advanced students of cosmology - in the achievement of an approach to science which is based upon simple

While it is true that the language of mathematics is a universal language, it is, nevertheless, a language which must

be learned before it can be used or understood.

It was principally for these reasons that this article is being written. Consequently, simple discussion, explanation

and analogy will be substituted for mathematics, to the greatest possible degree. We will risk, thereby, the scorn of

the mathematician, but may gain the gratitude and the comprehension of the non-math student.

Much of the material presented in these pages was taken from a series of lectures originally written and published

some years ago, but whose basic concepts are only now beginning to be accepted by cosmologists.

Since the study of cosmology embraces the microcosm as well as the macrocosm, we will begin this text with a

consideration of the most minute and fundamental particles of nature, insofar as they are known and understood

today. We will examine the forces which bind these particles together, but which may also under certain

circumstances, hurl them violently apart.

We will begin our examination of the universe by considering, briefly, the nature of four of its most minute and

fundamental entities: the neutron, the proton, the electron and the photon (or quantum of energy). No man has

been ever seen any of the four. So minute are they, that the most powerful microscope every made could not begin

to resolve them. Yet all of the matter in the universe is composed of the first three, and all of the changes which

occur in that universe come about as a result of the action of the fourth.

In order to achieve the basic understanding of the nature and properties of the electron, the proton and the neutron,

we will arbitrarily create or assume a fourth particle which we will call the ‘nullatron’ (editor's note: subsequently

discovered 10 years later, the neutrino). We will postulate that this particle has no charge, possesses no energy, and

consequently is not associated with any type of field. In fact we will assume that this particle has no property other

than that of inertial mass, or resistance to acceleration. We hasten to confess that, so far as we know, no evidence

of the existence of such a particle is available in our present technology and, because of its dearth of properties, its

existence would be exceedingly difficult to demonstrate by any presently know method. Nevertheless, the

assumption of such a particle offers an ideal starting point in our examination of the nature of matter, and so we will

assume the particle, if only to serve as an aid to understanding.

If, to the nullatron, we add a photon or, as it is more usually known, a quantum of energy, in such a way that the

energy is entirely contained within the particle, we will find that the particle has acquired several additional

properties. In adding the quantum of energy, we have supplied the particle with both a positive and a negative

charge. (See definition of energy in StarSteps, Fuel 2000.) Since these charges are united within the particle, there

will be no exterior electrical field, but a gravitational field will be created. This particle, which now exhibits the

properties of inertial and gravitational mass, has been named the neutron. Its existence was demonstrated in 1932

by Sir James Chadwick, an English Physicist.

If we could find a means of dividing the quantum of energy into its two component parts, and of drawing the

negative charge out of the body of the neutron, so that the charge formed a shell of force around the core, we could

convert the neutron into the simplest of all atoms, the atom of the element which we call Hydrogen. The simple

particle has now become a rather complex mechanism. The central core which retains almost all of the mass, and

from which the gravitational field still emanates, now has a positive electrical charge, and is know as a proton. The

shell of force, which consists entirely of the negative portion of the quantum of energy is known as an electron.

In most of our textbooks today, the electron is represented as a small particle in a precise orbit about the proton in

much the same manner as the earth orbits the sun. While this analogy works fairly well as long as we confine our

study to the field of chemistry, if we attempt to explain all of the observed properties of matter by nuclear

hypothesis, we will find that we require a somewhat more complex analogy.

Let us, therefore, attempt to create such an analogy, remembering that, like the nullatron, it is created only as a tool

of understanding. We will begin with the usual concept: a small particle in a simple orbit around the proton. We

will then assume that the electron is extended or ‘stretched out’ along the path of its orbit until it becomes a ring of

charge occupying, simultaneously, all parts of its orbit, but still having the same rotational, or angular velocity. If

we now rotate the ring upon an axis which passes through the proton and two opposite points in the ring, we will

create a sphere of charge about the proton which is uniform in density but characterized by precise angular

velocities about each of the two axes. While the assumption of these angular velocities in not particularly important

in our first approach to the nature of matter, they do become necessary to the explanation of some of the more

complex phenomena such as crystallization in solids, diffraction of light, etc.

Having examined the atom from inside outward, as it were, by theoretical creation, we should now be better

prepared to examine it from the outside inward, as we shall presently proceed to do.

