Transcript: We’re used to viewing the world through light, through visible radiation, but visible radiation is only intrinsically emitted from objects that are thousands of degrees Kelvin. Most objects we are surrounded with, the temperature of the Earth itself, is several hundred degrees Kelvin. According to Wien’s Law, thermal radiation from objects at several hundred degrees is 20 times smaller then thermal radiation from the surface of the Sun. This is infrared radiation emerging as waves too long for the eye to detect. For example, if a poker is heated up to be white hot, it will have a temperature of several thousand Kelvin. As it cools it goes through the colors of the rainbow from white to yellow to orange to dull red. As it continues to cool down to room temperature it is still emitting thermal radiation, but this thermal radiation shifts to wavelengths longer then the eye can detect to infrared waves.