In 1800, British astronomer Sir William Herschel discovered spectral regions beyond visible light.
Herschel obtained a colorful spectrum by separating sunlight with a prism. He then decided to measure the temperature emission of each color. By placing a thermometer between the colors, he tested which color had the highest temperature. The results showed that red light was warmer than the other colors. What was even more interesting was his realization that there was a spectrum of light beyond red; he discovered that these rays emitted heat beyond visible light.
Today, infrared cameras and sensors are a part of our daily lives, but the origins of this technology trace back to this discovery in the early 19th century.
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