Long before the discovery of relativity, science had discovered two fundamental principles – the conservation of energy and the conservation of mass. The first of these was worked out by Leibniz in the 17th century, and subsequently developed in the 19th century as a corollary of a principle of mechanics. Long before that, early man discovered in practice the principle of the equivalence of work and heat, when he made fire by means of friction, thus translating a given amount of energy (work) into heat. At the beginning of this century, it was discovered that mass is merely one of the forms of energy. A particle of matter is nothing more than energy, highly concentrated and localised. The amount of energy concentrated in a particle is proportional to its mass, and the total amount of energy always remains the same. The loss of one kind of energy is compensated for by the gain of another kind of energy. While constantly changing its form, nevertheless, energy always remains the same.
The revolution effected by Einstein was to show that mass itself contains a staggering amount of energy. The equivalence of mass and energy is expressed by the formula E = mc2 in which c represents the velocity of light (about 186,000 miles per second), E is the energy that is contained in the stationary body, and m is its mass. The energy contained in the mass m is equal to this mass, multiplied by the square of the tremendous speed of light. Mass is therefore an immensely concentrated form of energy, the power of which may be conveyed by the fact that the energy released by an atomic explosion is less than one tenth of one per cent of the mass converted into energy. Normally this vast amount of energy locked up in matter is not manifested, and therefore passes unnoticed. But if the processes within the nucleus reach a critical point, part of the energy is released, as kinetic energy.
Since mass is only one of the forms of energy, matter and energy can neither be created nor destroyed. The forms of energy, on the other hand, are extremely diverse. For example, when protons in the sun unite to form helium nuclei, nuclear energy is released. This may first appear as the kinetic energy of motion of nuclei, contributing to the heat energy from the sun. Part of this energy is emitted from the sun in the form of photons, containing particles of electromagnetic energy. The latter, in turn, is transformed by the process of photosynthesis into the stored chemical energy in plants, which, in turn, is acquired by man by eating the plants, or animals which have fed upon the plants, to provide the warmth and energy for muscles, blood circulation, brain, etc.
The laws of classical physics in general cannot be applied to processes at the subatomic level. However, there is one law that knows no exception in nature – the law of the conservation of energy. Physicists know that neither a positive nor a negative charge can be created out of nothing. This fact is expressed by the law of the conservation of electric charge. Thus, in the process of producing a beta particle, the disappearance of the neutron (which has no charge) gives rise to a pair of particles with opposed charges – a positively charged proton and a negatively charged electron. Taken together, the two new particles have a combined electrical charge equal to zero.
If we take the opposite process, when a proton emits a positron and changes into a neutron, the charge of the original particle (the proton) is positive, and the resulting pair of particles (the neutron and positron), taken together, are positively charged. In all these myriad changes, the law of the conservation of electrical charge is strictly maintained, as are all the other conservation laws. Not even the tiniest fraction of energy is created or destroyed. Nor will such a phenomenon ever occur.
When an electron and its anti-particle, the positron, destroy themselves, their mass “disappears”, that is to say, it is transformed into two light-particles (photons) which fly apart in opposite directions. However, these have the same total energy as the particles from which they emerged. Mass-energy, linear momentum and electric charge are all preserved. This phenomenon has nothing in common with disappearance in the sense of annihilation. Dialectically, the electron and positron are negated and preserved at the same time. Matter and energy (which is merely two ways of saying the same thing) can neither be created nor destroyed, only transformed.
From the standpoint of dialectical materialism, matter is the objective reality given to us in sense perception. That includes not just “solid” objects, but also light. Photons are just as much matter as electrons or positrons. Mass is constantly being changed into energy (including light – photons) and energy into mass. The “annihilation” of a positron and an electron produces a pair of photons, but we also see the opposite process: when two photons meet, an electron and a positron can be produced, provided that the photons possess sufficient energy. This is sometimes presented as the creation of matter “from nothing”. It is no such thing. What we see here is neither the destruction nor the creation of anything, but the continuous transformation of matter into energy, and vice versa. When a photon hits an atom, it ceases to exist as a photon. It vanishes, but causes a change in the atom – an electron jumps from one orbit to another of higher energy. Here too, the opposite process occurs. When an electron jumps to an orbit of lower energy, a photon emerges.
The process of continual change that characterises the world at the subatomic level is a striking confirmation of the fact that dialectics is not just a subjective invention of the mind, but actually corresponds to objective processes taking place in nature. This process has gone on uninterruptedly for all eternity. It is a concrete demonstration of the indestructibility of matter – precisely the opposite of what it was meant to prove.