AIM: The Earth Sun System Do Now: What determines the length of the day? What determines the length of year?

- This makes object appear to rise in the east and set in the west I. Earth’s Motions 1. Rotation: the turning or spinning of an object on its axis. - rotates 15o/hr. (24 hours) - counterclockwise - rotates West to East - creates night and day - This makes object appear to rise in the east and set in the west

What part of Earth’s imaginary grid system is connected to time? Mean solar day: looks at the sun and describes the time interval from one noon (sun’s highest point) to the next (24 hours). Sidereal day: time it takes Earth to make one complete rotation (360º) (23 hours, 56 minutes, 4 seconds) What happens to those missing 3 min and 56 seconds? Leap Year! How long is a day? What part of Earth’s imaginary grid system is connected to time? LONGITUDE

Earth’s rotation is proved by the motion of Foucault's Pendulum. When placed at the North/South Pole, the pendulum would appear to move in a circle. This apparent motion is caused by the Earth rotation. Do not copy *The pendulum always knocks down the pegs opposite each other in order

2. Revolution (orbit): motion of an object around a point in space. - gives us our year Earth is closest (perihelion) to the sun in winter. Earth is farthest (aphelion) from the sun in the summer.

3. Tilt Earth is tilted as it revolves around the sun. tilted by 23.5 degrees. creates different hours of daylight at different latitudes.

This reverses in the winter. Because of Earth’s tilt... The North pole receives 24 hours of light and the South pole receives 24 hours of darkness in the summer. This reverses in the winter. T H E S U N

II. Reasons for the Seasons - tilt and revolution gives us the seasons. We are tilted towards the Sun in the Summer We are tilted away from the Sun in the Winter

Closure: Obtain an “Earth’s Motion” worksheet from the back TOP bin. 2. 3. 4. 5. 6. 7. 8. 9. 10. 4 2 4 3 3 4 4 3 4