Learn about Earth

Earth is the third planet in distance outward from the Sun. It is the only planet in the solar system that has conditions suitable for life, at least as known to modern science.

The average distance of the Earth from the Sun is about 149,573,000 km (92,960,000 miles). The planet orbits the Sun at a speed of 29.8 km (18.5 miles) per second, making one complete revolution in 365.25 days known as a year. As it revolves around the Sun, the Earth spins on its axis (23.5 degrees tilted) and rotates completely once every 23 hours 56 minutes 4 seconds.

The fifth largest planet of the solar system, the Earth has an equatorial circumference of 40,076 km (24,902 miles), an equatorial radius of 6,378 km (3,963 miles), a polar radius of 6,357 km (3,950 miles), and a average radius of 6,371 km (3,960 miles). The planet's total surface area is roughly 509,600,000 square km (197,000,000 square miles), of which about 29 percent, or 148,000,000 square km (57,000,000 square miles), is land. The balance of the surface is covered by the oceans and smaller seas. The Earth has a mass of 5.976 1027 grams (or roughly 6 1021 metric tons) and a mean density of 5.517 grams per cubic cm (0.2 pound per cubic inch).

The Earth has a single natural satellite, the Moon. The latter orbits the planet at a average distance of slightly more than 384,400 km (238,870 miles). Its existance is the very cause of low and high tides.