Astronomy

Having accepted atomism, it is necessary to account for the differences between solid, liquid, and gaseous states. Matter in any of these states consists of molecules. Ice, water, and steam represent three states of the same compound of hydrogen and oxygen. Mercury, an element not a compound, can be solid, liquid, or gaseous. Usually a solid passes through a liquid state before becoming gaseous: however, it is possible, at certain temperatures and pressures, for solids to pass directly to the gaseous state or from gas to solid.

It has been seen that the result of heating a body (increase in temperature) is to increase the energy of motion (kinetic energy) of the molecules of which it consists. In the solid state the molecules are thought to be bound together by certain forces so that we have a condition of stability and, to a degree, orderly and permanent arrangement. For the present we need not be concerned with the details of shape and arrangement of the molecules. Perhaps it is sufficient to imagine a box full of egg-shaped rubber balls bound together by thin rubber bands. If the balls are hollow and contain a mechanism which will make them vibrate, we will have a vibrating mass, the individuals of which are limited in their movements. If the effect of the internal mechanisms could be controlled so that the agitation could be varied, we would be able to demonstrate in a crude manner the ” solid” at various temperatures.

When the temperature was increased to the proper value, the elastic bands would break and the individuals would be freed. They would then begin to bounce and collide haphazardly and would try to escape from the room. This would be a crude picture of a gas.

A crystal could be pictured the same as any other solid, but the molecules would be arranged in a more orderly manner.

If a room contains many elastic balls bouncing here and there, we have a picture of a gas. Suppose that a layer or two settles to the floor, but still is in an agitated state. This may be considered a crude model of a liquid above which is its vapor.

By rubbing two solids together their temperature is increased by an amount equal to the work done in overcoming friction. It may be considered that the molecules in the surface layers have been excited into more violent movement resulting in greater average kinetic energy, hence, in higher temperature.

Absolute zero is that lowest possible temperature at which the molecules of matter cease to vibrate. This logically follows from the kinetic theory of heat and of matter. Absolute zero is at about 4590 F. below the ordinary Fahrenheit zero or 4910 F. below the freezing point of water. On the Centigrade scale it is about 2730 C. below the Centigrade zero which is at the freezing point of water.

It is well known that a liquid is cooled by evaporation. If we consider that a liquid consists of molecules moving haphazardly (within certain limits) due to collisions with each other, some of these molecules will have sufficient speed to escape the attractions of their neighbors. These, then, find themselves in the space above the liquid and are now a part of the vapor above the liquid. Inasmuch as the only molecules which escape are those having a great enough velocity in a direction away from the surface of the liquid, it is obvious that the liquid is losing only those molecules which at the time of escape have much more than average kinetic energy. Such losses result in a lower average velocity of the molecules left in the liquid and therefore the temperature of the liquid decreases.

Inasmuch as the molecules of matter do not cease to vibrate or to move about until absolute zero is reached, it is obvious that there is much kinetic energy in bodies at ordinary temperatures. A piece of ice is cold to us, but it is relatively hot compared with liquid air and even more so compared with absolute zero. Here we must eliminate our sense of temperature and look at Nature without this prejudice. There is enough total kinetic molecular energy in a piece of ice the size of a baseball to raise a ton weight more than 30 feet vertically. If we could find a means of extracting the total kinetic energy of the molecules of a piece of ice of this size each second, we would have the equivalent of a motor of about two horse-power. It should be noted that the foregoing involves only molecular energy and not so-called chemical and atomic energy.

Other Applications of Atomism

The great success of the atomistic principle as it is involved in the kinetic theory of matter is one of the wonders of the modern scientific age. It is to be expected that it has found other applications equally fascinating and promising. It is now being pressed further into the service of explaining the structure of matter. Molecules are not only divided into atoms, but the latter are now known to consist of still smaller particles. The reality of the electron is thoroughly established. It takes 1800 electrons to equal in mass that of an atom of hydrogen which has the smallest mass among the atoms of elements.

When Maxwell (1873) propounded the electromagnetic theory of light (radiation), his achievement was epochal. The exact manner in which the radiant energy traversed space was not known, and the next epochal event was the founding by Planck (1900) of the quantum theory. Here we have the atomistic principle applied to energy instead of being confined to the material of the universe as it had been. In other words, in the quantum theory we have the atomistic idea applied to physical processes. We now have the atom of matter, the atom (electron) of electricity, and the atom (quantum) of action (a product of energy and time). Planck assumed the emission of radiation (from the sun, a lamp filament, etc.) to occur discontinuously. He conceived elements of energy of equal magnitude analogous to the equality of electrons, or atoms of a given element. Radiation or radiant energy is emitted of various wavelengths or frequencies which must be taken into account in laws of radiation. By inventing the quantum of action Planck was able to derive a law of radiation which explained the experimental data hitherto not understood. The elementary quantum of action is equal to the elementary quantum of energy multiplied by the frequency of the radiation. Thus again, we find science in a state which required a creative mathematical physicist to iron out inconsistencies, to put the finishing touches on existing theories, and to explain much of the accumulated data.

Now the physicist uses quanta as commonly as he does electrons and atoms and molecules. Bodies are built of molecules, the molecules of atoms, and the atoms of electrons (and protons) . Here we see the atomistic principle applied to ” material” (matter) and then to electricity (What shall we call it?). Finally, a physical process - the radiation emitted by the electrons - is divided into quanta. With such pictures of the universe being constructed we may cease to be surprised at anything, but our interest and admiration will grow. Will we ever get to the final foundation? Will mind be finally explained by the physicist?

These are mere glimpses of the electron theory and the quantum theory introduced to complete this portion of the picture for the present. They are so important, so modern, and 50 far-reaching that they are treated later in more detail.