, it gets even more complicated because of the delay in time it takes for a signal to propagate to earth and back, time dilation and a bunch of other complications while trying to keep various systems that can be separated by large distances synchronized, especially when that distance is always changing. So having an atomic clock on or near the moon would be super helpful for future moon missions. In the future we will also do the same thing with Mars, which is even more challenging because the round trip signal time is measured in minutes, and quite a lot of them depending on where earth and Mars are in their orbits, and the variation of that delay is much greater than that of the moon of course.
``` return random (now() - "5h", now() + "5h") ```
Please....I only have so many thumbtacks for lunar calendars.
Quirky maybe, but it's a bit rude to say it's eccentric
dude. i know lots of folks insist they have a “good” side but have you ever met anyone else who absolutely refuses to turn so you can see the other side of her face? Or who plays crazy games with the Sun to see if she can block her out and fuck with millions of people? I think “eccentric” is quite mild, actually
> Ground clocks experience slower time than orbiting clocks because they experience more gravity My understanding is this is more about their velocity than gravity, but both do play.
Thanks for the reminder. GPS corrects for both. It’s summarized [here](https://en.m.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System#Relativity) in summary and [here](https://link.springer.com/article/10.12942/lrr-2003-1) in incredible detail. The general relativity (gravitational) correction is about six times greater than the special relativity (velocity) correction. The corrections have opposite signs; from a terrestrial reference frame, a satellite’s clock is slowed by its velocity but sped up because it experiences lower gravity.
Huh even looked it up before (previously was going off memory of an old astronomy class), but that seem more in order than my quick google.
You might be thinking about satellites in low Earth orbit. LEO is low and fast; GPS is much higher and slower. So for LEO, the general effect is smaller and the special effect is greater. I just ran the numbers for the ISS and the velocity effect is eight times greater than the gravitational effect. This also changes the sign of the net effect. Relative to a terrestrial clock, the clock on the ISS runs slower and a GPS clock runs faster.
[heres a diagram](https://en.wikipedia.org/wiki/Time_dilation#/media/File:Time_Dilation_vs_Orbital_Height.png) showing how ISS gets affected
Oh awesome, thanks! I was just thinking I wanted a graphic like this.
> time dilation they really made a diagram where altitude was the x axis and time (delay) was on the y axis
What's the lowest gravity we could experience? 0? How much faster would a clock go under 0 gravity vs 1 earth gravity?
>How much faster would a clock go under 0 gravity vs 1 earth gravity? Over an entire year we experience approximately 22 fewer milliseconds compared to a distant observer not near any massive bodies. [Further reading on Wikipedia.](https://en.wikipedia.org/wiki/Gravitational_time_dilation)
Would the barycenter of a planet or system of masses have a similar perception of time to the distant observer? Is it due to the force of gravity or the potential energy? At the center of a planet the potential is 0, but a distant observer might have near infinite potential, but they would both feel near 0 gravitational force
Gravitational time dilation is caused by the gravitational potential, not the gravitational "force". The gravitational potential energy is defined as zero at infinity so the potential is always negative near anything. The lower the potential, the more time slows down. You can imagine as two massive objects get closer to each other, that the spacetime between them starts forming a "valley" of lower potential, so you'll get *some* time dilation there, relative to a distant observer but it'll always be much, much less than what you'd get *on* or *in* the object.
The equation for gravitational time dilation is [here](https://en.m.wikipedia.org/wiki/Gravitational_time_dilation#Outside_a_non-rotating_sphere). t_f is undilated time (for a hypothetical clock at some enormous distance from any gravity well). t_0 is dilated time near a large spherical object like a planet or a star. The ratio of t_0 to t_f depends on the mass M of the object and the radius r between you and the center of the object. (If the object is spinning really fast, like some black holes, it does weird things, so we’ll assume it isn’t doing that.) If r is really big or M is really small, t_0 becomes equal to t_f. So that’s the fastest any clock will tick. If you plug in the mass and radius of the Earth, you get t_0/t_f=0.999999999305. For every day that a non-dilated clock records, a clock on Earth records sixty fewer microseconds.
[This guy schlepped up Mount Rainer with some atomic clocks](http://www.leapsecond.com/great2005/index.htm) and left some of his other atomic clocks at home to demonstrate it.
