Why does the Moon keep changing its shape ?

The alignment of the Moon and the Sun determines the phase of the Moon.

The waxing crescent moon grows till it is about half full in the phase we call first quarter. From there it grows to full moon and then begins to shrink back to third quarter, waning crescent and finally back to new moon.

Phases of the moon as seen in the Northern Hemisphere

Phases of the moon as seen in the Southern Hemisphere

The images below show the different phases of the moon in one Lunar month for the Northern Hemisphere

Ss u n	Waning crescent	Last quarter (Half Moon)	Waning gibbous
	Day 25	Day 21	Day 17
		The Moon is 90 degrees west of the sun

	New Moon Day 0   The angular distance of the sun and moon is small, less than a few degrees.				Full Moon Day 14   The moon is 180 degrees from the sun.
1

	Day 3	Day 7	Day 10
	Waxing crescent	First quarter or Half Moon	Waxing gibbous
		The Moon is 90 degrees east of the Sun

When the bright part is getting bigger, the Moon is waxing. When it is getting smaller, the Moon is waning. When the Moon is more than half-lit, it is called a gibbous Moon. When the moon is less than half-lit, it is called a crescent Moon.

Take the Moon Challenge Drag the Moons to their correct places in lunar cycles. Why does the moon look different in the southern hemisphere? Moon Calendar showing both hemispheres

Times for the main phases

Introduction to the different moon phases