Lunar distance (astronomy)

From Wikipedia, the free encyclopedia
This article is about the average distance from the Earth to the Moon. For its other use in navigation, see Lunar distance (navigation).
Lunar perigee–apogee size comparison
Variation of the distance between the centers of the Moon and the Earth over 700 days.

In astronomy, a lunar distance (LD) is a measurement of the distance from the Earth to the Moon. The average distance from Earth to the Moon is 384,400 km (238,900 mi).[1] (about 389 LD is 1 AU, the Earth-Sun distance) The actual distance varies over the course of the orbit of the moon, from 356,700 km (221,600 mi) at the perigee and 406,300 km (252,500 mi) at apogee, resulting in a differential range of 49,600 km (30,800 mi).

High-precision measurements of the lunar distance are made by measuring the time taken for light to travel between LIDAR 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.[2][3][4] The recession rate is considered anomalously high.[5] By coincidence, the diameter of corner cubes in retroreflectors on the Moon is also 3.8 cm (1.5 in).[6][7]

The tidal dissipation rate varied in the Earth geological history.[8]

The first person to measure the distance to the Moon was the 2nd-century-BC astronomer and geographer Hipparchus, who exploited the lunar parallax using simple trigonometry. He was approximately 26,000 km (16,000 mi) off the actual distance, an error of about 6.8%.

The NASA Near Earth Object Catalog includes the distances of asteroids and comets measured in Lunar Distances.[9]

Distance between the Earth and Moon - sizes and distance to scale.
The Moon's distance from the Earth and moon phases in 2014.
Moon phases: 0 (1) - new moon, 0.25 - first quarter, 0.5 - full moon, 0.75 - last quarter.

See also

References

  1. ↑ NASA Staff (10 May 2011). "Solar System Exploration - Earth's Moon: Facts & Figures". NASA. Retrieved 2011-11-06. 
  2. ↑ http://curious.astro.cornell.edu/question.php?number=124 Is the Moon moving away from the Earth?
  3. ↑ C.D. Murray & S.F. Dermott (1999). Solar System Dynamics. Cambridge University Press. p. 184. 
  4. ↑ Dickinson, Terence (1993). From the Big Bang to Planet X. Camden East, Ontario: Camden House. pp. 79–81. ISBN 0-921820-71-2. 
  5. ↑ Bills, B.G., and Ray, R.D. (1999), "Lunar Orbital Evolution: A Synthesis of Recent Results", Geophysical Research Letters 26 (19): 3045–3048, doi:10.1029/1999GL008348 
  6. ↑ http://eclipse.gsfc.nasa.gov/SEhelp/ApolloLaser.html
  7. ↑ http://www.physics.ucsd.edu/~tmurphy/apollo/lrrr.html
  8. ↑ http://isotope.colorado.edu/~geol5700/Bills_1999.pdf - Lunar orbital evolution
  9. ↑ NEO Earth Close Approaches



This article is issued from Wikipedia. The text is available under the Creative Commons Attribution/Share Alike; additional terms may apply for the media files.