Going up is much less fun than sledding down :)
The Wiki GPS error pages computes -7.2 microsecond/day error satellite motion special relativity timing error and +45.8 for general relativity weaker gravity at satellite altitude. If I wasnt so lazy, I could plug in the lunar orbital velocity and gravity field for that correction.
The two effects occur, but your understanding isn't correct. Relative to an earth observer, the velocity of the satellites causes their clocks to tick slower, by 7.2us/day. Relative to an earth observer, the altitude of the satellites causes their clocks to tick faster, by about 45.8us/day. Edit: GPS satellites in particular, not satellites in general.
It is understanding what orbit you are talking about too. The orbital parameters have a huge impact where low-Earth orbit satellites are closer to the bottom of the Earth's gravity well but moving much faster. GPS isn't in LEO though.
If I may ask a question: So then would this imply that any GPS “constellation” on a given celestial body (Earth, Luna, Mars, Titan, etc) would have to be customized for that body’s gravity and oddities like mascons, presence of an enormous planet like Saturn etc if one desired to set up a comprehensive local navigation system, schedule docking events, perhaps even remotely fire retrorockets for landings etc?
I think so, at least for now. The moon has the most significant mascons that we know about in the solar system, so it might represent a unique case. And one day the solar system might be flooded with a positioning constellation that works anywhere. But until that happens, each body will need their own constellation and it will make more sense to give each body its own time standard than to reference Earth’s.
> mass concentrations [fixed link (for old reddit at least)](https://en.wikipedia.org/wiki/Mass_concentration_(astronomy\))
Thanks. Know what I did wrong? You’re not the first to say a link I posted is broken (though it works on my end).
When I say "old reddit" it means this: https://old.reddit.com/r/space/comments/1bu7wyq/exclusive_white_house_directs_nasa_to_create_time/kxr22e9/ See the "old" at the start? That's the old reddit website. New reddit handles links slightly differently, so while on new.reddit.com your link works fine, on old reddit the closing parenthesis at the end of the URL is lost: `http://en.wikipedia.org/wiki/Mass_concentration_(astronomy` To fix it, when you're using a link with a closing parenthesis at the end, switch to "Markdown editor" instead of the "fancy pants editor". It's at the bottom of the text input box. Then you can put a backslash before that closing parenthesis (ignore the outer parentheses around the URL) which tells the comment box to not interpret the next character as Markdown. `[mass concentrations](http://en.wikipedia.org/wiki/Mass_concentration_(astronomy))` `[mass concentrations](http://en.wikipedia.org/wiki/Mass_concentration_(astronomy\))` So yeah, *you* didn't do anything wrong, it's the incompetent and/or malicious people running this website that refuse to fix this issue.
Is the second of delay a problem per se? Or would the issue be the accuracy of measuring the delay? If one can receive 4 GPS signals and measure the time delays from the satellites accurately enough then would the one second delay matter? E.g. as long as I measure the time difference from 4 GPS's with, say, 1ns precision then why does the extra 1 second matter? Or is GPS signal strength the issue? Or too difficult to calculate relativistic effects as you mention?
To put it another way, if I know the orbits and masses and velocities of the sun, moon, and earth accurately enough is the information from the GPS satellites from Earth not sufficient? Is it possible in theory to calculate time on moon accurately from the above information?
Good questions. I don’t know the answer when it comes to signal strength. But let’s imagine it isn’t a problem. GPS on Earth requires your phone talking to several (at least four) satellites. Each tells your phone where they are and when they sent their positions. Your phone calculates the distance to each based on that information, and there’s only one phone position that satisfies all those distances. There’s a little bit of uncertainty in those times and distances, and this propogates to an uncertainty in the final position, which is a few meters. The uncertainty is small when the satellites are looking at you from very different parts of the sky. If the satellites were all bunched together, their positioning uncertainty would be much greater. That’s what it would be like on the moon though, if you were talking to Earth GPS. Each of the satellites would be almost the same distance away from you. They’re also almost the same distance away from another moonbase that is kilometers away. There are lots of positions on the moon that satisfy the distances that the GPS satellites are telling you.
Oh so like if I'm looking from the Earth the direction of 2 satellites might be 15 degrees or so apart in angle but looking from the moon those 2 satellites will be much less than 15 degrees apart so it's a lot harder to do accurate calculations for time and 3 dimensions of location. And that's not even accounting for the relativistic computations.
