This post is the next in a series that dates back several years. In fact, it's been going on for long enough that several posts ago I decided to upgrade the title from "50 Years of Science" to "60 Years of Science". And, if we group them together, this is the twenty-first main entry in the series. You can go to https://sigma5.blogspot.com/2017/04/50-years-of-science-links.html for a post that contains links to all the entries in the series. I will update that post to include a link to this entry as soon as I have posted it.
I take Isaac Asimov's book "The Intelligent Man's Guide to the Physical Sciences" as my baseline for the state of science when he wrote the book (1959 - 60). In this post I will review two sections, "Fission" and "The Atom Bomb". Both are from his chapter "The Reactor". We have now arrived at the last chapter in the book. So the end of the series is now in sight.
In "Fission" Asimov starts with the observation that "rapid advances in technology in the twentieth century have been bought at the expense of a stupendous increase in our consumption of our earth's energy resources". He saw this as simply a "supply" problem. "Where will mankind find the energy supplies needed"?
This tees up a discussion of various traditional sources like timber. I'll get back to that in a minute. What was not widely appreciated at the time was the cost in terms of pollution. We are now well aware of air pollution, water pollution, plastic pollution, chemical pollution, and the like. But, except for a few outliers like Rachel Carson with her book "Silent Spring", this was not a front line issue back then.
And the whole idea of worrying about an increase in the minute amount of carbon dioxide in the air? At the time, there weren't even any outliers worrying about this problem. But the '50s was when the foundations for our current concerns were being laid.
Carson's book was an indictment of the effects of DDT because of its unintended side effects. It was a very effective insecticide. But it also killed off all kinds of animals who were not its targets. This was one of the first analyses of the unintended consequences of various kinds of modern behavior.
Since then, we have learned of the deleterious effects of sulfur pollution spewed out by coal fired power plants (acid rain). We have learned that Freon refrigeration coolant damages the ozone layer. And on and on and on.
Regular measurements of carbon dioxide levels in the atmosphere (specifically at a remote astronomical observatory in Hawaii) were begun in the '50s. Studies demonstrating the dangers of inhaling cigarette smoke were started in the '50s. People knew that the extraction of oil, and particularly coal, made a mess of things. But that was assumed to be the primary negative effect of petroleum extraction.
Nobody, or at least almost nobody, worried then about what the effect of the "lead" additive, put into gasoline to boost engine performance, would be when it ended up in the atmosphere, and subsequently the lungs, and later the brains, of children.
It was soon determined that the effects were so devastating that lead additives were banned from gasoline. We later moved on to worrying about the lead that the paint we put on walls contained. Lead based paints were eventually banned. We now use latex based paint instead.
But all this was for the future. Asimov gives us a brief history of the use of timber by various civilizations. Forests were cut down in Greece, North Africa, the Near East, and in other places. This was done for fuel and so the land could be converted to agricultural use.
Asimov pegs the beginning of this behavior at a thousand or so years ago. It had actually started much earlier. But Asimov was forced to rely on the "historical" (i. e. written) record of events.
The ability of archeological and geological (i. e. unwritten) record had not been developed sufficiently back then to shed much light on these kinds of questions. That was to come later. Those sources eventually pointed to a much earlier date for the changes Asimov highlights.
Asimov notes that, not only did this change eliminate many of the handy sources of wood leading to a wood shortage. But the land cleared as a result was allowed to deteriorate. Now, most of it is no longer in good enough shape to be appealing to farmers. The result of this change in the characteristics of large tracts of land is a low density of occupancy that can't support modern civilizations.
Instead it is populated by people Asimov describes as "ground down and backward". We might quibble with Asimov's characterization of the worth of these people. But it is undoubtedly true that only low density activities were possible now that the land's ability to support high intensity agriculture had been lost.
This "cut down the forests" trend continued into the middle ages in Europe. This resulted in little remaining forested land there. The arrival of Europeans in the Americas saw a similar transformation. "Almost no great stands of virgin timber remain . . . except in Canada and Siberia."
Except that we now know that natives in both North and South America had a profound effect on forest structure well before Europeans arrived. What looked like "virgin" timber to European eyes was actually anything but. And it turns out that the situation was not as dire as Asimov painted it at the time.
Satellite imagery now allows us to accurately map the extent of forests. There was a lot more healthy forest around than is apparent from Asimov's statements. They were just in smaller stands, which he ignored.
