| Origin of name |
The name Earth comes from the Indo-European base 'er' from which similar names are derived in other European languages.
Earth Observation programme
Images of our planet from orbit are acquired continuously by several dedicated satellites. They have become powerful scientific tools to enable better understanding and improved management of the Earth and its environment.
|Surface gravity at equator||ms-2||9.798|
|Magnetic field at equator (x10-4)||T||0.305|
|Magnetic dipole moment (x1015)||Tm3||7.91|
|Tilt of dipole axis||°||11.7|
|Dipole field centre offset from planet centre (equatorial radii)||0.07|
|Number of natural satellites||1|
|Mean distance from the Sun (x106)||km||149.60|
|Mean distance from the Sun||AU||1.00|
|Sidereal orbit period||d||365.256|
|Sidereal rotation period||h||23.935|
|Length of day||h||24.000|
|Orbit inclination to Eliptic||°||0.000|
|Mean orbital velocity||kms-1||29.78|
|Maximum orbital velocity||kms-1||30.29|
|Minimum orbital velocity||kms-1||29.29|
- Sidereal orbit period
The time taken by the planet to complete exactly one orbit around the Sun with respect to the celestial sphere.
- Sidereal rotation period
The time in which the planet rotates around its axis exactly 360° with respect to the celestial sphere.
- Length of a day
Defined as the time between two successive sunrises over the meridian.
- Magnetic dipole moment
Calculated as the ratio of the magnetic field strength at the equator divided by the cube of the equatorial radius.