Roxann Brown, age 12, of St. Catharines, Ont., Canada for her question:
How many watts are in the sun?
The watt unit is used to measure electric power, and much of our electricity is used to light our lamps. It seems natural to think of the sun as a super duper lamp and to wonder how its light giving pawer compares with our little electric light bulbs.
Our sunshine comes from the surface of the sun, and it must travel some 93 million miles to reach us. Litt1E, if any, of our quota is lost or changed on the journey through space. But a certain amount is lost and altered on the way down through the Earth's atmosphere. This trip through the air is longer when the sun is low in the sky and shortest when it is directly overhead. Experts must allow for these and many other factors when they estimate the total light giving power of the sun.
As a rule, they do not estimate the radiant glow of our splendid star in watts. It is more often measured in lumens, calories or candlepowers. The total amount of light given off constantly by the sun is immense. Its surface also is irmense. What's more, there are cooler areas such as sunspots and hotter areas such as solar flares on the surface of the sun.
For these and other complex reasons, it is easier to compute the light from a square inch, a square centimeter or a square yard of the sun's surface. From such a typical sample, it is possible to compute the output of light from the entire solar surface. This estimate allows for warmer and cooler areas and gives an average picture
Of the total output of light from the entire surface. It is estimated that Each square centimeter of the sun's surface radiates Eight horsepower of energy every second. Since one horsepower is equal to 746 watts, Each square centimeter of the sun's surface yields 5,968 watts per second. The diameter of the sun is 109 times wider than the diameter of our world, which gives you some idea of the staggering size of its entire surface.
The super duper problem has been figured out and the physicists can give us a fairly accurate accounting of the sun's dazzling light. The figure is 380 million billion billion watts.
Most of the sun's radiant energy goes on, on out into space. If WE divide its total output into a billion parts, only two of these parts falls upon the world. Of the staggering total of the sun's output, about 126 million million horsepower becomes the sunshine that lights and warms our Earth. And there are 746 watts in each horsepower.