Radiant heating (or thermal radiation) is the transfer of heat (at the speed of light) from a warmer object to a cooler one by electromagnetic waves in the infrared spectrum. Like light (which is visible electromagnetic radiation), radiant heat is transmitted through space in a straight line and with virtually no impedance, i.e. no heat is lost to the intervening space between the objects. The sun, for example, heats the Earth radiantly during daylight hours. In your living room, a radiant floor, baseboard unit, or radiator transmits its heat to cooler objects, including people, in its direct line of sight. In fact, any two objects in sight of one another will transfer heat between them radiantly provided that there is a temperature difference. An important example is heat will be transferred from your body to colder objects in the room by radiation. Your sensation of comfort is dependent on how much heat your body generates versus how much heat your body loses to its surroundings… and heat loss by radiation to nearby cooler objects can be significant.