What is infrared light? It is a spectrum of light that we can’t see but that powerfully shapes our biology. You sense infrared light as “heat.” The heat you feel from the sun — that’s the sensation of infrared light. The feeling of heat you get when you put your hand close to an oven, toaster, or fire — that is also infrared light. The heat of another person’s body — infrared light again. Hot springs transfer heat to your body in the form of infrared light stored in the water itself. When you ta