Re: [tz] Time for a Lunar time zone? -Brooks
On 3/2/23 09:51, Brooks Harris wrote:
Will we need DST on the Moon? :-)
I hope not! The Moon's axis tilts only 1.5°, much less than the 23.5° of Earth's axis, so seasonal effects on sunlight duration are much less intense on the Moon and there should be less need for Earth-like DST. A more pressing issue is that the length of day (including daytime and nighttime) varies more on the Moon. Local Earth days vary by at most 0.008 hours from the mean of 24 hours (this variation is due to the eccentricity of the Earth orbit and the obliquity of the ecliptic). So people who think that every local Earth day is exactly 24 hours are not far off. Local lunar days, in contrast, are roughly 29.5 ± 0.25 Earth days (again, this includes both lunar daytime and lunar nighttime). That's more slop to deal with, relatively speaking, and dealing with varying-length days could be a bit of a problem for civil time on the Moon. Presumably ESA's boffins are on top of this.....
On 2023-03-02 04:47 PM, Paul Eggert wrote:
On 3/2/23 09:51, Brooks Harris wrote:
Will we need DST on the Moon? :-)
I hope not! The Moon's axis tilts only 1.5°, much less than the 23.5° of Earth's axis, so seasonal effects on sunlight duration are much less intense on the Moon and there should be less need for Earth-like DST.
A more pressing issue is that the length of day (including daytime and nighttime) varies more on the Moon.
Local Earth days vary by at most 0.008 hours from the mean of 24 hours (this variation is due to the eccentricity of the Earth orbit and the obliquity of the ecliptic). So people who think that every local Earth day is exactly 24 hours are not far off.
Local lunar days, in contrast, are roughly 29.5 ± 0.25 Earth days (again, this includes both lunar daytime and lunar nighttime). That's more slop to deal with, relatively speaking, and dealing with varying-length days could be a bit of a problem for civil time on the Moon.
Presumably ESA's boffins are on top of this.....
Researchers more precisely calculate how much faster time passes on the moon https://phys.org/news/2024-07-precisely-faster-moon.html
On 7/11/24 03:44, Brooks Harris wrote:
On 2023-03-02 04:47 PM, Paul Eggert wrote:
Presumably ESA's boffins are on top of this.....
Researchers more precisely calculate how much faster time passes on the moon https://phys.org/news/2024-07-precisely-faster-moon.html
That news article says "the team found that time on the moon ticks by at 0.0000575 seconds faster per day (57.50 µs/d) than it does on Earth." But the paper <https://arxiv.org/pdf/2406.16147> says this figure needs to be adjusted for the total orbital energies for the Earth and Moon, and later gives an adjusted figure of "56.02 μs/d, with the clock on the Moon’s surface running faster by that amount compared to a terrestrial clock. Additionally, there are periodic terms, the largest of which is due to the lunar orbit around the Earth that amounts to about 30.95 μs/d ...". Clearly precise lunar timekeeping will not be a trivial matter. It's still not clear to me what the relationship between the ESA and NASA is on this. Will there be a single standard for lunar timekeeping, or multiple standards? Will this be like the squabbles over the Prime Median in the 19th century?
On 2024-07-11 06:07 AM, Paul Eggert wrote:
On 7/11/24 03:44, Brooks Harris wrote:
On 2023-03-02 04:47 PM, Paul Eggert wrote:
Presumably ESA's boffins are on top of this.....
Researchers more precisely calculate how much faster time passes on the moon https://phys.org/news/2024-07-precisely-faster-moon.html
That news article says "the team found that time on the moon ticks by at 0.0000575 seconds faster per day (57.50 µs/d) than it does on Earth."
But the paper <https://arxiv.org/pdf/2406.16147> says this figure needs to be adjusted for the total orbital energies for the Earth and Moon, and later gives an adjusted figure of "56.02 μs/d, with the clock on the Moon’s surface running faster by that amount compared to a terrestrial clock. Additionally, there are periodic terms, the largest of which is due to the lunar orbit around the Earth that amounts to about 30.95 μs/d ...".
Clearly precise lunar timekeeping will not be a trivial matter.
It's still not clear to me what the relationship between the ESA and NASA is on this. Will there be a single standard for lunar timekeeping, or multiple standards? Will this be like the squabbles over the Prime Median in the 19th century?
Is there a Prime Meridian on the Moon? Will there be Lunar Time Zones?
On 2024-07-11 04:33, Brooks Harris via tz wrote:
On 2024-07-11 06:07 AM, Paul Eggert wrote:
On 7/11/24 03:44, Brooks Harris wrote:
On 2023-03-02 04:47 PM, Paul Eggert wrote:
Presumably ESA's boffins are on top of this.....
Researchers more precisely calculate how much faster time passes on the moon https://phys.org/news/2024-07-precisely-faster-moon.html
That news article says "the team found that time on the moon ticks by at 0.0000575 seconds faster per day (57.50 µs/d) than it does on Earth."
But the paper <https://arxiv.org/pdf/2406.16147> says this figure needs to be adjusted for the total orbital energies for the Earth and Moon, and later gives an adjusted figure of "56.02 μs/d, with the clock on the Moon’s surface running faster by that amount compared to a terrestrial clock. Additionally, there are periodic terms, the largest of which is due to the lunar orbit around the Earth that amounts to about 30.95 μs/d ...".
Clearly precise lunar timekeeping will not be a trivial matter.
It's still not clear to me what the relationship between the ESA and NASA is on this. Will there be a single standard for lunar timekeeping, or multiple standards? Will this be like the squabbles over the Prime Median in the 19th century?
Is there a Prime Meridian on the Moon? Will there be Lunar Time Zones?
I'd imagine that meridian would have to be the mean line separating the Earth facing near side and the far side? As the lunar terminator rotates giving us phases, I'd expect we would have to deal with divisions having a mean totalling ~29.5 days, but a bit like Earth polar latitudes, with day and night each taking ~14.75 days. I would expect time zones might operate as in Antarctic bases, keeping the zone of the associated organization for human wake-sleep cycles. -- Take care. Thanks, Brian Inglis Calgary, Alberta, Canada La perfection est atteinte Perfection is achieved non pas lorsqu'il n'y a plus rien à ajouter not when there is no more to add mais lorsqu'il n'y a plus rien à retirer but when there is no more to cut -- Antoine de Saint-Exupéry
On Thu 2024-07-11T12:07:17+0200 Paul Eggert via tz hath writ:
It's still not clear to me what the relationship between the ESA and NASA is on this. Will there be a single standard for lunar timekeeping, or multiple standards? Will this be like the squabbles over the Prime Median in the 19th century?
The IAU already has a defined coordinate system for the moon. This new international arrangement will be akin to what happened in 1968 as the old agreement on using Greenwich and the poles gave way to the new reality of satellite geodesy and atomic clocks resulting in a terrestrial reference frame where Greenwich is not zero and the poles are not where the rotation axis intersects the surface of the earth. -- Steve Allen <sla@ucolick.org> WGS-84 (GPS) UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 https://www.ucolick.org/~sla/ Hgt +250 m
participants (4)
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brian.inglis＠systematicsw.ab.ca -
Brooks Harris -
Paul Eggert -
Steve Allen