Does cold radiate outwards? What’s the process by which a hot object becomes cold?
In: Physics
Cold isn’t really a thing that physically exists. An object is cold when it is a lower temperature (typically by a decent amount) than a reference point (often what’s comfortable for a person). When it’s in reference to humans, there’s the added caveat of it needing to be able to transfer heat relatively well (fun little experiment, put a piece of plastic in the freezer with a piece of metal and see which one feels colder after a few hours). Heat flows from areas of high concentration (hot things) to areas of low concentration (cold things).
The atoms and molecules in a substance are moving and have a certain amount of energy contained in them. On a macroscopic scale, this is thermal energy. So the molecules in a hot piece of metal are moving faster and contain more energy than the ones in a lower temperature piece of metal. This energy is lost through three methods.
Conduction: This is when a solid is in physical contact with another solid and the atoms transfer energy from one solid to another.
Convection: This is when heat is transferred by moving fluids at a macroscopic level. This can be a solid to a fluid (or vice versa) or fluid to fluid. At an atomic or molecular level this occurs by atoms and molecules bouncing off of each other.
Radiation: This is when individual atoms loose energy by emitting light (think of a hot piece of metal). At lower temperatures this isn’t much and is often way less than conduction and convection. At high temperatures, you get things like the sun. In space conduction and convection don’t really work, leaving radiation.
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