We must remember that the atom which we have created is the simplest of all the atom family. It is known as 1H1

or ‘normal’ hydrogen.

If we add a neutron to the proton which is at the center of this atom, we create a particle called 1H2 or deuterium.

This atom is still hydrogen and has chemical properties identical with those of 1H1. The mass and weight,

however, are now twice as great. For this reason, 1H2 is frequently referred to as heavy hydrogen.

If we add a second neutron to the nucleus we will have 1H3 or tritium. It is still chemically identical with 1H1 but

has three times the mass. It is sometimes known as heavy, heavy, hydrogen.

It becomes apparent that the chemical properties of the element are determined by the number of electrons in the

shell and the number of protons in the core.

In the three types of atom which we have considered, each contained one electron and one proton, and all are

therefore considered to be atoms of the same element. They are known as Isotopes of the element.

If we attempt to add a third neutron to the nucleus, we will find that the field condition within the atom is now such

that a considerable amount of force will be required, and that the act of forcing the neutron into place will cause its

quantum of energy to divide spontaneously. The negative charge will be emitted from the neutron, and as a second

electron, will join the first in the shell of force surrounding the atom The remaining portion is now positively

charged and so becomes a proton.

The atom now contains two electrons, two protons and two neutrons. We have created an atom of the second

element in the series called Helium. Its name was taken from the Greek word ‘helios” (The Sun) because it was

discovered by a spectrographic analysis of the sun’s atmosphere a quarter of a century before it was discovered on

earth.

In symbolic terminology, this atom is described as 2HE4. The letters represent the name of the element, the

number preceding the letters gives the number or orbital electrons, and the number following the letters gives the

total number of protons and neutrons contained in the nucleus.

If we consider (theoretically) to build up our atom by the addition of neutrons, we will find that, in each step of the

process, we can create a certain number of isotopes. That is, we can add a certain number of neutrons without

changing anything but the mass of the atom. If we exceed this number, the force required to insert the next neutron

will cause it to emit the negative portion of its charge, becoming a proton and adding another electron to the shell.

Thus the next higher element in the atomic scale is formed. If we continue this process long enough, we will

eventually have created atoms of all the known elements, and all of their possible isotopes.

In building the next element after helium, that is: lithium, we would have to insert two neutrons simultaneously,

since there is no known combination of five nuclear particles which will remain together for any appreciable time.

It should also, perhaps, be mentioned at this point, that the number of electrons which will occupy a single shell of

force is limited. If, after a shell containing this number of electrons has been formed, more electrons are emitted

from particles within the nucleus, they will not be absorbed by the shell but will pass through it, to form a second

shell outside the first, and so on.

Let us now expand our scale of observation for a moment so that we may consider a drop of ordinary water. If we

divide the drop into two equal parts, we will find that each of the two parts retains all of the properties which were

possessed by the original drop. Each of the parts is still water. We might repeat this division many times without

changing anything except the size of the parts, but eventually we would reach a particle which could not be further

divided without producing a complete change in its properties. This particle is called a molecule and is defined as

being the smallest particle of a complex substance or 'compound' which can exist as that compound.

A molecule is composed of two or more atoms which have come together in such a way that some of the electrons

in the outer shells have expanded their orbit so as to create a new shell which encloses all of the atoms. The several

atoms will then behave to some extent as though they were one.

If we divide the molecule of water, we find that it is composed of two atoms of our simplest element, hydrogen, and

one atom of a somewhat more complex element called oxygen.

The word 'atom', as related to particles of matter, originated in the philosophy of ancient Greece. In the fifth

century B.C., the Greek philosophers, Democritus and Leucippus, set forth the postulate that all substances are built

up of small units which are not capable of further division. They named these particles Atoms, a word meaning

indivisible.

In one of the peculiarities of the progress of human knowledge that, although this theory was enunciated more than

2,000 years ago, it is only within recent years that we have come to accept fully the first portion of this concept, and

at the same time we have worked vigorously and successfully to disprove the latter portion. We have demonstrated

that the atom is not an indivisible particle, but is actually a complex mechanism made up of a number of

cooperating parts.

We can see that the atom is far from being the solid, indivisible particle which the Greek philosophers imagined.

Indeed, the atom is practically all space! It is, however, a space which is filled with powerful fields, and it is the

operation of these fields that makes the atom behave as though it were a solid, indestructible particle.

