Asimov starts with Aristotle. He is one source for the idea that everything is composed of four elements: earth, water, air, and fire. To this traditional list Aristotle added ether, some kind of "fifth element" that was what the heavens above the earth were composed of. This place above the earth is where the celestial spheres of classical astronomy resided, for instance. And, as Asimov notes, the ancients had no notion of a vacuum, an absence of everything. And the ancients, at least those who followed the Greek way of thinking, subscribed to the idea that in some sense perfection existed. The celestial spheres were perfectly spherical for that reason, for instance.
The fact that nothing actually seemed to be perfect was some kind of perceptual failure on the part of humanity. But this led to a lot of arguments along the lines of "it has to be that way because 'X' is perfect (or the best or whatever). Anything that is less than perfect is obviously wrong. So we can discard without further debate any idea that requires the perfect to be replaced by the less than perfect." This line of thinking took a long time to overcome and held progress back for a goodly length of time. Replacing circular orbits (circular = perfect) with elliptical orbits (actually mathematically and geometrically very similar to circles but still less than perfection) was one of the critical nails in the coffin that buried this argument. But back to the air.
In spite of massive evidence to the contrary there were supposedly concentric shells of earth, water, air, and fire (with a super shell of ether at the top of the hierarchy). One of the problems with these ideas, Asimov notes, was that it should have been possible to use a pump to raise water to any height. But it turns out there was some kind of magic 33 foot limit. Investigations of this problem led to the conclusion that air had a small but definite weight and that there must be a limit to the height of the "air column". Further investigation led to Boyle's law that doubling the pressure halved the volume of a fixed amount of air (and later, any gas). This in turn led to the Montgolfier brothers inventing the hot air balloon. Others replaced hot air with other gases like Hydrogen. These gas balloons could rise to greater heights and this in turn led to the idea that the atmosphere has various layers. The first two to receive names were the troposphere and the stratosphere. Since these early days various other layers have been defined and named.
World War II saw the discovery of the jet-stream, actually jet streams. At the time Asimov was writing his book there was little thought about the interaction of jet streams and weather. But we now know they play a critical role. They are meandering flows of high speed winds, winds often reaching 500 miles per hour. The streams themselves but also the locations of the meanders have a powerful influence on the pattern of movement of air masses. This in turn heavily influences the tracks storms follow and, even more importantly, precipitation patterns.
Until roughly a year before I write this California suffered severe drought conditions for four years running. In the most recent year the weather has changed completely and the state is now experiencing higher than usual amounts of rain and snow. In both cases the reason behind these patterns are changes in the shape and intensity of the jet stream. With the jet stream meanders in one configuration all wet air was routed away from California resulting in a severe drought. With them in another configuration a greater than usual amount of wet air was directed over the state. The drought in California ended when the jet stream meanders switched to a new configuration. Jet stream patterns now figure heavily into medium and long range weather forecasts.
In 1960 the first weather satellite, Tiros I was launched. Since then the number and sophistication of weather satellites has grown by leaps and bounds. It is unimaginable that a modern TV weather forecast would be without "satellite photos" showing cloud patterns. A large amount of other data of meteorological significance is now also collected via satellite observation. And in the past decade or so this has been joined by Doppler radar images.
The technology requires sophisticated radar equipment, possibly available in 1960. But it also requires massive amounts of computer power to process the data from the radar. Computers of that time were not anywhere near capable enough to do the job. And Doppler radar allows not only the amount of water vapor in the air to be measured but also the direction it is moving in. When I was younger I remember the occasional large storm emerging from out of the North Pacific with little or no warning and wrecking havoc far and wide. Somehow the satellite pictures did not allow the weather people to accurately gage the size of the storm. But a Doppler radar unit pointing out to sea was installed on the coast a few years ago. It should make those kinds of surprises a thing of the past.
