US reckons it's about time the Moon had its own time zone

NASA, which isn't known for timeliness, has been tasked by the White House with implementing a Coordinated Lunar Time (LTC) zone for the Moon traceable to Coordinated Universal Time (UTC). Until now, most missions have operated on UTC, the successor to Greenwich Mean Time (GMT), as the reference time to work from. However, …

[Anonymous Coward]

I propose that LTC should be based on EDT, the time for more than half of the year in Washington DC.

(And more conveniently for me, the time for more than half the year where I am. Should be all year, END EASTERN STANDARD TIME!)

[Doctor Syntax]

It would make more sense to abandon the EDT. That way you get midday at 12::00 and midnight at 24:00 all year. What should it be called? How about ERT - Eastern Real Time.

[Grinning Bandicoot]

Real is a DC are oxymoron!

[Anonymous Coward]

> EDT, the time for more than half of the year in Washington DC.

> END EASTERN STANDARD TIME!

Well, ok, we'll end EST - but are you sure nobody will be upset we've turned DC into glass?

[AndrueC]

The White House cited [PDF] the example of an Earth-based clock observed by someone on the Moon that would appear to lose an average of 58.7 milliseconds per Earth day.

I blame Albert Einstein's family. Apparently his relatives cause a lot of trouble.

I think that's what my physics professor said anyway.

[Catkin]

If Bob Moon hadn't pointlessly invented it in 1960 then we wouldn't have to deal with this issue or werewolves.

[FIA]

Wasn't it that uncle that was in the army?

[Drishmung]

El Reg has misquoted. It's microseconds, not milliseconds. (According to the linked PDF anyway).

[yetanotheraoc]

proofreading

The subhead even says microseconds. Milliseconds was probably just an unfortunate slip from writing too fast, and then when you read it over it doesn't seem wrong. Grammar, check. Spelling, check. Decimal points, oh hang on.

[Natalie Gritpants Jr]

Surely Coordinated Lunar Time is CLT

Is LTC some sort of French phrase? Hope not because they haven't put boots on the moon yet.

[ThatOne]

Re: Surely Coordinated Lunar Time is CLT

French? No, not at all, in French UTC would be "Temps Universel Coordonné" (TUC).

To quote Wikipedia: "The official abbreviation for Coordinated Universal Time is UTC. This abbreviation comes as a result of the International Telecommunication Union and the International Astronomical Union wanting to use the same abbreviation in all languages. The compromise that emerged was UTC."

Coordinated Universal Time = UTC, so Coordinated Lunar Time = LTC.

[bombastic bob]

Re: Surely Coordinated Lunar Time is CLT

Based on what we did when I was on a sub decades ago, switching clocks to 'Zulu Time' (UTC) once outside of territorial waters, using adjusted UTC would be the best and makes the most sense. All you need to do is make sure that Lunar time exactly tracks UTC based on the time it takes for a radio signal from Earth to reach the surface of the moon at the center of its face and we're good. Then we can make adjustments for craft in flight as needed.

[on a sub daylight cycles only make sense when at periscope depth or on the surface. For everyone else to keep regular schedules, Zulu makes the most sense when submerged, which is most of the time]

[Claptrap314]

Re: Surely Coordinated Lunar Time is CLT

Except that the distance between the Earth and Luna varies by about +/- 5%. You don't want that kind of variability...

[ldo]

Re: using adjusted UTC would be the best and makes the most sense

That won’t work, because of the 58.7µs/day time dilation factor. You cannot simply base lunar time zones off an Earth-centric time reference; the Moon needs its own time reference—its own set of atomic clocks, running independently of the Earth-based ones.

[Anonymous Coward]

Re: using adjusted UTC would be the best and makes the most sense

Surely you could if you just have an elastic definition of how long a second is.

[Anonymous Coward]

Re: using adjusted UTC would be the best and makes the most sense

> elastic definition of how long a second is

No can do, no matter where you take your clock, a second is a second is a second, as measured by the physical process going on inside that box just in front of you.