Having examined the individual atom and learned of its characteristics, let us now consider the effect which atoms

will have upon each other, when several are in the same vicinity.

We will picture two hydrogen atoms, side by side, but completely alone in space. We will postulate that the atoms

are not in motion with respect to each other, and that no fields or other influences are present except those which

are produced by the atoms themselves. We will assume that the two atoms are separated by a distance of two

diameters. That is: the distance between the orbits of the electrons is equal to twice the diameter of the orbit.

We have learned that the electron consists entirely of a negative charge and that ‘like charges tend to repel each

other’. Therefore, a force field will be set up which will tend to ‘push’ the atoms farther apart. We also know,

however, that the proton has a gravitational mass, and consequently, a gravitational field will be created which will

tend to pull the atoms closer together.

The mass of the proton is more than 1800 times that of the electron, and the gravitational field is considerably more

powerful, if measured at the same distance. However, in the case of the two atoms, the effective distance for the

gravitational field must be measured between the protons, while the electrical field must be measured between the

closest points of the two orbits. (The full charge of the electron must be considered to act simultaneously in all parts

of the orbit.)

At this point we must recall the rule first propounded by Sir Isaac Newton, that the amount of force created by a

field is in proportion to the inverse square of the distance separating the two points between which the force acts.

In our example, the two atoms are separated by a distance equal to twice their diameter. If we assume that each

atom has the same diameter, and if we choose the radius of the atom as a unit of measurement, we find that the

protons are separated by a distance equal to 6 radii; while the shells are only 4 radii apart. The distance ratio

therefore is 6 to 4.

We will further assume that at this point, the attraction of the gravitational field is greater than the repulsion of the

electrical field. The two atoms will, therefore, begin to approach each other, or to ‘fall together’. When the shells

have reached a distance of one diameter, or two radii, we find that the protons are now four radii apart, or that there

is now a distance ratio of 4 to 2. If the atoms continue to approach until the shells are 1 radius apart, the distance

between the protons will be three radii, or a ratio of 3 to 1, etc.

We can readily see that, whatever the relative strength of the two fields to begin with, there will be a distance at

which the attraction of the gravitational field will be exactly balanced by the repulsion of the electrical field. We

will call this the ‘critical distance’. We cannot call it the stable distance because the atoms would not actually stop

at this point. In falling together, the atoms would have acquired momentum, and this momentum would carry them

inward to a point where the repulsion was greater than the attraction. Then the atoms would ‘bounce’ apart and

because of acquired momentum, would again pass the critical distance in their outward movement. Since the atom

may be considered as a perfectly elastic body, and since no friction is involved, this bouncing back and forth, or

oscillation, as it is usually called, can and does continue indefinitely, each atom constantly seeking it critical

distance, but always being carried beyond it by the momentum of its search.

As our understanding of nature progressed, however, it became apparent that what we call ‘light’ is simply a form

of electromagnetic radiation.

Electromagnetic radiation may be defined as ‘Primary energy’, since all of the changes which occur in matter come

about, either as a direct or as a secondary effect of its action.

This primary energy is divisible into very small, but definite units or particles which have been given the name of

‘quanta’ in the plural, or quantum, in the singular.

The known spectrum of electromagnetic radiation covers a tremendous range of frequencies, from long radio waves

on the low end, to high energy cosmic rays, on the other.

Near the center of this spectrum is a narrow band of frequencies, covering about one octave, which we call ‘visible

light’ because radiation of these frequencies can be perceived by the human eye. We divide this band of frequencies

into seven narrower band which we call colors. Starting from the highest frequency and going down, we name these

colors violet, indigo, blue, green, yellow, orange and red. All of the hues, shades, and tints of color which the

human eye can perceive are created by some combination of these seven frequencies.

It was the quantum, or individual particle of radiation in this particular portion of the frequency spectrum to which

the term photon was originally applied. The usage of the term, however, has since been expanded to include a

considerably wider band of frequency.

Just below the red of visible light is another, and somewhat wider band which we call infrared. Except for the fact

that its frequency is below the range of the human eye, infrared has all of the characteristics of visible light, plus the

characteristic that its photons are readily absorbed by the electronic shell of force about an atom.

Each different type of atom, of course, has its own characteristic set of frequencies, and only photons in matching

frequency bands will be absorbed. However, most of the photons whose frequency lies within the infrared portion

of the spectrum are readily accepted by almost all types of atoms. It is, therefore, with these infrared photons that

we are particularly concerned at the moment.

