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Our Solar System
• Solar System – Collection of 8 planets and
their moons in orbit around the sun
• The Sun is the center of our solar system
• All of the planets including the planet earth
move around the sun in paths…..called orbits
• It takes our earth one full year or 365 days to
orbit the sun
Our Solar System
• As the earth moves around the sun the moon
also orbits the earth
• We usually say that the moon takes 29.5 days
to orbit the earth (1 month)
• Astronomers figured this out a long time ago
and have therefore predicted the phases of
• Note: NASA says it only takes 27.3 days for the
moon to orbit the earth
• The moon is just a very large rock orbiting the
• It is not like the sun that generates it’s own
• In fact the moon does not generate any light
• The reason we see the moon in the day/night
is because if reflects the light from the sun
• The moon is like a big round mirror that reflects
light…..from the sun
• No matter what phase the moon is in, half of it is
always facing the sun. That half is always lit up
and is the half that we see here on earth.
• The other half of the moon is facing away from
the sun and is always in darkness….hence the
phrase: The dark side of the moon
• Question: If half of the moon is always lit up
by the sun. Why does it change to different
shapes throughout the month?
• Answer: The moon never really changes it’s
shape! But as it orbits the earth, how we see
it from our position on earth, changes in
relation to the moons position, relative to the
Phases of the Moon
• In other words – as the moon moves in its
orbit, it just looks like different parts of it are
lit up and these are called the Phases of the
• Note: We will examine this question in
greater detail during our group science
Phase 1 – New Moon
• There are 8 phases of the moon, starting with
one that is very hard to see.
• The first phase of the moon is called the “New
• This occurs when the moon is in between the
sun and the earth
Phase 1 – New Moon con’t
• The lighted side of the moon faces away from
the earth. So the moon that we see looks very
dark and hard to detect with our eyes
• You can’t see a new moon because the sun’s
rays cannot reach any part of the moon (from
earth’s view) to light it up.
• The moon is
approximately ¼ the
size of the earth
• However the moon has
less density than the
earth…..if they were the
• The first person to walk
on the moon was Neil
Armstrong…on July 20th,
• They travelled from
earth to the moon in 3
• His first step was with
his left foot
• “That’s one small step for man, one giant leap
Phase 2 - Waxing Crescent Moon
• Waxing… means growing (to its full moon
• A sliver of brightness is visible on the right.
• The dark part of the moon is still what is most
visible to Earth at this point.
Phase 3 - First Quarter or Waxing
• The moon is to the left of the earth and sun
• This is what we call a half moon
• It looks like half of the moon but really it is
only a quarter because we only see half of the
moon even when it is a full moon.
• Here the right side of the moon appears
lighted and the left side of the moon appears
Phase 4 - Waxing Gibbous Moon
• The word Gibbous means “more than half full”
• More than half of the moon can be seen on
the right side
• The bright surface is larger than the Half-
Moon but smaller than a full Moon.
Phase 5 - Full Moon
• The sun, earth, and
moon are lined up, with
the lighted side of the
moon facing the earth
• It happens 2 weeks
after the new Moon
• We call it a full moon
even though it is only
the front half of the
moon that is lit up
• The moon has no atmosphere, so it doesn’t
have weather. There is no wind or rain on the
moon. Because of this, the footprints on the
moon left by the astronauts will stay for
millions of years.
• Atmosphere of Earth: Is a layer of gases
surrounding the planet Earth that is retained
by Earth's gravity
• Clouds are formed in earths atmosphere…not
so on the moon
• Earths atmosphere protects us from extreme
heat and cold….not so on the moon
• Earths atmosphere protects us from being hit
by meteors…not so on the moon.
• The surface of the moon isn’t flat. It has lots of
craters. They were formed by meteorites
hitting the moon.
Phase 6 - Waning Gibbous Moon
• Waning moon…means that the moon is
decreasing in size
• As the moon grows smaller, away from being a
full moon, it is called a waning gibbous moon.
• The right edge of the moon appears dark or
invisible and more than half of the moon can
now be seen on the left side
Phase 7 - Last Quarter Moon or
• The moon is to the right of the earth and sun
• This is also called a half moon
• This time the left side of the moon appears
lighted and the right side of the moon appears
dark (Opposite the First Quarter moon)
Phase 8 - Waning Crescent Moon
• A sliver of brightness is
visible on the left side
of the moon….opposite
the waxing crescent.
• The dark part of the
moon is still what is
most visible to Earth
but is now on the right
side of the moon.
Moon Phase Summary
• The complete phases of Moon are from the
new moon to the full moon and then back to
new moon again.
• When the Moon is changing from new moon
to full moon, it said to be waxing, or growing
Moon Phase Summary con’t
• When the Moon is changing from full moon to
new moon, it is said to be waning, or growing
• During waxing, the right side of the Moon is
• In contrast, during waning the left side of the
Moon is illuminated.
• A lunar month is the amount of time it takes
for the Moon to pass through each of its
phases (new moon, half, full moon), and then
return back to its original position
• Although we give names to certain phases,
each night the change is actually gradual.
• The gravitational pull of the Moon, though
less than that of the Earth, is strong enough to
causes water in the oceans to shift slightly
toward the moon as it passes overhead. This is
seen as a rise or fall in water levels along the
oceans shores which we call the tide.
• The level water on the beaches around the
world rise and fall every twelve hours.
• When the water level is the highest it is called
• When it is the lowest it is called low tide.