In reading this interesting article on BBC, it states:
*“The first thing that had to happen seems almost comical to us today. We had to discover that air was actually made of something, that it wasn’t just empty space between objects. In the 1600s, amateur scientists discovered a bizarre phenomenon - the vacuum, air that seemed actually to be composed of nothing and that behaved differently from normal air. Flames would be extinguished in a vacuum. A vacuum seal was so strong that two teams of horses could not pull it apart.” *
"In 1659, the English scientist Robert Boyle had placed a bird in a jar and sucked out the air with a vacuum pump. The bird died, as Boyle suspected it might, but curiously enough, it also froze. If a vacuum was so different from normal air that it could extinguish life, that meant there must be some invisible substance that normal air was made of. And it suggested that changing the volume or pressure of gases could change their temperature. "
I a little confused here. You can blow air out of you mouth and feel it on your hand. When people went out on a windy day and were almost blown over, what did they think was pushing them?
Is this more of a semantics confusion or did people really not understand that air existed? Maybe it was more of the idea that there could be a space where air could NOT exist (as in a vacuum)?
Yes, people knew there was “air”; in many cultures, it was considered one of the basic components of the world, one of the elements. What they didn’t know is that it actually contained “bits of something smaller, a lot of which could also be found in other things” and that it didn’t fill every volume that wasn’t filled by something else. They didn’t know what was air made of, and they didn’t know that you could have “absence of air”, that you could have absence, in fact, of all elements.
Take into account that the article was written by someone who also writes about “amateur scientists”. That was the only kind, at the time, it’s not as if it was possible to get a PhD in a STEM field!
One can understand that the wind produces some kind of force, but if you can’t see or measure the air you don’t know that it’s a substance. Should we assume now that magnets are emitting some kind of substance that makes them repel or attract other magnets? At a time when much of the physical world can only be described in magical terms it’s not surprising people didn’t have a clear understanding of the principles involved.
I think this was the general idea. As you noted, there is obvious physical evidence that there is some kind of invisible substance around us.
But the behavior of vacuums was surprising in some ways. Who knew that a flame required air to keep burning? A person might have known that putting a flame under water would extinguish it. But throwing a pail full of water on a fire also extinguished the flame. The reasonable supposition was that there was some special property in water that extinguished fire. But cut off a flame from air and it was extinguished without any water being present.
And a vacuum seal is even more inexplicable. But two hollow halves of a ball together and they fall apart. But pump out the air between them and they stick together. Why? There wasn’t anything between them that was making them stick together. There was literally nothing between them. It wasn’t anything external to the ball - the conditions outside the ball remained unchanged. So somehow the nothingness inside the ball was producing an effect that made the two halves stick together. But how could nothing produce an effect? Didn’t you need something to be present to produce an effect? If the effect could appear without something to cause it, why wasn’t the effect appearing everywhere?
There isn’t really. If there was some kind of invisible substance around me then I could feel it, I could touch it, it would hinder my movements, it would settle into hollows or buckets and become thicker in those places and so forth. Air has none of those properties.
Sure, wind can do some of those things. But wind is something that occurs. You can get out of the wind. The wind dies down. But when I go inside, there is no wind, and clearly I am no longer surrounded by wind.
Wind moves all sorts of things, it moves trees and dust and water. But that isn’t some sort of substance, it’s an active force. Warmth heats thing up, but that doesn’t mean that warmth is some sort of invisible substance. Light from the sun illuminates things, but that doesn’t mean that light is some sort of invisible substance. Things fall though the air to the ground, but that doesn’t mean that falling is some sort of invisible substance. These are all active forces. Just as we define warmth as that which heats things up and light as that which illuminates, and falling as that which moves something form high to low, so we define wind as that which moves without being seen. We don’t posit some invisible substance that allows warmth from the sun to heat things up or light from a candle to illuminate a room or a fruit from a tree to fall form the ground, and we don’t posit some invisible substance that allows wind from the sky to move trees.
The idea of air being some sort of invisible substance had to come before there was any understanding that wind is moving air. If you ask a child under 8 or so, they will see no connection at all between wind and something moving. Wind is something like trees *being *moved. It isn’t *caused *by something moving, it isn’t caused by anything. It just is. A tree is moved by the wind. If you ask what moves the trees, they will say “the wind” and look at you like you are an idiot. There is no need to assume some other thing moves to cause the tree to move, any more than there is a need for something else to move in order for an apple to fall to the ground. The movement is the description and the explanation.
