Cycles and Interactions Chapter 4 Lesson 4
 Earth is the third planet from the sun, our nearest star, orbiting at
an average distance of 150 million kilometers.
 The Earth spins in space on its axis.
 The Earth’s spins means that its axis extends from the North Pole
to the South Pole. The Earth spins around this stationary line in a
west to east direction. The spin is called a rotation. The Earth
completes one rotation every twenty-four hours.
 The earth rotates from west to east.
 At any time, half of the planet is facing the sun while the other half
of the Earth is turned away from the sun. The half that is in
sunlight experiences day, and the half that is in darkness
experiences night.
 Because the Earth rotates, all parts of the planet experience both
night and day in each twenty-four-hour rotation.
 The Earth is moving in a path around the sun in a path called a
orbit. This orbit, often described as an ellipse, resembles a very
slightly flattened circle.
 It takes the Earth approximately 365 days to complete one orbit,
or revolution, of the sun. This time period is defined as one year.