As summer gives way to autumn, we're seeing a little less of the Sun each day. It rises a little later and sets a little earlier -- a pattern that'll continue until December.
The sunlight we do see is completing a remarkable journey -- a journey that begins deep inside the Sun's heart.
Like most stars, the Sun produces energy by combining the nuclei of hydrogen atoms to make helium in its super hot and dense core. In fact, the Sun burns through about 700 million tons of hydrogen every second. But not all of the hydrogen becomes helium. Instead, in a reaction described by Albert Einstein's famous equation E equals m c squared, a small fraction of the hydrogen is converted to energy.
This energy is in the form of X-rays, which are invisible to human eyes.
But as the energy travels the hundreds of thousands of miles to the Sun's surface, it's transformed. It gets absorbed and then re-radiated by other atoms -- as ultraviolet energy, and later as visible light. It takes hundreds of thousands of years for energy created in the core to reach the surface.
After that, it's a quick jaunt to Earth -- a little over eight minutes. The atmosphere scatters some of the sunlight, which is why the sky looks blue. Other light reflects from the ground and trees and buildings, and into our eyes. The eyes send a signal to the brain, which converts the signal into a picture of the world around us -- a picture painted by light from the Sun.
Script by Damond Benningfield, Copyright 2008
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