4 ms·

NASA is working on new clock for the Moon

53 points by ivan_gammel 3y ago

asicsp 3y ago
Dupe: White House wants Moon to have its own time zone, Coordinated Lunar Time (CLT) https://www.bbc.co.uk/news/science-environment-68722032 https://www.bbc.co.uk/news/science-environment-68722032 https://news.ycombinator.com/item?id=39916102 https://news.ycombinator.com/item?id=39916102 (219 points | 2 days ago | 242 comments)
aeinbu 3y ago
> Unlike on Earth, the moon will not have daylight saving time Glad to hear that :) DST has caused my team our fair share of headaches and troubles…
- Aaargh20318 3y ago
  DST is the dumbest thing ever and especially now with global warming. IF you want to move the clock in summer to make things more convenient, move it back an hour, not forwards. Due to DST we have less time to spend outside in the evenings. The sun stays out much longer, especially here in the more northern part of Europe. With DST, once you get off work it's simply too hot in the direct sunlight to be outside comfortably. It only gets comfortable outside around 10 in the evening, at which point it's almost time to go to bed. By moving the clock backwards instead of forwards you get 2 additional hours of outside time. Another advantage is that you have a more time for your bedroom to cool down a little before going to sleep.
  - ink_13 3y ago
    I'm not a "capitalism gives you brain worms" kind of person, but the idea that we should literally change the location of the sun in the sky because that's what's most convenient and the hours of work are sacrosanct is always the weirdest take to me. Why go through all this farrago? There's only one time that really means anything, so have noon at noon (modulo your time zone) and then live your life the way you want.
    - throw-the-towel 3y ago
      Why do you think "noon being at noon" is sacrosanct though? Urban life is not centered at 12:00 any more, you are way more likely to be awake at 8 pm than at 4 am.
      - ink_13 3y ago
        "8PM", like most timekeeping, is a human invention devoid of intrinsic meaning. Noon is the only time that means anything in relation to the world: it's when the sun is directly overhead*. Analog clocks are tiny mechanical sundials for a reason. Have noon (the time) at noon (when the sun is overhead). All else is details. * - yeah, yeah, in the middle of a timezone, you're very clever if you thought this was a gotcha
- 1970-01-01 3y ago
  >DST has caused my team our fair share of headaches and troubles… I hate to break the news to you, but "NASA wants to come up with a new clock for the moon, where seconds tick away faster" So your team will leap away from those DST headaches into transcoded seconds headaches. Now incorporate negative leap seconds into this time correction soup and everything will be just fine.
nprateem 3y ago
They should go decimal, then so should we
- non-chalad 3y ago
  SQUATCH internet time?
waynenilsen 3y ago
This is going to cause so many bugs.
gooseus 3y ago
I say it's about time there was a sensible Lunar clock for the Loonies. Free Luna!
technothrasher 3y ago
Ok, I'm thoroughly confused. I get that the vibration frequency of the atomic clock is faster in the lesser gravity. But why does that require an entirely different time system? Isn't it as simple as adjusting your computation when your reading the frequency to account for the faster tick? I mean, you have to calculate that anyway since the frequency isn't an interval of one second here on earth either, and is different depending upon which element you're using in your atomic clock.
- amelius 3y ago
  https://m.youtube.com/watch?v=wteiuxyqtoM https://m.youtube.com/watch?v=wteiuxyqtoM
- fsh 3y ago
  This is not what happens. The influence of the different gravitational acceleration on the moon compared to the earth is completely negligible for atomic clocks. However, the surface of the earth is at a lower gravitational potential than the surface of the moon. According to General Relativity, this leads to gravitational time dilation: Time passes slower on the surface of the earth than on the surface of the moon.
  - couchand 3y ago
    You are theoretically correct (the best kind of correct). However: Is this difference of a magnitude exceeding everyday nonrelativistic clock drift?
    - fsh 3y ago
      Yes, this is a huge effect relative to the stability and accuracy of modern atomic clocks. Even a few hundred meters of elevation difference on earth is easily visible in clock comparisons and has to be accounted for.
      - robertlagrant 3y ago
        But to what extent? 1s a day? 1s a century?
jessriedel 3y ago
This is the fourth time I’ve see an article about this without any giving a concrete example of a real planned experiment that would depend on this level of sensitivity. (GPS cannot be used on the moon, nor does GPS require the user to have an ultra-precise clock.) The actual White House proposal https://www.whitehouse.gov/wp-content/uploads/2024/04/Celestial-Time-Standardization-Policy.pdf https://www.whitehouse.gov/wp-content/uploads/2024/04/Celest... mentions precision spatial positioning and its use for spacecraft docking, but this does not require having a separate reference clock anymore than it’s needed to use GPS at high altitudes on Earth. (Again, the GPS system does not require the user to have a high-precision clock.) They also mention the dependence of the SI units on the unit of time, which really suggests the writer has no idea how measurement precision is achieved.
- mattficke 3y ago
  My understanding that this is to enable things like a lunar GPS system, which requires the satellites themselves to have precise clocks that are synchronized with each other. > They also mention the dependence of the SI units on the unit of time, which really suggests the writer has no idea how measurement precision is achieved. Say more? I thought an accurate clock would be necessary to derive a reference meter and kilogram measurement.
  - jessriedel 3y ago
    > which requires the satellites themselves to have precise clocks that are synchronized with each other. Yes, the satellites themselves need to keep track of their GR-induced drift relative to the other satellites. But we don’t typically describe this as needing a new timekeeping system (or new timezone, or whatever) for each satellite. We just say the GPS system makes corrections for GR, which it does. And in any case, this takes place on the satellites, not the lunar surface, which is what is mentioned in the announcement. > I thought an accurate clock would be necessary to derive a reference meter and kilogram measurement. So first, the fundamental SI definitions are almost never used in the field to make measurements. For the vast majority of field experiments, the measuring equipment is calibrated back at a lab using a reference system, which itself was calibrated using a chain of multiple intermediaries that eventually trace back to the fundamental SI definition. But the equipment necessary to connect to the fundamental definitions are extremely expensive and delicate, which is why it’s only done occasionally and in a few labs specialized for the purpose. Second, even if you were measuring absolute lengths in the field with the distance light traveled in 10^X ticks of a cesium atomic clock or whatever (as opposed to the much more mundane task of measuring relative length changes with interferometry), it would all work perfectly fine if you did it within a local region of uniform gravitational field. The only reason you need to worry about the difference in clock speeds is if you are comparing event timing being done in different places where the clocks are running differently (as happens with GPS, or something like the LISA gravitational wave experiment, but which is otherwise quite unusual). Like, don’t get me wrong, I can sort of imagine that NASA is actually planning such experiments. But then they should be mentioned in an announcement like this.
tumidpandora 3y ago
can we use this as an opportunity to drop DST across the solar system? Why does moon get preferential treatment over Earth? Rise up earthlings.
alberth 3y ago
HN 3-days ago | 246 comments https://news.ycombinator.com/item?id=39916102 https://news.ycombinator.com/item?id=39916102
deleted 3y ago
[deleted]