Let us now return for a time to our two hydrogen atoms. We will assume that a proton of infrared radiation, emitted

perhaps millions of years before from as star millions of light years away in space, strikes the shell of force about

one of our two atoms. If the photon is absorbed, the additional energy thus gained, will cause the shell of force to

expand. The expansion of the electronic orbit places the electrons closer together than they were before, while the

distance between the protons remains the same. If the two atoms had been poised exactly at the critical distance

prior to the absorption of the photon, we would now find that a net repulsion existed, and the two atoms would

‘bounce’ apart seeking the new point of stability, or critical distance where the two fields would again be in

balance.

The shell of the atom does not, however, retain these photons indefinitely, but is constantly emitting them. With

each emission, of course, the shell becomes one size smaller.

The mean time between successive emissions is determined by two factors, first the nature of the particular atom,

and second by the number of photons which are present in the electronic shell. Each time the shell receives a

photon its diameter increases by a precise amount, and with each emission it shrinks by the same amount.

If the number of photons received within a given time, is greater than the number emitted, the two atoms will

constantly tend to move farther apart. If the number emitted is greater, the atoms will tend to move closer together.

If we now learn that the photon of infrared radiation is also know as the unit of radiant heat, we immediately find

that we are able to predict one of the fundamental rules of nature, which is that the addition of heat energy to a body

of matter will tend to cause that matter to occupy a larger volume of space, or in simple words to expand. The loss

of heat energy from a body of matter will tend to cause that matter to occupy less space, or to contract. We can

make this prediction confidently, even though we may never have heard of this rule or observed it in operation.

Let us now assume that each of our two atoms receive a number of photons simultaneously. The orbits of the

electrons, in springing outward, would approach very near to each other, and thus produce a very strong repulsion

between the atoms. This repulsion would cause an outward movement of the atoms, with a very high rate of

acceleration. By the time they had reached their new critical distance, their velocity might be so great that they

would continue to move apart indefinitely. As soon as they had passed the critical distance, of course, the repulsion

would become an attraction, and the outward motion of the atoms would begin to slow down. As they moved apart,

however, because of the increasing distance between the protons, the attraction would also become constantly

smaller.

We can see that if the atoms had achieved a sufficiently high original velocity, the attraction would diminish at a

greater rate than the velocity, so that there would always be some outward velocity remaining. The minimum

velocity at which this continuous expansion would occur, is known as the ‘escape velocity’ of the atom.

We have often heard the term, escape velocity, used in connection with the firing of rockets to the moon or to some

planet. In this case it is defined as the minimum original velocity which must be imparted to a missile if it is to

escape completely, from the gravitational field of the earth. The principle is exactly the same. The gravitational

field of the earth exerts a retarding force upon the missile, which constantly slows its outward motion. This

retarding force, however, diminishes steadily as the distance from the earth increases, so that if the original velocity

is sufficiently high, the retarding force will diminish more rapidly than the velocity, and the missile will continue on

and on until it comes into the influence of some other gravitational field and begins to accelerate in that direction.

The velocity of escape from the earth is usually given as being between 7 and 9 miles per second depending upon

whether the missile is being fired toward the moon or away from it: whether it is being fired in the direction of the

earth’s rotation or in the opposite direction: the position of the sun, whose gravitational field produces its own

effect upon the trajectory of the missile; and several other minor factors.

In the case of the atom, the velocity of escape depends upon the type and mass of the atom, its temperature, the

number and position of other atoms present, etc. It is, however, always a precise velocity for any given type of atom

under any given set of conditions.

So far, in our examination of the nature of matter, our entire universe has consisted of two lonely hydrogen atoms.

By the examination of these two atoms, however, we have learned something of the basic forces which actuate all

atoms, whatever their size or number.