But we have since gone a long way toward cutting those down too in the half century since. We have also denuded large areas of Amazonia, Asia, and other places that weren't even on Asimov's radar.
As Asimov notes, civilization writ large moved on to "fossil fuels", coal and oil. They are resources that "cannot be replaced". As a result, "man is living on his capital at an extravagant rate". So we will reach "peak production" in the '80s. It turns out that people were talking about this as a problem even back in the '50s.
Asimov's prediction was remarkably accurate. He missed by a decade or so. His miss was caused by various unanticipated events like the Arab Oil Embargo. But we reached peak oil pretty much when he said we would.
So, why don't we now have an oil shortage? A technology fix came along that Asimov couldn't have anticipated. Fracking, fracturing the rock that held oil so that it could escape and be pumped to the surface, was unknown at the time the book was written.
Horizontal drilling, and other technological tricks that make fracking economically feasible were also beyond the technology of his day. But they were also not needed back then. The oil fields of West Texas and the Middle East were producing vast quantities of oil that was easy to extract using unsophisticated techniques.
All forecasts, including Asimov's, assumed that the technology would get better and that the price, after adjusting for inflation, would rise. A price rise makes it economically feasible to employ more complex and more expensive technology.
And for many decades the oil industry hewed closely to those assumptions about the state of the technology and the state of the market. (The Arab oil embargo's effect was only to the timing of price increases.) It was only when we actually reached, or appeared to reach, peak oil that the industry became willing to try "crazy" ideas. Horizontal drilling and fracking were two of the crazy ideas that panned out.
There has always been far more coal in the ground than there is oil. As a result, estimates of when "peak coal" would hit have pointed to a date in the relatively far future. Asimov's estimate of the twenty-fifth century was in line with estimates of the time. What has done coal in is not availability. There is still plenty of it around. Instead, it has been economics.
Coal has a much lower energy density than oil. It is also much messier to make use of. There was a substantial industry devoted to making various chemicals out of coal in the 1800s. But when oil became readily available industry quickly switched to oil and never looked back. Today coal is pretty much restricted to being used to make steel and electricity.
Coal is dirt that contains a lot of carbon. But it's still dirt. Separating the carbon from the dirt leaves a lot of nasty, useless, stuff behind. Coal also throws lots of nasty stuff into the air when you burn it. For a long time the alternatives to coal were expensive enough that people put up with these disadvantages.
But inexpensive natural gas has been widely available for several decades now. It is far cheaper to ship than coal. All you need to ship it from here to there is a pipe from here to there that is a few inches in diameter. Natural gas does throw a lot of carbon dioxide into the air. But it throws far less than coal does. And carbon dioxide is pretty much the only nasty thing it does throw into the air.
The list of nasty things that coal throws into the air over and above carbon dioxide is nearly endless. I will just mention three. First, there is the sulfur that I noted earlier. Then there is arsenic. Yes the poison featured in countless murder mysteries. Finally, there is Mercury. It too is truly nasty stuff once it's airborne.
In Asimov's time, and for a couple of decades afterwards, the oil industry threw natural gas away by "flaring it off", literally burning it to get rid of it. But eventually they caught wise. It's low expense, convenience, and widespread availability has made it quite popular.
To make a coal fired power plant you need to build a large, dirty, expensive, and complex structure that is a terrible neighbor. To build a natural gas fired power plant capable of producing the same amount of power you need a few modified jet engines connected to generators.
"Gas" power plants are cheap to build, cheap to maintain, require far less land, and don't make much noise or mess. So they can be sited almost anywhere. Natural gas fired power plants have done far more to kill off coal than everything else combined.
Asimov then moves on to the question of efficiency. Theoretical efficiency, the best efficiency that thermodynamics allows, has been covered previously, both by Asimov and by me. It will not be revisited. Asimov notes that thermocouples, devices that convert heat directly to electricity, are only capable of an efficiency of 10%. A steam generator of the time was capable of an efficiency in the 30-40% range.
We are still mining "efficiency" as a method of stretching supplies. We now have appliances and light bulbs that are much more efficient than they used to be. Jet engines used on airplanes are much more efficient than the ones used in 1960. Insulating homes better increases efficiency.
Building lighter cars, and other vehicles, helps. The Ford F-150 pickup truck now contains a lot of aluminum in order to improve its efficiency by reducing its weight. We now have Hybrid cars. They can get by with a much smaller and, therefore, lighter engine. The search goes on. Increased efficiency is helpful but not a game changer.