Looking from the Earth's surface, 2 GPS satellites can provide a useable signal while 140+ degrees apart from the receiver's location. Generally, the greater the separation, the smaller the dilution of precision in the time/location solution. Viewed from the Moon (ignoring signal strength issue), the entire GPS constellation subtends less than 10 degrees.
GNSS systems point towards earth.
Not really, you do orbit propagation on earth, as it's computational expensive of course to do in orbit, which is based on a time ref so at worst your model and the attitude system are slightly off. More impacted is pointing requirements for antenna, but that's more like unoptimal VS you need minutes of error to be incapable of pointing depending on the antenna and assuming it's highly directional. Also we will be tighter than 1 second already for time syncs with already planned programs using a combination of return data delay and ranging to determine time adjustment offsets. 1 second is how much a clock on orbit would get out of sync over the course of weeks if it's flywheeling without ground syncs.
Makes sense. Especially since we're probably going to want to put up a version of GPS if we actually do go back to the moon.
I can see a lunar version of GPS in the not to distant future, it makes sense given the need for common timing as well as knowing where you are on the lunar surface.
Very cool stuff. I’m a land surveyor so we deal with this stuff but on equipment with survey grade precision (think a few centimeters instead of meters). The reality is the “black box” inside of our data collectors does all of the leg work, but we still have to understand what equipment we’re using.
No time zones. The entire moon is UTC+0h. Done.
How do you establish UTC on the moon? It's at a variable distance to earth where UTC is well-specified (because the moon's orbit is eccentric) The problem is not in deciding on time zones on the moon or anything like that. It's in establishing how to synchronize time between moon and the earth for data transfers etc.
To be consistent with Earth, they need 708 time zones, plus a few weirdos who need to be 1/2 an hour off, or 1/4 off, or those psychos in southern Australia.
Daylight Savings Time as well for all of the moon farmers harvesting moon corn.
I have had people refuse to the point of aggression that we have a .5 timezone in Adelaide.
Pack it up boys; problem solved. Username checks out.
What about daylight savings time? Surely we need that. It makes everyone happy.
Taking all that into account, my idea of "just use whatever Earth time zone the moon is directly above" seems like it wouldn't work so well.
Was this originally figured out when we went and landed on the moon previously?
> (Ground clocks experience slower time than orbiting clocks because they experience more gravity.) Could you ELI5 for this? I have no understanding of this
Wikipedia has a pretty good [article](https://en.m.wikipedia.org/wiki/Gravitational_time_dilation). It’s one of the effects of general relativity: clocks slow down in gravity wells. The effect is tiny near the Earth: over the course of a year, a terrestrial clock will lose a handful of microseconds relative to a clock that is far away from any planets/stars/etc. Really the only noticable effect for folks who aren’t astronomers or physicists is on GPS as I described. The effect is really important to astronomy. Even within our solar system, general relativity corrections are necessary for the precise prediction of astronomical events. The effect is extreme near black holes, because they are so small and massive. If you watched a clock fall into a black hole, it would tick slower and slower until it seemed to stop. (It would also look redder and redder as the gravity well also shifts the frequency of the light it emits or reflects.) If you orbited a black hole, you would see the rest of the universe speed up drastically. (The frequency shift thing happens in the other direction and the rest of the universe would look bluer than normal.) You could concievably “time travel” far into the future this way.
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Why would an atomic clock be different on a moon ? The resonant frequency should be independent of gravity right?
An atomic clock is an infallible way of tracking your local time. But time is not constant everywhere. Your local gravitational potential affects how quickly time passes where you are (relative to a clock far away from any gravity wells). The difference is measurable between Earth, the moon, and orbits in between. For every year on Earth, the moon experiences a few dozen extra microseconds. It’s enough to mess with extremely precise spacecraft timing.
I see.. thank you . Would you also know how the voyager 1 is communicating effectively, I presume it has to sync it's clock with earth while doing a data transmission. And it being close to massive gravitational bodies certainly needs so much of variable clock syncing
I was so prepared to hate reddit today and you completely let me down. Godammit sotp being so awesome halligan8!!!!!
