farmdoc's blog post number 457

It is 384,403 km from Earth – about 30 times Earth’s diameter. Its diameter is 3,474 km – about 27% of Earth’s. It’s almost spherical – its equatorial radius is 1,738 km and its polar radius is 1,736 km. Its volume is 2% of Earth’s. About 59% of its surface can be seen from Earth, but only 50% at any one time. Its force of gravity is about 17% of Earth’s. It orbits Earth each 27.3 days. Its average orbital speed is 1.02 km/second. Its phases repeat each 29.5 days. Its average surface temperature is 107°C during the lunar day and -153°C during the lunar night. It’s responsible for Earth’s tides. Its larger appearance when closer to Earth’s horizon’s an optical illusion. It has no magnetic field, no wind and no water. It’s the inspiration for many songs including these [1, 2, 3]; for the word ‘lunatic’ stemming from the Latin word ‘luna’ denoting the traditional folklore link between madness and its phases; and for a walk made famous by Michael Jackson. The first spacecraft that touched it and photographed its far side in 1959, were Russian. Twelve people – all American men – have walked on it. The last was Eugene Cernan on 13 December 1972. The first was Neil Armstrong (pictured) at 0256 GMT on 21 July 1969 which in Eastern Australia was 12:56 p.m. That was 40 years ago today. And seven days after my father died.