As long as we are dealing with only two interacting atoms, we are observing absolute forces and specific actions

which result therefrom. If we add a large number of other atoms to our original two; as we must if we are to build

matter from our atoms, all that we can observe is the statistical result of a large number of forces and actions, each

of which is absolute in itself, but contributes only minutely to the resultant action of the whole.

number of individual atomic or molecular actions. If we do not understand the individual forces and actions, we

memorizing blindly the observed results of certain conditions. It is for this reason that we have spent so much

time in observing our two atom universe, but we should now be ready to furnish our lonely atoms with some

If we examine the illustrations to follow at the conclusion of this brief, we will see that the two atoms with which

we have become so familiar, are now surrounded by many other similar atoms. We will assume that our two friends

have just absorbed some photons of energy, and are ‘bouncing’ apart. We can see that before they have gone very

far, each of them will intrude upon the critical distance of some other atom, and will bounce from that atom in a

direction which will be determined by the angle at which the impact occurred. The atom which was ‘struck’ would,

of course, acquire some of the momentum of the striking atom, and its own path and velocity would be altered

accordingly. We could create much the same effect of we were to place a large number of billiard balls upon a

billiard table, and rush about it with a cue stick, rapidly striking various balls at random, and in different directions.

The balls struck would acquire velocity (kinetic energy), some of which would be transmitted to the first ball which

it struck. If we moved fast enough, we would soon have all of the balls in constant motion.

The air friction, the rolling friction on the table, and the fact that the balls are not perfectly elastic, would all tend to

slow the balls down. Therefore, if we assume that our strokes are all of uniform amplitude, the average speed of the

balls would be proportionate to the number of strokes which we delivered in a given unit of time.

In the case of the atoms, the cue strokes are represented by the photons which they absorb. There is no friction, and

the atoms can be considered as being perfectly elastic bodies, but the slowing effect is still present because of the

fact that the atoms constantly emit photons as well as absorb them.

By comparison with our billiard table experiment, we can see that the average velocity of the atoms will be

proportionate to the total number of photons per unit volume, which are in circulation at any given moment.

If two or more atoms have combined to form a molecule, the outer shell of electrons which now encloses all of the

atoms, absorbs the photons and produces an effect much the same as in the case of individual atoms.

There are, of course, other means by which the velocity of atoms or molecules may be increased. These means will

be considered in the following chapter.

The term “temperature’ and ‘heat’ are often confused in the mind of the beginning student. In most text books on

physics the statement is made that the ‘temperature’ of a body of matter is the measure of the rate of motion of its

particles. In simple words, a body of matter is said to be at a high temperature when the atoms or molecules which

compose that body are moving at high velocities, and therefore coming into frequent and violent collision with their

neighbors. The temperature is said to be low when the particles are moving at low velocities and the collisions are

relatively gentle. If the motion should cease entirely, the matter would be said to be at the temperature of absolute

zero.

Each atom emits photons at a rate that is proportionate to the total number of photons which it contains. This ratio is

the same for all atoms of a given element, but varies with each different type of atom or molecule.

Suppose that we have an atom of hydrogen, and an atom of mercury. Let us assume that the atom of hydrogen emits

one photon per second for each ten photons contained in its electron shell. The atom of mercury, on the other hand,

emits one photon per second for each two photons contained. We can see that if we added one hundred photons to

an atom of mercury, we would increase its emission rate by 50 photons per second, but if we added one hundred

photons to an atom of hydrogen we would raise its emission rate by only ten photons per second.

The total kinetic energy possessed by the particles of a body of matter, is known as the active heat of the body,

while the total number of photons still contained within the electron shells of the particles is known as the latent

heat of the body. The ratio between the active heat and the total heat energy of a body of matter is know as the

‘Specific’ heat of the material of which the body is composed.

The figures which we have given for the emission ratio between hydrogen and mercury are not, of course the

correct ones. To give precise figures for these two elements we would have to deal in micro- seconds instead of

seconds, and employ figures with a number of decimal places. We have used simple figures only for the purpose for

forming mental pictures of what goes on in, and between, the atoms, in order to gain a better understanding of those

often confused terms, ‘temperature’ and ‘heat’.

The specific heat of each element is different, and also changes when the elements join to form compounds. That is,

when atoms join to form molecules, a change occurs in the amount of heat which must be added in order to raise

the temperature to a given degree.

Every element and every compound, however, has a precise ratio of specific heat. Many of these can be found in

any handbook on physics or chemistry. The specific heat of water (h20) has been chosen as the standard or

reference point. Its specific heat is, therefore, said to be 1.000. Since the specific heat of water is high compared to

most other compounds or elements, the values of the others are shown as decimal fractions of one.

