For the navigation unit, see Lunar distance (navigation).
Lunar distance
A lunar distance, 384,399 km (238,854 mi), is the Moon's average distance to Earth. The actual distance varies over the course of its orbit. The image compares the Moon's apparent size when it is nearest and farthest from Earth.
General information
Unit system
astronomy
Unit of
distance
Symbol
LD,
Conversions
1 LD in ...
... is equal to ...
SI base unit
3.84399×108 m
Metric system
384399 km
English units
238854 mi
Astronomical unit
0.002569 au
Lightsecond
1.28 ls
The instantaneous Earth–Moon distance, or distance to the Moon, is the distance from the center of Earth to the center of the Moon. Lunar distance (LD or ), or Earth–Moon characteristic distance, is a unit of measure in astronomy. More technically, it is the semi-major axis of the geocentric lunar orbit. The lunar distance is on average approximately 385,000 km (239,000 mi), or 1.28 light-seconds; this is roughly 30 times Earth's diameter or 9.5 times Earth's circumference. Around 389 lunar distances make up an AU astronomical unit (roughly the distance from Earth to the Sun).
Lunar distance is commonly used to express the distance to near-Earth object encounters.[1] Lunar semi-major axis is an important astronomical datum; the few millimeter precision of the range measurements determines semi-major axis to a few decimeters; it has implications for testing gravitational theories such as general relativity,[2] and for refining other astronomical values, such as the mass,[3] radius,[4] and rotation of Earth.[5] The measurement is also useful in characterizing the lunar radius, as well as the mass of and distance to the Sun.
Millimeter-precision measurements of the lunar distance are made by measuring the time taken for laser beam light to travel between stations on Earth and retroreflectors placed on the Moon. The Moon is spiraling away from Earth at an average rate of 3.8 cm (1.5 in) per year, as detected by the Lunar Laser Ranging experiment.[6][7][8]
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instantaneous Earth–Moon distance, or distance to the Moon, is the distance from the center of Earth to the center of the Moon. Lunardistance (LD or Δ ⊕ L {\textstyle...
Lunar Laser Ranging (LLR) is the practice of measuring the distance between the surfaces of the Earth and the Moon using laser ranging. The distance can...
what amounted to a horizontal lunar parallax of 1° 26′, which was much too large. He then derived a maximum lunardistance of 64+1/6 Earth radii. Because...
and other selected bodies are used in the practice called "lunars" or the lunardistance method, used for determining precise time when time is unknown...
A moonbase, lunar base, or lunar colony is a facility on or below the surface of the Moon, enabling human activity on the Moon. As such, it is different...
experiments at sea trying out the lunardistance method, proposed annual publication of pre-calculated lunardistance predictions in an official nautical...
method of determining longitude, the main theory was the Method of LunarDistances, advanced by Astronomer Royal Nevil Maskelyne). The artist William...
asteroid close approaches to Earth in 2023. The average distance to the Moon (or lunardistance (LD)) is about 384,400 km (238,900 mi), which is around...
same side of the Moon to always face Earth. Because of this, the lunar day and the lunar month are the same length, at 29.5 Earth days. The Moon's gravitational...
contacting the antisolar point. This type of lunar eclipse is relatively rare. The relative distance of the Moon from Earth at the time of an eclipse...
excavate low albedo material, for example basaltic-lava deposits on the lunar maria. Thermal rays, as seen on Mars, are especially apparent at night when...
The Lunar Roving Vehicle (LRV) is a battery-powered four-wheeled rover used on the Moon in the last three missions of the American Apollo program (15...
sphere King tide – An especially high spring tide Lunar Laser Ranging experiment – Measuring the distance between the Earth and the Moon with laser lightPages...
l d s {\displaystyle ld_{s}} is the lunardistance at syzygy, l d a {\displaystyle ld_{a}} is the lunardistance at the greatest apogee of the year, and...
successful two-man landing missions, twelve men walked on the lunar surface, six of whom drove Lunar Roving Vehicles as part of the last three missions. Three...
Moon rock or lunar rock is rock originating from Earth's Moon. This includes lunar material collected during the course of human exploration of the Moon...
solutions within 1° and 0.5°. Rewards were given for two solutions: lunardistances, made practicable by the tables of Tobias Mayer developed into an nautical...
appearance of the dark areas (known as lunar maria) and the lighter-colored highlands (and some lowlands) of the lunar surface. There are various explanations...
Astronomical measure uses: Earth radius R🜨 ≈ 6,371 km Lunardistance LD ≈ 384402 km. Average distance between the center of Earth and the center of the Moon...
size. Lunardistance (LD), the distance from the centre of Earth to the centre of the Moon, is a unit of measure in astronomy. The lunardistance is approximately...
crewed spaceflight, including the longest crewed lunar landing mission (12 days, 14 hours), greatest distance from a spacecraft during an extravehicular activity...
satellites on board ship. Both Harrison's watch and lunar-distance observations based on Mayer's lunar tables produced results within the terms of the Longitude...
Hipparchus observed (at lunar eclipses) that at the mean distance of the Moon, the diameter of the shadow cone is 2+1⁄2 lunar diameters. That apparent...
less than 1 lunardistance (0.0025696 AU (384,410 km; 238,860 mi)) from Earth in 2023. As most asteroids passing within a lunardistance are less than...
of longitude at sea by the method of lunardistances. In the very early twentieth century, comparison between lunar theory and observation was used in another...
the Moon Geology of the Moon Lunar soil Lunar water Gravitation of the Moon Internal structure of the Moon Lunar swirls Lunar water Magnetic field of the...
Ghaffarian, and Tim Crain, to provide lunar surface access, lunar orbit delivery, and communication from lunardistance. Intuitive Machines holds three NASA...
The Lunar Seismic Profiling Experiment (LSPE) was a lunar science experiment, deployed by astronauts on the lunar surface in 1972 as part of Apollo 17...
Global Information
