1. Description of the moon phases

The revolution of the Moon around the Earth makes the Moon appear as if it is changing shape in the sky. This is caused by the different angles from which we see the bright part of the Moon's surface. These are called "phases" of the Moon. Of course, the Moon doesn't generate any light itself; it just reflects the light of the Sun. The Moon passes through four major shapes during a cycle that repeats itself every 29.5 days. The phases always follow one another in the same order.

Today's Moon Phase by the U.S. Naval Observatory

The moon phases were understood as early as 500 BC by the Greeks. The key clue is that the phase of the Moon correlates with its angular distance from the Sun. For instance, the Moon is in its crescent phase when it is near the Sun in the sky but full when it is opposite the Sun. The Greeks realized this implies the Moon is a solid sphere, in orbit about the Earth, half of which is always illuminated by the Sun.

In the figure above you are looking down on the Earth's North Pole. The Earth spins counterclockwise (in 24 hours), and the Moon orbits counterclockwise (in 27 days). The fraction of the Moon's sunlit hemisphere which we can see from Earth determines the lunar phase at any time. We see a "full," "crescent," or dark ("new") Moon depending on the angle between the Sun and Moon as viewed from Earth.

Waxing Crescent Moon
"Waxing" means growing and refers to
the size  of the illuminated part of the moon that is increasing.

Waxing Gibbous Moon

Full moons are generally a poor time to conduct astronomical observations, since the bright reflected sunlight from the moon overwhelms the dimmer light from stars.
 

Waning Gibbous Moon
"Waning" means shrinking.
When the the Moon is said to be waning, we see a little less of the Moon each day until it completely disappears when the Moon is New.

Waning Crescent Moon
 

• Blue Moons
  There are also months with two full moons. The second full moon in a month is known as a blue Moon. Because this happens fairly infrequently, it has resulted in the expression "once in a blue moon."
   
• Months without a full moon
  There are months in which no full moons occur. For example, there was a full moon at 18:25 universal time on Feb. 28, 1991. This means there was no February full moon in east Asia and the Pacific, where it was already March. Years in which February lacked a full moon are 1809, 1847, 1866, 1885, 1915, 1934, 1961, 1999, 2018, 2037, 2067, 2094 (Meeus 1995, Odenwald)
  
  
• Moon rise times
  The New Moon always rises at sunrise.
  The first quarter Moon rises at noon.
  The Full Moon rises at sunset.
  The last quarter Moon rises at midnight.
  Moonrise takes place about 50 minutes later each day than the day before.
   
• Today's moon phase screensaver
  With the StarMessage screensaver you can see the current moon phase inside the stars of the night sky. If you are interested in the current moon phase I recommend that you download the free trial version of the program. You can click here get it »
   

Buy now for only $12.95

- or -

• Lets you write your name, your wishes, or your love messages with the stars of the night sky.
• Shows the current moon phase.
• Notifies you about the upcoming full moon and the full moon name and percent of the moon illuminated.
• Falling stars might make your wishes come true.
• Calms you with tender sounds of ocean waves, birds, lullabies.
• Shows famous quotes of love, peace, wisdom and humor.
• Is easy to install or to remove.
• Carefully engineered, to use minimum disk and memory space from your computer. It does not overload your computer.
• And much more ... »