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.
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(Thermal energy ≠ heat, it’s a common misconception. Heat is thermal energy only during transition, so it’s incorrect to say “Cold is the absence of heat”. Cold is the absence of thermal energy.)
“Cold” is a real sensation we feel, however it’s misleading because you’re not feeling something called cold. You’re feeling a bit of the thermal energy in your body leaving you to know an object is cold. You’re feeling heat being transferred away from you. And if you feel cold, that just means you don’t have enough thermal energy for the body to like it.
Something can have a lot of thermal energy, which makes it hot. It can have not a lot of thermal energy, which makes it cold. Things can only have or not have thermal energy, it can’t have something called “cold”.
“The countryside is the absence of a city” is not quite an accurate comparison. I think more accurate comparisons could be:
* Darkness is the absence of light. You flick on a light, there’s light. You turn it off, now there’s darkness. But there isn’t actually something called darkness that is filling the room, it’s just that there isn’t any photons in the room, making you experience darkness.
* A vacuum is the absence of matter. If you go into the vacuum of space, you’ll die. So it’s definitely a real concept and a word that describes an observable thing in the world. However, it’s not like there’s a thing there called vacuum. You can have a bottle with nothing in it, you can have a bottle with air in it, but you can’t have a bottle with a substance called “vacuum” in it.
* Crimelessness is the absence of crime. You can commit crimes. You cannot commit crimelessness. The only way to be free from crime is to avoid crimes, not to have more of crimelessness. The only way to be cold is to have less thermal energy.
* Tiredness is the absence of energy. (In this case, “energy” doesn’t fit the physics definition of the word, but it’s similar in the sense that we can have energy and feel energetic and be able to do a lot of work. When we are tired, we say we don’t have a lot of energy. We don’t say we are having a ton of tiredness. We sleep to refill energy, not to have something called tiredness leave our body like an exorcist getting a demon to leave.)
I hope at least one of these examples can resonate with you.
Your example is not really good because the countryside is a real thing. It’s a category of real things like farmland, forest, swamp, etc.
There isn’t something physical that is called cold, it’s just how to name the absence of heat. Same as shadow isn’t a real tangible things, it’s just the absence of light.
To try and explain how “cold is the absence of heat” does “dry is the absence of water” make sense? In order for something to be wet you need to have water present. If there is no (or very little) water it is dry. In order for something to be warm it needs to be releasing energy in the form of heat. If there is no energy being released as heat then it is cold.
Cold is a real, meaningful and useful concept in daily life.
Cold is not a concept in physics. There is no way to measure or even define “cold.” It is only correct to say that there is no such thing as cold in the context of physics.
This is limited to one domain of science – physics. For example, in biology, cold is a useful concept.
Your SO is correct if you were talking about physics and incorrect in any other context.
The not so ELI5… Heat is a measure of enthalpy in a substance. Which is to say, it’s the measure of the average random kinetic molecular energy within something. On an atomic scale, things vibrate and bump into each other. The faster they vibrate, the more they bump. The more they bump, the more energy they transfer into their surroundings. Absolute zero then is the point at which all vibrations stop. “Cold” is a relative term that just means less molecular energy than some other thing. Refrigeration works by transferring some of the energy out of your food and into your kitchen.
People are getting it a bit backwards, cold is not the absence of heat, it is the absorption of energy from the surrounding area into an object, that’s what makes it feel cold. Heat is the opposite were it is giving of energy into the surrounding environment.
If you had the absence of heat the object would not be cold but neutral to the temperature of the surrounding environment, to feel cold it must be drawing/absorbing energy because that is what we perceive as cold
if you want to heat something up, you add heat
if you want to cool something, you don’t add cold, you remove heat
in case the retort is “but my air conditioner adds cold air to the room & that cools it down”
no, it takes in air, removes heat from it & places that air back into the room.
that’s why window units are window units, the heat is spit out the back to the outside.
also why central air units are outside the house but water heaters can be inside.
(central AC is spewing the removed heat, water heater is not putting out removed “cold” it’s just adding heat to the water inside it)
It’s like how darkness is the absence of light.
Light is a thing that exists both physically (we can interact with it and make lasers) and conceptually (we can unambiguously imagine something being well-lit).
Darkness is not a thing that exists physically (by definition it has nothing to interact with, and we can’t make “anti-lasers”), but it exists conceptually (we can unambiguously imagine something being not well-lit).
A better analogy would be, “dark is not a thing, it’s just the absence of light”. Light has properties, it interacts with other things, in that sense it is real. Dark is not a “thing” in the same sense.
Heat is the irregular motions and jiggling of atoms, while cold just is the absence of heat.
It’s like saying “death is the absence of life” and “life is the absence of death”
The statement makes sense in both, but in a way it’s only one direction. No one says life is the absence of death.
Many people have already explained why cold/heat/energy. It’s the same way.
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