average distance between earth and moon in km
Lunar distance (astronomy) Lunar distance (LD or   Δ ⊕ L   {\textstyle \Delta _{\oplus L}} ), also called Earth–Moon distance, Earth–Moon characteristic distance, or distance to the Moon, is a unit of measure in astronomy. It is the average distance from the center of Earth to the center of the Moon. More technically, it is the mean semi-major axis of the geocentric lunar orbit. It may also refer to the time-averaged distance between the centers of the Earth and the Moon, or less commonly, the instantaneous Earth–Moon distance. The lunar distance is approximately a quarter of a million miles (7008400000000000000♠400000 km).[1]
Earth The total surface area of Earth is about 510 million km2 (197 million sq mi).[13] Of this, 70.8%,[13] or 361.13 million km2 (139.43 million sq mi), is below sea level and covered by ocean water.[121] Below the ocean's surface are much of the continental shelf, mountains, volcanoes,[91] oceanic trenches, submarine canyons, oceanic plateaus, abyssal plains, and a globe-spanning mid-ocean ridge system. The remaining 29.2%, or 148.94 million km2 (57.51 million sq mi), not covered by water has terrain that varies greatly from place to place and consists of mountains, deserts, plains, plateaus, and other landforms. Tectonics and erosion, volcanic eruptions, flooding, weathering, glaciation, the growth of coral reefs, and meteorite impacts are among the processes that constantly reshape the Earth's surface over geological time.[122][123]
Orbit of the Moon The Moon orbits Earth in the prograde direction and completes one revolution relative to the stars in approximately 27.323 days (a sidereal month). Earth and the Moon orbit about their barycentre (common center of mass), which lies about 4,600 km (2,900 mi) from Earth's center (about 3/4 of the radius of Earth). On average, the distance to the Moon is about 385,000 km (239,000 mi) from Earth's centre, which corresponds to about 60 Earth radii. With a mean orbital velocity of 1.022 km/s (2,290 mph),[8] the Moon appears to move relative to the stars each hour by an amount roughly equal to its angular diameter, or by about half a degree. The Moon differs from most satellites of other planets in that its orbit is close to the plane of the ecliptic, and not to Earth's equatorial plane. The plane of the lunar orbit is inclined to the ecliptic by about 5°, whereas the Moon's equatorial plane is inclined by only 1.5° to the ecliptic.
Perihelion and aphelion Earth is about 147.1 million kilometers (91.4 million miles) from the Sun at perihelion around January 3, in contrast to about 152.1 million kilometers (94.5 million miles) at aphelion around July 4 â€” a difference of about 5.0 million kilometers (3.1 million miles). (These dates change over time due to precession and other orbital factors, which follow cyclical patterns known as Milankovitch cycles. For a table of these dates for various years, see Apsis.)