Asimov then mentions "renewable energy". See! The idea is older than you think. He mentions wood (you can always grow more), wind, and water. At the time hydro-electric dams were popular, especially in my neck of the woods. The problem is that by 1960 most of the best locations in the U. S. for building a hydroelectric dam were already in use. Not much room for growth.
And two major problems have since come to light. The one that gets the most ink is the fact that dams screw up the ability of fish to migrate. The less noted problem is that dams also block the silt and debris that rives wash down to the sea. This results in the reservoir behind the dam "silting up". But it also interferes with that silt and debris moving down stream where it turns out it is needed.
Beaches are not permanent. Instead, they are maintained by being continuingly renewed by sand that is transported from upstream by rivers. As this and other problems have emerged we have moved from building dams to tearing them down.
Wind had been a source of energy for hundreds of years by this point. The Dutch windmill being only an obvious example. In 1960, however, wind power was seen as only appropriate for use in a few niche categories. In fact, in the roughly 50-100 year period preceding the publication of Asimov's book, maritime commerce had converted from wind power in the form of sails to fossil fuel power in the form of engines powered by coal or oil.
Since then, high efficiency "wind turbines" have been deployed widely. And the rate at which they continue to be rolled out is only accelerating. The idea of using wind to generate large quantities of electricity wasn't on anybody's mind in 1960.
Asimov then moves on to sun power. There is the direct method, using mirrors to concentrate the sun's heat. This was only a gleam in the eye of various futurists in 1960. Direct sum power is now widely used as the power source for desalinization plants. It is used in a few places to make electricity. But the technology has not caught on an any big way.
Asimov then moves on to something that has caught on in a big way, what we now call the solar cell. Solar cells were at the "proof of concept" stage of development at the time of the book. A few satellites used them as a power source. That was about it. The problems were practical. Solar cells were too inefficient (they were only capable of capturing a few percent of the power contained in sunlight) and they were expensive to make.
Tremendous progress has been made on both fronts. Solar cells that have efficiency ratings in the 15-20% range are widely available. Solar cells with efficiencies in the 20-30% range, and using a number of different formulations, look to be widely available soon. And they can now be economically manufactured literally by the acre.
The efficiencies have improved to the point that people find it cost effective to cover the roof of their house with them. Such a setup can easily power an entire house and leave power to spare. And this even applies to the more northerly parts of the U. S. Commercial "solar farms" now provide power that is as cheap as or cheaper than power from traditional power plants powered by coal or natural gas.
In the case of both wind and solar there is a problem to be solved. They are "intermittent". They either depend on the sun shining or the wind blowing. There are a couple of ways to handle this. They boil down to a much more capable and robust national electrical grid. This would allow surplus power generated here to make up for shortages there. So far, nearly zero money has been invested in this. That is criminal.
The second approach is storage. If we have enough power stored to run the entire national grid for two days then we should be able to smooth any dip that comes down the pike. (Probably considerably less capacity would be sufficient.) Here, the problem is technological.
There is no storage technology that scales to that quantity at a reasonable cost. As a result, what's currently being done is to install gas fired generating plants all over the place and use them to backstop renewable sources. It works but it is not the right solution.
And, it turns out, all the attention showered by Asimov on these various technologies is just a setup for what he actually wants to talk about. As the title gives away, what Asimov wants to talk about is "atomic energy".
Most of what we think of when we think of energy is "chemical energy". It comes from rearranging the bonds between electrons orbiting various atoms. Chemists call these rearrangements "chemical reactions". Any form of fire or explosion is chemical energy in action. The amount of energy available may seem enormous. But it is tiny compared to the "nuclear reactions" physicists study.
The amount of chemical energy available in a gram of material is modest. It might amount to what you get by striking a match. At best, it amounts to the amount of energy released by a small firecracker. The amount of nuclear energy that can be released by the same gram of material can literally level a city. It leveled Hiroshima and Nagasaki.
It was a slow process discovering what nuclear reactions were capable of and how they worked. Chadwick was the first to get an inkling of how to study the nucleus in 1932. The neutron was electrically neutral. That made it a good choice as a probe to use to study the nucleus without having to worry about pesky electrical effects. Fermi was the first to observe that "slow" neutrons worked better than "fast" ones.
Rather than going with Asimov's explanation of slow neutrons versus fast ones, try this. Imagine that the nucleus of an atom is a water droplet and a neutron is as particle of sand. If the sand particle hits the nucleus at high speed it just drills though leaving the water droplet pretty much unchanged.
