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 all of them together, this is the eighteenth main entry in the series. You can go to http://sigma5.blogspot.com/2017/04/50-years-of-science-links.html for a post that contains links to all of the posts 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 be reviewing two sections: "Particles and Waves" from his chapter titled "The Waves", and "Fire and Steam" from his chapter titled "The Machines".
"Particles and Waves" is a discussion of the early days of Quantum Mechanics. Plank had introduced the idea that light, or more generally electromagnetic radiation, had both a particle aspect and a wave aspect.
By the 1920s it was obvious that dualism was not limited to electromagnetic radiation. Einstein had also introduced the dualism between mass and energy. His famous equation was just the way you converted one to the other. In 1915 with General Relativity he had done the same thing with space and time, creating the word spacetime to emphasize the degree with which they were intertwined.
And it was not just ethereal things like spacetime and electromagnetic radiation that had a dual nature. In 1923 de Broglie came along and predicted that down to earth particles, in this case electrons, could be made to behave in a distinctly wave-like manner. In 1927 an experiment done at Bell Labs proved this prediction correct. This surprising development was put to good use almost immediately in the form of the "electron microscope".
The sharpness with which a microscope is capable of resolving images depends on the wavelength of the "light". (Modern techniques have been developed to fudge this "rule" somewhat.) The wavelength associated with an electron microscope is in the X-Ray band, much shorter than the "visible" band our eyes are sensitive to. So electron microscopes are capable of taking sharp pictures of things that are much smaller than anything a standard light microscope can handle.
At the time of this discovery and right through to the time of publication of Asimov's book, electron microscopes were expensive and very hard to use. So they were used in very limited situations. Technological advances haven't make them as cheap and easy to use as a light microscope. But both cost and difficulty have plunged. So they are far more ubiquitous now. This has improved both their availability and their frequency of use.
The first crude electron microscope was built in 1932. The first practical one was built in 1937. But by "practical" I mean a device that was hand built by skilled technicians in a well equipped laboratory. All of these early machines were one of a kind devices with no two of them being identical. It would take a number of decades before you could order a standard model out of inventory from one of several "laboratory supply" companies.
Asimov speculates that some day a "Proton microscope" will be built. For reasons I am not going to get into, the heavier the particle, the shorter the wavelength. A Proton, weighing in at roughly 2,000 times as heavy as an electron, has a much smaller wavelength. That means that it can be used to "see" things that are even smaller than the kinds of things an electron microscope can see.
Proton microscopes are now a reality. As are devices that utilize even shorter wavelengths than the wavelength associated with a Proton microscope. These devices are all fantastically expensive and fantastically difficult to build and operate. So their usage is roughly similar to that of the electron microscope in the '30s.
By now, roughly 1930, things in this area of physics have been getting more and more confusing as the decades had passed. The simplicity and clarity of Newtonian mechanics kept getting dealt blow after blow. Things seemed to keep getting wronger and wronger. And for a long time it was not obvious how to build a new theory to replace Newtonian mechanics. Sure, it was wrong. But what was right?
The experimental proof of the existence of "matter waves" (particles like electrons demonstrating wave-like properties) actually helped rather than hurt. It pointed out the direction in which the new theory must lie. A consistent set of ideas kept popping up in situation after situation. They were completely bizarre but they seemed to be the way things worked in a wide variety of situations.
One of these places was in the nucleus of atoms. Bohr had come up with a model in which electrons orbited the nucleus. But if electrons behaved just like the planets in our solar system did then all kinds of problems arose. And by this time it was well known that electrons confined themselves to a small number of fixed "orbitals".
Electron orbitals were quantized in a way that planetary orbits were not. Schrodinger widened the gulf. He considered the wave nature of electrons and decided they did not travel in circular "planetary" orbits. He decided further that they didn't even have a fixed position in the way a planet orbiting the Sun does.
He could get things to work by focusing on the wavelength that de Broglie had calculated for the electron. He went on to come up with a whole "wave mechanics" to explain all this. Well, "explain" is not the right word. But what he did do was come up with a way to make calculations that got the right answer.
But trying to model the "reality" his equations described turned out to be a fools errand. There just wasn't a "planets orbiting the sun" (or any other kind of) model that could be created that matched either the equations or the reality.
Physics and much of science had made great progress by developing models and then using them to guide their exploration. But several decades of "quantum" this and that, now followed by "wave equations" and other developments left scientists feeling extremely uneasy. They did not want to be cut loose from their models.
