Bob Moler's Ephemeris Blog

This is Ephemeris for Tuesday, January 19th. Today the Sun will be up for 9 hours and 20 minutes, setting at 5:33, and it will rise tomorrow at 8:13. The Moon, 1 day before first quarter, will set at 12:36 tomorrow morning.

The Earth has an axial tilt to its orbit of the Sun of 23 ½ degrees. So the Earth has seasons, the cycle of which last one orbit of the Sun, or one year. Our Moon on the other hand has a 5 ½ degree axial tilt to its orbit of the Earth, but more importantly for future moon colonists, has only a degree and a half tilt compared to the Earth’s own orbit of the Sun. So there are spots at the north and south poles that never get the Sun’s heat or light. The Moon’s south polar region is more rugged with more and smaller craters than the north, so has collected, over the eons, what seems to be a great amount of water ice that is cold enough to be stable in the vacuum of space. That makes it an ideal place to build a sustainable lunar base.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The Moon’s south pole area on the left and north pole on the right. The cyan color shows shadowed areas where ice is located. Credit NASA