Emittance and Equations? AAAUGH!

Emittance happens when an object (like the Sun) creates electromagnetic radiation of some type (light, x-rays or heat). Everything in the universe made of matter emits some kind of radiation. The amount of emission depends of what its temperature is.

Scientists use something called the Stefen-Boltzmen equation to figure out how much energy an object gives off. In the equation... Energy is equal to a constant multiplied by the temperature to the fourth power. That means...

E (energy) = j (constant) * T4 (temperature)

Laws? Take Them Away!

Scientists also use Wein's law which proves that the wavelength is inversely proportional to the temperature. That means the longer the wavelength, the colder the piece of matter. A really hot piece of matter will have a high emission of short wavelength (high energy) radiation.

You should think about temperature and light now. What happens when you see a big iron beam holding up a building? It's grey or even black. Now think about the smelter where they pour the iron (Fe). It's very liquid and very hot. It's also very bright, giving off a white light. That's a good example of Wein's law.

What Does This Mean To Me?

This means that a super bright star with a very high level of energy emission is hot. It's not hot like a light bulb. It's hot like the center of a nuclear reactor. That heat and brightness will help you understand that it is giving off much more energy than just visible light. For our Sun, it's enough energy to heat most of the planets in the Solar System.

The Earth gives off much less energy. It wouldn't even glow if the Sun wasn't around. But because of our molten core, there is energy released in the form of infrared radiation (heat). Other planets are much colder than Earth and give off very little energy. We should say that they emit much less energy.

What does this really mean to you? Don't touch super bright obejcts. They are hotter and will probably burn you because of the energy they are emitting.

Next page on the Earth's energy.
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