Not exactly a great citation, but the Wikipedia article on the history of heat suggests that their understanding was not very good.
For what it is worth, marginally related ideas seemed to be going around at least by the end of the sixth century since I seem to recall an argument in the Talmud about whether or not transfer of heat by itself from a non-kosher thing to a kosher thing could make the kosher thing non-kosher. But it is possible that I was reading that with a too modern perspective. I’ll try to track down the section and see what it says.
Yeah, I read the wikipedia page looking for something. And certainly no one would say they had a good understanding of thermodynamics. Usually different ancient philosophers had different opinions about these sorts of things so I would not surprise me if a few prominent figures had the basic idea down. They definitely associated fire with heat, and fire in most accounts was an element. In seems plausible that they might have believed cold simply involved the absence of fire.
Yes. The relevant experiment would be a study of how gases expand when heated, leading to the ideal gas law, which has a special case at absolute 0.
The special case distinguishes between cold being a real entity (and heat being neg-cold) and heat being a real entity (and cold being neg-heat); because it proves that heat has a minimum, and cold a maximum, rather than the other way around.
Probably, by considering how there are several ways to “create” heat (burning, rubbing things together, as Oscar says), but none of “creating” cold. That makes more sense in a model where heat is a substance that can be transmitted from object to object, and cold is merely the absence of such a substance.
They did well enough to figure out or intuit or guess that a simpler explanation was better: You’re not giving them enough credit, as some went beyond that chemistry.
“For it is necessary that there be some nature (φύσις), either one or more than one, from which become the other things of the object being saved… Thales the founder of this type of philosophy says that it is water.”
So granted that they could narrow it down to one “element”, was it possible for them to do better than to guess as to the nature of thermodynamics? To guess which is the absence of the other?
As my reply to your original comment indicates I give them plenty of credit—I’m not sure they didn’t guess that cold was the absence of heat.
You have the pre-socratics a bit mixed up. Heracletus and Thales are before the five element system of Aristotle. Heracletus only had three elements in his cosmology and fire was the most important. Some ancient cosmologies made one element central...I’m not sure what that has to do with the question?
But certainly it is possible some of them surmised that cold was the absence of fire or something like that.
A number of substances have high enthalpy heats of solution, and appear to “create” cold when added to water. Some, like calcium chloride, would likely have been known in Classical Greece.
Edit: My mistake. Dissolution of calcium chloride is actually exothermic. I’m not sure if any salts which have high endothermic dissolution occur in a naturally pure state.
How would this belief pay rent if one doesn’t have a lot of chemistry to start off with and hasn’t done a very large set of experiments? Would it look any different than cold is the absence of heat? The flowing behavior can be easily explained either way.
Also, one thing that’s very clear from a lot of history is how much the ancients could have learned if they just were a bit more wiling to do direct experiments. They did them but only on rare occasions. There’s no reason that the scientific method could not have shown up in say 200 BCE.
A description of an experiment they could have done would be a fine answer to my question, even though they weren’t inclined to do them.
Perhaps the experiment is obvious to you? I don’t know what it would be.
How would this belief pay rent
This is a good question and I’m not confident it could or couldn’t. It’s more a thought experiment to rethink how much medium-hanging fruit there is today. If they could have figured it out even though it couldn’t have paid rent, so much the better.
Perhaps the experiment is obvious to you? I don’t know what it would be.
That’s my problem. I can see sets of experiments that form long chains that eventually get this result, but I don’t see it as an easy result by itself.
I suppose that if they had kept experimenting with Hero’s version of the steam engine they might have started to develop the right stuff. That might be the most natural way that it could have gone.
Part of the problem is that in order to get decent chemistry you need to do enough experiments to understand conservation of mass. And when gasses are released that requires very careful measurements. And in order to even start thinking in that vein you probably want enough physics understanding to understand that mass matters a lot. (There’s good reason that conservation of mass becomes a discussed and experimented with issue after Newton and Galileo and all those guys had developed basic physics). Then, if one has steam engines also and has a notion of work, one can start doing careful experiments and see how things function in terms of specific heat (how different substances take different amounts of heat to reach the same temperature). If one combines that with how gases behave and has that gases are composed of little tiny particles then a pseudokinetic theory of heat results.
I know however that the caloric theory of heat didn’t require a correct theory of gases. This makes me wonder if there’s an easier experimental pathway, whether this is a lucky guess, or whether it is just that there are a lot more examples in nature of things that seem to produce heat than things that seem to produce cold. (As has already been noted in this subthread, there are definitely things that would seem to produce cold.)
“Heat” isn’t a thing either. It’s all just molecules bopping around. A very smart person might have been able to deduce this (or at least raise it as a possibility) by thinking about the fact that rubbing two sticks together makes heat.
The original theory of thermodynamics grew out of things like this, except the possibility that they considered had to do with a “caloric fluid”. All objects had this particular fluid stored inside of them, and by rubbing the sticks together or something like that, you could simply release the fluid while gradually breaking down the object. Which is a reasonable conclusion, assuming you don’t have all the historical background that we do in atomic physics.
Was it possible for the ancient Greeks to discover that cold is the absence of heat?
I’m not confident they didn’t know that. Cite?
Not exactly a great citation, but the Wikipedia article on the history of heat suggests that their understanding was not very good.
