Rotation & Revolution http://studyjams.scholastic.com/studyjams/j ams/science/solar-system/day-on-earth.htm The study of the moon, Astronomy stars and other objects in space. Axis The imaginary line that passes through the Earth’s center and the North and South poles. 23.5° angle/tilt Rotation Earth’s rotation, or spin, on its axis (23.5) causes day or night. Night & Day • The Earth rotates on it’s axis every 23hrs and 56 mins (almost 24 hrs) • The sun shines on only ½ of the Earth at a time. – ½ of the Earth is experiencing night time. While the other ½ is in daylight! What Is Rotation? • For every complete rotation one day has passed. Earth spins counter- clockwise. Sunset from space Orbit –Earth’s path as it revolves around the sun. –Earth’s orbit is not circular. It revolves in an oval shape called elliptical •Revolution or orbit – The time it takes for the earth to make one complete revolution around the sun is called a year. One Revolution = 365.25 days or One Year - This is why we have a leap year every 4 years! Revolution Causes changes of the seasons? Seasons are caused by 1. Earth’s revolution around the Sun 2. the unchanging tilt of the Earth’s axis. Common Misunderstandings: Earth’s changing distance to the Sun does not cause seasons! The north pole tilts towards the sun It is Summer time in countries in the Northern Hemisphere. It is Winter time in countries in the Southern Hemisphere. One more time…We have seasons because: 1. The tilt of the Earth’s axis 2. The revolution of Earth around the Sun. .