Bob Moler's Ephemeris Blog

This is Ephemeris for Monday, March 18th. Today the Sun will be up for 12 hours and 4 minutes, setting at 7:53, and it will rise tomorrow at 7:46. The Moon, 1 day past first quarter, will set at 5:41 tomorrow morning.

When one gazes upon the moon tonight the thought of where the moon came from comes to mind. Did it form with the Earth? Was it captured by the Earth? The latest thought on the origin of the moon centers around a grazing collision with the Earth of a Mars sized body that has been given the name Theia, the mother of Selene the goddess of the Moon, shortly after the Earth was formed. This is based on the Apollo mission discoveries that the composition of the rocks on the moon are approximately the same as those of the Earth. It has been known for some time that there are two dense masses within the Earth about halfway from the surface to the center. One geologist has put forth the idea that these masses could have been the core of Theia that sank down into the Earth.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). They may be different for your location.

Addendum