Space The Moon National Geographic Society

About Moon Phases

The Moon's Orbit . It may help to know a little about the moon's orbit to understand what is happening during each of the moon phases. It takes the moon the same amount of time to orbit the Earth as it does to complete a full rotation on its axis i.e. approximately 27 Earth days. This orbit has been affected by the Earth's gravitational pull which has helped to slow the moon's orbit

Learn how the Sun's light creates the eight Moon phases, or shapes, that we see each night. See diagrams, examples and activities to explore the Moon's appearance and orbit.

As we know, Earth's orbit revolves around the sun and the moon orbits Earth. The moon is quottidally locked,quot meaning the moon is rotating on its own axis at the same rate it orbits Earth unlike Earth, which rotates at a different rate than it orbits the sun, hence we have both days and years.The tidal lock means the same hemisphere of the moon is always pointing at or visible from Earth.

Think of the phases labeled quotnew moon,quot quotfirst quarter,quot quotfull moon,quot and quotthird quarterquot as the numbers 12, 9, 6, and 3 on a clock, respectively. For those of us in the Northern Hemisphere, the moon travels in a counterclockwise orbit. Each of these primary moon phases marks a quarter of the lunar cycle and lasts only a moment.

There are eight main Moon phases New Moon This is when you can't see the Moon easily at all, because the part that is illuminated by the Sun is on the side of the Moon pointing away from Earth.This phase happens when the Moon is between the Sun and Earth. Because the Moon's orbit around the Earth is tilted by about five degrees, it's usually either above or below the Sun.

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 quotbetweenquot lunar phase names is by breaking out and defining 4 words crescent, gibbous, waxing, and waning. The word crescent refers to

A waning gibbous moon occurs when more than half of the lit portion of the Moon can be seen and the shape shrinks or quotwanesquot in size from one day to the next. The waning gibbous phase occurs between the full moon and third quarter phases. The last quarter moon or a half moon is when half of the lit portion of the Moon is visible after the

The last quarter phase sees the Moon once again half lit, but this time it is the opposite side from the first quarter. Finally, the waning crescent phase brings the cycle to a close, with just a thin crescent of light visible before the Moon returns to its new moon position, ready to start the cycle anew. The Editors of Encyclopaedia Britannica

The moon reaches the next phase at about day 10. It is at 135 between the Earth and sun and we can see about three quarters of the moon. This is called the waxing gibbous phase. After roughly 2 weeks, the moon is in line with the Earth which sits between it and the Sun at 180.

Phases of the Moon 4.9 - Understand the lunar phase cycle. We are familiar with looking at the Moon and seeing it change shape. Sometimes it is a thin crescent, sometimes half full and totally full. Sometimes we may see an outline of the remainder of the Moon. This effect is called 'Earthshine'. The full Earth is reflecting light back to