Up to and including the time of the book balloons were an important tool in the weather man's arsenal. And that continues to be true today. But their days are probably numbered. Thousands of weather balloons are currently being launched each day. But they are a single use package and that makes them expensive. Drones and other techniques are now becoming available that can gather more data at less cost. So the routine use of weather balloons will probably end within a decade.
The Tiros I satellite mentioned above was launched on a rocket. Modern rocketry, the kind not associated with fireworks, only dates back to 1801. And the scientific foundations of rocketry were laid down by an American, Robert Goddard, and a Russian, Konstantin Tsiolkovsky, in the first half of the twentieth century. Very little has changed since, Elon Musk not withstanding. The latest SpaceX rocket differs little from the Russian Lunik III rocket that returned the first pictures of the far side of the moon in 1959. The instrumentation and guidance computers have advanced by leaps and bounds but the motors and fuel have changed little.
The era of manned spaceflight had not begun at the time of the book's writing. The first man in space was a Russian, Yuri Gagarin. But his flight took place in 1961. The Russian 1957 launch of Sputnik I, the first "artificial moon", initiated the "space race" between the US and the USSR, as Russia was then constituted. The high point, at least in US eyes, was the "Apollo" moon landings between 1969 and 1972. But since then, without the political and propaganda necessity of "beating the other guys", manned space exploration has languished. The computer of 1960 was, by modern standards, a small crude affair with extremely modest capabilities. Modern computers are literally a million times more capable. This has made the robotic space probe possible. And the results have been spectacular.
In outer space electronics are much easier to keep healthy than people. So long duration missions based on equipment that consumed tiny amounts of power and no air or food became possible. One or more missions have now been sent to every planet, including the dwarf planet Pluto. Long duration missions to Venus, Mercury, Mars, Jupiter, Saturn, comets, and the asteroid belt have all been successfully undertaken. Meanwhile, the International Space Station flounders along and nothing much of interest, either to scientists or to the general public, happens there. There is talk of tourist flights to the edge of the atmosphere (arbitrarily defined as 100 miles up) and even a publicity stunt manned flight around the moon. Various schemes are also afoot to colonize Mars. But all the "man/woman in space" stuff looks like wishful thinking to me.
Asimov then moves on to the composition of the atmosphere in "The Gases in the Air". The ancients considered the atmosphere to be a simple, homogeneous substance. That started changing in the seventeenth century. The first component discovered is a minor one, Carbon Dioxide. Next up to be discovered were Oxygen (a little less than 20%) and Nitrogen (roughly 80%). Much later Argon was discovered. Nitrogen, Oxygen, and Argon combine to make up 99% of what air consists of. Carbon Dioxide and the other trace components together add up to less than 1%.
At the time of writing the small amount of Carbon Dioxide in the air did not seem to make much difference. We now know better. Carbon Dioxide is a powerful greenhouse gas. Sunlight is a combination of many frequencies of light. The visible light that we can see is only one part. The air is transparent to visible light. It is also somewhat transparent to infrared light. The way a greenhouse works is that the glass passes sunlight light in so that it can be absorbed by plants, etc. But this causes things inside the greenhouse to warm up. Warm things emit infrared light. The glass traps the infrared light inside and the greenhouse gets warm.
The earth as a whole works the same way. Sunlight of many frequencies hits the earth. This warms things up and infrared light is emitted. The temperature of the earth is governed by the balance between these two processes. If the earth emits a lot of infrared light it cools down. If it emits very little it warms up. Carbon Dioxide behaves like the glass in a greenhouse. It traps the infrared and doesn't let it escape to space. So the more Carbon Dioxide in the air the less infrared light escapes to space and the warmer the earth gets. Scientists have been measuring the average amount of Carbon Dioxide in the air since about 1960 and it has been increasing. It goes up during parts of the year and down during other parts. But on average it goes up. And if you average out the temperature of the air over a reasonable amount of time, it is going up too.
