Rob: Any form of matter that we can think of having a temperature, no matter how hot or cold, gives off thermal energy.
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Rob: A chair, a book, food, me.
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Rob: Everything around us, even the Earth itself, radiates thermal energy. Thermal energy forms the primary source of what we call infrared radiation. Infrared being the section of the electromagnetic spectrum that is just beyond visible light in terms of wavelength size. We cannot see infrared radiation. In fact, humans can only see a very small portion of the electromagnetic spectrum, but technology allows to detect and image matter in this very important part of the spectrum. NASA, NOAA, and other agencies, use thermal infrared imagery to study Earth systems in a way beyond what we could ever see. Through infrared data, we can study ocean and ice changes, map deforestation and forest fires, and monitor soil moisture and detect diseased vegetation. In fact, nearly every time we look at a weather report, from a heat wave to a hurricane, we are using thermal infrared imagery. Satellites detect infrared energy in a way that lets us study the Earth's weather patterns over both day and night, which is crucial for predicting the weather to come. In a way, it's as if the whole planet becomes visible to us at any time of day. Just over 200 years ago, Sir William Herschel discovered the existence of infrared by studying the sunlight passing through a simple prism. The prism separated all the colors that make up sunlight in an array called a spectrum.
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Here's a simple classroom activity that lets us see the phenomenon Herschel first observed. Herschel measured the temperatures of the different colors and found that the temperatures increased as he measured from violet to red. But what really struck him was the observation just beyond the visible spectrum. First, measure the ambient temperature of the box by placing the thermometers in the shade. Once the prism is adjusted for the widest spectrum possible, place the thermometers in the blue, yellow, and in the area just beyond red. Measuring over time, we will see the temperatures increase as we approach this infrared section of the spectrum. It may seem like a big jump to go from a prism on a box to the advanced imagery satellites provide around the globe, but it all helps to explain how there is more to light and energy than meets the eye.