Post #1592861

2024-04-05 17:02 UTC

I keep seeing the news about lunar time presented as “the Moon is getting its own time zone.&quot; What&#39;s actually happening is the Moon is getting its own time *standard*. The problem being solved is that time passes slightly more quickly on the Moon compared to Earth (due to General Relativity) and so the Moon needs its own time standard for precise measurements and navigation. UTC is the time standard for measuring time on Earth, and LTC is being created for the Moon. #GeneralRelativity #time

Replies (9)

@dgoldsmith@mastodon.social 2024-04-06 19:26

If you're curious why time passes more quickly on the Moon, it's this: https://en.wikipedia.org/wiki/Gravitational_time_dilation Because Earth's gravity is higher, there’s more time dilation than on the Moon (by about 58.7 microseconds per day, or 2.144 seconds per century). One way to think about it is that the local neighborhood of spacetime for someone standing on the Earth's surface is boosted (“tilted”, in a 4D sense) relative to that for someone far away from any massive body. #GeneralRelativity #time

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@foolishowl@social.coop 2024-04-05 17:49

@dgoldsmith It's kind of mindblowing.

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@michaelbradley@mstdn.ca 2024-04-05 20:13

@dgoldsmith Given that UTC stands for Coordinated Universal Time (at least in English), it seems like it's in need of a renaming. Perhaps Coordinated Terrestrial Time? I wonder if this will continue for other important celestial bodies? I wouldn't be surprised if at least Mars got its own time standard codified. Wikipedia mentions an "MTC", but only as a "proposed" standard based on Mars's orbit instead of atomic clocks.

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@adamshostack@infosec.exchange 2024-04-08 21:22

@dgoldsmith I'm really not sure that replacing MET is needed just yet, but it's a very optimistic move. (MET, as you probably know, is mission elapsed time, which has been fine and will remain fine until we have satellites around the moon or other long term presence.)

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@dantheclamman@scicomm.xyz 2024-04-08 21:29

@dgoldsmith yeah, way more amazing and deeper than a time zone honestly

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@attilakinali@society.oftrolls.com 2024-04-08 23:30

@dgoldsmith You seem to be knowledgeable on this topic. Could you explain why we do not just compensate for gravitational red shift on the moon the same way we do for the various NMI labs that are at different altitudes and thus run at slightly different rates? Why do we need LTC when just using UTC with the correct definition of the second (i.e. defined at zero gravitational field) would be sufficient?

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@TheDarcBird@social.vivaldi.net 2024-04-09 02:28

@dgoldsmith is UTC the same as GMT

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@trabex@newsie.social 2024-04-09 05:32

@dgoldsmith Wait, time passes more quickly on the moon? How does that work? Is it something influenced by planetary gravity?

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@florian@augsburg.social 2024-04-09 10:14

@dgoldsmith @msc why not Beats

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