Eli5 is there no such thing as cold?


My SO said the above statement and gave me an explanation “Cold is the absence of heat or energy”, it does make sense however in my head it is like saying (in very simplistic terms) “the countryside is the absence of a city” and that is just a ridiculous statement.

In: 66

Cold, in the way that it’s commonly meant, is a relative measure, and it’s relative to things like cool, warm, hot, etc. However heat (not hot) is an objective measure of a specific type of energy. Cold things have less of this energy than hot things. This is what people mean when they say that “cold is the absence of heat”.

It depends on the context. You are right that in concrete terms heat exists and cold doesn’t. But in relative terms humans, and other animals, experience feelings of hot and cold.

Cold is indeed the absence of heat/energy but it is still a useful concept. The lack of something is still something. Gravity may not seem that important in space since there is no or very little gravity when you’re not near large celestial bodies but whether it’s the lack of or greater magnitudes of gravity, it’s still important.

In a way, there is no such thing as cold. Cold itself is not an energy or a force. Cold is the absence of heat. The reason people use this expression is to remind people what hot and cold actually are. Temperature is basically movement; it is kinetic energy of the molecules. More movement equals more heat. There isn’t a negative type of movement where things get colder if they move more. It’s a single function.

“The countryside is the absence of a city” is not an equivalent statement. For example, the surface of the sun has no cities, but you would not call it the countryside.

Cold is like having one hundred people (people being atoms)walk very slowly in an enclosed space. It gives time for the people walking slowly to interact with each other if they want to (form bonds and other cool chemical stuff for atoms). Being Hot is those 100 running as fast as they can in that enclosed space, they don’t have time to talk to each other since they’re running so quick and they bump off of each other, sometimes causing you rip something from those people by accident.

And what dictates whether they walk or run? Energy. It’s not so much the absence of energy, but the level of energy that determines hot or cold. Absence of energy has never been seen or recreated in a lab, as far as we know it’s possible but it’s never been seen. Hope that helps!