Of Science and Scientists; 16; Are Atoms Real?

Our home's real now. Nobody has ever seen an atom. Yet scientists count them. They even build y o models which show how atoms are in space but can be counted and located and weighed. Then surely atoms. That one was real. But of course if the chap who asked the question

had only said are flying saucers real we might have had something to argue about. But Adams after all this isn't 1810 are 1910 this is today. But you can't see them. What of it. Yeah but you can breathe it and feel it pushing against you on any windy corner. Things can be real without being visible. But come to think of it we're being a bit superficial. Our question Are Adam Israel invites us to do some hard thinking about the word real and about what the scientist knows about atoms. After all the word real is one of the most important in the language and more than a little tricky. We all use it and have a feeling for its meaning. But there isn't any clear and generally accepted definition. All of us will agree as to the importance of a proper sense of reality to feeling for the

distinction between reality and illusion reality in fiction reality and myth. This is the mark of sanity maturity and education. An insane person is one who lives in a world of delusion. Out of touch with reality. Because you cannot face it. A child who daydreams over a minute over much. And it's been spent. Stories as a child the imperfect feeling for reality. The ignorant superstitious and credulous. Like the child in their imperfect sense of reality. Among primitive men. Fact and fancy have always been fantastically intertwined. The archaeologist tell us that in the ancient civilizations of Egypt and Babylon the shoppe distinction We draw today between dreams hallucinations and almost sight was not generally drawn nor was there a clean separation in thought between appearance and reality. It was the Greeks who first interpreted they were directed by our senses.

Where the light and color sound taste smell and touch as a world of appearance behind which there must be a world of reality. From this point of view we can regard science which began with the Greeks as an attempt to lay bare the real world behind the camouflage of appearance. You see Rod thrust up likely into the water appears to be broken that the water shirkers. But in reality it is as straight as the sun appears to rise in the Aist and sink in the way. Just in reality according to Copernicus and Galileo the sun stand still. It appears to move only because we see it from a moving earth which spins on its axis as it slowly swings around its sun centered orbit. Brianna they suggest truth and fact. Truth is sometimes defined as agreement with reality. Thus the scientific exploration of reality is a

part of man's great quest for truth. And the scientific way of getting at reality is his most powerful aid in the search for truth. From this point of view the deeper the scientist goes in his exploration of the physical universe the more he understands the closer he is to reality. Yet the real world is what lies behind the world of appearances than the world of the atoms electrons photons and electric waves disclosed by modern science can well be regarded as the real physical world. So let's look at this world of atoms. Physicists and chemists believe that matter is granular that it is composed of particles we call them atoms too small to see individually even in a high powered microscope. They tend to unite in small tightly knit groups called molecules. These models they represent atoms joined together into molecules different kinds.

Sometimes the atoms remain a thing in this case we call them single atom molecules. Please know the distinction between atoms and molecules is for many purposes unimportant do not worry if I sometimes see and seem to use the words interchangeably. A sample of any pure substance consists of an enormous number of molecules or atoms of the same species they are conceived to be in perpetual chaotic haphazard motion. We call this invisible motion of invisible particles. Thermal agitation the energy of this motion is heat. The intensity of the motion is measured by temperature as the temperature rises. The pace of the motion is increased as the temperature falls. The motion slowed down until at the absolute zero four hundred and sixty degrees below the ordinary zero. To all intents and purposes it ceases this conception of matter and

heat helps us to understand the three fundamental states of matter or liquid. Solids and liquids the molecules are huddled together whereas in a vapor or gas they're relatively far apart on the average solids and liquids are held together by strong forces of attraction which atoms and molecules exert on each other when in contact. You know they are on the other hand the attractive forces are unimportant. Most solids are crystal and by the crystals are small and mashed together as in this piece of granite or whether they are separate. In these other cases this is quartz and rock salt in a crystal such as a rock song. The molecules for my regular pattern like the cells of a honeycomb each atom and molecule is bound to a fixed position by the attractions of its neighbors.

The pattern of this structure determines the natural accidental shape of the crystals and the shapes of the pieces. And when the pieces fall on when it is broken. Let us not try to imagine what goes on inside as solid as it is heated up. Let me show you a crude model of a few atoms or molecules in the interior of a solid at the absolute zero. Each rest at its fixed equilibrium position as heat is that of the molecules are set into vibration at higher temperatures the pace of the motion increases until finally you disorganize the structure. The attractive forces are no longer able to hold the molecules near their home bases. The material loses its definite form and melts it now forms a liquid that accommodates its shape to that of any contending vessel. This is what happens

when we melt a candle. In the case of a liquid the binding forces though insufficient to maintain a solid structure are still able to keep the molecules huddled together in a compact mass. If a molecule on the outside of a drop of water is given an accidental shell toward the surface the combined attractions of its neighbors are usually able to prevent its escape. Occasionally however the accidents of the thermal dance will give a surface molecule a much larger push than usual with the result that it does escape from the drop into the surrounding air and molecule evaporates it debtor's that they first state our gaseous state. In ordinary air Steve or any gas the molecules are far apart on the average. They collide with one another but most of the life of any molecule is

