More Moon and Venus There’s a thin crescent Moon in the western
sky this evening. It stands a little above Venus, the radiant
“evening star.” Sunlight illuminates only about a tenth of the
lunar hemisphere that faces our way — a bare sliver against the
fading color of twilight. As the nights pass by, though, that
sliver will grow larger as the Sun casts its light on an
increasing fraction of that hemisphere of the Moon. It’ll light
up exactly half of the Moon just about the time the clock
strikes midnight on New Year’s Eve — a point in the Moon’s cycle
known as first quarter. The Moon will continue to grow fatter
over the following week, as it passes through its “gibbous”
phase — when the Sun illuminates more than half of the visible
lunar surface, but not quite all. That phase ends when the Moon
is “full” on the night of January 8th. After that, the phases
run in reverse, with darkness engulfing a larger slice of the
lunar disk until the Moon is “new” on the night of the 22nd.
That whole cycle is the result