1. Earth in Space

2. All planets REVOLVE around the sun. Revolution is the movement of one object around another. One revolution equals the time it takes to make one trip around the sun. One revolution for EARTH equals one year (365.25 days) Orbit is the path an object takes around another object

3. One rotation is the time a planet takes to make one turn on its axis. One rotation equals one day (24 hours) Most planets spin in a west to east motion except for Venus and Uranus which spin backwards (east to west). This is called Retrograde Motion. Uranus also spins on its side. All planets ROTATE on their axis. Rotation is the spinning of an object on its axis Axis is an imaginary line that passes through the object – an example is that Earth’s axis runs through its center and the north and south poles

4. **** Earth has seasons because its axis is tilted as it revolves around the sun **** Solstice – when the sun is farthest north or south of the equator – occurs in the summer and winter Equinox – when the noon sun is directly overhead at the equator – occurs in spring and fall

5. Gravity and Motion Inertia – tendency of an object to resist change in motion Newton’s First Law of Motion – object at rest will stay at rest and an object in motion will stay in motion ** Inertia and gravity keep Earth in orbit around the sun** Force – a push or pull Gravity – force that attracts all objects toward each other Law of Universal Gravitation – every object in the universe attracts every other object Mass – amount of matter in an object Weight – force of gravity on an object