Q. Regards infrared radiation, conduction and convection, is infrared radiation the starting point, the fundamental source of heat energy (thermal energy), and the fundamental source of the other two? I’m thinking that the Sun predates the Earth by 30 million or so years so the first heat energy put into the Earth was infrared radiation from the Sun. This in turn has caused, over the aeons, much conduction and convection but are those two forms of heat transfer by-products of the more basic form, ie, radiation? I’m also thinking in terms of convection in a living room. Convection (the movement of air of varying density circulating the room?) is the main way in which the room is heated but the starting point for the process is radiation (from the radiator), yes?