spent so far from its neighbors that it lies beyond the range of their attractive forces. The molecules are free. Aside from an occasional collations this is only a suggestion. Now the way in which the molecules move in. Actually the molecules in a gas move at high speed in straight lines interrupted occasionally by a collision because of gas in comparison with a liquid or solid. Is it then the population of molecules the gas is no cohesion. And it expands to fill in a container in a container in which you put it like this. I've been describing very briefly the three states of matter solid liquid and

gas use in terms of the atomic molecular theory. In other words I've been giving you glimpses of the world of atoms. Let me assure you that such pictures shed a lot of light on the behavior of matter when it is heated or compressed or expanded. The atomic picture is equally useful in the interpretation of chemical reactions. Each element is conceived of as composed of a corresponding species of atoms. When two elements unite to form a compound the atoms of the elements are combined to form molecules of the compound. Water for example is a compound of the molecules each of which contains two atoms of hydrogen and one of the element oxygen. This conception find thousands of confirmations in the air in the detail study of chemistry. There are no chemical or physical facts with which it does not harmonize. Moreover the atomic theory asserted not only to explain the already known facts

about the physical and chemical transformations of matter it is suggested an enormous variety of experiments that in turn suggest new facts about Adam's structure and properties in the light of our constantly growing knowledge of the details of the world of atoms. We are able to understand such things as why a glass and alcohol are transparent while iron and copper are not. Why a clean surface of silver gleams. Why a mixture of gasoline and air explodes bile and they've been lit by a match. We understand too why there are 91 elements found in nature that have atoms like that then you're a medium and no more. Why radium Thore and uranium are radioactive while oxygen nitrogen and iron are not how it is that the sun has been able to pour out vast quantities of heat for billions of years and does so still. These are deep questions. Fifty years ago I would hardly have dared ask most of them. Today we ask them and we know the answers and knowledge of the world of atoms brings power as well as

understanding power to control chemical processes to create a vast variety of new and useful materials such as Nylon. The technology and technological achievements of modern America rest firmly on our understanding of the world of atoms. In fact if the world of atoms is not real it would seem that American industry is built on an illusion. But perhaps you want to remind me at this time that the world of battens is a world of theory and if you are a hard boiled realist you may have a deep instinctive distrust of theory. You may say is it not true that the world of atoms is an imaginary world dreamed up by scientists to explain chemical experiments and chemical processes. No matter how useful these ideas are how can you be sure that atoms are real in the same sense the chairs trees and houses are real. Isn't it true that in many cases there are several theories that fit the same facts haven't the

scientists again and again had to change their spheres didn't die in style and idea of relativity upset the well established and useful theory of motion. You do not even upset our ideas of time and space. How then can we be sure that the theory of atoms will not be swept away by some future scientific revolution. These are hard questions though some of them have obvious answers. To be sure on the world of atoms is the world of scientific theory and scientific theory do change constantly. But the point to remember is this. When a fundamental theory with a wide range of applications is replaced the new theory must explain all the facts and relations explained by the old theory. Therefore it inevitably resembles the old theory in many respects and by our present theory of atoms we are able to tie together a dashed quantity of facts. Therefore we can be sure that any new theory that takes place must preserve the truly essential features of our present one. So always add on. So as

science makes new discoveries about the structure of matter we can expect subtle modifications of our present theories. But the abandonment of atoms is unthinkable. That would make nonsense of modern physics and chemistry mature science never destroys itself. It made changes but not its skeleton and the atomic idea is part of its skeleton. Moreover we have certain crucial types of experiment that point so directed toward the reality of atoms that the evidence seems truly overwhelming. I want to show you several direct proofs of atomic and molecular reality. First of all there's the Brownian motion you have to use this to see. Under the lenses of this microscope are fine particles of minerals suspended in water nothing else. The particles do not sit still therefore form an unceasing irregular motion as if they were a lot. They are not alive. All such particles execute is Brownian motion. If they are small enough.

Take a look. You see a particular. Various sizes. So letting in the water and drifting about. Look carefully at the smaller particles. They move somewhat irregularly and sometimes change their cautions because they are they move because they are small enough to share in the general temperature agitation of the water molecules that surround them. They are jostled by the invisible water molecules just as a ship at sea is jostled by the waves about the movement of a large ship is much less violent than that of a small small boat. So here the larger particles are less active. This is thermal agitation made visible. These particles are not molecules they're bits of powder but their motion proves the existence of a concealed thermal agitation. They give striking confirmation of the atomic conception of the nature of matter and heat. But I can do better than this. For example today it is a commonplace

matter to regard individual events in the atomic world. This recording is made easy by the existence of radioactive atoms atoms that spontaneously explode from time to time as they explode. And such atoms throw off high speed projectiles. There are several kinds but one variety of these projectiles is the alpha particle. This is an atom of helium that carries a double electrical charge. You say I'm not a particle alpha particle if you rejected into the air by a radioactive atom. It passes through thousands of molecules and knocks chips out of many of them. When a molecule is struck by a flying off a bottle it is commonly broken into two parts one carrying a positive charge and the other negative. The charged particles fragments of atoms or molecules are called ions. The process by which they're farmed is called ionization. Now I'm going to observe the production of

