In 1800 AD, British scientist William Herschel discovered that the red light in sunlight is surrounded by a light source that cannot be seen by the naked eye, with a wavelength of 1000μm ~ 5.6μm "far infrared", when irradiated by this light source. , will have the effect of radiation, penetration, absorption and resonance to the organism. However, according to the theory of black body radiation, it is not easy for ordinary materials to generate sufficient intensity of far-infrared rays. Usually, special substances must be used for energy conversion, and the heat absorbed by it will be released through the vibration of internal molecules to emit far-infrared rays of lower frequency. come out.