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EARTH’S PLACE IN THE
UNIVERSE
REVOLUTION, ROTATION, &
LOCATION
STARTER
Which statement describes the motion of Earth around the sun?
A. The speed of Earth is constant regardless of its distance from the sun.
B. The speed of Earth is constant because the distance remains the same between
Earth and the sun.
C. Speed increases the farther Earth is from the sun and decreases the closer it is
to the sun.
D. Speed increases the closer Earth is to the sun and decreases the farther it is
from the sun.
THE SUN
Center of our solar system
Source of all energy in our solar
system
Moves as planets tug on it so it orbits
the solar system’s midpoint or
barycenter
BARYCENTER
Point between two objects where they balance
each other
barycenter animation
MOVEMENTS OF EARTH
Revolution: The movement of the
Earth around the sun.
The Earth moves around the Sun constantly
at an average speed of 106,000 km/hr.
Revolution (or Orbital Period) = 365.24 days
MOVEMENTS OF EARTH
Rotation: The movement of the
Earth as it spins on its axis.
 1 rotation = 24 hours
 side facing sun = daytime
 side facing away from sun = nighttime
 creates the “setting” and “rising”
appearance of the sun
THE REVOLVING EARTH
Because of the elliptical shape of the
orbit, the earth is not always the
same distance from the sun
(perihelion & aphelion)
THE REVOLVING EARTH
The “tilt” of Earth’s axis is about
23.5 degrees
As the earth revolves around the sun,
its point of axis does not change –
always points to Polaris
(North Star) for now
PRECESSION
Change in direction of axis, without any change in tilt
Changes stars near the Pole but does not affect seasons (angle
stays same)
Like a spinning top
Polaris will not always
be the North Star
Precession video
THE REVOLVING EARTH
When the point of axis is TOWARD the
Sun
Northern Hemisphere has longer periods of
daylight & warm temperatures (summer)
Southern Hemisphere has shorter periods
of daylight & cooler temperatures (winter)
THE REVOLVING EARTH
When the point of axis is AWAY from the
Sun
Southern Hemisphere has longer periods of
daylight & warm temperatures (summer)
Northern Hemisphere has shorter periods
of daylight & cooler temperatures (winter)
NORTHERN & SOUTHERN
HEMISPHERES
NORTHERN HEMISPHERE
EQUATOR
SOUTHERN HEMISPHERE
THE REVOLVING EARTH
http://www.classzone.com/books/earth_science/terc/content/visualizations/es0408/es0408page0
1.cfm?chapter_no=visualization
NUTATION
Wobbling around the axis
Changes the angle by ½ degree one way or the other
Occurs over 18 year period
Caused by moon
Slight decrease or increase of seasons
VOCABULARY CARDS
Word
Definition
Picture
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