Archives » Lagrange Points

Moon’s Transit of Earth

This isn’t a view any human of even the relatively recent past could ever have seen: the Moon passing in front of the Earth:-

Full Mooon, Full Earth

From Astronomy Picture of the Day 7/8/15, this photo – taken by NASA’s Deep Space Climate Observatory (DSCOVR) spacecraft – is captioned Full Moon, Full Earth, but of course it’s a New Moon; from the surface of the Earth all of the Moon would appear dark. The hemisphere of the Moon seen in the photo is of course its far side (which isn’t dark, except briefly: it gets as much sunlight as the near side does, only in reverse proportion.)

The DSCOVR spacecraft is situated at the Earth-Sun L1 Lagrange Point (see diagram – not to scale – below) where the orbit of a satellite is stable. As such it is perfectly placed to observe the Moon transit the Earth as above, which from its perspective occurs twice a year.

Earth-Sun Lagrange Points

free hit counter script