MARVELS OF ENERGY.

Otago Witness, Issue 3085, 30 April 1913, Page 75

MARVELS OF ENERGY.

WHAT WE KNOW AND WHAT WE HAVE YET TO LEARN. (By Charles R. Gibsox, F.R.S.E.)

In our large engineering works and factories we have evidence of an immense amount of energy being utilised continually, and It is not easy to realise that all this energy has been existent for ages past) indeed from the creation of “the heaven and the earth.” The conservation of matter is realised more easily than is the conservation of energy. It requires no special power of imagination to picture every particle of matter as having existed in some form or another from the beginning. It would make a most fascinating story if we could trace the ‘‘life history” of any one atom of matter. Nor is it difficult to realise that, despite all the transformations of matter, it will still exist in some form. That even the atoms of matter composing our own bodies will exist long after “we have shuffled this mortal coil,” or as Shakespeare has it in another part of his “ Hamlet” :

Imperious C.-esar, dead, and turned to clay, Might stop a hole to keep the wind away. —The Conservation of Energy.—

The conservation of energy is just as real as is the conservation of matter. The engineer can neither create nor destroy energy; he can merely transform and transfer it. When our forefathers desired to go across country from one place to another they had to depend upon their own personal energy or upon the energy of domesticated animals. To-day we sit upon inanimate machines, and the only personal energy we have to supply is that very small amount required to control the machine. But the energy which impels our motor-cars was existent in the days of our forefathers; we have only found a means of tapping this source of energy. The Chinaman who saw an electric car for the first time was surprised, and remarked, “No pushee, no pullee, go like mad!” Imagine what would be the surprise of one of our great-grandfathers if he could stand on one of our streets, or on a busy London thoroughfare, and see all the horseless carriages in use ! There is little doubt that our own surprise would be equally great if we could return to time and space a few centuries hence. We know of boundless stores of energy around us, which at present we cannot tap. The man who could tap the internal energy contained in an ordinary laboratory flask of hydrogen gas would have sufficient energy to drive a railway locomotive fo! a year. -—Energy Beyond Our Beach.— u, t to uppv.Uute A.e W. statement, which is based upon Sir J. <l. Thomson's estimate that the energy contained in one gram of hydrogen could raise a million tons through a height exceeding 100 yards, we must have a dealconception of the constitution of matter. We, know that matter consists of extremely minute particles or molecules, that a molecule of iron is the smallest particle of iron which can exist, and that this molecule is far bclo.w the range of vision of the most powerful microscope. We know that this molecule of iron is composed of atoms. We call them atoms of iron, but they are not little specks of iron; the iron atom does not possess the properties of iron. An atom ot iron, an atom gold, and an atom of hydrogen are all made of the very same stuff. All atoms are merely little revolving systems of particles of electricity. Our knowledge of the construction of these atoms is not complete. We know that an atom must consist of counter-balancing quantities of positive and negative electricities. We have laid our hands on the particles of negative electricity and christened them “electrons,” but we have not succeeded in definitely isolating the positive electricity. In other words, we have not detected positive electricity apart from matter. The negative nartides or electrons are well known to us; their mass and their electric charge have been measured. From whatever source these electrons have been obtained, they have been found to be identical in every respect. Until we can discover the nature of the positive part of the atom we may picture it as a tiny sphere of positive electricity, within which the group of negative electrons are revolving in a miniature solar system. > In radio-active substances, such as radium, we know that some of lhes n atoms are going to pieces, and we find these electrons being shot off with terrific force, their velocity being about 100,000 miles per second. This enables ns to realise the gigantic amount of energy locked up within the atoms, of which there are millions of millions in a piece of copper no larger than a pea. The radio-active phenomena of radiinn are duo to the disintegration of only one in every 10,000 million atoms per second, so that the transformation of the radium is an extremely slow process. We are quite conscious of this immense store of energy within the atoms, but we know of no means of tapping it. However, with the ever-increasing accumulation of knowledge it seems reasonable to suppose that at some far distant time man may discover some means of freeing a fraction of this boundless store of energy. But for the present this is quite outside the province of the engineer. —Chemical Energy.— When we say that chemical changes occur in substances it is just another way of saying that the atoms of matter have rearranged themselves in different combinations. The atoms hold on to one another by electrical attraction ; it is this electrical union which we call chemical union. We say that water is a combination of hydrogen and oxygen—that a molecule of water is two hydrogen atoms electrically united to one oxvgen atom. By means of electric force we can separate