53 points by ivan_gammel 3y ago

Dupe: White House wants Moon to have its own time zone, Coordinated Lunar Time (CLT) https://www.bbc.co.uk/news/science-environment-68722032 https://www.bbc.co.uk/news/science-environment-68722032 https://news.ycombinator.com/item?id=39916102 https://news.ycombinator.com/item?id=39916102 (219 points | 2 days ago | 242 comments)

aeinbu 3y ago

> Unlike on Earth, the moon will not have daylight saving time Glad to hear that :) DST has caused my team our fair share of headaches and troubles…

Aaargh20318 3y ago
DST is the dumbest thing ever and especially now with global warming. IF you want to move the clock in summer to make things more convenient, move it back an hour, not forwards. Due to DST we have less time to spend outside in the evenings. The sun stays out much longer, especially here in the more northern part of Europe. With DST, once you get off work it's simply too hot in the direct sunlight to be outside comfortably. It only gets comfortable outside around 10 in the evening, at which point it's almost time to go to bed. By moving the clock backwards instead of forwards you get 2 additional hours of outside time. Another advantage is that you have a more time for your bedroom to cool down a little before going to sleep.
- ink_13 3y ago
  I'm not a "capitalism gives you brain worms" kind of person, but the idea that we should literally change the location of the sun in the sky because that's what's most convenient and the hours of work are sacrosanct is always the weirdest take to me. Why go through all this farrago? There's only one time that really means anything, so have noon at noon (modulo your time zone) and then live your life the way you want.
  - throw-the-towel 3y ago
    Why do you think "noon being at noon" is sacrosanct though? Urban life is not centered at 12:00 any more, you are way more likely to be awake at 8 pm than at 4 am.
    - ink_13 3y ago
      "8PM", like most timekeeping, is a human invention devoid of intrinsic meaning. Noon is the only time that means anything in relation to the world: it's when the sun is directly overhead*. Analog clocks are tiny mechanical sundials for a reason. Have noon (the time) at noon (when the sun is overhead). All else is details. * - yeah, yeah, in the middle of a timezone, you're very clever if you thought this was a gotcha
1970-01-01 3y ago
>DST has caused my team our fair share of headaches and troubles… I hate to break the news to you, but "NASA wants to come up with a new clock for the moon, where seconds tick away faster" So your team will leap away from those DST headaches into transcoded seconds headaches. Now incorporate negative leap seconds into this time correction soup and everything will be just fine.

