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Timekeeping on the Moon

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"Moon time" redirects here. For Earth calendars using the Moon, see lunar calendar.

Timekeeping on the Moon is an issue of synchronized human activity on the Moon and contact with such. The two main differences to timekeeping on Earth is the length of a day on the Moon, being the lunar day or lunar month, observable from Earth as the lunar phases, and the differences between Earth and the Moon of how differently fast time progresses, with 24 hours on the Moon being 58.7 microseconds (0.0000587 seconds) faster,[1] resulting from the different masses of the Moon and Earth, the effect being called gravitational time dilation.

History

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See also: History of timekeeping devices
an astronaut with short hair and wearing a watch, flight suit and commset looks at the camera
Buzz Aldrin wearing an Omega Speedmaster watch during Apollo 11 mission in 1969

The technology used for the timekeeping devices deployed to the Moon have varied over the decades. Several Omega Speedmasters have been on the Moon, synched to Central Standard Time (CST).[2]

The Apollo Guidance Computer (AGC) kept a triple-precision count of time in a real time clock cuing from a quartz oscillator; a standby option (although never used) would allow it to update this count every 1.28 second (~0.78 hertz) — more often when not standing by. In addition to maintaining the clock cycle, computer timekeeping allowed the AGC to display the capsule's vertical and horizontal movements relative to the Moon's surface, in units of feet per second.[citation needed]

Coordinated Lunar Time

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Coordinated Lunar Time (LTC) is a proposed primary lunar time standard for the Moon.[3] In early April 2024, the White House asked NASA to work alongside US and international agencies for the purpose of establishing a unified standard time for the Moon and other celestial bodies by 2026.[4] The White House's request, led by the Office of Science and Technology Policy (OSTP), called for a "Coordinated Lunar Time", which was first proposed by the European Space Agency in early 2023.[3][5]

As of October 2024, there is no lunar time standard. As a result, activities on the Moon are coordinated using the time zone of where a mission's headquarters is based.[6] For example, the Apollo missions utilized the Central Time Zone as the missions were controlled from Houston, Texas.[7] Likewise, Chinese activities on the Moon run on China Standard Time.[citation needed] As more countries are active on the Moon and interact with each other, a different, unified system will be needed.[7]

As part of an ongoing global billionaire space race[8][9] and a wider international space race between the United States and China,[10][11] a need exists for a universal time-keeping benchmark so that lunar spacecraft and satellites are able to fulfill their respective missions with precision and accuracy.[12] Due to differences in gravitational force and other factors, time passes fractionally faster on the Moon when observed from Earth.[13][14]

Under the Artemis program, and supported by the Commercial Lunar Payload Services missions, astronauts and a proposed scientific moonbase are envisioned to take place on and around the lunar surface from the 2020s onwards.[15] The proposed standard would therefore solve a timekeeping issue.[16] According to OSTP Chief Arati Prabhakar, time would "appear to lose on average 58.7 microseconds per Earth-day and come with other periodic variations that would further drift Moon time from Earth time".[17]

The development of the standard is set to be a collaborative effort, initially amongst members of the Artemis Accords, but will be meant to apply globally. The initial proposal of the standard calls for four key features:[18]

  • traceability back to Coordinated Universal Time,
  • accuracy sufficient for navigation and science,
  • resilience to disruptions, and
  • scalability to potential environments beyond cislunar space.

LunaNet, an upcoming lunar communications and navigation service under development with the European Space Agency, calls for a Lunar Time System Standard which the LTC is meant to address.[19]

In August 2024, the US National Institute of Standards and Technology furthered development of the proposal by releasing a draft for the standard focused on defining the framework and mathematical model. The draft takes into account the gravitational differences on the Moon and was published to The Astronomical Journal.[20]

See also

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References

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  1. ^ Ramirez-Simon, Diana (2024-04-03). "Moon Standard Time? Nasa to create lunar-centric time reference system". the Guardian. Retrieved 2024-04-06.
  2. ^ "The Watches That Went to the Moon". Air & Space Magazine | Smithsonian Magazine.
  3. ^ a b "Telling time on the Moon". European Space Agency. February 27, 2023. Archived from the original on April 3, 2024. Retrieved April 3, 2024.
  4. ^ Roulette, Joey; Dunham, Will (2024-04-03). "Exclusive: White House directs NASA to create time standard for the moon". Reuters. Archived from the original on 2024-04-02. Retrieved 2024-04-03.
  5. ^ "Should the Moon Have a Time Zone? Europe Pushes for 'Lunar Reference Time'". NBC Philadelphia. March 1, 2023. Archived from the original on March 1, 2023. Retrieved October 26, 2024.
  6. ^ Rao, Joe (May 9, 2023). "What time is it on the moon? How a lunar clock debate led to an out-of-this-world timepiece". Space.com. Archived from the original on April 3, 2024. Retrieved April 3, 2024.
  7. ^ a b Gibney, Elizabeth (2023). "What time is it on the Moon?". Nature. 614 (7946): 13–14. Bibcode:2023Natur.614...13G. doi:10.1038/d41586-023-00185-z. PMID 36693973. S2CID 256230630. Archived from the original on 2023-04-03. Retrieved 2024-04-03.
  8. ^ Nguyen, Terry (February 2, 2022). "It's the dawn of a new space age — at least for billionaires". Vox. Retrieved April 9, 2024.
  9. ^ Kuthunur, Sharmila (April 7, 2024). "White House directs NASA to create a new time zone for the moon". Space.com. Retrieved April 9, 2024.
  10. ^ Roulette, Joey; Bhattacharjee, Nivedita; Woo, Ryan (January 12, 2024). "In moon race with China, U.S. setbacks test role of private firms". Reuters. Retrieved April 4, 2024.
  11. ^ Tumlison, Rick (July 20, 2023). "Return to the moon: The race we have to win (again)". Space.com. Archived from the original on January 12, 2024. Retrieved April 4, 2024.
  12. ^ Lea, Robert (March 1, 2023). "Does the moon need its own time zone? We may need to decide soon". Space.com. Archived from the original on January 24, 2024. Retrieved April 4, 2024.
  13. ^ Ramirez-Simon, Diana (2024-04-03). "Moon Standard Time? Nasa to create lunar-centric time reference system". The Guardian. ISSN 0261-3077. Archived from the original on 2024-04-03. Retrieved 2024-04-03.
  14. ^ Kuthunur, Sharmila (2024-04-22). "What time is it on the Moon? We might soon know". Astronomy Magazine. Retrieved 2024-04-24.
  15. ^ "Telling time on the Moon". esa.int. Archived from the original on 2024-04-03. Retrieved 2024-04-03.
  16. ^ Thorsberg, Christian (April 4, 2024). "NASA Will Create a New Time Zone for the Moon, Called Coordinated Lunar Time". Smithsonian. Archived from the original on April 4, 2024. Retrieved April 4, 2024.
  17. ^ Irwin, Lauren (April 3, 2024). "NASA tasked with creating a time zone for the moon". The Hill. Archived from the original on April 3, 2024. Retrieved April 4, 2024.
  18. ^ Prabhakar, Arati (April 2, 2024). "Policy on Celestial Time Standardization in Support of the National Cislunar Science and Technology (S&T) Strategy" (PDF). The White House. Archived (PDF) from the original on April 4, 2024. Retrieved April 4, 2024.
  19. ^ Foust, Jeff (2024-04-03). "White House directs NASA to develop lunar time standard". SpaceNews. Archived from the original on 2024-04-05. Retrieved 2024-04-03.
  20. ^ "What Time Is It on the Moon?". NIST. 2024-08-12.
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