7 ms·
What time is it on the moon?
- flemhans 4y agoUTC?
- tuwtuwtuwtuw 4y agoInteresting question. Someone should write an article about it.
- jabo 4y agoThis is going to make time zone math a bit more complicated than it already is.
- deleted 4y ago[deleted]
- nostromo 4y agoIt’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 agoThis 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 agoSpecifically: 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 agoFar less the number of towns than the amount and precision of interactions amongst them.
- roydivision 4y agoOr 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 agoUnfortunately, 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.
- classified 4y agoWhat, no Daylight Saving Time?
- zokier 4y agoMaking the timescale just utc would mean that moon-seconds would not match si-seconds, which sounds very problematic.
- d--b 4y agoGood luck with that one. It sounds like one of these problems without any good solution. You know something is going to break because someone will screw up the conversion. I feel this is a case where it'd be better to have something totally different. Like time written in letters rather than digits. So that there would be no way to mistake one for the other. I work in finance, and it's always a lot easier to spot rescaling problems when dealing with jpy than any other currency. The fact that 100 yens ~ 1 usd makes any mistake glaringly obvious.
- jtrip 4y agoSo, people are suggesting UTC and such. Someone on masto suggested using Pulsars. https://mastodon.social/@CosmicRami@aus.social/109753434934226964 https://mastodon.social/@CosmicRami@aus.social/1097534349342... > Why build a timescale that ONLY works for the Moon? Then, we need atomic clocks on all spacecraft ... or a Martian timescale. Scalability is key here, and we are lucky as we can build a GALACTIC timescale through ... you guessed it .... pulsars! A pulsar-based-timescale using the timing of pulsars around the galaxy, so all locations and receivers can tap into it universally. This also has the benefit of not having to build GNSS on the far side of the Moon, protecting its pristine radio heritage for #astronomy. Here's some further reading: https://academic.oup.com/mnras/article/427/4/2780/971096?login=false https://academic.oup.com/mnras/article/427/4/2780/971096?log... https://academic.oup.com/mnras/article/491/4/5951/5612203 https://academic.oup.com/mnras/article/491/4/5951/5612203 https://www.esa.int/kids/en/news/ESA_test_a_new_pulsar_clock https://www.esa.int/kids/en/news/ESA_test_a_new_pulsar_clock
- gorgoiler 4y agoGNSS could just turn itself off on the far side of the moon? You could even use a mechanical timer to turn the whole satellite back on — Battlestar Galactica style low tech solutions.
- grugagag 4y agoIf people ever live on the moon they’ll need some time similar to earth’s to somehow fall into circadian cycles to be of any use
- ykovalenko 4y agoTime does not exist it is only concept
- dredmorbius 4y agoExistence and concepts are also "only concepts". Sufficiently significant, influential, and/or widely-adopted concepts can have very real impacts. Dismissal or belittling on this basis alone really adds nothing to this (or most other) discussions.
- deleted 4y ago[deleted]
- mnw21cam 4y agoSurely this is a problem that has already been well and truly solved by the earth-based GPS systems. They are based on a collection of different satellites that are all in different positions with independent clocks that tick at slightly different rates, yet the overall outcome is a reasonably coherent notion of what the current time is. Couldn't the lunar positioning system be formed as an extension of that?
- moring 4y agoThe funny thing is that GPS satellites operate in the context of special relativity, where events can occur in reverse order depending on the observer's velocity, so the whole notion of an "overall outcome" is pointless...
- mjburgess 4y agoEvents can't occur in a "reverse" order. At sufficient distances, the evolution of two regions is entirely causally independent, so there is no sense of simultaneity. Otherwise, the causal order of events is always defined. Different observers may have "more information" about some events over others, but over ordinary (even multi-galactic) distances, events are well-ordered and sequential.
- planede 4y agoEvents are partially-ordered. Two events that can't have causal relationship between them are incomparable causality-wise.