There are confounding factors. But scientists have studied them all. Volcanoes emit Carbon Dioxide. But their influence is easily measured. The earth is closer to the sun at some times and further away at other times. This too is easily measured. There are complex techniques for figuring out where the Carbon Dioxide comes from. More and more of it every year comes from burning fossil fuels: coal, oil, and natural gas.
There are other greenhouse gasses besides Carbon Dioxide. The two most common ones are water vapor and Methane. But there are weather processes that keep the amount of water vapor in the air relatively constant when averaged over time and space. Methane in actually a much more powerful greenhouse gas than Carbon Dioxide. A pound of Methane gas traps much more infrared radiation than a pound of Carbon Dioxide. But Methane flushes out of the air relatively quickly and Carbon Dioxide doesn't. When you factor "residency time" in Carbon Dioxide has a much bigger impact.
All this and more have been carefully investigated by scientists and by far the biggest contributor to global warming in the burning of fossil fuels. But all this was in the future and not even imagined when Asimov was writing. The basic mechanisms (i.e. the greenhouse effect of Carbon Dioxide) were understood at the time. But there didn't seem to be any reason to investigate further because there was no perceived problem.
So far we are talking about the lower atmosphere. It didn't take scientists long to figure out that the composition of air changed with altitude. Initially there was a lot of speculation and not much data. One theory had it that the upper atmosphere might contain large amounts of Hydrogen and Helium. It doesn't, a fact established before the book was written. If you go high enough you do find something interesting, Ozone. This is a highly ionized form of Oxygen. Other atoms and molecules that are generally not found at sea level were also discovered. In general the upper part of the atmosphere is bombarded with high energy particles. This causes strange things to happen. And some of those strange things are dangerous. But fortunately other lower layers of the atmosphere shield us from this bad stuff.
One of the contributing factors to understanding the upper atmosphere was the discovery of ions. These are molecules that do not have the usual number of electrons. If the molecule is short electrons it will have a positive charge. If there are extra electrons it will have a negative electric charge. The discovery of ions predated the discovery of electrons. Ions only made sense, however, after electrons were discovered.
All of chemistry boils down to the interactions between the electrons of different atoms. There are different kinds of chemical bonds but these are fundamentally just different ways for electrons to interact with ions and other electrons. The basics of this were understood by the time the book was written but at best they could handle simple cases. At about the time the book was published a theory called Quantum Electrodynamics (QED) was being developed. It allowed more complex situations to be analyzed. Since then advances in theory (i.e. QCD - Quantum Chromodynamics) and the available of massive amounts of computer power have allowed more and more complex situations to be handled.
Experiments with radio, starting about 1900 in at least in some cases produced surprising results. Radio waves normally travel in a straight line. Yet sometimes they will sometimes bend to follow the curvature of the earth. This lead to the naming of the Heaviside layer and investigations of what we now call the Ionosphere. At the time it was assumed that other than the odd radio nut this was of little interest to anybody else. We now know better. Decades later the effect of CFC chemicals on the Ozone layer was discovered. The Ozone layer is critical to our health and CFC chemicals were damaging it. So they were phased out. And the problems caused by CFCs are now much reduced and on their way to total elimination.
And while we associated Ozone with the upper atmosphere it turns out to also occur in trace amounts at sea level. And it has the nasty characteristic of combining with car exhaust to produce smog. At one time the problem became particularly acute in Los Angeles. As a result various regulations governing car exhaust have been put in place and ground level Ozone is now routinely monitored. Here too we have a success story. The smog problem in Los Angeles and elsewhere is pretty much a thing of the past.
Other problems are caused by some components of exhaust from Diesel cars. This has resulted in various rules and regulations that have gone a long way to reduce these negative impacts. But there are costs involved. And Volkswagen decided the costs were too high. So they engaged in an elaborate scheme to cheat. They were caught and forced to pay billions of dollars in damages and penalties.
In Asimov's time that last 1% seemed of primarily academic interest. That has definitely turned out to not be the case. It is yet another example of a situation where "useless" scientific investigations eventually turn out to be critical.