If you get annoyed that your clock on Earth doesn't agree with one on the Moon, you are going to be utterly vexed once you've taken it all the way back to Clavius to wave in front of the Customer Service desk and they are both ticking away in perfect synchrony.

[willi0000000]

Re: using adjusted UTC would be the best and makes the most sense

Clavius? . . . so that's where they hid customer service.

[A.P. Veening]

Re: using adjusted UTC would be the best and makes the most sense

Yup, next to the monolith.

[aks]

Re: using adjusted UTC would be the best and makes the most sense

The second is defined as part of SI https://en.wikipedia.org/wiki/Second

The same atomic clocks used on earth would run differently if they were moved to the moon https://en.wikipedia.org/wiki/International_Atomic_Time

That's the reason they're suggesting placing atomic clocks on the moon.

I do like the Customer Service reference. We've all been there.

[ldo]

Re: and they are both ticking away in perfect synchrony.

A clock taken to another gravity well for any length of time will not magically make up the accumulated discrepancy when you bring it back. If you had it down there for, say, two weeks, it will still be showing a discrepancy of close to a millisecond.

[Bebu]

Re: using adjusted UTC would be the best and makes the most sense

《That won’t work, because of the 58.7µs/day time dilation factor.》

Which is the subtilty that might easily escape anyone deprived of the benefit(?) of a physics education.

I don't think the two frames, terrestrial and lunar, can be synchronised by a simple additive factor.

I think its mostly a general relativistic effect (the result of the planet's mass distorting the surrounding space-time:)... so well beyond the ken of the π = 3 legislators.

Sounds like a simple problem but its probably asking the question "what does synchronising two clocks running in different non-inertial frames actually entail or mean?"

UTC being a planetary time, like LTC would be, I was wondering how the GPS satellites and UTC sort themselves out and apparently there is a thing called TAI (international atomic time en français) which is concensus of several hundred atomic clocks with a time dilation correction applied to get the corresponding proper time at sea level. Proper time is a concept from relativity. :)

Looking forward to loony time and will certainly set my wristwatch as it will never implement the terrestrial insanity of daylight saving time. Although converting from LTC to :Australia/Brisbane (no dst) might involve a twelve term polynomial. :)

[ravenviz]

Re: Surely Coordinated Lunar Time is CLT

By adding the moon to definitions, UTC is no longer Universal but Terran, so TTC Shirley.

[Howard Sway]

it's about time the Moon had its own time zone

Well, a full lunar day (full rotation, day + night) is about 28 Earth days long, and due to gravitational locking, this is exactly the same time it takes to go round the Earth. In other words, a day is the same length as a year on the moon - which means every day would be your birthday if you were born there, and it would last the equivalent of 28 Earth days! Who would care what the time on the blue planet in the sky is then, because every day would be party time!

[ldo]

Re: a full lunar day (full rotation, day + night)

A lunar day (“synodic month”) is about 29½ Earth days. The period of the Moon’s orbit (“sidereal month”) is about 27⅓ days.

There are other kinds of “month” as well.

[yetanotheraoc]

Paging Neil

"an Earth-based clock observed by someone on the Moon that would appear to lose an average of 58.7 milliseconds per Earth day"

That's one small leap second for a man, one giant leap second for mankind.

I'm a little confused by the "observed" part though. Doesn't the "observation" also have to make the trip?

[that one in the corner]

Re: Paging Neil

> "an Earth-based clock observed by someone on the Moon that would appear to lose an average of 58.7 milliseconds per Earth day"

> I'm a little confused by the "observed" part though. Doesn't the "observation" also have to make the trip?

The light used to make the observation will also take time to travel from Earth to the Moon, and that time will also vary as the Earth rotates, the Moon orbits, that orbit recedes etc etc.

