Quick Facts: Mythology: The Layers: Water: Magnetic Field:

Mother Earth

Quick Facts:
Earth is the third planet from the Sun and the fifth largest.
The Earth is the densest major body in the solar system.
Distance from the Sun: 149,600,000 km (92,900,000 miles or 1.00 AU)
Period of Revolution: 365.26 days
Diameter: 12,756.3 km (7,926 miles)
Mass: 5.9736e24 kg
Satellites: The Moon
The interaction of the Earth and the Moon slows the Earth's rotation by about 2 milliseconds per century. Current research indicates that about 900 million years ago there were 481 18 hour days in a year.

Mythology:
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 hundreds of other names for our planet in other languages. In Roman Mythology the goddess of the Earth was Tellus. The Greek god was Gaia, Mother Earth.

The Layers:
The Earth is divided into several layers which have distinct chemical and seismic properties: Crust, Upper mantle, Transition region, Lower mantle, D'' layer, Outer core, and the Inner core. The crust varies considerably in thickness, it is thinner under the oceans, thicker under the continents. The inner core and crust are solid; the outer core and mantle layers are fluid. The various layers are separated by discontinuities which are evident in seismic data; the best known of these is the Mohorovicic discontinuity between the crust and upper mantle.

Water:
71 Percent of the Earth's surface is covered with water. Earth is the only planet on which water can exist in liquid form on the surface. Liquid water is, of course, essential for life as we know it.  The heat capacity of the oceans is also very important in keeping the Earth's temperature relatively stable. Liquid water is also responsible for most of the erosion and weathering of the Earth's continents, a process unique in the solar system today.

Magnetic Field:
Earth has a modest magnetic field produced by electric currents in the core. The interaction of the solar wind, the Earth's magnetic field and the Earth's upper atmosphere causes the auroras. Irregularities in these factors cause the magnetic poles to move relative to the surface; the north magnetic pole is currently located in northern Canada.