Gravity causes planets to orbit stars in ellipses, with those closer to the star moving faster. The moon's gravity also causes ocean tides on Earth. Eclipses occur when the sun, Earth, and moon align, blocking light. The phases of the moon are caused by the changing portion of the moon illuminated by the sun as it orbits Earth monthly.

1. Planetary Motion, Eclipses, Tides, & Phases of the Moon

2.  Rotation – the spinning of a body (an object)
on its axis
 Orbit – the path that a body takes as it travels
around another body
 Revolution – one complete trip around an
orbit.

3.  Johannes Kepler – ancient astronomer that
studied how planets move.
 1st Law – planets do not move in a circle; they
move in an elongated circle called an ellipse.
 2nd Law – planets move faster when they are
closer to the sun.
 3rd Law – planets that are farther from the sun take
longer to orbit the sun

4. Pull of gravity
(like a shorter
string)
Faster orbit
Pull of gravity (like a
longer string) slower
orbit
http://www.windows.ucar.edu/tour/link=/physical_science/physics/mechanics/o
rbit/ellipse.html

5.  What allows planets close to the sun to move
faster and also to keep bodies (like the moon)
in orbit? Gravity

6.  24 hours – the time required for Earth to
rotate once on its axis
 It takes 23 hours & 56 minutes.
 Axis – the imaginary line that runs from the North
Pole to the South Pole
▪ Earth is tilted at 23.5
 Earth spins in which direction?
Counterclockwise. Therefore the sun rises in
the east and sets in the west.

7.  Seasons are caused by Earth’s tilt and its rotation
around the sun.
 Equinox – occurs when the sun is directly above the
equator. The number of daytime hours and
nighttime hours are equal.
 Vernal equinox – March 21st is the beginning of spring.
 Autumnal equinox – Sept. 23rd is the beginning of Fall.
 Solstice – when the sun is the furthest from the
equator.
 Summer solstice – beginning of summer – June 22nd
 Winter solstice – beginning of winter – Dec. 22nd

9.  Solar Eclipse – when the moon comes in
between the Earth and the Sun
 The shadow of the moon falls on part of the
Earth

10. http://www.iayc.org/eclipse/sofi_composite_2_crop.jpg

11.  Lunar Eclipse – when the Earth comes in
between the sun and moon.
 The shadow of the Earth falls on the moon.

13.  Tide - The rise and fall of
the water level in the
oceans caused by the The Moon is pulling the
force of gravity Water on this side.
between the Earth and
the moon
 High Tide – when water
facing the moon and
water on the opposite
side of the moon bulges.
The moon is pulling the Earth
 Low Tide – happens Away from the water on this
between the 2 high tides side.

14.  Spring tide – both the
sun and moon pull on
the ocean water (High
tide is more extreme.)
 Neap tide – the sun
and the moon pull
opposite of each other
(High tide is less
extreme.)

15.  Satellite – any natural or man-made object
that revolves around a planet
 The moon is a satellite of Earth
 Earth only has one satellite.
 Some planets have several, some have none.
 Luna – the name of the Earth’s moon

16.  Rocks from the moon have been found to be
4.6 billion years old.
 The moon has no atmosphere, so there is no
wind & no weather.
 The surface therefore remains unchanged –
Neil Armstrong’s footprint is still there!
 The moon appears to be the largest object in
our night sky, but that’s only b/c it’s the
closest.

17.  It is only ¼ the size of Earth.
 The sun is 400 times larger than the moon
even though the sun appears smaller in our
sky.
 The moon looks bright in the sky, but it does
not give off its own light. The moon reflects
light from the sun like a giant mirror.
 We only see the same side of the moon b/c
the moon rotates on its axis and revolves
around the Earth at the same speed.

18.  The Moon seems to change shape as
different parts of the moon are lit by the sun.
 These are called phases of the moon.
 Demonstration

19.  Full Moon - when the moon's disk is light
 Gibbous Moon - when we can see roughly ¾ of the
moon's disk
 Quarter Moon – (half moon) when we can see one half
of the moon's disk (one-quarter of the entire moon's
surface)
 Crescent Moon - when we can see only a sliver of the
moon's disk (the side of the moon facing us)
 New Moon - when the moon's disk is dark (and
invisible to us)
 Waning Moon - when the moon seems to be getting
smaller
 Waxing Moon - when the moon seems to be getting
bigger