If, however, the sand particle is moving very slowly it gets absorbed by the water droplet. A slow neutron being absorbed by the nucleus of an atom allows it to interact with the other nuclear particles. That interaction was what Fermi was looking for. (We'll get to medium speed neutrons later.)
Physicists summarize this behavior by talking about the "cross section". In a given set of circumstances the nucleus has a given cross section. For a fast neutron the cross section is very small, the size of a catcher's mitt, for instance.
For a slow neutron. the nucleus has a big cross section, something like the broad size of a barn. This led physicists to cheekily invent a unit called the "barn" to describe nuclear cross sections. Other than noting that it is very small, I am going to leave its actual value unspecified.
Atomic nucleuses are very complex beasts. We know a lot more about them now then we did in 1960. But, for our purposes, we are going to ignore all that and just assume that atomic nucleuses consist of a bunch of protons and neutrons somehow all stuck together. We are going to dive into nuclear chemistry only far enough to note that changing the number of protons or neutrons in a nucleus changes the nature of the beast.
Since neutrons are neutral, if we change the number of neutrons we don't change what kind of element we are dealing with. Changing the number of protons changes that. There is literally a one-to-one correspondence with the number of protons and the type of element. But changing the number of neutrons does make a difference. Often it changes the degree to which the atom is radioactive.
In the simplest case, Hydrogen with no neutrons is not radioactive. Hydrogen with one neutron is radioactive. Hydrogen with two neurons is highly radioactive. If an element is highly radioactive it has a good chance of decaying, blowing up into two or more assemblies, each containing an assortment of protons and neutrons.
Several scientists set out to bombard Uranium with slow neutrons. They thought that the neutron would be absorbed and somehow turned into a proton. This would result in the creation of a small amount of whatever element 93 was.
Fermi took a crack at it. Hahn and Meitner took a crack at it. (Meitner had to stop work and flee because this was '30s Europe and she was Jewish.) Strassmann replaced her and the work continued.
Eventually they figured out what had happened and what had happened was a big surprise. What had happened was what we now call "nuclear fission". (Surprises happen all the time in science.) As you might have guessed by now, instead of absorbing the neutron and staying intact, the Uranium nucleus had undergone fission. It had broken into pieces and one of those pieces was a Radium atom.
Except that turned out to be wrong too. What had actually been created was an atom of Barium. Marie Curie's daughter Irene and Irene's associate Savitch were among the most prominent to go down the Radium rabbit hole and end up with nothing to show for it.
It was Meitner (yes, the same Meitner), in an article in "Nature" in 1939, who was the first to point to Barium. Her insight was later confirmed by a number of groups. She also was the one who named the process "fission". On to "The Atom Bomb".
This chapter is really just a continuation of the previous one. Asimov continues the story without missing a beat. He starts out by noting that the fission of a Uranium nucleus, specifically a U-235 nucleus (he skips over this detail), produces about two neutrons.
If both of these neutrons each end up causing the fissioning of an additional Uranium nucleus then we have the makings of a "chain reaction". And, since each fission results in the release of a tremendous amount of energy, we have the makings of a source of a whole lot of energy.
Numerous physicists saw the possibilities of nuclear chain reactions. The fissioning of a single ounce of Uranium produces the same amount of energy as burning 90 tons of coal, or 2,000 gallons of fuel oil, or 600 tons of TNT, according to the calculations Asimov publishes.
If Asimov's numbers are to be believed, the Hiroshima bomb would have been the result of fissioning about a pound of Uranium. I believe Asimov's figures deliberately understate the amount of energy produced by fissioning an ounce of Uranium, possibly because the correct value was classified at the time.
As Asimov notes, this discovery was made in 1939 on the even of World War II, a War that everybody could see coming well before it arrived. The military applications of nuclear fission were obvious and troubling. Most scientists viewed the possibility of Nazi Germany making use of this information with alarm.
Asimov then goes on to review the story of the mostly American effort that resulted in the development of the Atomic Bomb and its use against Japan. Szilard went to Einstein who, in turn, wrote a letter to FDR. He, in turn, authorized the "Manhattan Project", so named because it was run by General Lesley Groves, director of the Manhattan Engineering District of the U. S. Army Corps of Engineers. Groves, in turn, recruited Robert Oppenheimer as lead scientist.
