Transcript Earth and the Moon in Space

What are
the motions
of the
Earth?
Earth and the Moon in Space
• The Earth and the moon are part of
the sun’s planetary system.
• Pulled by the sun’s gravity, the
Earth-moon system revolves or
travels in a closed path around the
sun.
• It is inertia that keeps the Earth in
motion around the sun.
Earth in Space
As Earth orbits the sun, it
rotates or spins on its
axis.
The axis is an imaginary
line that passes through
Earth’s center and its
North and South Poles.
Earth’s axis is tilted
about 23 ½ °.
Earth’s Rotation
The North Pole of
Earth always points
toward Polaris or the
North Star. It is the
brightest and last star
of the Little Dipper.
Earth’s Rotation
Because of the Earth’s
counterclockwise rotation, the Sun
appears to rise in the East and set in
the West. The Sun’s motion is
East to West.
The Length of the Day
• Earth’s rotation results in day
and night. When a location on
Earth faces the sun, it is day in
that place. When that location
faces away from the sun, it is
night.
• A day is defined as the time
that it takes a planet to rotate
once on its axis.
Earth’s Revolution
A revolution is the movement of a
planet or other body orbiting another
body.
One complete revolution of the Earth
around the Sun takes 365 ¼ days.
What is the difference between
orbit, revolution, and rotation?
A planet rotates on its own axis
and revolves around the sun in a
path called an orbit.
What causes the seasons?
The tilt of the Earth is responsible
for the seasonal differences we
see and feel throughout the year.
Solstices and Equinoxes
Spring Equinox ~ March 21
Summer Solstice ~ June 21
Fall Equinox ~ September 22
Winter Solstice ~ December 21
The dates of the equinoxes and solstices are
only approximate dates. The actual length of a
year is about 365 ¼ days. We have to add an
extra day to a year every four years to keep the
seasons synchronized with the Earth’s
revolution (leap year).