these atoms; we can decompose the water. When the water has disappeared we have in its place two volumes of hydrogen to one volume of oxygen. By means of a spark we can get these hydrogen and oxygen atoms to reunite and form water. This change of partnership is so energetic and so sudden that we say an explosion has occurred. The engineer makes use of such chemical changes in gas, oil, and petrol engines. He takes advantage of the fact that during certain chemical changes the atoms of matter suddenly occupy a greatly increased space. The union of the atoms of matter contained in petrol vapour with the atoms contained in the gases of the atmosphere suddenly forms a mass of highly-heated gases, the particles of which are in an intensely energetic state of vibration, and seek to fill a space far greater than the confined space of the engine cylinder in which the transformation takes place. The excited particles have to force their way out of the cylinder as best they can, and in doing so they bombard and move the piston, which turns the crank and drives the wheels. We have a sudden transformation of chemical energy into mechanical energy. —Heat Energy.— In the case of the steam engine the transformation of energy is not so direct. The chemical change in which the atoms of matter in the coal unite with the atoms of the gases of the atmosphere to form a flame is not one sudden union of the two masses of matter, but a continuous production of a mass of gaseous matter in which the molecules are in a state of very energetic vibration. The temperature of a body is due to the vibratory movement of its molecules, so we have a very hicrh temperature in the gaseous flame. We get these energetic molecules to pass on their energy lo the molecules of water in the boiler, and as soon as the water molecules reach a certain stale of vibration (212 deg Fahr.) they get beyond attractive distance, spreading themselves to fill any available space. This gives us the expansive power of steam, which James Watt showed us how to utilise in forcing the piston to and fro in the cylinder. —Electrical Energy.— It is apparent from what has been said in the foregoing paragraphs that all electrons are not locked up within the atoms of matter. Otherwise we should have no knowledge of electrons except from the comparatively infinitesimal quantity set free by radio-active bodies. Quite apart from the electrons constituting the atoms of matter there are myriads of free or roaming electrons, which may be transferred from one lump of matter to another. A body with an excess of electrons is raid to'be charged with negative 1... i it v. and a bodv with a deficiency ~f ,-U,< runs is described as positively charged. But in the engineering world it j,; ch , ' , tric currents and not oh.-clrie charge.,, mat are of interest. Ar. electric current, is due to the transfer (J elections from atom to atom within a conductor. When the ejections are handed from atom to atom along the conductor we describe is as a direct or continuous current, and when the electrons merely surge to and fro from atom to atom w describe the result as an alternating current. In both cases the energy is transmitted through the surrounding’ tether of space and not through they conductor. A simple illustration is that of the old needle telegraph, in which we have a magnetic needle poised within a coil of wire which surrounds it at some distance and is not in contact with it at any point. The electric current in the wire merely passes in the neighbourhood of the magnetic needle. The electrons moving in the wire disturb the surrounding aether in which the magnetic needle is situated, and this oat her disturbance affects the electrons within tire magnetic needle, causing it to take np a different position. So it is in our tramway system ; the energy is conveyed through the wilier surrounding the conductor, and the electro-magnetic forces take place between coils of wire which do not touch one another. It is the collier which carries the energy. In the early days the best method we knew for producing an electric current was bv means of chemical energy. The chemical energy of the battery was transformed into electrical energy. With the aid of the electron theory we can form a picture of this transformation of energy. The atoms of matter in the battery when changing partners give up some of their spare electrons, leaving an accumulation of electrons on one of the two battery elements or plates. These electrons are passed on from this element through the conducting wire to the other element in the battery. This motion of electrons from atom to atom along the conductor, which may be made any convenient length, gives us a direct or continuous current. But it was only when Michael Faraday discovered that electric currents could be produced by simply moving a coil of wire in a magnetic field that electrical engineering became possible. In a dynamo the essential parts are one coil of wire rapidly revolving in the vicinity of a second coil, having an iron core in order to increase its magnetic effect, and we arc able to transform the mechanical energy of any prime mover into electrical energy. —Different Forms of Energy.— When one sees a really good protean actor on the stage it is difficult to realise that all the characters are the same individual. Energy is a grand protean actor, and it is difficult to realise that all the different forms of energy are merely transformations of the same entity. " In heat energy we have the motion of molecules. In chemical energy we have the motion of atoms. In electrical energy we have the motion of electrons. lii mechanical energy we have the motion of masses of matter. In addition to the transformation of energy we have its transference or transmission. This is very apparent in the kinetic energy of moving bodies, when one

moving body sets a stationary body in motion, transferring the kinetic energy directly from one body to the other. It is evident that the kinetic energy of a body depends npon the amount of motion it possesses. The case of potential or strain energy is not so simple, nor is it so direct. When we wind up a watch or clock we- store potential energy in the mainspring. But ■where does the energy reside? We have not altered the metal of the spring. We picture the molecules of the metal vibrating to and fro according to the temperature, but never in contact with one another. The molecules are connected by the intervening eether, and it is this fether connection or link which we strain. If we overstrain it the molecules are forced beyond their attractive distance, and can no longer hold together; the metal spring is, broken. Again, when we lift a weight ‘we strain the tether between the weight and the earth, so that these two tend to pull together again. Although we cannot tell the physical nature of gravitation, it is quite evident that the tether is the medium of gravitational energy. All potential energy resides in the tether. W T e have noted already that the tether is the medium of electric and magnetic energy. This mysterious aether of space is the vehicle -also of all radiant energy. which includes light, radiant heat, actinic rays, and electric waves, such as are used in wireless telegraphy. All energy in the nether must mean some distinct form of motion of the aether. It goes without saying that all tetherial energy must be. transformed through the medium of matter before we become conscious of it. This is true even of the one aether organ we possess; we do not feel the aether waves which impinge upon our eyes. —As Dead as a Door-nail. — When we say that a body is as dead as a door-nail, it is evident that the remark can refer only to the kinetic energy of the body. A body at rest cannot impart motion to another body. But the door-nail may be lying on the top of a building, in which case it possesses considerable potential energy. In any case, it contains heat energy; its molecules are in a state of vibration. There is also what we might term cohesion energy, by means of which the particles of metal cling together. This cohesion is a modified form of electrical attraction. In the case of some steel wire a pull of 100 tons to the square inch is required to overcome tins cohesion energy. Again, within the door-nail there is in each molecule of iron the electrical energy binding atom to atom, and within each atom the energy of revolving electrons, compared with 'which all other energy is insignificant.