The map shows the geographical distribution of 
                              the solar radiation incident on the earth's surface 
                              each year. Depending on the shape of the sun's apparent 
                              path (solar ecliptic), the amount of radiation decreases 
                              towards the polar regions. 
                            On the land area worldwide, this results in a solar 
                              radiation of at least 200,000,000 TWh per year. 
                              (For comparison: 9 billion people, each requiring 
                              2,000 watts, would have a total annual energy demand 
                              of 160,000 TWh.)