Third planet in distance outward from the Sun. Believed to be
about 4.56 billion years old, it is some 149,600,000 km
(92,960,000 mi) from the Sun. It makes one revolution, or one
complete orbit of the Sun, in about 365.25 days. As it revolves,
it rotates on its axis once every 23 hours 56 minutes 4 seconds.
The fifth largest planet of the solar system, it has an
equatorial circumference of 40,076 km (24,902 mi). Its total
surface area is roughly 509,600,000 sq km (197,000,000 sq mi),
of which about 71% is water. Earth's atmosphere consists of a
mixture of gases, chiefly nitrogen and oxygen. Its only natural
satellite, the Moon, orbits the planet at a distance of about
384,400 km (238,900 mi). Earth's surface is traditionally
subdivided into seven continental masses: Africa, Antarctica,
Asia, Australia, Europe, North America, and South America. These
continents are surrounded by four major bodies of water: the
Arctic, Atlantic, Indian, and Pacific oceans. Broadly speaking,
Earth's interior consists of two reg