Explaining Science

Until the outbreak of the global pandemic there was a good chance that mankind would return to the Moon in the next ten years, even if the deadline of project Artemis to have a manned mission in 2024 was a little ambitious. It will be some time before the effects of the current crisis on the manned space program can be evaluated.

The last humans to visit the lunar surface were the Apollo 17 astronauts back in December 1972, who spent only three days there. It is interesting to consider what it would be like to be on its surface for a period of a least a month and watch at first-hand how the lunar surface changes over time.

The Apollo 17 crew (L to R) Harrison H. Schmitt, Eugene Cernan, Ronald E. Evans – image from NASA.

In 1972 Schmitt and Cernan were the last humans to walk on…

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Explaining Science

Although the Moon is much smaller and less massive than the Earth its gravitational field still has significant effects on the Earth. The most noticeable of these are tides, the periodic rise and fall of sea levels.

High and low tides- Images from Wikimedia Commons

Causes of Tides

The average Earth- Moon distance is 384 400 km. This, however, is the distance of the centre of the Moon from the centre of the Earth and the Earth itself is 12 740 km in diameter. So, the point on the Earth’s surface which is closest to the Moon is on average a distance of 378 030 km away and the point on the Earth’s surface farthest away a distance of 390 770 km. The principle cause of tides is that the pull of the Moon’s gravity is stronger at the area of the Earth closest to the Moon and weaker at the area…

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At last, some new translations! Kepler’s first five footnotes to Somnium. He’d hit his stride by Footnote 2:


2020-05-28 05_24_24-II _ The Somnium Project