- moring 4y ago> Events can't occur in a "reverse" order. At sufficient distances, the evolution of two regions is entirely causally independent, so there is no sense of simultaneity. This discussion is essentially about whether "events can occur in reverse order for different observers" is the right way to say "the order of time coordinates of two spacelike-separated events is reversed for different observers". This was in reply to: > the overall outcome is a reasonably coherent notion of what the current time is The notion of an observer-independent "current time" implies simultaneity which doesn't exist in SR, and if you mistakenly assume an observer-independent "current time" which you'd likely assume to be the time axis of your own frame of reference, then two spacelike-separated events would be reversed for some observer who did the same but moves with almost speed-of-light relative to you. Please keep in mind that I wanted to point out the irony in using GPS for a universal reference time without giving an intro into special relativity.
- dsign 4y agoAs a noob, I recently went down the rabbit hole of time-setting for astronomy and space applications. It's an absolutely fascinating topic. Having the same time in two places which are very distant apart, are in different inertial frames, or are in any combination of inertial and non-inertial, well, it's very difficult. The rhythms of life, and special and general relativity get in the way. But the need to convert from one time system to the other arises all the time. For example, if you want to to know if somebody looking from Newcastle, Australia, will be able to have direct line of sight to the asteroid 253 Mathilde on the night of the 23rd of September of 2177, then you need to work with UTC (which accounts for Earth changes in rotation speed which are unpredictable) and with coordinate frames which are inertial to the solar system (to apply Kepler laws). So you not only need to keep track of unpredictable things like Earth's rotation altering the precision of time, but also the drift caused on clocks by relativity. Note that problem here is that people live on Earth, and they want their time to reflect sunrises and sunsets, and they want it to track other natural cycles like the seasons. So we have UTC and UTC+n . Similarly, people living on the Moon may want to have a timesystem that reflects their sunraises and sunsets. But none of that matters to laws of physics that use a more fundamental notion of time, e.g. orbits. JPL has somewhere a set of routines that convert between different time-systems, and some software packages like Mathematica also come with the functionality. It does make sense to add a new timesystem for each body with strong enough gravity where people is going to live.
- throw0101c 4y ago> then you need to work with UTC (which accounts for Earth changes in rotation speed which are unpredictable) IIRC, that accounting will stop if leap seconds are eliminated.
- defrost 4y agoFurther down that rabbit hole, consider timekeeping and data aquisition for the SKA (Square Kilometre Array) project with radio telescopes in both Australia and South Africa. Consider a common target of interest over 48 hours .. one side of the planet is rotating toward the target, the other side away from the target, both are sampling the same signal spectrum with varying doppler effects .. oh, and the planet is moving toward or away or at some angle in its orbit about the sun, so there is another relative motion. Now, for better resolution, the same target is viewed again some six months later - earth is now the other side of the sun, the planets relative motion has changed, and locations in Australia and South Africa are now reversed in their motions toward and away. This all poses some issues when data signal stacking.
- college_physics 4y ago> The idea is to produce a Solar System internet if that is the idea then why not think forward and setup a clock system based e.g. on Lagrange points, away from the gravitational field peculiarities of this or that body?
- ElevenLathe 4y agoIn Andy Weir's /Artemis/, the Moon in on Kenyan time, because that's where all the rockets take off from. This is in turn because they had land on the equator and created something like a Shenzhen (low or no tariffs, friendly regulation for foreign capital, etc.) for space launches.
- jrd259 4y agoIf the moon uses a different time than UTC, it will also be necessary to define the switchover procedure and a boundary for spacecraft from Earth, which presumably launch using a terrestrial clock.
- User23 4y agoThe relativity problem is already solved. If it weren't GPS wouldn't work. It's somewhat complex, but it basically boils down to defining the Earth as the preferred reference frame (Earth Centered Inertial System, or ECI) and doing the necessary transforms[1]. [1] https://apps.dtic.mil/sti/pdfs/ADA516975.pdf https://apps.dtic.mil/sti/pdfs/ADA516975.pdf
- dave333 4y agoThe lunar "day" is actually nearly a solar month and it makes sense to call that a month. However on a shorter timescale, it makes sense for the "day" to be the interval for one rotation of the earth relative to the moon. So at noon each day, the same point on the earth is facing the moon, say the Greenwich meridian. So this lunar day would be slightly longer than the earth solar day, roughly 30.53/29.53 earth days or 24 hrs 49 minutes approx. Would make sense to call such lunar days something different like "earths." So you would say something like "5 earths until the sun sets." Makes sense to also keep day hour minute and second the same as earth synced with UTC.