For what it is worth, marginally related ideas seemed to be going around at least by the end of the sixth century since I seem to recall an argument in the Talmud about whether or not transfer of heat by itself from a non-kosher thing to a kosher thing could make the kosher thing non-kosher. But it is possible that I was reading that with a too modern perspective. I’ll try to track down the section and see what it says.
Yeah, I read the wikipedia page looking for something. And certainly no one would say they had a good understanding of thermodynamics. Usually different ancient philosophers had different opinions about these sorts of things so I would not surprise me if a few prominent figures had the basic idea down. They definitely associated fire with heat, and fire in most accounts was an element. In seems plausible that they might have believed cold simply involved the absence of fire.
Yes. The relevant experiment would be a study of how gases expand when heated, leading to the ideal gas law, which has a special case at absolute 0.
The special case distinguishes between cold being a real entity (and heat being neg-cold) and heat being a real entity (and cold being neg-heat); because it proves that heat has a minimum, and cold a maximum, rather than the other way around.
Probably, by considering how there are several ways to “create” heat (burning, rubbing things together, as Oscar says), but none of “creating” cold. That makes more sense in a model where heat is a substance that can be transmitted from object to object, and cold is merely the absence of such a substance.
What if they built a building or found a cave where wind ran over a bucket or pool of water, cooling the air?
http://en.wikipedia.org/wiki/Evaporative_cooler#Physical_principles
http://en.wikipedia.org/wiki/Windcatcher
“Water produces cold” is a plausible hypothesis for someone using Earth/Air/Water/Fire chemistry.
They did well enough to figure out or intuit or guess that a simpler explanation was better: You’re not giving them enough credit, as some went beyond that chemistry.
Heracletus:
Aristotle speaking about Thales:
See also here.
So granted that they could narrow it down to one “element”, was it possible for them to do better than to guess as to the nature of thermodynamics? To guess which is the absence of the other?
As my reply to your original comment indicates I give them plenty of credit—I’m not sure they didn’t guess that cold was the absence of heat.
You have the pre-socratics a bit mixed up. Heracletus and Thales are before the five element system of Aristotle. Heracletus only had three elements in his cosmology and fire was the most important. Some ancient cosmologies made one element central...I’m not sure what that has to do with the question?
But certainly it is possible some of them surmised that cold was the absence of fire or something like that.
A number of substances have high enthalpy heats of solution, and appear to “create” cold when added to water. Some, like calcium chloride, would likely have been known in Classical Greece.
Edit: My mistake. Dissolution of calcium chloride is actually exothermic. I’m not sure if any salts which have high endothermic dissolution occur in a naturally pure state.
How do I know those processes are actually producing creating heat and not just destroying cold?
ETA: And to be clear, where by “I” I mean someone with roughly ancient Greek knowledge levels.
How would this belief pay rent if one doesn’t have a lot of chemistry to start off with and hasn’t done a very large set of experiments? Would it look any different than cold is the absence of heat? The flowing behavior can be easily explained either way.
Also, one thing that’s very clear from a lot of history is how much the ancients could have learned if they just were a bit more wiling to do direct experiments. They did them but only on rare occasions. There’s no reason that the scientific method could not have shown up in say 200 BCE.
A description of an experiment they could have done would be a fine answer to my question, even though they weren’t inclined to do them.
Perhaps the experiment is obvious to you? I don’t know what it would be.
This is a good question and I’m not confident it could or couldn’t. It’s more a thought experiment to rethink how much medium-hanging fruit there is today. If they could have figured it out even though it couldn’t have paid rent, so much the better.
That’s my problem. I can see sets of experiments that form long chains that eventually get this result, but I don’t see it as an easy result by itself.
I suppose that if they had kept experimenting with Hero’s version of the steam engine they might have started to develop the right stuff. That might be the most natural way that it could have gone.
Part of the problem is that in order to get decent chemistry you need to do enough experiments to understand conservation of mass. And when gasses are released that requires very careful measurements. And in order to even start thinking in that vein you probably want enough physics understanding to understand that mass matters a lot. (There’s good reason that conservation of mass becomes a discussed and experimented with issue after Newton and Galileo and all those guys had developed basic physics). Then, if one has steam engines also and has a notion of work, one can start doing careful experiments and see how things function in terms of specific heat (how different substances take different amounts of heat to reach the same temperature). If one combines that with how gases behave and has that gases are composed of little tiny particles then a pseudokinetic theory of heat results.
I know however that the caloric theory of heat didn’t require a correct theory of gases. This makes me wonder if there’s an easier experimental pathway, whether this is a lucky guess, or whether it is just that there are a lot more examples in nature of things that seem to produce heat than things that seem to produce cold. (As has already been noted in this subthread, there are definitely things that would seem to produce cold.)
“Heat” isn’t a thing either. It’s all just molecules bopping around. A very smart person might have been able to deduce this (or at least raise it as a possibility) by thinking about the fact that rubbing two sticks together makes heat.
The original theory of thermodynamics grew out of things like this, except the possibility that they considered had to do with a “caloric fluid”. All objects had this particular fluid stored inside of them, and by rubbing the sticks together or something like that, you could simply release the fluid while gradually breaking down the object. Which is a reasonable conclusion, assuming you don’t have all the historical background that we do in atomic physics.