Annaleise Faint of Riverdale School asks :-

Why does heat travel?

Geoffrey Barnes, a physicist at Massey University, responded.

Heat may travel in three possible ways; by radiation, by convection, and/or by conduction.

Heat from the hot surface of the Sun travels through space and air in the form of (infrared) waves, like light or radio waves, but having an invisible frequency or ‘colour’. These waves are self-propelled.

Convection involves the movement of ‘blobs’ of liquid or gas, warmer fluid expanding (atoms jiggle more) and being buoyed upward.

Some solids are good at the conduction of thermal (heat) energy, which flows through the material. To explain heat conduction, I will quote the words of Nobel Laureate Richard Feynman1, who had a unique combination of dazzling intellect, and simplicity:

“Jiggling Atoms. Nothing is really as it seems. We’re used to hot and cold, but all that “hot” and “cold” are is the speed that the atoms are jiggling – they jiggle more and it corresponds to “hotter”, and “colder” is jiggling less. So if you have a bunch of atoms – a cup of coffee, maybe, sitting on a table – the atoms are jiggling a great deal, they bounce against the cup, and the cup gets shaking. The atoms of the cup shake, and they bounce against the saucer. The “hot” thing spreads its heat into other things by mere contact – the atoms that are jiggling a lot in the hot thing shake the atoms that are jiggling only a little in the cold things, so that the heat, we say, goes into the cold thing.”