1、地球赤道得扁率仅为十万分之一，通常视为圆 2cFhttp:/www.windows.ucar.edu/eclipticequatorPeriodic part:Nutation23o27ObliquityMean(secular)part:PrecessionView of two U.S.spacecraft on the surface of the moonDescription:View of two U.S.spacecraft on the surface of the moon,taken during the second Apollo 12 extravehicular ac
2、tivity(EVA-2).The Apollo 12 Lunar Module is in the background.The unmanned Surveyor III spacecraft is in the foreground.NASA GOV2/tclkm31.0km09.122921333km17382.18652.05132520626/sin a-bcalRlR，轴和极轴分别为拟合，设两个赤道月球可以用三轴椭球体。，最小时最大时为离的变化而变化，月球的角直径随月底距。可得月球半径月球平均角直径地从月球表面逃逸。以气体分子能轻而易举的热运动速度，所气体分子在月面高温下，远小于
3、月球表面的逃逸速度为。为地球表面加速度的为月球表面的重力加速度km/s38.26/1,/623.1/10672.6/222112smkgmNGRGmgThe Moon as imaged with an 203 mm f/7 newtonian and a Nikon CoolPix 4500 with afocal projection through a 40 mm Kellner on November 19,2002.http:/www.unm.edu/abqtom/observing_the_moon.htmOblique view of the lunar far side as
4、photographed by the crew of Apollo 11.The large crater at center is IAU crater#308(179 E,5.5 S)with a diameter of about 80 kilometers.The rugged terrain visible here is typical of the lunar far side.The smooth dark areas on the Moons surface are called maria(plural for mare;Latin for seas).These vol
5、canic plains are made up of a rock type known as basalt,similar in composition to the rocks found in Hawaii.They cover 17%of the surface area of the Moon.The maria contain physical features such as pits and channels,but lack large volcanos.This image was taken by one of NASAs Lunar Orbiters in 1967
6、http:/solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=800Plato and the lunar Alps,photographed by Alan Friedman of Buffalo,New York.http:/science.nasa.gov/headlines/y2006/08feb_lunaralps.htm ETSSESTETS111222则地球的公转周期恒星月周期朔望月周期月龄是对月相的定量描述，从朔日起算到各月相所经历的时间，以日为单位。The partial phases and totality during
7、a 1982 lunar eclipse.This photo is centered on Earths umbral shadow(本影).It shows the various stages of the eclipse and the Moons relative position with respect to the umbra during the three and a half hours of the eclipse.1984年5月30日日环食时见到的倍利珠现象，该日环食已经接近全食。，月偏食的食分小于于月全食的食分大于或等径之比。时进入本影部分的视直月食的食分定义为食甚
8、。，但很接近，日环食的食分虽小于，日全食的食分大于日偏食的食分小于日全食和日环食：住的部分）为太阳视圆面半径被遮的值（日偏食：食甚时的标志。以食甚时被遮掩的量为度量交食达到的程度，天文学上用“食分”来日月日日日111111/The giant impact theory best explains why the Moon is very much like the Earths mantel and contains very little nickel/iron.The creation and evolution of the Earth and Moon are closely rel
9、atedPaintings of the Moon(a)about 4 billion years ago,after much of the meteoritic bombardment had subsided and the surface had somewhat solidified;(b)about 3 billion years ago,after molten lava had made its way up through surface fissures to fill the low-lying impact basins and create the smooth maria;and(c)today,with much of the originally smooth maria now heavily pitted with craters formed at various times within the past 3 billion years.