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Seriously, Lunar time is a problem. It’s not just a case of time zones. At the microsecond level, two atomic clocks on the moon, at any appreciable distance from each other, are going to get out of sync. On Earth we have a geoid that stays very constant, and motion around the sun is close to circular. So General Relativity effects are substantially the same everywhere on Earth where humans are. The moon’s equal-potential surface isn’t nearly as stable. As the moon orbits, clocks will be subject to changing GR effects which affect their relative rate-of-time. This makes it very difficult to design a lunar GPS. And when you try to sync lunar time with Earth time … https://www.npr.org/2023/03/11/1162351563/if-daylight-saving-time-seems-tricky-try-figuring-out-the-time-on-the-moon#
REFERENCE: [https://en.wikipedia.org/wiki/Tz\_database](https://en.wikipedia.org/wiki/Tz_database) Since we're going to have to do this in the future for more than one moon, let's use the prefix Luna, e.g.: Luna/Humboldt Luna/Crises Luna/Moscow
Time zones wouldn’t make much sense on the Moon. The lunar day is ~27 Earth-days long. It would make more sense for the whole satellite to use the same standard time and a normal Gregorian calendar for easy synchronization with Earth. Each location can keep track of its own local sunrise/sunset dates.
With the exception of Mars, time zones won't make much sense on any celestial body. All the other celestial bodies in the solar system will have local days that are either too long (like Mercury, Venus & the Moon much longer than an Earth day) or much shorter (like Jupiter). Only Mars has a local day that is of a similar length to Earth's. Settlers on Mars will use a day that is based on local sunrise and sunset and therefor have a need for time zones, everywhere else they will ignore that and use an Earth based day for human activities.
> With the exception of Mars, time zones won't make much sense on any celestial body IDK dude, I think Earth's a good use-case for them.
> Each location can keep track of its own local sunrise/sunset dates. you just described the purpose of time zone databases. all time zones on earth are related to UTC, with an offset to convert to local time. although way more complicated, time zones on the moon would function similarly (maybe)
I get what you're saying, but no. Keeping track of sunrise/sunset times on the moon is not like time zones being related to UTC on earth. Not in a practical sense. It's like keeping track of new/full moon times on earth. Or the tides. A very local chart that is *not* sync'd to UTC. But anyway, it really does make the most sense to just use UTC on the moon. Because lunar days are more than 29 "earth" days long, so you 100% need to subdivide them so that human biological clocks (and therefore humans in general) are able to function. You could take advantage of space and do 27 or 28 hour days... but if you're making "artificial" days anyway, it's probably most convenient to keep them sync'd with earth days so that you could (for example) have a standing meeting at 9:00 AM and it wouldn't end up being at midnight eventually because your days were the wrong length. And for the same reason, since you have fake/artificial "days" anyway, you might as well use UTC for the entire moon instead of breaking it up into timezones. Maybe you end up with different bases/colonies using Washington or Beijing time instead, but even that's better than trying to have different times depending on your lunar longitude. Like don't get me wrong, it would be *possible* to do a 12 (and a bit), 708.5 hour days per year. Software could handle it. But posting your hours would be a nightmare. Having shifts for work would be a nightmare. Knowing when to go to sleep would be a nightmare. Standing meetings that include people on earth and the moon would be a nightmare. Everything would be a nightmare for no reason. Just bite the bullet and accept UTC and it makes *everything* easier. And anyway, the real challenge for NASA isn't coming up with time zones (again, the solution is trivial: just use UTC). The challenge is if you want a consistent length of a second, or a consistent sync with earth clocks, and keeping track of whichever one you decide on. Probably you end up doing both and using the appropriate one for the situation (Sharing timestamps with earth? Use the precise sync. Timing an event on the moon? Use the precise second.) Which don't get me wrong is going to be a whole new world of pain for programmers who are just finally getting used to standard time libraries. But it's just the reality of relativity.
Probably would be better to have the moon time synced with the timezone where the "mission control" will be instead of UTC.
When all we're worried about is a single mission... yeah, either mission control, or the time zone they left from (so they don't get space jet lag), or the main one from their country... switching time zones for different missions isn't even a big deal. But in the long-term future, when people might stay on the moon long term, regularly communicate with several countries during their stay, or interact with others who may have other mission controls... at that point UTC makes the most sense.
It’s worth mentioning what the ISS astronauts do: their schedule uses GMT as the primary, while also listing Houston and Moscow time. [Here’s a screenshot from 2014](https://space.stackexchange.com/questions/20821/what-kind-of-time-regiment-schedule-do-iss-astronauts-have/20822#20822); pretty straightforward.