As we mentioned at the end of the last chapter, the emission or absorption of photons is not the only means of

changing the velocity, and therefore the temperature, of atoms or molecules. Obviously, any application of kinetic

energy to the particles will have the same effect.

Let us imagine that a blacksmith is striking his anvil with a hammer. As the face of the hammer comes in contact

with the face of the anvil, the outer layer of particles on the face of the hammer, because of their momentum, will

intrude upon the critical distance of the outer layer of particles on the face of the anvil. When the repulsion caused

by this intrusion tends to halt the forward motion of the first layer of particles, the second layer, which has equal

momentum, will intrude upon the critical distance of the first, the third layer will intrude upon the second, and so on

throughout all of the trillions of layers of particles in the hammer. A compression wave will be produced which will

race back and forth through both the hammer and the anvil until the linear kinetic energy of the hammer has been

converted to a proportionate increase in the random velocity of the particles of both masses. We can see that the

temperature of the masses would be increased by an amount which is directly proportional to the momentum of the

hammer.

If instead of striking the anvil, we were to rub the face of the hammer against the anvil the same effect would be

created. Since the surfaces are not perfectly smooth, projections from one surface would interlock with projections

from the other. Large numbers of particles would be forced from their normal positions. Some of these would snap

back into place when the opposing projection has passed, and some would be torn away entirely. In either case

however, the temperature of the mass would be increased by an amount which was proportionate to the force

applied to the hammer, and the distance which it was moved.

The striking of the anvil would be described as ‘work by impact’ while the rubbing action would be described as

‘work by friction’.

Before going farther in our study of the phenomenon which we call heat, it might be well to consider briefly, the

three states of matter which result from the various degrees of heat energy or temperature which the matter may

possess at a given time.

Let us consider first, a quantity, or block of atoms or molecules in which the total number of photons contained is

small. The orbits of the electrons, and therefore the size of the atom is also small. The oscillation or ‘bouncing’ of

each atom will continue, but the path of each bounce will be small because the atoms or molecules are quite close

together, and their critical distance is small. Since none of the particles reach escape velocity, each particle will

remain in the same relative position with respect to the others. The mass will retain its shape indefinitely, and a

considerable amount of outside force would have to be applied to cause the body to change in shape. This condition

is known as the solid state of matter.

If, to such a block of matter, we suddenly added a large quantity of energy in the form of photons, the orbits of the

atoms would spring outward, the velocity of their oscillation would increase tremendously, and soon every particle

would acquire a velocity greater than its escape velocity. The particles in the interior of the mass could not

immediately escape because they would still be bouncing about among their neighbors, but the field of each particle

would now be repelling all of its neighbors, and the mass would expand rapidly. The particles on the outside of the

mass would move outward indefinitely, leaving the next layer free to escape and so on. Matter in this condition is

known as ‘gas.’

Specifically, a gas is defined as being a body of matter in which all, or virtually all of its particles have velocities in

excess of the escape velocity for the particular conditions in which they exist.

We can readily see that a gas, if released in a vacuum, will expand indefinitely, and if released within a solid

container will expand until it is uniformly distributed throughout the volume of the container. Each atom or

molecule, upon colliding with another, will glance off in a new direction, and will continue in that direction until

another collision occurs.

The average, or ‘mean’ distance which a particle travels between such collisions is know as ‘the mean free path.’ In

a dense, or ‘compressed’ gas the mean free path would be a very tiny fraction of an inch, but in a very rarified gas,

it might be many feet.

A liquid can be defined as a body of matter whose particles have velocities either slightly below or slightly above

their natural escape velocity. Most oils or liquid metals, for instance, can be described as matter whose particle

velocities are so close to that of escape that the additional force applied by a gravitational field such as that of the

earth is sufficient to cause the particles to escape, or ‘flow’ in the direction of the force applied by the field. If such

matter were removed from the influence of exterior fields, and released in space, it would immediately assume the

shape of a sphere, which shape it would retain indefinitely so long as no exterior force were brought to bear. It

would, therefore have the characteristics of a very soft solid.

A glass of ordinary water, on the other hand, has the characteristics of a gas, which is prevented from expanding by

the pressure of the atmosphere around it.

