Why does the Moon have Phases?
The new moon is essentially invisible because it is between the earth and sun and therefore lost in the glare of the sun. Even on day 2 or 3 it is tough to spot the moon because it is just the tiniest sliver and still very close to the sun. 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.
The first and last quarter moons mark the halfway points between the new moon and full moon. The first quarter moon is illuminated on the right hand side. The last quarter moon is illuminated on the left hand side. It seems conflicting to call a half full moon first of last quarter, but the quarter refers to the position of the moon in the sky, not it's phase. A quarter moon is one quarter of a full circle (90 degrees) away from the sun.
The lighted part of the Moon always points the way to the Sun. This means that a waxing crescent moon in the western sky at sunset has the lighted part on the right which is the direction of the Sun. The sequence of the lunar phases always proceeds with the lighted part of the Moon growing from right to left until the moon reaches full. After full moon, the light recedes from right to left until new moon.
The line boundary between dark and light on the Moon is called the terminator. It is rarely an even line because the surface of the Moon is not smooth. The terminator is closest to a straight line at first and last quarter. Librations affect exactly what portion of the face of the Moon is facing the Earth, during first and last quarter phase, the terminator's exact location may vary. This is illustrated when the terminator does not line up with the Moon's meridian at first and last quarter. In other words, you'd think that during first and last quarter when the Moon is half full, that the meridian (the imaginary line which runs from north to south on the Moon,) would be right on the terminator, but it isn't so. In fact the terminator can be almost 8 degrees off to either side of the meridian.The StarrySkies Lunar Eclipse Pages
Total Lunar Eclipse: Second Moon Show of the Year takes place November 8
What is a Lunar Eclipse
Why we don't have a Lunar Eclipse every month
Rating a lunar eclipse - the Danjon Scale
Photographing a Lunar Eclipse
Myths and Lore about Lunar Eclipses
The Lunar Eclipse that Saved Christopher Columbus
Moonstats - Lunar Vital Statistics
Why we see only one side of the Moon - librations
Moon Tales: The Night the Moon fell - 1939 Springfield, Missouri
Moon Tales: When the Moon saved the Sun - New York 1835
Moon Trees - Have you got one in Your Town?
Multimedia Moon - Images and Video clips of the Moon
3D Moon - Catch the Moon in 3D (note: you will need 3D glasses)
South Polar The Sun Asteroids Comets Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto
Copyright © 1995 - 2008
Kathy Miles, Author, and Chuck Peters, Systems Administrator
URL reveals our email address after you solve a reCAPTCHA (image containing two words).