But when a clock is constantly losing (or gaining) you don't need to observe it frequently to observe the effect - you can imagine[1] waiting a few of years between peeking at the timepieces, measuring the distance[2] between Moon and Earth at the point of each clock observation to compensate. Then you'll see the cumulative drift and can point out that this is way outside the combined error bars for the two observations, so celebrate down the pub lads.

Whether or not the drift makes a genuine difference to performing any day to day operations, worth enshrining in a Lunar Time Zone, is another matter.

And from whose point of view does this new time zone actually work?[3]

After all, the astronaut's watches (and caesium clocks) will automatically convert themselves to tick at the local rate as soon as they arrive on site, so measuring durations in experiments will give the same results on Earth and Moon.

Differences in astronomical observations? Umm, tricky - I'll have to drink more coffee before trying to think that one through (do pulsars tick at different absolute rates from different observation sites? Gibber!)

[1] as good physicists do

[2] ok, just keep the round trip time and divide by two to get the adjustment for the observation - and none of your "that doesn't truly measure the one way trip time"!

[3] yes, I know that syncing actions between systems on the Moon needs to be done locally, but by the time you need the precision the clocks to give the reference will be in situ and that whole setup will be decoupled from Earth-based time. The whole concept of time zones is only relevant between two distinct locations and here we are discussing Earth versus Moon, not even separate locations across the Moon.

[ThatOne]

Re: Paging Neil

> (do pulsars tick at different absolute rates from different observation sites? Gibber!)

They always tick at the same rate, but your measurement of this interval will vary, obviously...

[Pete 2]

Time for change

It sounds rather imperialistic for one country to impose it's time system on an entire celestial body.

Especially as every country that lands people / machines on planets or moons could equally decide to use their own local timezone (and probably already do). Irrespective of the state of illumination of their station on that surface.

What would be far better would be a globally accepted set of principles that would set the standard, much as exists on Earth.

[sarusa]

Re: Time for change

It's the US working with the EU. Which the UK would have a hand in if they hadn't had their petulant angry toddler fit eight years ago. Nor is this going to 'imposed' on anyone else. There's no way they can force China, India, Russia, Japan, or anyone else to use it. This is UTC for the Moon, and everyone on Earth uses their own TZ and then converts from/to UTC as convenient.

It's just a thing that is needed for proper operations when 'what's the exact time on the Moon down to a couple microseconds' actually matters. It needs to exist in some form, so the people who work together the most (NASA and ESA) are getting together to decide on their own standard for a rock solid Moon time. Then their collaborators at JAXA, sometimes ISRO, etc. can use it if they're doing joint missions, and they might as well use it otherwise unless they really want to design their own for nationalist reasons. If this standard just ends up being 'UTC with adjustments for the Moon orbiting the Earth' that's pretty darn uncontroversial. Unless of course you're China or Russia, but nobody cares if they're off doing their own stuff on their own time. Especially since the only thing Russia can do with the Moon at this point is crash things into it.

[phils]

Re: Time for change

I'll be sticking to Greenwich Moon Time.

[I ain't Spartacus]

Re: Time for change

It's the US working with the EU.

sarusa,

Nope. It's the US working with the European Space Agency. Which has 22 members (the EU has 27), including the UK, Switzerland and Norway (who aren't in the EU).

[Paul Herber]

Everybody knows the moon is made of cheese. Cheddar local time shall be the lunar standard.

(Cheddar is a town in Somerset, England).

Cheese icon.

[Dizzy Dwarf]

Crikey, Gromit!

[Paul Herber]

We are alll crackers.

[Benegesserict Cumbersomberbatch]

Of course, the French will insist that ESA uses the time in Rochefort. The cheese it's made of is as strong as rock, after all.

[Anonymous Coward]

Pardon? Roquefort-sur-Soulzon, s'il vous plait.

[43300]

(Cheddar is a town in Somerset, England).

More a village than a town. It's got caves. And tourist-tat shops.

