In the spring and fall, each hemisphere receives similar amounts of light.
Whichever hemisphere is tilted closer to the sun experiences summer, while the hemisphere tilted away gets winter. This axis of rotation is tilted 23.4 degrees away from the plane of Earth's orbit around the sun, giving us seasons. Astronomers define this distance as one astronomical unit (AU), a measure that serves as a handy cosmic yardstick.Įarth rotates on its axis every 23.9 hours, defining day and night for surface dwellers. During this circuit, our planet is an average of 93 million miles away from the sun, a distance that takes light about eight minutes to traverse. Though we can't feel it, Earth zooms through its orbit at an average velocity of 18.5 miles a second. Since our calendar years have only 365 days, we add an extra leap day every four years to account for the difference. Our dance around the sunĮarth orbits the sun once every 365.25 days. Find out the origins of our home planet and some of the key ingredients that help make this blue speck in space a unique global ecosystem. Earth is the only planet known to maintain life.
