Earth-Sun Relations

Earth-Sun Relations - Earth-Sun:1 Solar Energy and...

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Earth-Sun:1 Solar Energy and Earth-Sun Relations Solar Energy Earth’s Rotation Earth’s Orbit & Seasons Today, we are going to generate energy in the Sun, get that energy to Earth and see why we have seasons. Solar Energy As we’ve seen, the Sun is a mass of mostly hydrogen. The center of the Sun is called the core and it is extremely hot (15 million °C) and very dense. Under these conditions, nuclear fusion takes place and the hydrogen is converted to helium. In this process, energy is released. This energy slowly makes its way to the surface, taking about a million years to get there. At the surface are occasional sunspots , which are regions of cooler temperature somehow caused by magnetic fields. Ever since Galileo discovered sunspots, they have been observed and, for unknown reasons, follow an eleven year cycle. Some people have tried to connect sunspot activity to climate change, but the evidence is pretty weak. But back to the main story. This energy reaching the surface of the Sun heats it up and, as we know, it gives off electromagnetic radiation based on its temperature, which is roughly 6000 °C. If we plug this temperature into the Stephan-Bolzman equation, we find that the Sun is giving off about 63 000 000 watts per square meter. Using Wein’s Law, we find that the peak wavelength is about 0.5 micrometers, which happens to be in the visible wavelengths and is yellow. Planets close to the Sun receive more intense solar radiation than planets further away. The inverse square law says that the intensity of the radiation is inversely proportional to the distance squared. (Inversely proportional means that as one goes up, the other goes down.) In the diagram, a and b get the same amount of radiation, but it is more intense (more per unit area) at a and more spread out at b.
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Earth-Sun:2 a b Based on the distance from Earth to the Sun and the amount of radiation given off by the Sun, we can calculate that 1367 watts per square meter per second of
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This document was uploaded on 10/27/2011 for the course GEOG 1401 at Texas Tech.

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Earth-Sun Relations - Earth-Sun:1 Solar Energy and...

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