EARTH

Description
Quantitative Information
Moon



Earth is the third planet from the Sun and the fifth largest planet in the Solar System. It is the largest of the four inner rocky planets and the densest major body in the Solar System.
Earth is the only planet whose English name does not derive from Greek/Roman mythology. The name derives from Old English and Germanic. There are, of course, hundreds of other names for the planet in other languages.

It was not until the time of Copernicus (the sixteenth century) that it was understood that the Earth is just another planet.


Earth revolves around the Sun in an elliptical orbit of low eccentricity.
The distance from Earth to the Sun determines the intensity of the solar irradiance.


Earth rotates around its axis, giving rise to day and night.
The rate of rotation is relatively rapid.
Earth's rotation axis is tilted at 23.5.
This tilt gives rise to the seasons.

The seasons modulate how much solar radiation is received at a point on Earth's surface through the course of a year.


Earth has one large satellite, The Moon.
Gravitational interactions between the Earth and the Moon produce tides that affect the entire planet; this tidal effect is most noticeable in Earth's oceans, but there are also tides in the atmosphere and the geosphere.

These tidal effects

dissipate energy in overcoming friction during the constant movement of material in the two bodies and so

are gradually slowing Earth's rotation rate (producing a longer day).

have gradually stopped the rotation of the Moon.

are causing the Moon to slowly recede (increase in distance) from Earth.
Earth has a modest magnetic field produced by electric currents in the core. The interaction of the solar wind, Earth's magnetic field, and Earth's upper atmosphere causes the auroras.



Quantitative Information

ORBIT:
Mean Distance From The Sun: 149.6M km/~92.96M mi/1 Astronomical Unit (AU)/8.32 lt min (= semi-major axis of Earth's orbit)

Eccentricity: 0.017 (0 = perfect circle, so this is small; as a consequence the Earth-Sun distance varies only ~2% through the course of a year)

Orbital Inclination: 0.0 (Earth's orbit defines the ecliptic plane)

Average orbital velocity: 29.8 km s-1
PERIOD OF ONE ORBITAL REVOLUTION: 1 terrestrial year = 365.256 days

SHAPE:
To first order, spherical.

Diameter of equivalent volume sphere = 12,756 km (7,926 mi)

To second order, oblate spheroidal, with a slight flattening of the poles and a slight bulge at the equator.

Polar radius =

Equatorial radius =
VOLUME:

MEAN DENSITY: 5.52 gm cm-3

MASS: 6.04 1013 Gt

SURFACE GRAVITATIONAL ACCELERATION: 9.8 m s-2

PERIOD OF ONE ROTATION: 1 day = 23 hr 56 min

AXIAL TILT (relative to plane of orbit): 23.45

INCOMING SOLAR RADIATION:
"Solar Constant" = 1368 W m-2 0.1 to 0.2% on this total (but the energy in the UV portion can vary by 100 to 200%). Value is for a distance from the Sun of 1 AU.
SURFACE FEATURES:
Tallest Mountian:

Deepest Oceanic Trench:
Sunlight Intensity at Mean Distance (Solar Constant):

Mean Temperature: 289K/16 C/60F



Moon:
The Moon
In proportion to its size, Earth has the largest moon in the Solar System. A case can be made that the Earth-Moon system is a "two-planet" system.