nprateem 3y ago

They should go decimal, then so should we

non-chalad 3y ago
SQUATCH internet time?

waynenilsen 3y ago

This is going to cause so many bugs.

gooseus 3y ago

I say it's about time there was a sensible Lunar clock for the Loonies. Free Luna!

technothrasher 3y ago

Ok, I'm thoroughly confused. I get that the vibration frequency of the atomic clock is faster in the lesser gravity. But why does that require an entirely different time system? Isn't it as simple as adjusting your computation when your reading the frequency to account for the faster tick? I mean, you have to calculate that anyway since the frequency isn't an interval of one second here on earth either, and is different depending upon which element you're using in your atomic clock.

amelius 3y ago
https://m.youtube.com/watch?v=wteiuxyqtoM https://m.youtube.com/watch?v=wteiuxyqtoM
fsh 3y ago
This is not what happens. The influence of the different gravitational acceleration on the moon compared to the earth is completely negligible for atomic clocks. However, the surface of the earth is at a lower gravitational potential than the surface of the moon. According to General Relativity, this leads to gravitational time dilation: Time passes slower on the surface of the earth than on the surface of the moon.
- couchand 3y ago
  You are theoretically correct (the best kind of correct). However: Is this difference of a magnitude exceeding everyday nonrelativistic clock drift?
  - fsh 3y ago
    Yes, this is a huge effect relative to the stability and accuracy of modern atomic clocks. Even a few hundred meters of elevation difference on earth is easily visible in clock comparisons and has to be accounted for.
    - robertlagrant 3y ago
      But to what extent? 1s a day? 1s a century?

jessriedel 3y ago

This is the fourth time I’ve see an article about this without any giving a concrete example of a real planned experiment that would depend on this level of sensitivity. (GPS cannot be used on the moon, nor does GPS require the user to have an ultra-precise clock.) The actual White House proposal https://www.whitehouse.gov/wp-content/uploads/2024/04/Celestial-Time-Standardization-Policy.pdf https://www.whitehouse.gov/wp-content/uploads/2024/04/Celest... mentions precision spatial positioning and its use for spacecraft docking, but this does not require having a separate reference clock anymore than it’s needed to use GPS at high altitudes on Earth. (Again, the GPS system does not require the user to have a high-precision clock.) They also mention the dependence of the SI units on the unit of time, which really suggests the writer has no idea how measurement precision is achieved.

mattficke 3y ago
My understanding that this is to enable things like a lunar GPS system, which requires the satellites themselves to have precise clocks that are synchronized with each other. > They also mention the dependence of the SI units on the unit of time, which really suggests the writer has no idea how measurement precision is achieved. Say more? I thought an accurate clock would be necessary to derive a reference meter and kilogram measurement.
- jessriedel 3y ago
  > which requires the satellites themselves to have precise clocks that are synchronized with each other. Yes, the satellites themselves need to keep track of their GR-induced drift relative to the other satellites. But we don’t typically describe this as needing a new timekeeping system (or new timezone, or whatever) for each satellite. We just say the GPS system makes corrections for GR, which it does. And in any case, this takes place on the satellites, not the lunar surface, which is what is mentioned in the announcement. > I thought an accurate clock would be necessary to derive a reference meter and kilogram measurement. So first, the fundamental SI definitions are almost never used in the field to make measurements. For the vast majority of field experiments, the measuring equipment is calibrated back at a lab using a reference system, which itself was calibrated using a chain of multiple intermediaries that eventually trace back to the fundamental SI definition. But the equipment necessary to connect to the fundamental definitions are extremely expensive and delicate, which is why it’s only done occasionally and in a few labs specialized for the purpose. Second, even if you were measuring absolute lengths in the field with the distance light traveled in 10^X ticks of a cesium atomic clock or whatever (as opposed to the much more mundane task of measuring relative length changes with interferometry), it would all work perfectly fine if you did it within a local region of uniform gravitational field. The only reason you need to worry about the difference in clock speeds is if you are comparing event timing being done in different places where the clocks are running differently (as happens with GPS, or something like the LISA gravitational wave experiment, but which is otherwise quite unusual). Like, don’t get me wrong, I can sort of imagine that NASA is actually planning such experiments. But then they should be mentioned in an announcement like this.

tumidpandora 3y ago

can we use this as an opportunity to drop DST across the solar system? Why does moon get preferential treatment over Earth? Rise up earthlings.

alberth 3y ago

HN 3-days ago | 246 comments https://news.ycombinator.com/item?id=39916102 https://news.ycombinator.com/item?id=39916102

deleted 3y ago

[deleted]