Our Planet, the Earth

The Home of Mankind: the Earth

The Earth is the third planet from the Sun in the Solar System. It is the fifth largest planet. The Earth is the terrestrial planet with the largest diameter, mass and density. The Earth is the only known planet in the Universe where life exists. According to current theories, the Earth formed 4.57 billion years ago, and life appeared on its surface within one billion years.

The rotation and orbit of the Earth

While the Earth revolves around the Sun once, it rotates on its axis about 365.26 times. This period is called one year. The orbital velocity of the Earth is 30 km/s.
Our planet rotates (relative to the Sun) once every 24 hours.

The Earth in the Solar System

The Earth is located in the Solar System. The Solar System consists of the Sun,
the eight planets – one of which is
the Earth; the moons of the planets, asteroids and comets.

The Earth’s age: 4.5 billion years

Diameter: 12 756 km

Circumference: 40 075 km

Mass: 5.974 · 1024 kg

Average density: 5.52 g/cm3

Proportion of dry land and seas: 29.2% / 70.8%

Number of moons: 1

Surface gravity: 1 g (gravitational acceleration 9.81 m/s2)

Surface temperature: between –70 °C and +56 °C; 15 °C on average

Rotational period: 23 h 56 min (relative to stars)

Rotational velocity: 1674 km/h (at the Equator)

Orbital period: 365.25 days

Average orbital speed around the Sun: 107 218 km/h

Escape velocity: 11.19 km/s

Scientists gathered information about the inner structure of the Earth by studying seismic waves, which show that it is layered in spherical shells: the crust, the mantle, the outer and the inner core. The crust and the outermost, partly molten layer of the mantle constitute the rocky layer (lithosphere). The Earth is surrounded by the hydrosphere, the atmosphere and the biosphere.

About two thirds of the surface of Earth is covered by water; the remaining one third is covered by land mass.
The atmosphere of the Earth is made up mainly of nitrogen (78%) and oxygen (21%). Other important components are water vapour, argon and carbon dioxide.