Rotation and Orbits | Introduction
Introduction
Earth, like all the planets in our solar system, is in constant motion. All of the planets revolve or orbitThe path followed by a body (such as a planet) in its travel around another body (such as the Sun). around the Sun. An orbit is when one object in the universe goes round another one without touching it. For Earth, it takes about 365 days to complete one orbit around the Sun. Without Earth's rotation and orbit, the world would be a far different place. The rotation gives Earth its night and day. That allows the many life forms on Earth to remain at a comfortable temperature, warming during the sunlight hours and cooling down at the night. It affects the direction of wind and the ocean's daily tides. The orbit and tilt of rotation also give Earth its four seasons.
All the planets in the solar system also rotateTo turn around on an axis or center., or spin, as they orbit the Sun. On average, Earth rotates once every 24 hours—or more precisely, 23 hours, 56 minutes, 4.091 seconds. The complete rotation of an object with respect to the stars is called a siderealThe system of time to measure a day based on the motion of the stars. (pronounced sy-DEER-ee-awl) day.