Timekeeping on the Moon is an issue of synchronized human activity on the
Moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width ...
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
A lunar day is the period of time for Earth's Moon to complete one rotation on its axis with respect to the Sun. Due to tidal locking, it is the time the Moon takes to complete one orbit around Earth ( Earth rise to Earth set) plus about 2.2 ...
or
lunar month
In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month.
Variations
In Shona, Middle Eastern, and Europ ...
, observable from Earth as the
lunar phases
Concerning the lunar month of ~29.53 days as viewed from Earth, the lunar phase or Moon phase is the shape of the Moon's directly sunlit portion, which can be expressed quantitatively using areas or angles, or described qualitatively using the ...
, and the differences between Earth and the Moon of how differently fast time progresses, with 24 hours on the Moon being 58.7
microseconds
A microsecond is a unit of time in the International System of Units (SI) equal to one millionth (0.000001 or 10−6 or ) of a second. Its symbol is μs, sometimes simplified to us when Unicode is not available.
A microsecond is equal to 100 ...
(0.0000587 seconds) faster,
resulting from the different masses of the Moon and Earth, the effect being called
gravitational time dilation
Gravitational time dilation is a form of time dilation, an actual difference of elapsed time between two events as measured by observers situated at varying distances from a gravitating mass. The lower the gravitational potential (the close ...
.
As of early 2024, there is no lunar
time standard
A time standard is a specification for measuring time: either the rate at which time passes or points in time or both. In modern times, several time specifications have been officially recognized as standards, where formerly they were matters o ...
. Instead, the time on the Moon is different for each country involved. Thus, American activities on the Moon run on the time zone of their mission control centre, while Chinese activities on the Moon run on
China Standard Time
The time in China follows a single standard UTC offset, time offset of UTC+08:00 (eight hours ahead of Coordinated Universal Time), even though the country spans almost five geographical time zones. The official national standard time is called '' ...
. As more countries are active on the Moon and interact with each other, a different, unified system will be needed.
In 2024, the
White House
The White House is the official residence and workplace of the president of the United States. It is located at 1600 Pennsylvania Avenue Northwest, Washington, D.C., NW in Washington, D.C., and has been the residence of every U.S. preside ...
asked
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeedi ...
to establish a unified
Coordinated Lunar Time
Coordinated Lunar Time or LTC is a proposed primary lunar time standard for the Moon. In early April 2024, NASA was asked by the White House to work alongside domestic and international agencies for the purpose of establishing a unified standard ...
standard for the Moon and other celestial bodies by 2026.
The
European Space Agency
, owners =
, headquarters = Paris, Île-de-France, France
, coordinates =
, spaceport = Guiana Space Centre
, seal = File:ESA emblem seal.png
, seal_size = 130px
, image = Views in the Main Control Room (120 ...
has proposed a lunar reference time for the Moon to solve this issue.
History
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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).
The
Apollo Guidance Computer
The Apollo Guidance Computer (AGC) was a digital computer produced for the Apollo program that was installed on board each Apollo command module (CM) and Apollo Lunar Module (LM). The AGC provided computation and electronic interfaces for guidan ...
(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 The foot per second (plural feet per second) is a unit of both speed (scalar) and velocity (vector quantity, which includes direction). It expresses the distance in feet (ft) traveled or displaced, divided by the time in seconds (s). The correspon ...
.
See also
*
Month
*
Lunar year
A lunar calendar is a calendar based on the monthly cycles of the Moon's phases (synodic months, lunations), in contrast to solar calendars, whose annual cycles are based only directly on the solar year. The most commonly used calendar, the Gr ...
*
Timekeeping on Mars
Though no standard exists, numerous calendars and other timekeeping approaches have been proposed for the planet Mars. The most commonly seen in the scientific literature denotes the time of year as the number of degrees from the northern vernal ...
*
International Celestial Reference System and its realizations
*
Nautical time
Nautical time is a maritime time standard established in the 1920s to allow ships on high seas to coordinate their local time with other ships, consistent with a long nautical tradition of accurate celestial navigation. Nautical time divides the ...
*
Sidereal time
Sidereal time (as a unit also sidereal day or sidereal rotation period) (sidereal ) is a timekeeping system that astronomers use to locate celestial objects. Using sidereal time, it is possible to easily point a telescope to the proper coor ...
References
category:timekeeping
category:moon
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