The phases of the moon and eclipses were studied and understood as early as the
fourth century B.C.  Philosphers like Aristotle studied and wrote about these
phenomena.  The moon is always going through different phases, this is why it
always appears a different shape in the sky.  The moon is also going through
it’s own cycle, which is why it can be in different parts of the sky at
different times of day, sometimes out in the night and sometimes out in the day.
        The reason the moon changes it’s shape everytime it appears is because the moon
is not itself luminous.  The sun’s rays are what makes it illuminated.  Like the
earth, only half of the moon is in daylight at one time.  Depending on how much
of the moon’s daylight hemisphere is turned to our view we see the moon in
different shapes.  The way and the order the moon’s shape appears in the sky can
be explained by  8 phases.
        The time when none of the moons daylight hemisphere can be seen is the first
phase, of the new moon.   Any time the shape of the moon is getting bigger, it’s
called the waxing stage.  The 2nd moon phase is called waxing cresent because
the moon is still a cresent shape.  The 3rd  is the first quarter phase, this is
where it is a half-moon.  The 4th is the waxing gibbous phase in which the moon
is greater than half a circle and still getting bigger.  The 5th is the full
moon in which the moon is  a perfect circle.  Any time when the moon’s shape is
getting smaller is called waning.  The 6th stage is called waning gibbous
because the moon is getting smaller but still bigger than a half-circle.  The
7th is the third quarter phase in which the moon is a semi-circle again.  The
8th is the waning cresent phase in which the moon is still getting smaller and
also a cresent shape.
        To grasp the moon’s phases even better it may help to try an experiment:
        Stand about six feet away from a bright electrical light outdoors at night and
hold a tennis ball in your hand.  If the ball is viewed from various sides,
portions of it’s illuminated hemisphere that are visible will represent the
phases of the moon.
 
 
 
 
 
 
 
 

Eclipses
        All eclipses have to do with the positions of the sun, moon and earth.

Solar Eclipse:  A solar eclipse is when the moon passes exactly between the
earth and the sun , temporarily hiding the sun from view.  This happens when the
moon is new and positioned on the line joining the earth and sun.
Lunar Eclipse:  A lunar eclipse is when the moon passes through the earth’s
shadow.  This will occur when the moon is full and the moon is directly in the
path of the sun to earth, because the sun has to be behind the moon to cast the
earth’s shadow onto it.

By Valerie Leussler Hr. 5

Abell, George O.  The Exploration of the Universe fifth edition;  Saunders
College Publishing, Chicago, 1987.