vines by off of particles or other kinds of particles. For that matter in several ways the simplest is to make use of the fact that any gas containing an appreciable number is a temporary electrical conductor. You can send a post or other electrical current through it amplify the pulse and use it to trigger off a loud speaker. This is the principle of the Geiger counter. Where do you buy prospectors hunting for your rainy M and for many of the purposes this instrument makes a clicking noise when it is in the presence of radioactive rays are the ever present stray cosmic rays. Each of these clicks regards an individual atomic explosion producing enough to raise or a stray cosmic ray as the ray enters the instrument it triggers off the pulse of a car which clicks in the loudspeaker hears a block of uranium. If I bring

this. Other guy. Crazy under the influence of the alpha particles which are constantly being emitted from the surface uranium these clicks mean flying particles moving with enormous speed. A particular subject and by the spontaneous explosion of atoms of your brain. Notice you can't see an individual uranium out. Atoms are flying off a particle. But you can hear it right. Or do you object to saying that you have heard my voice when it comes to you over a telephone wire by the way of the unspeakable complications of a television recording. This is pretty impressive proof of the reality of that. But we can do better. We can see the track made by flying out particles as these particles flying through the air. Each lays behind it trailer track a positive and negative vibe. These islands are as invisible in an ordinary microscope

as the alpha particles themselves as invisible as all individual molecules atoms or subatomic fragments. But there are ways to convert the invisible trail into a visible one. One way developed by CD-R Wilson is to allow the on trails to fall in chilled moist air for example. Maybe on this piece of dry ice. You say that the moisture of my breath forms a cloud when it's chill chilling creates a fall by condensing water vapor into a multitude of tiny visible drops of water. If there are islands present in such moist air the water drops condense on them first. If the zines are distributed along the trail left by an alpha particle the water droplets fall on the line are tracked where the alpha particle passed by. Those are these tracks you can build a glass enclosed cloud chamber similar to this one.

Inside the tracks are easy to photograph. They break when they tell interesting stories. Here for example is an iron trail photograph showing a pattern about the tracks from radioactive you. Here is a similar group of tracks from radioactive polonium. Here you can see what happens when the tracks in the field of a large electromagnetic bending of these tracks is due to the interaction of the charge carried by the alpha particles and the magnetic field. It proves that the particles carry positive electric charges. Now suppose the radioactive material that you use as the source of alpha rays is itself a gas next to the air in this case the spontaneous explosions which object the rays can start anywhere in the chamber and may move in any direction. Here is a single track from an atom of

radon in such a chamber in the case of Thor on another radioactive gas the explosions occur in pairs in rapid succession. We observe pairs of trails diverging from a common point. Let me object and yet again to throw around into this cloud chamber. At first you see a cloud formed by a confusion of ions as the gas enters and as the gas distributes itself out a bit you can see pairs of tracks. Each pair of on trails is automatically transformed into a pair of water dot fails sharply defined at first and then slowly fading. Now if you still have a lingering skepticism about the reality of atoms and molecules

you might ask yourself the question what are those tracks. What makes the Geiger counter click. How can such effects occur if matter is not composed of atoms. Professor Kimball has left us with a question. Did he do it just. Well I think I don't think so. I believe he only wanted you to decide whether you wanted to call atoms and molecules and ions. Now they are all not. Here is what I would say to this question. I take it that you and I and Professor Campbell think that our POWs are real now and that is at this certain place then in space it occupies a certain volume and it has to wait. What Professor Campbell has told you about molecules and atoms shows that they are in these three as I suspect

just like apples. Well not exactly a short but very very nearly so. So I would say that molecules and atoms. I have a couple and that goes to. But either way if you were to deny that that would simply move the discussion to another plane. But on that plane we should still hold the same view of atoms as an outpost. I believe. In the crowd chamber pictures which Professor Campbell showed us we saw tracks being made which consisted of illuminated water droplets. They were very much like the luminous tax made at night by a bullet all by him. I should think stopping it taking our atmosphere. So seeing this we say that some kind of small object which someone thought of calling an alpha particle behaves like it place a

boat that we can collect many of these particles and we find that what we've got is he gets show then we say these particles are constituents so he and gas that these atoms Moldova they must be electrically charged in order to be moving on curved tracks in the cloud chamber. As we have seen hence they are speaking more clearly helium ions gas molecules because we can find out how many they are in a cubic inch of Fosse they fly and so far all I've done are you know because we can not only count them off. We can locate them in space as they build up a case the light is like B. I'll hop out it goes because they behave like you do but it's these classes of things molecules atoms and ions. Small

chunks of matter sometimes electrified sometimes not and did fling the chunks of matter such as apples simply in being so then even a much smaller show of my own answer to both questions which I give you for what it's worth is if you know then two and the same goes for molecules and also fall. But note that Campbell didn't mention today any all that kind of particle. Maybe they are maybe they're not. I believe they are. But that poses another question. This is educational television.