In the modern world we are so inculcated with this knowledge from such a young age that we just take it for granted that the wind is evidence of the presence of an invisible air. But we were taught that. We didn’t derive it from our own observations and we never would have, any more than we would have derived gravity from watching things fall.
I hate to admit this but, as a kid I was always interested in science (and my older brothers were into cars). The first time I read about the ole’ timey idea of outer space consisting of “the ether” my very first thought was,* “Wait, they thought the solar system was filled with starting fluid!!! That wouldn’t be good…”*
By 1600 it was clearly known that air existed and could be used, long before that people knew that fanning fires created more heat. The problem remained that you couldn’t see air, you couldn’t feel it when it wasn’t moving, you couldn’t measure it. Other substances aren’t like that. Whatever they thought air was, they didn’t think it was similar to water or rocks or anything else tangible.
I disagree. I feel it would be pretty easy to deduce the existence of air from some basic observations.
First, as you noted, is the wind. There’s obviously something moving that you’re feeling.
More importantly, you can create this movement. You can stand in a sealed room and wave a fan back and forth and create a tangible breeze. So whatever it is that the wind is created out of exists around us at all times. We may only experience it when it moves but it’s still there even when it’s motionless.
We can also feel the air when we move through. A person running and riding a fast horse will experience the feeling of wind blowing against them even when the air is still to somebody in the vicinity who isn’t moving.
And we have bodies of water to prompt out insight. Water can be seen and felt when it’s motionless but we experience the same effects of running water that we get from wind and the same effect of resistance when we swim through water that we get when we run through air. So a half-way intelligent person would be able to deduce that there must be some fluid substance that works like water and that we move through this substance the same way a fish moves through water.
There’s also breath. Breath not only gives us another way to move air; it also shows us another sign that air exists. Everyone can see that breathing is vital to life. If you can’t breath, you die. And it’s not the physical act alone that keeps you alive. If you cover somebody’s mouth and nose, they can still move their throat and lungs but that movement alone won’t keep them alive. Breathing obviously involves some substance going in and out of the body.
I am not a pre-1600’s human being, but my take on it is that they knew there was such a thing as “air” but they had no idea it was of the same nature as other tangible stuff. To them, air was basically nothingness. Nothingness to us means something different than it did back then. When they realized there was a difference between air and a vacuum, that’s what was so surprising. They had been mistaken about the properties of nothing.
Before gases were discovered and understood, people thought that wind and breath and other things of that nature were just properties of emptiness.
Now we know about quantum foam and on a very small scale, turns out that nothingness isn’t so different from air after all! (ok that’s a major simplification or whatever but hopefully you take it as entertaining and not gospel)
Observation of bubbles in water and the knowledge that you could yourself blow bubbles in water until boredom sets in would indicate that air is something rather than nothing, and that you are taking it in and expelling it rather than somehow generating it yourself.
Somewhere along the line they got the idea that diseases could be caused by something (a “miasma”) in this thing called air; one such disease was even named bad air (mal-aria, malaria).
Drowning and suffocation would seem to suggest that a need for air was of consequence.
The idea of a sail to propel watercraft is quite old and widespread.
It seems to have been very common knowledge that air existed, but its nature was not clear.
People deduced the existence of air thousands of years ago, in the same way that they deduced the existence of such similar and closely related substances/elements as light, darkness, fire, etc. but what they meant by ‘air’ had only a limited overlap with what we mean by ‘air’ and there was no real consensus on exactly what was going on until the modern era. Take a look at Classical element - Wikipedia for instance.
[QUOTE=wiki]
Sicilian philosopher Empedocles (ca. 450 BC) proved (at least to his satisfaction) that air was a separate substance by observing that a bucket inverted in water did not become filled with water, a pocket of air remaining trapped inside.
[/QUOTE]
which sounds nicely modern and scientific but then:
[QUOTE=wiki]
Air is primarily wet and secondarily hot.
[/QUOTE]
or alternatively that it has the characteristics of being “Blunt, Subtle and Mobile” as compared to e.g. Fire which is 'Sharp, Subtle and Mobile". These sound very strange to us but in the context of what they knew and were describing it was reasonably coherent.
With the benefit of thousands of years of painstaking philosophy, study and experimentation passed on to us in elementary school it is easy to look back mockingly on the seemingly bizarre logic chains used to explain natural phenomena, but I think it’s fairer to say that they did the best with what they had available and they usually had a good enough grasp for most practical purposes.
Can someone explain how the vacuum pump was conceived, designed, and built before air was known to be a tangible substance? . . . Ancient astronauts maybe?
