What time is it on moon? Europe pushing for lunar time zone | Hacker News Reader

What time is it on moon? Europe pushing for lunar time zone

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65 pointsbelter65 comments

The ESA article gives much better rationale and explanation on what and why new timescale is needed, and why its relevant to define now: https://www.esa.int/Applications/Navigation/Telling_time_on_...

I'm slightly annoyed by media calling it time zone when the main focus is really on new time scale; I find it actually unlikely that timezones would be involved at least at this stage.

I have a difficult time reasoning about "local times" being more useful than say, UTC, for off-earth locations. The ISS used UTC and it feels right.

Sure, Mars is close enough to Earth that it could work, but the Moon takes 28 days to rotate. Other bodies have even more extreme cycles.

The article is light on details but I sure hope they're just talking UTC.

And for the record, local time can be very useful -- knowing when the sun is up will always have some value. E.g. exploration, agriculture, travel, energy. I just don't see how it works for humans to be human and communicate with other humans.

The issue is that time runs faster on the moon, so clocks will get out of sync, or you need to define a lunar second which will be different from an earth second. So pure UTC is not going to make it.

General relativity strikes again.

A quick search yields 59 microseconds per day, right? That doesn’t seem significant at all for people to people interactions (21ms per year).

For automated systems that’s of course a different challenge and I think rather than clocks it may be useful to think about causality signatures if you’re comparing across the moon and earth. But even for automated systems, the time delay between earth and the moon is going to swamp 59 microseconds except for a minority of use cases that need ultra precise clocks that work across vastly different inertial frames.

Now for local operations on the moon? You probably don’t want UTC but that’s probably better established by sending scientists and engineers to the moon and letting them figure out what would make sense. Until then UTC is fine I think

GPS satellites comes to mind.

Yes, GPS satellites are a good example. We don't keep a "GPS time zone"[1] or define "GPS second" to account for that - we calculate the dilation the satellite gets due to relativity (e.g. https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_...), treat that dilation as a predictable "error" from the correct (Earth) time, and adjust for that.

[1] There actually is a time zone called "GPS time", however, that explicitly doesn't include the relativistic effects, it has the same second length as UTC, not what an atomic clock on a GPS satellite would measure, it differs from UTC only in how it counts days - in "GPS time" there's always 86400 seconds in a day and leap seconds are never added to adjust for Earth's rotation speed.

The same way it makes sense for GPS to use Earth-based timescale instead of something like TCG[1] or TCB[2], it makes sense for lunar positioning to use lunar based timescale.

> There actually is a time zone called "GPS time", however, that explicitly doesn't include the relativistic effects

It does include the relativistic effects of Earth

[1] https://en.wikipedia.org/wiki/Geocentric_Coordinate_Time [2] https://en.wikipedia.org/wiki/Barycentric_Coordinate_Time

Obviously no Astronaut is going to miss their teams daily standup call over this.

But it’s already an issue for gps satellite precision and if you want to go into precise scientific experiments it’s probably also an issue, especially once we get into long-term experiments. Not to speak off a manned base.

So it makes sense to consider what can be done - and a defined lunar timezone with a known (tough changing) offset would not be the worst of all options.

Definitely do not redefine the second. So many of our scientific units are based on the definition of a "second" as we see it on Earth, you'd throw everything into chaos. I believe one of the characters in The Moon is a Harsh Mistress pointed this out, as the newly-empowered Lunar government was considering redefining time to match the lunar day/night cycle.

(In that book, they certainly recognized "semi-lunars" reflecting the lunar day and night cycle, but, since Loonies, by and large, lived in pressure domes or underground, those didn't matter unless you were actually going to the surface. It definitely affected when people went out on the surface, why they went, and--because of the solar radiation hazard during bright semi-lunar--how long they stayed out.)

Seconds are now defined on atomic transitions, which can be measured at the moon and used to form a base clock that other clocks sync to, although I'm pretty certain loonies would instead use an earth seconds-based clock with corrections, periodically ensuring that they stayed in sync.

Remember that time we accidentally crashed a rover or something into Mars because someone forgot to convert their units? That was as hilarious as it was unfortunate.

It was because there were two modules, one that used lbs-seconds for impulse and one that used newton-seconds for impulse. The spec dictated newton-seconds.

There is literally zero need to have long-term tracking of "Moon time". For all long-term (day/week/year scale) you can work in whatever Earth time zone suits you best, and when the clocks will drift - no matter if that drift is due to relativity or plain old inaccuracy - just sync them to Earth time.

Yes, an isolated non-adjusted clock on the moon would have slowly accumulated some drift from the correct time, but who cares about that? For use cases which need extreme accuracy, do explicit adjustments for the time dilation in these specific conditions, just as we do for GPS satellites, instead of trying to define a single moon-wide lunar second or some offset from UTC.

> knowing when the sun is up will always have some value

Some, but it's terribly inaccurate - it varies by latitude and even midday can be off by 3 hours depending which part of country or autonomous zone you are in.

I could see a version of GMT where noon or mignight occur when your habitat is directly over the prime meridian.

But then the lunar days and hours wouldn’t line up with earth days.

I think a lot of comments are missing the idea that this is a single timezone, not many. The sun is always "up" on some side of the moon. Establishing a common time reference is for coordination of activities on the moon.

I imagine that the human-human verbiage with respect to sun angles might go something like, "at 2 MoonST the sun will be at a 4pm position for the rover and a 6pm position for the base. In two days, the sun will have moved about 1.7 hours later for both locations."

> The sun is always "up" on some side of the moon.

I don't understand the relevance of this. The sun is always "up" on some side of the Earth, too.