We can demonstrate this if we take a glass of water which is at, say 100 degrees Fahrenheit, place it in a bell jar,

and suddenly remove the air from the jar. The water will immediately begin to boil quite briskly. If we maintain the

temperature of the water at 100 degrees and pump out the gas as it is formed, the glass will soon be empty,

demonstrating that its particles do have velocities above those necessary for escape. Actually, even though we do

not remove the air, molecules of the water will constantly be escaping from the surface in spite of the downward

bombardment of the air molecules, and the glass would eventually become empty. This, much slower process of

escape by the mingling of the molecules of a liquid with the molecules of a surrounding gas is known as

evaporation.

In any standard text- book on physics, three methods of heat transfer are usually discussed. These three types of

heat movement are known as, conduction, convection, and radiation. Conduction is defined as being the transfer of

heat energy from particle to particle in a solid substance.

Convection refers to the transmission of heat, usually in a gas or liquid, where the heat is carried from one point to

another by the motion of the gas or liquid which contains it.

Radiation, of course refers to the transmission of heat by the emission of photons, or quanta of heat energy.

In order to gain a simple understanding of heat transfer from the nuclear standpoint, let us perform an imaginary

experiment, in which all three of these types of transfer.

We will clamp a bar of iron in a machinist’s vise, and to the upper end of the bar, we will apply the flame of an

oxy-hydrogen torch.

When two atoms of hydrogen combine with an atom of oxygen, a molecule of ordinary water is formed, but the

joining of the atoms causes a large number of the photons of energy contained in the atoms, to be emitted almost

instantaneously. The water which is formed, instead of appearing as a liquid, becomes a gas at a tremendously high

temperature. The gas is emitting large numbers of heat quanta, and also a few of the higher frequency photons

which we call light.

The heat quanta, striking and being absorbed by the atoms of iron in the bar, cause a great increase in the velocity

of their motion. The molecules of the gas, of course, have velocities far above that of escape, and as these

molecules strike the particles of iron, a large percentage of their kinetic energy is transmitted mechanically, just as

the motion was transmitted by the balls of our billiard table experiment. The energy which is transmitted from

particle to particle within the bar itself is known as conducted head.

Since the incandescent gas is moving from the point of combustion at the tip of the torch, to the surface of the iron,

its motion is carrying its supply of kinetic energy to the surface of the iron. This process is described as

‘convection’ because the heat is being ‘conveyed’ from one point to another by the motion of the gas which

contains it.

The photons of infrared energy which are emitted at the point of combustion, do not, of course, follow the flow of

gas, but radiate in all directions at the velocity of light until they strike and are absorbed by the iron, or some other

body of matter. This type of heat transfer is, therefore, known as ‘radiation.’

The iron particles are now approaching their escape velocity. If we continue to add heat, we will soon find that the

force of the earth’s gravity will be sufficient to cause those particles, which are moving in the direction of its

attraction, to move beyond their normal range. The mass will begin to move, or ‘flow’ in the direction of the

gravitational attraction. When this occurs, we say that the iron has ‘melted.’

Having observed the transfer of heat from a gas to a solid, by heating the gas, let us see if we can raise the

temperature of a gas without adding any heat.

We will imagine a simple steel cylinder, closed on one end, and with a closely fitting piston in the other. Through a

small hole in the closed end we will insert the bulb of an ordinary mercury thermometer, sealing it so that no gas

can escape from the cylinder. If we allow this apparatus to rest quietly upon a table in our laboratory, and maintain

a constant air temperature in the room we will find that the air inside the cylinder, the air outside the cylinder, and

the material of the cylinder itself will soon reach the same temperature. If we now suddenly push the piston halfway

down in the cylinder, so that the gas within is compressed to half of its original volume, we will find that the

temperature of that gas has risen sharply. The total number of photons in circulation has not increased, but because

the volume has been reduced, more photons are in circulation per unit volume. This means, of course, that the walls

of the cylinder, which are in contact with the gas, will receive more photons, per unit area, than they were receiving

before the gas was compressed. The walls of the cylinder are, therefore receiving heat energy from the gas.

The total kinetic energy of the gas within the cylinder also remains the same, but because of the compression, the

mean free path of the particles is shortened. Collisions become more frequent and more violent. This increase of

oscillation rate is also transmitted to the walls of the cylinder.

Since the bulb of the mercury thermometer, which we inserted into the cylinder, is surrounded by the compressed

gas, a proportionate amount of the energy will be conducted to the mercury in the bulb, causing it to expand. By

observing the amount of expansion of the mercury, we can measure the rise in temperature caused by the

compression of the gas.