But requiring a model that seemed anything like day to day experience was holding things back. At the time this concern was confined primarily to the physics community. Since then it has spread to all corners of society. It is one of the things driving the modern anti-science movement.
So Schrodinger dealt a blow to the idea that an electron was this tiny marble orbiting the nucleus like a small planet. Heisenberg proceeded to demolish this simple, comfortable model. He developed something called "matrix mechanics" do describe what was going on.
He replaced the simple "variable" of an Algebraic (or Calculus or other branches of higher mathematics) with a matrix. The "X" of "X + Y = Z" fame wasn't a number. It was a grid of numbers. The form looked the same. You still saw terms connected with operators like plus or minus or times or whatever. But a term had internal structure.
Mathematicians had worked out the "mathematics of matrixes" long since, if you restricted yourself to regular algebra. This new mathematics required much higher forms of math. But the techniques developed for dealing with matrixes in an algebraic situation could and were extended to provide techniques for dealing with this new regime. It was fiendishly difficult but it could be done. And Heisenberg showed how it should be done for his formulation.
I'm going to spare you from delving into any of this. But there is a consequence of Heisenberg's matrix mechanics that we have all become more or less familiar with. That's his "Uncertainty Principle".
Asimov, master explainer that he is, starts in the right place. Heisenberg concerned himself with a seemingly simple question: "where's the electron right now?" The obvious way to find out is to shine a light on it and look for it. But what, exactly does that mean? And what would you see if that's what you did?
Electrons are small and light. That means they can easily be pushed around by something like the photons that light is composed of. So, the very process of trying to find out where the electron is inevitably changes its position. In short, the process of trying to observe an electron introduces some uncertainty in its location. You can never be truly sure exactly where it is.
That's where Asimov leaves things. It is a "natural" explanation that doesn't give anybody any trouble. But Asimov is doing us a disservice. What Heisenberg really believed, and what physicists now also believe, is not that there was some technical limitation that rendered positions uncertain.
Rather, Heisenberg believed that the position of an electron is inherently uncertain. Even if you could come up with a clever experimental technique that would permit measuring the location of an electron without bouncing something off of it, that wouldn't be enough. Even though you avoided changing its location by bouncing your probe off of it, you would still find that you couldn't nail the exact location of the electron down.
Asimov then goes on to briefly discuss the philosophical ramifications of this uncertainty. They are widespread and profound. Religion has been debating the subject of "free will" for millennia.
If the world is "deterministic", then you can predict all future events with complete accuracy if only you know the present to a high enough degree of precision. In a deterministic universe free will is literally impossible. Instead, "what will be, will be."
If there is no free will then the concept of sin makes no sense. If you murder someone but the laws of the universe (determinism) tell us that you had no choice then it's not your fault. Since you had no choice in the matter you do not deserve to be punished. Uncertainty provides a scientific justification for believing that free will is possible.
Uncertainty means that we can't know everything. But that begs the question: can we know anything? I could go on. But lots of books have been written on all this. And some of the people who wrote them are a lot smarter than I am.
Asimov leaves us here on the verge of Quantum Mechanics. So he and we will now move on to a new chapter, "The Machine", and a new topic, "Fire and Steam".
With this section we move from the weirdness of Quantum Mechanics, or at least the run up to it, and to the world of backyard mechanics. As Asimov observes, "[t]he whole civilization of mankind has been built on finding new sources of energy and harnessing them in more efficient and sophisticated ways".
He blithely continues from there as if "onward and upward" was all there was to it. I'll have something to say about this later. In the mean time, "we shall make a rapid survey of the engines, machines, and instruments" that have made this ascent possible.
The first of these is fire, "discovered" perhaps a half a million years ago according to Asimov. Current suggestive but not definitive evidence for the use of fire puts the date at about 1.4 million years ago. The oldest date for which we currently have incontrovertible evidence of human use of fire is 780,000 years ago.
Fire provides warmth. But it also enables cooked food to become a diet staple. Cooking not only warms food. It also chemically modifies it in ways that make otherwise inedible food edible. There are numerous other benefits to cooked food.
Fire, or more broadly, the release of chemical energy, provides what Asimov describes as "a practically limitless supply of energy". But, as an energy supply, it has many limitations. This is particularly true in the pre-industrial age. In this period mankind was pretty much limited to burning wood.
Burning wood provides more energy than human muscle power can provide. But, by modern measures, the amount of available energy is limited. And in a pre-industrial world it can't be used for much beyond supplying heat for warmth and for cooking. Oh, and the development of the lamp did enable it to be used to provide a modest amount of lighting.