Many people equate timezone to mean a slice from pole to pole that has a similar Sun angle. If the moon has exactly one timezone, then that timezone describes the time on the entire surface and has no 1:1 analog with sun angle for a given spot within the timezone.

Wouldn't there be 2 or 4? The day side, the night side, and arguably the twilight sides?

The moon is tidally locked with the Earth but that doesn’t mean there is always one side that is bright. Ie: the moon has “days” as well… they are just longer than Earth days.

By 2 or 4, do you mean time zones? If so, why? Why not just a single coordinated time?

Yes, I know the moon has days and nights. Each is roughly 2 weeks Earth time.

> By 2 or 4, do you mean time zones?

yes

> If so, why? Why not just a single coordinated time?

I'm not proposing, refuting, or endorsing anything. This thread is just me trying to understand what it is you were saying.

I don't believe the moon has a dark side and light side. both sides get light / dark. The moon is locked with earth, not the sun. I could be wrong though

Thats correct according to my understanding as well.

the same part of the moon (the far side) always faces away from the earth as you say, and at any time, at least part of the moon is in shadow, which would be a "moving dark side"

Why not use UTC ? On the moon, a time zone will be tough since each side of the moon is dark/light for about half a month.

I really hope someone has considered Daylight Savings Time on the moon.

There’s no need for daylight savings time on the moon. The day night cycle on the moon takes a month, and plus there’s no farmers up there yet.

Does the moon have seasons?

Edit: no seasons on the moon :(

It's more about out competing the Nazi war production on the dark side.

Farmers have nothing to do with DST. Farmers don't live their lives by clocks anyway. Farmers universally think DST is stupid, and the ag industry is usually opposed.

https://nebraskapublicmedia.org/en/news/news-articles/not-a-...

It's high time the Moon had a time zone. I own over 1000 acres I bought several years ago through the Lunar Embassy and it gets so confusing not having Moon standardized time.

what do you plan to grow on those 1000 acres? Moon cheese?

But i thought the moon was already made of cheese!

it's not farming, it's mining

Sounds about the right size for a lunar theme park.

With blackjack and hookers?

but the moon milk cows are at the moment getting decimated by the moon cheese lovers in a mad rush to make more pizza; they're at war!

it's a risky time to do moon business, there's even a faction that would get rid of the moon cuz it's not something they have back home and they don't get it

Moo Cheese.

Lunar nightshades

> For now, a moon mission runs on the time of the country that is operating the spacecraft.

Even more confusing since most spacefaring nations span across multiple time zones. Getting a lunar time zone that everyone can theoretically follow seems like a practical idea. It'll be interesting to see how this works on Mars, which would need to have its own planetary time zones (if there aren't already).

Timezones are a practical construct for humans. I'm not sure Mars needs its own planetary time zones until humans are living on it - I don't know what purpose it would otherwise serve.

Come on, even Earth doesn't need timezones.

So You Want Continuous Time Zones [0] ? Or maybe you want to abolish them entirely [1] ?

[0] https://qntm.org/continuous

[1] https://qntm.org/abolish

The solution is obviously Swatch Internet Time.

Abolish them entirely. Your second link is silly and is not a serious counterargument.

It's just as valid as a non-silly post.

If you get rid of time zones, people will replace them with an ad hoc system that does most of the same things but worse. The current implementation could be improved some, but time zones in general are close to the least worst option.

I think having a unified time everywhere is a really obvious advantage. Time being measured differently based on geographic location is completely silly. You would still need to look up how a different location is scheduled but you also need to do that with timezones so there's no disadvantage, only an advantage.

We do have a unified time everywhere, UTC.

Putting time zones on top means people have to look up less.

UTC is effectively a timezone.

Putting tomezones on top means people have to look up more.

Please explain how you would do unified time without UTC?

I would use UTC of course. Why would you do anything else?

Then I don't understand what point you were making when you said "UTC is effectively a timezone."

But if it was notably more convenient, I would expect to see more people using it right now, even when it's not the default.

It's a matter of compatibility, e.g. you're not going to start measuring length in meters when everyone else in your country is using feet. That's why I said UTC is a time zone, nobody uses it outside of the UTC time zone, therefore nobody uses it outside of the UTC time zone.

I mean each city used to have their own time zone and we got rid of that.

The next step is to just get rid of the country-sized timezones. Sure the sun doesn't rise in US West as US East at the same time but it also doesn't rise at the same time in Florida as it does in Maine.

Those links have many falsehoods like claiming that UTC is a time zone. UTC±00:00 or Z is, but not UTC; "Continuous Time Zones" is self-contradictory.

The Earth doesn’t need them? But wasn’t the concept of a time zone invented because someone was always late to the train station and it was leaving him behind? We would at least need one giant time zone with an international date line.

It was needed for running railroads but the issue was a bit more important than being late for your train and missing it. When you are running trains in opposite directions on the same track it is pretty important to have your clocks well synced so you don't have head-on collisions.

Having your clocks well synced is not enough to stop collisions.

Relativistic drift would be a thing over long distances and times.

Mars rover engineers already work on Mars local time interestingly enough. So right now there's functionally as many Mars time zones as there are current missions on the planet.

https://futurism.com/the-byte/nasa-scientists-live-work-mars...

Not just humans - if you have multiple agencies with multiple assets that need to interact then you need to agree on a common time.

Absurd. Clearly we use Star dates off the earth.

Previously in the lunar time discussion: https://news.ycombinator.com/item?id=34525701

Andy Weir answered this already. The moon is on Kenya time.

This title is a lot better than the last submission.

https://news.ycombinator.com/item?id=34982157

Reply on news.ycombinator.com