Asimov goes into some detail about both the technical details of how an atomic bomb works and the difficulties involved in building one. I am going to skip over most of that. If you are interested, check out "The Making of the Atomic Bomb" by Richard Rhodes. it is excellent. In lieu of what Asimov and Rhodes have to say on the subject, here are some observations.
The Manhattan Project was, by far, the biggest, most expensive, and most difficult project undertaken anywhere in the world up until that time, It involved constructing massive facilities at Hanford Washington (primarily Plutonium production), Oak Ridge Tennessee (primarily enriched Uranium production), and to a lesser extent, at Los Alamos New Mexico (Research and Development, final bomb assembly). Although it was a mostly U. S. effort, it involved a great deal of help and support by the United Kingdom. It also involved substantial help and support by Canada and several other countries.
As we all now know, the U. S. succeeded in building three working devices, the test bomb that was exploded at the "trinity" site near Alamogordo New Mexico, and the two production bombs, one of which was exploded over Hiroshima Japan and the other over Nagasaki Japan. Fortunately for all of us, the German effort ended up going nowhere. If you want to know more about this very interesting story, I recommend "Heisenberg's War" by Thomas Powers. Back to Asimov.
As he notes, the U. S. had a monopoly on the Atomic Bomb for only four years. Unbeknownst to most, the Russian intelligence agencies had completely penetrated the Manhattan Project. They managed to spirit away all the information they needed to build their own device. Sakharov, their chief scientist, took no shortcuts, however. So the Russians were able to develop a robust program that was soon able to move beyond just the cloning of American designs.
No doubt, the intelligence the Russians collected sped things up. But, once everyone knew such a thing was possible, duplicating the feat was simply a matter of devoting the necessary resources. The Russians succeeded in 1949.
The British succeeded in '52. The French succeeded in '60. The Chinese succeeded in '64. Since then, several other countries have succeeded. The newest member of the "nuclear club" is North Korea. South Africa is unique in having developed the expertise necessary to join the club, but then shutting everything down and walking away from it.
He then moves on to what was at one time called the "Super", a bomb based not on nuclear fission but on nuclear fusion. Again, I am going to skip over the details. If you are interested, I would suggest reading "Dark Sun" by Richard Rhodes. Here too I will confine myself to some observations.
In the immediate aftermath of the War many nuclear scientists were not even sure what later came to be called a "Hydrogen Bomb" could even be built. The nuclear part of it was well understood. Smash together two Hydrogen nucleuses under appropriate circumstances, and they will fuse to become a single Helium nucleus. And that fusion will release a tremendous amount of energy.
The problem was in creating the "appropriate circumstances". It turns out that X-Rays were the key ingredient. An Atomic Bomb can be tuned to release tremendous amounts of the appropriate kind of X-Rays. Then it was determined that an appropriate type of mirror could be used to focus the X-Rays on a tank of Hydrogen, which could be located off to the side. With these two ideas in hand, the problem of how to build an H-bomb, as it came to be known, was solved.
This turned out to be all you needed to build a "proof of concept" device. But the design was not practical as a weapon. "Mike", the only bomb built using this design, weighed something like 42 tons and was too big to fit into an airplane. But then another idea, dissolving the Hydrogen in Lithium, came along and enabled a "miniaturized" design that was practical for use as a weapon. The rest, as they say, is history.
Again, the U. S. was first, but not for long. The U. S. set "Mike" off in 1952 and had working miniaturized devices shortly thereafter. The Russians were not far behind. They first succeeded in '53. They later went on to set off the largest H-bomb ever exploded in the late '60s. It was a 100 Megaton (million tons of TNT equivalent) design that had been deliberately downrated to only 50 megatons.
It's still holds the record for the largest H-bomb ever set off, but not because bigger bombs can't be built. It's because anything over 10 megatons is a complete waste. Large H-bombs blow the top of the atmosphere off. This causes a "stovepipe" effect. All the energy flows up the stovepipe and out into space. Viewed from anywhere but space, all large H-bombs behave just like a 10 megaton H-bomb. Such is the strange logic of nuclear warfare.
Asimov finished off his discussion with the fission-fusion-fission bomb. I am going to skip it. Instead, I am going to leave you with an optimistic thought. Everyone, from science fiction writers to scientists and philosophers, who seriously contemplated nuclear weapons during this period (say 1935-1965), came to the conclusion that "if it can be built then it will be used". But no nuclear weapon has been used in battle since 1945, seventy-five years ago. And the chances of that streak continuing indefinitely keeps getting better and better. Peace out.
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