# EARTH’S PLACE IN THE UNIVERSE REVOLUTION, ROTATION, & LOCATION.

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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 EQUATOR NORTHERN HEMISPHERE 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 Sentence