[sarusa]

'Time Zone'

It's a little weird since the Moon is locked to the Sun, so if you're in the center of the bright side, that's noon, and it's always noon! Any place on the Moon is always the same time by the way we think about time (the progression of the Sun).

Of course I realize that's functionally useless, so basically lock it to some time zone on Earth plus corrections for it orbiting the Earth. If they tie it to UTC as 'baseline time' with the corrections that seems pretty reasonable?

[Benegesserict Cumbersomberbatch]

Re: 'Time Zone'

Erm, it's tidally locked to the Earth. That's why the face of the man in the moon always looks at us and the really cratery bit is the half that faces away from us.

At a point on the lunar surface there's a sunrise and sunset, once per lunar month, but Earth just sort of hovers in the same place in the sky, nutating a little because of the elliptical orbit and tidal precession.

Apollo astronauts only saw Earthrise when they were in orbit around the moon, not when they were on it.

[AndrueC]

Re: 'Time Zone'

That's why the face of the man in the moon always looks at us and the really cratery bit is the half that faces away from us.

You are of course absolutely correct but can I point out that the 'face of the man in the moon' only applies to those observing it from the northern hemisphere of the Earth. In the southern hemisphere it's something else.

As for people observing from the equator don't arsk me. It does my 'ead in just to think about it :)

[Benegesserict Cumbersomberbatch]

Re: 'Time Zone'

Speaking as a resident of Down Under (albeit only 17°S at the moment), pareidolia works just as well from up here as down there in the north.

[Bebu]

Re: 'Time Zone'

《Speaking as a resident of Down Under (albeit only 17°S at the moment), pareidolia works just as well from up here as down there in the north.》

pareidolia - Darwin beer and Australian politics can have this effect too I believe. :)

[Anonymous Coward]

Bunnies!

"You are of course absolutely correct but can I point out that the 'face of the man in the moon' only applies to those observing it from the northern hemisphere of the Earth. In the southern hemisphere it's something else."

For our Oriental cousins I believe it's a rabbit. It's odd - I grew up with the story of the man in the moon, but was never able to see it. The rabbit I could see almost immediately, despite being at an odd angle.

[ThatOne]

Re: Bunnies!

It took me years to see the man in the moon. Now I can see both (from pretty high in the northern hemisphere), the man('s face) and the rabbit.

[Neil Barnes]

Sixty microseconds a day, eh?

That's, ooh, one part in fourteen billion, give or take.

Not sure my wristwatch is that accurate...

[ldo]

Re: Not sure my wristwatch is that accurate...

I have owned two quartz watches in my life. Each one, when I got it, would consistently gain about a second a day. The first one, I was able to get adjusted to an accuracy of about a second a month. And it stayed that way for the rest of its working life.

When that watch expired a quarter-century later, I got the second one. By this time, when I asked at various clock/watch shops about adjusting the crystal frequency, I was met with blank stares—or they would tell me it wasn’t possible. Finally I was referred to a retired watch-repairer who knew what I was talking about. Unfortunately his calibration machine didn’t work, so he had to tweak the trimmer capacitor through guesswork. After several visits, he was able to get the error down to a second or two a week. At that point I gave up and decided not to bother him any more.

After that, I stopped wearing a wristwatch.

[Anonymous Coward]

Re: Not sure my wristwatch is that accurate...

> he had to tweak the trimmer capacitor through guesswork.

Isn't that a task you could have attempted, if you were interested in getting the accuracy? Couple of small tools, a steady hand and you get nerd bonus points.

[ThatOne]

Re: Not sure my wristwatch is that accurate...

If you're that concerned with precision, you can buy a cheap radio-controlled watch (mine's a CASIO), which is always utterly precise (at least precise enough for timekeeping through an eyes-brain interface).

[tiggity]

Re: Not sure my wristwatch is that accurate...

