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Moon Phases Diagram

Moon Phases Simplified

It's probably easiest to understand the moon cycle in this order: new moon and full moon, first quarter and third quarter, and the phases in between. 

As shown in the above diagram, the new moon occurs when the moon is positioned between the earth and sun. The three objects are in approximate alignment (why "approximate" is explained below). The entire illuminated portion of the moon is on the back side of the moon, the half that we cannot see. 

At a full moon, the earth, moon, and sun are in approximate alignment, just as the new moon, but the moon is on the opposite side of the earth, so the entire sunlit part of the moon is facing us. The shadowed portion is entirely hidden from view. 

The first quarter and third quarter moons (both often called a "half moon"), happen when the moon is at a 90 degree angle with respect to the earth and sun. So we are seeing exactly half of the moon illuminated and half in shadow. 

Once you understand those four key moon phases, the phases between should be fairly easy to visualize, as the illuminated portion gradually transitions between them. 

An easy way to remember and understand those "between" lunar phase names is by breaking out and defining 4 words: crescent, gibbous, waxing, and waning. The word crescent refers to the phases where the moon is less that half illuminated. The word gibbous refers to phases where the moon is more than half illuminated. Waxing essentially means "growing" or expanding in illumination, and waning means "shrinking" or decreasing in illumination. 

Thus you can simply combine the two words to create the phase name, as follows:
After the new moon, the sunlit portion is increasing, but less than half, so it is waxing crescent. After the first quarter, the sunlit portion is still increasing, but now it is more than half, so it is waxing gibbous. After the full moon (maximum illumination), the light continually decreases. So the waning gibbous phase occurs next. Following the third quarter is the waning crescent, which wanes until the light is completely gone -- a new moon.

Let's have a look!!

The 8 phases of the Moon

             

Phase 1 - New Moon - The side of the moon that is facing the Earth is not lit up by the sun. At this time the moon is not visible. 

Phase 2 - Waxing Crescent - A small part (less than 1/2) of the moon is lit up at this point. The part that is lit up is slowly getting bigger.

Phase 3 - First Quarter - One half of the moon is lit up by the sun at this point. The part that is lit up is slowly getting bigger.

Phase 4 - Waxing Gibbous - At this time half of the moon is lit up. The part that is lit is slowly getting bigger. Waxing means to slowly get bigger.

Phase 5 - Full Moon - The side of the moon that is lit up by the sun is facing the Earth. The entire moon is lit up at this point.

Phase 6 - Waning Gibbous - The moon is not quite lit up all the way by sunlight. The part of the moon this is lit is slowly getting smaller. Waning means to slowly get smaller.

Phase 7 - Last Quarter - Half of the moon is lit up but the sun. The part that we can see lit up is slowly getting smaller.

Phase 8 - Waning Crescent - A small part of the moon is lit up at this point. It is getting smaller by the minute.

The Phases of the Moon

Phases of the Moon

What is the phase of the moon?
The changing shape of the bright part of the Moon that we see is called its phase. 

What causes part of the Moon to be lit up?
The moon is illuminated because it reflects the light from the sun. The part of the moon facing the sun is lit up. The part facing away from the sun is in darkness.

What causes the different phases of the Moon?
The phases of the Moon depend on its position in relation to the Sun and Earth. As the Moon makes its way around the Earth, we see the bright parts of the Moon's surface at different angles. These are called "phases" of the Moon.
 

What are the different phases of the Moon called?
The phases of the moon work in a cycle starting with the new moon.

There are eight phases of the moon

The phases are named after how much of the moon we can see, and whether the amount visible is increasing, or decreasing each day.

 

It takes our Moon about 29.5 days to completely cycle through all eight phases. This is known as a Lunar month

The Phases of the Moon

As the moon circles the Earth, the shape of the moon appears to change; this is because different amounts of the illuminated part of the moon are facing us. The shape varies from a full moon (when the Earth is between the sun and the moon) to a new moon (when the moon is between the sun and the Earth).