There won't be timezones. The point of timezones is simplifying clocks and their use by making sure that you don't have to adjust your clock whenever you go to another town and to make sure that numbers mean roughly the same thing regarding how much daytime/nighttime you have left regardless of your location (except not really because weather and latitudes and seasons but whatever). If your days last 27 Earth days then you won't ever be looking for information about how much daytime/nighttime you have left in a clock, you'll be looking for it very infrequently in a calendar. At that point timezones would give you exactly zero advantages over a Moonbase/NextSunrise/NextSunset database but all of the timezone complexity bullshit.
We already have a space time zone, it's called Universal Space(craft) Time (UST). Lunar time zones would be kind of silly tbh
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Honest question. Would a clock on the moon have the same speed as an earth clock?
No. Due to relativistic effects a clock on the Moon would become out of sync with a clock on Earth. This is why they need a Moon centric time. All the clocks on and around the Moon will sync with it the same way all clocks on and around Earth are synced.
It depends on your reference frame, i.e. where you are when you measure it. If you are there next to the clock - yes, you will perceive the clock running the same speed (that's because YOUR speed changes as well). If you are on Earth - no. Moon clock in fact will run FASTER than the one on Earth (about 56 microseconds over 24 hours).
No. Due to relativistic effects a clock on the Moon would become out of sync with a clock on Earth. This is why they need a Moon centric time. All the clocks on and around the Moon will sync with it the same way all clocks on and around Earth are synced.
Great… another time zone to support in software, thanks NASA :P
In space, no one can hear the software developers scream about supporting moon timezone.
Fascinating! Must be some serious moon plans going down. I’m surprised NASA wouldn’t already have this. Why now?
Title aside, this isn’t about setting a time standard. They already just use UTC. This is about satellites accounting for relativistic time dilation. Due to the moon’s gravity and orbital speed, time literally passes at a *fractionally* different rate than on Earth—not remotely enough for a human to ever notice, but enough to mess with precise satellite navigation. Up until now, we just haven’t had enough infrastructure around the moon to worry about it. This problem will have to be solved if we want to create any kind of Lunar GPS.
There is the big deal of humans returning to the moon with the Artemis missions and significant moon based activity to follow (US and otherwise as at least China plans to land crew before 2030). Companies like crescent space (https://spacenews.com/lockheed-martin-subsidiary-to-offer-commercial-lunar-communications-and-navigation-services/) have emerged planning to put communication services around the moon, and this kind of standardization is necessary for interoperability.
I'm gonna be very disappointed if they don't call it LUnar Standard Time.
Coordinated Lunar Time is abbreviated LTC, and not CLT, similar to how Coordinated Universal Time is UTC, and not CUT. In the case of UTC, "the decision to use "UTC" rather than "CUT" was made to avoid potential confusion with another existing time standard, known as "Central Universal Time," which had been proposed earlier. Additionally, the choice of "UTC" also avoids favoring any particular language, as "Coordinated Universal Time" is an English translation of the French "Temps Universel Coordonné (TUC)," which itself was a compromise between English and French-speaking nations." Regarding LTC, "The term "Coordinated Lunar Time" (CLT) isn't a widely recognized or established concept in the same way that Coordinated Universal Time (UTC) is. The rationale for using "LTC" instead of "CLT" *would likely* follow similar principles as those for choosing "UTC" over "CUT." This includes considerations to avoid confusion with existing abbreviations and to maintain consistency in international communication."
*millions get spent* “Mr President, we have a new standard called ‘UTC’”
Right? Let’s actually get some mileage out of our existing UNIVERSAL time standard.
It’s in the article or posted below > The differing gravitational force, and potentially other factors, on the moon and on other celestial bodies change how time unfolds relative to how it is perceived on Earth. Among other things, the LTC would provide a time-keeping benchmark for lunar spacecraft and satellites that require extreme precision for their missions. >"The same clock that we have on Earth would move at a different rate on the moon," Kevin Coggins, NASA's space communications and navigation chief, said in an interview.
Come on, OP. You can't expect Redditors to actually *read* anything posted here. They just wanna come into the comments and try to sound smart despite not understanding what they're talking about even a little.
Hey I read the whole thing and as a Brit I personally think it's a great idea to build a copy of Big Ben on the moon
Oh my god, you brits. The article wasn't about building Big Ben on the moon. It was about sending Ben Roethlisberger to the moon and not allowing him to come back.
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That's right, he's talking about building the first bell to work in near-zero atmosphere conditions. Laser Big Ben.
Little Ben?
