Earth spinning around once every 24 hours (rotation), resulting in day and night
Earth moving in a path around the Sun (revolution), resulting in one Earth year
the length of daylight and darkness varying with the seasons
weather changing from day to day and through the seasons
the appearance of the Moon changing as it moves in a path around Earth to complete a single cycle
The Sun and other stars appear to move in a recognizable pattern both daily and seasonally.
Earth's Sun is an average-sized star. The Sun is more than a million times greater in volume than Earth.
Other stars are like the Sun but are so far away that they look like points of light. Distances between stars are vast compared to distances within our solar system.
The Sun and the planets that revolve around it are the major bodies in the solar system. Other members include comets, moons, and asteroids. Earth' orbit is nearly circular.
Gravity is the force that keeps planets in orbit around the Sun and the Moon in orbit around the Earth.
Most objects in the solar system have a regular and predictable motion. These motions explain such phenomena as a day, a year, phases of the Moon, eclipses, tides, meteor showers, and comets.
The latitude/longitude coordinate system and our system of time are based on celestial observations.
Moons are seen by reflected light. Our Moon orbits Earth, while Earth orbits the Sun. The Moon's phases as observed from Earth are the result of seeing different portions of the lighted area of the Moon's surface. The phases repeat in a cyclic pattern in about one month.
The apparent motions of the Sun, Moon, planets, and stars across the sky can be explained by Earth's rotation and revolution. Earth's rotation causes the length of one day to be approximately 24 hours. This rotation also causes the Sun and Moon to appear to rise along the eastern horizon and to set along the western horizon. Earth's revolution around the Sun defines the length of the year as 365 1/4 days.
The tilt of Earth's axis of rotation and the revolution of Earth around the Sun cause seasons on Earth. The length of daylight varies depending on latitude and season.
The shape of Earth, the other planets, and stars is nearly spherical.
These motions explain such phenomena as the day, the year, seasons, phases of the moon, eclipses, and tides.
Gravity influences the motions of celestial objects. The force of gravity between two objects in the universe depends on their masses and the distance between them.
The orbit of each planet is an ellipse with the Sun located at one of the foci.
Earth is orbited by one moon and many artificial satellites.
Earth revolves around the Sun with its rotational axis tilted at 23.5 degrees to a line perpendicular to the plane of its orbit, with the North Pole aligned with Polaris.
During Earth's one-year period of revolution, the tilt of its axis results in changes in the angle of incidence of the Sun's rays at a given latitude; these changes cause variation in the heating of the surface. This produces seasonal variation in weather.
The characteristics of the planets of the solar system are affected by each planet's location in relationship to the Sun.
The terrestrial planets are small, rocky, and dense. The Jovian planets are large, gaseous, and of low density.