Bad Astronomy: Misconceptions and Misuses Revealed, from ...

PHASE THE NATION 63
Your eyes aren’t playing tricks on you. This effect is called
earthshine. From the Moon, the Earth goes through phases, too.
They are opposite the Moon’s phases, so when the Moon is full as
seen from the Earth, the Earth would be new as seen from the
Moon, and so on. The Earth is physically bigger than the Moon,
and it also reflects light more efficiently. The full Earth as seen
from the Moon would look many times brighter to you than the
full Moon does on the Earth.
This brightly lit Earth illuminates the new Moon pretty well,
faintly lighting what would normally be the dark part of the
Moon’s surface. If you look through a telescope or a pair of binoculars,
there’s even enough light to spot craters on the surface. The
effect is even more amplified if the lit side of the Earth is covered
by clouds, making the Earth an even better reflector of sunlight.
Earthshine is a pretty name for this, but there’s an even more
poetic one: it’s called “The old Moon in the new Moon’s arms.”
The phases of the Moon are both more complicated and more
subtle than you might have thought. If you had any misconceptions
about them before reading this section, let’s hope it was just
a phase.