The realization that air was a material substance was not a sudden event. Experiments like that led to the understanding of air as a gas. The problem here isn’t that people didn’t know that air existed, the problem was that air seemed to be distinctly different from all other substances known at the time and it’s behavior couldn’t be well explained with the established knowledge of the time.
My previous post was unclear as to the point I was trying to make. My bad. I’ll try again.
The BBC article that is cited in the OP implies that the concept of a vacuum was unknown prior to 1600.
Aristotle said, “Nature abhors a vacuum.” So the concept was being discussed at least 2000 years earlier. In the first century, Heron of Alexandria invented some interesting toys; some of which showed that he had at least some understanding that air is a fluid.
I’m sure earlier humans did have some of the misconceptions discussed in this thread. So I guess my point is the trivial assertion that the understanding came much earlier than 1600.
First of all, I’ll say as a disclaimer that I don’t read Old English, but I found Thomas Wright’s “Popular Treatises on Sciences Written in the Middle Ages”, in which he quotes a tenth century tract on Astronomy, which says, in part.
It then goes on to talk about the wind.
The text claims to be based on a text by the Venerable Bede, so I decided to check what he said about the air. I’m not going to quote it, but basically, he said,
- All living things breathe it
- It is lighter than water but heavier than fire
- It sustains the flight of birds
- It bears up the clouds, which are made of water suspended in it
- The demons cast out of heaven make their abode there
- It’s more pure the further it is from the earth and the closer to heaven
- The lower part contains fire, hail, snow, ice, and winds
- Wind is air stirred up and agitated, as can be seen by the example of a small fan
9 Air trapped within the earth causes earthquakes as it tries to escape - Air can cause pestilence and disease
7 out of 10 ain’t bad for 1400 years ago.
I count 4 out of ten. 3 if we demand unambiguously correct.
- Fish don’t breathe air, for example.
- Air isn’t less dense than fire. Hot air is lighter than cold air, but it air isn’t heavier than fire no matter how you spin it.
5.There are no demons on the air. - Air at altitude isn’t any more pure. Air further from sources of pollution are more pure, but air high above a dirty city will be less “pure” than air at ground level in the middle of a forest.
- How exactly air “contains fire” is ambiguous.
- I’m not a geologist, but I’m fairly sure that earthquakes are not the earth farting.
- Air can not cause pestilence or disease. Pasteur, Snow et. al. ruled that out long ago.
What do you figure for the density of fire?
Fire is a reaction involving fuel. Its density is slightly less than that of the fuel. I guess a hydrogen fire is less dense than air, but it is unlikely that hydrogen fires were what a dark ages author was referring to.
I think when he says air “contains fire”, he’s talking about lightning, or maybe the sun.
And his argument that fire is less dense than air is because fire goes up. Flame points upward, and the smoke from flame rises. Therefore, it must be less dense than air. QED