The extra heat absorbed by the walls of the cylinder will gradually be passed along to the air outside, until the gas

inside has reached its original temperature. It now, however, contains less heat than it had before. By compressing

the gas, we have literally ‘squeezed’ some of the heat out of it.

If we now draw the piston out to its original position, the gas will expand to fill its original volume. The mean free

path of the particles will be lengthened, the collisions, will be fewer, and the number of photons emitted, per unit

area will be smaller than the number which the gas received from the walls of the cylinder. In other words, its

temperature has gone down, and the gas is now taking back from the cylinder, the heat which it gave up when it

was compressed. A proportionate amount of heat will, of course, also be taken from the bulb of the thermometer,

causing the mercury to contract, and thus to indicate the lower temperature.

Almost all of the commercial and household refrigeration systems in use today are based upon the principle of

compressing a gas in one part of the system, dissipating the heat released at that point, and then allowing the gas to

expand in another part of the system, so that it will continuously take up heat from that part.

In our experiment with the cylinder and the piston, we discovered that a considerable amount of force was required

to push the piston into the cylinder. Much more than that would be required to over come the friction between the

piston and the cylinder. We also noted that as long as the gas was compressed, a force continued to act upon the

piston, tending to push it back out to its original position. We can readily understand why this should be so. In fact,

even our brief consideration of the actions of gas particles has enabled us to predict that it would be true, even

before we performed the experiment.

When the surface of a solid is in contact with a gas, the particles of the gas because they are moving at random in

all directions, are constantly impacting, or beating upon the particles of the solid. The millions of tiny impacts

which occur each second, produce a constant thrust or force upon the surface of the solid. We call this force ‘the

pressure’ of the gas.

We can see, at once, that the amount of this pressure, upon a given area will be determined by three factors. First –

the number of particles which strike the given area in a given time. Second – the velocity of the striking particles.

Third – the mass of the striking particles. We can also see that the number of particles which will strike a given area

in a given time will be determined by the number of particles contained within a give volume of the gas, and upon

the rapidity with which they oscillate.

These facts bring out the close relationship which exists between temperature and pressure in a gas.

Stated as briefly as possible, the temperature is the measure of the total kinetic energy present, per unit volume,

while the pressure is the force which that kinetic energy exerts, per unit area, upon any restraining surface.

For example, the air which we breathe is a gas composed principally of two elements, oxygen and nitrogen. But for

two preventative factors, all of the earth’s atmosphere would long since have been diffused into space. The first

factor is the earth’s gravitational field, which constantly tends to draw all of the particles back to the surface. The

second is the fact that the particles at the outer edge have lower temperatures and therefore lower velocities than

those near the surface.

If we assume that we are at sea level, and that the temperature of the air is 0 degrees centigrade (32 degrees

Fahrenheit) the number of particles in each cubic inch of space will be about 400 quintillion. (400, million, million,

million.) The average velocity of the particles will be about 1,760 feet per second, or twenty miles per minute. This

velocity becomes even more remarkable when we realize that average distance which any of these particles can

travel before colliding with another is only about four millionths of an inch. This means that each particle

undergoes an average of more than five billion collisions per second. The kinetic energy of these collisions is

sufficient to produce a constant force of 14.7 pounds upon each square inch of surface which receives these

impacts. This is why we say that the air pressure at sea level is equal to 14.7 pounds per square inch.

We can readily see that the individual forces and masses of atomic or nuclear particles are exceedingly small when

compared to our usual standards of measurement. Most of the quantities with which we must deal in the study of

nuclear physics are so infinitesimal in comparison with our everyday standards, that it has been necessary to create

new and much smaller units of measure in order to deal readily with these minute quantities.

Since these standards of measure may readily be found in any test book, we have not dealt with them here. We have

considered the photon, the neutron, and the electron without determining their size or mass. We have discussed the

constant rapid motion of the atom without measuring the particles, the length and their mean free path, or the

frequency of collision (except for the one example, air, which we have just considered.) All of these quantities are

listed in handbooks, created for the engineer or the physicist who must obtain specific answers to specific problems.

In this text we are primarily concerned with bringing about a simple understanding of the significance of these

factors, and the conditions which cause them to exist.

We will therefore take leave of our particles for a time in order to consider a few of the least understood factors of

nature, gravity, space and time.