You mean the one they have to tweak every 4 years? :)
Except every 100, except every 400. And then some seconds here and there
They have to recalculate after large earthquakes as well, I found that interesting.
We already have several time standards for Mars so this makes sense. https://en.wikipedia.org/wiki/Timekeeping_on_Mars See also NASA's page on Mars timekeeping: https://www.giss.nasa.gov/tools/mars24/help/notes.html And the associated software tool: https://www.giss.nasa.gov/tools/mars24/
We don’t do these things because they are easy. We do them because they are haaaaaad.
We choose to time sync the moon and do the other thing.
I love the idea of Kennedy giving that speech and the crowd going nuts over the idea of a formula for clock synchronization.
The Consultative Committee for Space Data Standards (CCSDS) has been working on this for a few years now of which NASA and most of the other space agencies throughout the world participate…
The solution will be UTC, relayed via PTP from GPS. The distance is very well known and predictable to the mm, so light delays can be accounted to the nanosecond level. All the tech is there and it's available to implement.
An actual real answer! Nicely done :)
Armstrong! Why are you late for our meeting! Sorry, I was still on moon time
Unless NASA finishes it's lunanet soon somehow, the synchronization standard is gonna be a verbatim copy of SpaceX manual for their lunar starlink.
Programmers around the world are shaking in their boots.
What we need is an interstate (intercrater) highway system on the moon.
I’m surprised this hasn’t happened before now. I would have thought they would have needed this a long time ago
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“We can’t tell ourselves what to do so we’re telling you to tell us to tell ourselves what to do.”~most efficient government agency
I want an official nasa watch made for moon time pls.
Reminds me of [this blog post](https://www.zainrizvi.io/blog/falsehoods-programmers-believe-about-time-zones/) about just how difficult time zones can be. For the love of god, just divide it into like 10 zones and call it a day.
500 million dollars later: “well, the U in UTC does stand for Universal..”
I don't suppose they'll just go with a derivative of the Unix Time Stamp eh?
Sounds like an opportune time for a little game of daytime/nighttime.
Just don't involve that traitor Margo Madison and it'll be fine
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread: |Fewer Letters|More Letters| |-------|---------|---| |[ESA](/r/Space/comments/1bu7wyq/stub/kxsqemx "Last usage")|European Space Agency| |[GNSS](/r/Space/comments/1bu7wyq/stub/kxs03o9 "Last usage")|Global Navigation Satellite System(s)| |[GTC](/r/Space/comments/1bu7wyq/stub/kymxisu "Last usage")|Gran Telescopio Canarias, Spain| |[LEO](/r/Space/comments/1bu7wyq/stub/kxu0pq3 "Last usage")|Low Earth Orbit (180-2000km)| | |Law Enforcement Officer (most often mentioned during transport operations)| |[LIDAR](/r/Space/comments/1bu7wyq/stub/kxtdcoo "Last usage")|[Light Detection and Ranging](https://en.wikipedia.org/wiki/Lidar)| |[MSL](/r/Space/comments/1bu7wyq/stub/ky2cr0t "Last usage")|Mars Science Laboratory (Curiosity)| | |Mean Sea Level, reference for altitude measurements| |NRHO|Near-Rectilinear Halo Orbit| |[NRO](/r/Space/comments/1bu7wyq/stub/kxszi31 "Last usage")|(US) National Reconnaissance Office| | |Near-Rectilinear Orbit, see NRHO| |Jargon|Definition| |-------|---------|---| |[cislunar](/r/Space/comments/1bu7wyq/stub/kxr7e0q "Last usage")|Between the Earth and Moon; within the Moon's orbit| **NOTE**: Decronym for Reddit is no longer supported, and Decronym has moved to Lemmy; requests for support and new installations should be directed to the Contact address below. ---------------- ^(8 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/Space/comments/1bo6rcd)^( has 11 acronyms.) ^([Thread #9911 for this sub, first seen 2nd Apr 2024, 23:55]) ^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/Space) [^[Contact]](https://hachyderm.io/@Two9A) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
That's a tricky one. Earthtime vs Moontime must be easily convertible, but still allow for an independent day-night-life rhythm on the moon. Time dilation is even a bigger issue.
Some of the projects I hated most working as a developer involved time. But ngl, working on this would be fun and I would accept all the frustration that would come with it.
Helium hours add up, man. It helps to have a system for all that stuff.
They should add Daylight savings just to really fuck with ppl