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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“Heat” is how much the atoms and molecules in a thing are vibrating. Everything that exists in the universe has _some_ amount of heat energy. There is no such thing as cold energy. Something feels “hot” if it has _more_ heat energy, and transfers that heat into your skin. Things that feel “cold” have _less_ energy and sucks some of your heat energy out of your skin. Hot and cold are relative terms.
Imagine a pile of coins. Now imagine a smaller pile of coins. Now imagine an empty pile of coins (no coins). In the physical sense, can you have fewer coins than no coins? (You could owe money, but you can’t put negative coins on a table)
Heat is the same way. The smallest amount of heat is no heat (it’s called absolute zero). You can say that one thing is colder than another (one pile of coins is smaller than another), but it just means that the colder place has less heat.
Cold is relative. Ask several people how they define cold and you’re liable to get a couple to a few different answers. *Temperature* is the actual measurement of thermal energy and various ranges of temperatures are what people quantify is what is hot or cold.
Basically it depends on if you’re talking to normal people or to Physicists.
If you are talking to normal people, cold is a thing. Things can be cold, get colder, and cold can “spread” if you stick ice to something.
If you are talking to a Physicist, cold is the absence of heat. Things do not “get cold” because that is just them “losing heat”. Things are not “cold” they just have “a smaller amount of heat”. Cold does not spread, that is heat leaving the thing you stuck the ice to and entering the ice, melting it into water.
We can’t always be 100% correct like that or things get too cumbersome. It’d be like if I told you a car is going 60mph, but you corrected me and said, “Nope! You forgot to account for the Earth’s rotational velocity, orbital velocity, and how even our solar system and The Milky Way are constantly moving throughout the universe. That car is moving way faster than the speed of sound!”
Too many incidents like that and people stop inviting you to parties.
Imagine you have a box of crayons. One of the crayons is super bright and colorful, like a shiny gold crayon. The other crayon is plain and doesn’t have any color, like a clear crayon.
Now, when you color with the gold crayon, you’re adding lots of bright color to the paper. This is like when something is hot; it has a lot of energy.
But when you color with the clear crayon, you’re not really adding any color. It’s not that you’re adding “no-color” to the paper; you’re just not adding any color at all. This is like when something is cold; it doesn’t have much energy.
So, when we say “cold is the absence of heat,” it’s like saying the clear crayon is the absence of color. It’s not that “cold” is a thing by itself; it’s just what we feel when there’s not much heat or energy around.
And just like the countryside isn’t the “absence of a city” but a different kind of place, “cold” is a different kind of feeling we get when there’s less heat. But in science terms, we think of cold as having less energy compared to something hot.
And the more you think about it the worse it’s probably going to get. Tomatoes are berries, strawberries are fruit. What that means is that tomatoes genetically and characteristically are most similar to raspberries than they are to celery whereas strawberries are more like apples than they are like raspberries.
When your physics teacher tells you there’s no such thing as cold, he’s being a bit pedantic… of course there’s such a thing as cold. But he’s trying to liberate your mind from how we currently perceive hot and cold and introduce you to the guiding mechanism for how hot and cold works. Because really when you think about the physics, there really isn’t hot either. There’s just heat. And heat is energy and the first law of thermodynamics says that no energy is created nor destroyed it merely changes form.
So now you need to wrap your mind around, if heat isn’t created or destroyed… how do things get hot and cold? Well, a place that feels colder has less heat than a place that feels hot.
But if no energy can be created nor destroyed…. how do some places get hotter? Well, thermal energy (heat) can move. And as a principal heat moves kinda like water… a path of least resistance to the areas that have the least of it. To picture it if you have an area without water and an area with an abundance of it, the water will flatten out until the whole area has some water.
Heat does basically the same thing.
Now what’s really going to blow your mind is how a furnace, heat pump, and air conditioning work when heat can’t be created nor destroyed.
Why do you think “the countryside is the absence of a city” is a ridiculous statement? What is ridiculous about it?
I d’know “the countryside is the absence of a city” kindof -is- what heat is, in an abstract way. Water is probably a better metaphor, a cold object is like an empty lake, if you connect it to a full lake, the water will flow in rapidly at first, then slow down as the level of water gets more similar between the two bodies. In a related way, the less water you have in your lake, the harder it is to remove, since you need a more empty lake to extract that water, and the removal will be slower since the level is similar between empty and almost empty.
Eli5: I’m from Florida, where its very hot. My friend is from Alaska, where its often very cold. Today it’s 60° out, and it feels a little chilly to me, but my friend says its still warm.
Heat is a discretely measurable property. You can’t measure cold with a thermometer. But this is true of many things. You can measure caloric intake, but you can’t measure hunger or fullness. You can measure hours of sleep, you can’t measure tiredness.
“Cold” isn’t a thing in the same way that “black light” isn’t a thing. And no, not the ultraviolet “black lights” but actual black color light.
Or hows about this – you could potentially give someone heat. You could NOT potentially give someone cold (you could take their heat though, which is where the confusion comes from). Cold just isn’t a “thing” as much as it is a description of relative heat.
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