I have one of those radio ones - though when abroad & times significantly different (e.g. go from UK to somewhere in the Americas) I also wear (on other wrist) a cheap & basic watch that I set to "local time" pre travel, as it saves the hassle of doing a few sums to calculate local time from radio watch (when tired & "jet lagged" easy to get it wrong) - though you do get some odd looks with 2 watches, but fairly vital to know UK time so I don't wake up a family member with a message at what would be silly o clock in the UK..

.. Plenty of areas of the world where no radio signal available (e.g. parts of S America) so it stops being super accurate.

[ldo]

Re: cheap & basic watch that I set to "local time" pre travel

My Android phone, as ancient as it is, has a clock app that can show the time in multiple time zones at once. And of course it automatically stays in sync with a time reference, and automatically adjusts for daylight saving. So who needs a wristwatch nowadays?

[Bebu]

Re: Not sure my wristwatch is that accurate...

《.. Plenty of areas of the world where no radio signal available (e.g. parts of S America)》

And Australasia too. Saw a not so cheap Seiko radio watch on special and investigated - I think USA, China (parts) and EU were about it. I understand Seiko also market solar watches that use GPS instead but are in no sense cheap (en-US: inexpensive. ;)

[Christoph]

Re: Sixty microseconds a day, eh?

We now have clocks which are accurate to much better than one second absolute.

That's one second in 13.8 billion years, the time since the Big Bang.

[Primus Secundus Tertius]

Gravity-free standard

It would make more sense to define a time standard in a gravity-free zone. Earth, moon, Jupiter, the centre of our galaxy, would then be variants of the standard.

So set up a standard half way between our galaxy and Andromeda. OK, there may be a few technical comms problems with the distances involved, but unless we have the technology to overcome that, the whole discussion about time zones is pointless.

[Bebu]

Re: Gravity-free standard

Given a massive black hole resides at the centre of the galaxy time keeping might be a bit peculiar around its event horizon and probably somewhat meaningless on the other side.

Gravity free might be a big ask even in intergalactic space - probably great chunks dark matter or some other equally ineffable substance drifting about iceberg-like ready to stuff up your clocks.

At a certain point in life the only time that is likely to matter is the time left. :)

[JimmyPage]

Surprised it's only just come to the fore.

Am I alone in being slightly taken aback this hasn't been settled before ?

[I ain't Spartacus]

Re: Surprised it's only just come to the fore.

JimmyPage,

There was a plan to put in lunar communication satellites as part of the Apollo program. But it didn't happen due to some combination of time and budget issues.

In the last few years we've had lunar satellites that were sent up on individual missions - but we've included them in the network to help communicate with various lunar landers. For which everything having synchronised clocks probably didn't matter all that much - seeing as quite a bit of the communication was ad hoc.

But if we're going to have the lunar gateway and maybe regular trips to the Moon - with the prospect of some kind of lunar base, or at least a few lunar installations - then I guess a small satellite comms and navigation constellation is going to start to look quite attractive. At which point it makes sense to try and get this sorted out beforehand.

[Dvon of Edzore]

Re: Surprised it's only just come to the fore.

Lunar science, and space science in general, has an excuse that previous missions were so short, horologically speaking, that any relativistic differences in time were completely swamped by propagation delays and, in the case of deep space probes like the Voyager series, Doppler effect on radio frequency. Now that longer duration missions are being planned such that specific locations on the surface will matter, the precision timing requirement of satellite-based location measurement comes into play. A moon-based Coordinated Lunar Time network has become necessary and practicable only recently.

[ITS Retired]

We get this moon time working and

some dope will want Daylight Saving Time for it. Bet on it.

[Grinning Bandicoot]

Re: We get this moon time working and

Daylight time allows me to lay slug-a-bed until its time for the proper infusion of caffeine, the neighbors to leave for work and enough time for home projects in sunlight.

[Grinning Bandicoot]

Okay lets say our clock lands on the moon and starts generating a precise time tick. Let us also declare the site Zero Longitude. The question then is how at 50 degrees does the signal get used? There are no non-relalivistic means for the time to be shared. A couple of remarks have implied a means and if Clark were still around make him happy