Early efforts to look beyond wood (and, to a modest extent, fats and oils burned in lamps and stoves) first began in the "Dark Ages", the medieval period in Europe. There some people discovered that coal could be burned.
The military necessity of making high quality swords and other military devices led to an interest in high temperature metallurgy. Coal made access to high temperature furnaces easier. And that led to a move from iron to steel in weaponry. But coal remained confined to this niche use for a long time.
The medieval period also saw the introduction of wind and water driven "mills" to grind grains and for other purposes. Asimov also notes that this period in time saw the introduction of explosives (a semi-legitimate adjunct to his subject), and the development of the magnetic compass (an illegitimate adjunct as it was not a method for harnessing significant amounts of energy). Finally, he notes the use of coal and other energy sources to produce glass started during this period. Very little glass was made before the industrial age so I will grant the subject only a very modest degree of legitimacy as an appropriate adjunct.
But almost all inanimate energy use was then derived from the burning of wood for heating and cooking purposes. And Asimov doesn't even mention the harnessing of wind power for transportation uses by means of sails. Using sails to power boats actually precedes the medieval period by perhaps a thousand years.
Asimov gives a brief history of the use of explosives in a military context, noting that cannons featured prominently in the Battle of Crecy in 1348 and were in general use from then on. He then takes a detour into movable type. That was an important development, Guttenberg's Bibles were printed in about 1450, but made little difference in the availability or use of "fire and steam". (He also notes the importance of the nearly simultaneous replacement of parchment with paper as being an important development.) He then returns to the subject at hand.
At the end of the seventeenth century attention was paid to the problem of removing water from mines. The obvious solution is the pump. This presented two subproblems. The first one was the most obvious. Where do you get the energy to run the pump from? The most obvious solutions were manpower and animal power. Both had limitations.
The second one was the odd fact that you could suck water up at most 33 feet. Why? Asimov doesn't address this issue here because he already talked about it elsewhere. See http://sigma5.blogspot.com/2017/04/50-years-of-science-part-8.html for my discussion of his section on "The Atmosphere". Water can only be pulled up 33 feet because that's how tall a column of water needs to be to balance out the pressure of the atmosphere at sea level (about 15 pounds per square inch). Back to pumps.
One idea was to fill a chamber with steam then pour some cold water in. This would cause the steam to condense. That would leave a vacuum behind which could be used to suck the water up out of the mine. The first one to get a "steam engine" to work was Savery. (BTW, at the time "engine" just meant any kind of clever device.) Savery's engine worked. But it was dangerous and inefficient.
But this is often true. Someone figures out how to do something "at all". The first device works but not very well. Then others can see what he did and refine it so that it works better. Soon the child or grandchild or great grandchild of the original device works very well. And that's what happened in this case.
Newcomen came along less than a decade later with his "new and improved" steam engine in 1698. It was far less dangerous and a lot more efficient. But it still didn't work all that well. Newcomen's design was state of the art for more than 60 years. But then Watt came along and came up with the first relatively efficient steam engine. That's why we associate Watt with the invention of the steam engine.
He also gets most of the credit because Watt engines were used for something other than pumping water out of mines. In 1787 an American, Fitch, put a Watt engine in a boat and made it move. The boat was a success from a technical point of view but a failure from a financial point of view. So we have forgotten Fitch and remember Fulton instead.
The "Clairmont", Fulton's steam powered ship, was a success in every way. In the 1830's, less than thirty years later, steam powered ships were routinely crossing the Atlantic Ocean. During this same period the "screw propeller" replaced "sidewheel" and "sternwheel" paddlewheels as the method of propulsion.
In parallel with the advent of waterborne steam propulsion came the advent of steam powered land vehicles. Stephenson built the first of what we now call "steam locomotives" to power what we now call a railroad train in 1814. Designs improved rapidly. As a result the first "transcontinental railroad" was in operation in the US by 1869.
Steam power created the ability to travel by sea more quickly and more comfortably that had heretofore been possible using wind power. Railroads were quicker, more comfortable, and cheaper, than traveling in a stagecoach powered by horses. The steam engine revolutionized transportation by making it possible to apply far more energy in a far more controlled fashion than had bee possible prior to its invention.
I could go into my discussion of the whole "onward and upward" business when it comes to energy consumption here. But I am going to leave that discussion for a later day and end here.
No comments:
Post a Comment