2. Rotation and Revolution What causes night and day? What causes the seasons to change?

3. Rotation What does Rotation mean? Rotation occurs when something is spinning around an axis. What are some examples of things that rotate? Tops, Ballerinas, Figure skaters, cyclones, Tornadoes, a merry-go- round, Earth How do we know that the Earth rotates? (evidence!) 1.Star trails: trails made with time exposure, circular paths that occur because the planet is moving and not stationary. 2.Coriolis Effect: Winds curve because of the Earth’s rotation. 3.Ocean currents curve clockwise in the northern hemisphere, and counterclockwise in the southern hemisphere. 4.Foucault pendulum: The movement of a pendulum. It does not actually move, it is the Earth moving that causes the pendulum to appear to change the direction of its swing.

4. Axis and rate of rotation Earth rotates on its axis, which is tilted at 23.5 o Earth’s axis points to Polaris the “North Star” 360 o rotation = 24 hours Therefore, the Earth rotates at a rate of 15 o per hour (or 1 o every 4 minutes) Effects of rotation:

5. This is why we have different standard time zones. Each time zone is centered on a longitude line that is divisible by 15 o Each of these are know as time meridians. We start standard time zones at the Prime Meridian. So how do we know what day it is when we cross time zones? The International Date Line at 180 o represents the longitude line where the date changes.

6. Night and Day What causes night and day? The side of the Earth that is facing the sun has daylight, the side of the Earth away from the sun has night. It takes 24 hours for the Earth to complete one rotation. The Earth is tilted on it’s axis at a 23.5 degree angle. The Earth’s tilt is always in the direction of the North Star. What is another name for the North Star? Polaris This tilt is what causes our days to get longer in the summer and shorter in the winter. Because of the Earth’s rotation the sun appears to rise in the east and set in the west.

7. What does Revolution mean? Revolution is the movement of Earth around the sun. How do we know the Earth revolves around the sun? 1.Changing views of constellations 2.parallax: apparent shift in position of stars Revolution

8. Path and rate of Revolution How many days are in 1 year? 365.24 days How many degrees are in a circle? 360 degrees Earth moves about 1 o around the sun every day http://www.classzone.com/books/earth_science/terc/content/visualiza tions/es0408/es0408page01.cfm?chapter_no=visualization The equinox is the time of year when daytime and nighttime are equal. (vernal & autumnal) Summer solstice - This day has the longest period of daylight (max tilt towards sun) Winter solstice - The shortest day of the year (max tilt away from sun)

9. Seasons What two things cause the difference in the seasons? 1.The angle of the sun’s rays 2.The length of the days There are two kinds of rays from the Sun: 1.Direct- occurs when Earth is tilted toward the Sun 2.Indirect-occurs when Earth is tilted away from the Sun In the Summer, we get the direct rays from the sun and the days are longer. (But we are farther away from the Sun) In the Winter, we get indirect rays from the Sun and the days are shorter. (But we are closer to the Sun) Why does this happen?

10. Checkpoint! 1.The Foucault pendulum proves the Earth’s… a)Rotation b)Revolution c)Parallax d)Time meridian 2. The speed of rotation at the north pole is? a)0 km/hr b)1300 km/hr c)1690 km/hr d)Cannot be found 3. Which is NOT an effect of rotation? a)seasons b)Measuring time c)Time meridian d)Date line 4. How many degrees on longitude separate each time meridian? a)0 degrees b)5 degrees c)10 degrees d)15 degrees 5. T or F: The spinning of Earth on its axis is called