The sun provides almost all of the energy available on the earth, minimal amounts come from the gravity of the moon (tides) and from thermal energy in the lithosphere.

The radiant energy which reaches the earth from the sun supplies the energy budget for the globe.

Incoming Radiation

Once light rays reach the earth, they are:

1. Reflected - By clouds or surface.
2. Absorbed - In the atmosphere or by the lithosphere
3. Converted - Into Thermal Energy, or Chemical Energy (through Photosynthesis)

The nature of the earths surface determines how much of the incoming solar radiation is converted into thermal energy (as heat) and how much remains as light and is reflected.

Albedo: The percentage of solar radiation that is reflected from the surface

Outgoing Radiation

Every object in the universe radiates energy. The wavelength of the radiation depends on the temperature of the source. The sun is millions of degrees, therefore it emits radiation of a short wavelength. The earth, on the other hand, is fairly cool (15�c) and it emits radiation of a long wavelength.

The energy reaching the earth is energy in
The energy released from the earth is energy out

These two energy flows form an energy balance and maintain our cozy temperature at 15�c

The Lithosphere

"The soils and rocks of the earth's crust and uppermost mantle"

The earth's crust is a solid shell estimated to be from 20 to 115 km thick. Below that is another dense shell, the mantle, believed to be approximately 44800 km deep.

The lithosphere is perhaps the simplest yet least well known of the four spheres, though, new technology has enabled scientists to probe deep beneath the earth's surface by studying vibrations in the different layers of the lithosphere.