Far infrared rays are essential to plant growth and, by extension, to all organic matter. But it was only in 1800 that William Herschel, the German-born British astronomer, discovered them.
For the first time, it was concluded that heat could be transmitted by an invisible form of light, that is to say neither by convection (hot air transfer) nor by conduction (propagation between solid bodies). In short, infrared rays heat objects and not the air, which holds very little heat.
Far infrareds are waves of energy measured in micrometres (or nanometres) and, contrary to common misconceptions, not in temperature.