Reality used to be a concept dealt with by philosophy and not science. This was changed by Galileo, when he divided physical phenomena into two classes. The first of these, what he called the “primary qualities”, were suitable for scientific treatment and analysis, because they did not depend on the presence of a person. This independent existence freed them from the vagaries of individual observations Such subjective observations could be affected by health, ability to concentrate and a host of other personal factors, which affected the “secondary qualities” and made them unfit for scientific study. These secondary qualities did require the presence of a person and applied, in Galileo’s opinion, to all observations made by the senses of smell, touch, hearing and taste.
Galileo’s primary qualities were very few in number and Rene Descartes later reduced them to just two, matter and motion. These qualities were independent of people. Their reality was therefore objective. On the other hand, the secondary qualities, which needed the presence of a person to register them through the senses mentioned, were subjective. These two realities, subjective and objective, were deeply embedded in philosophical traditions, dating back thousands of years to the ancient Greeks and beyond. In these philosophies, all physical phenomena in our world of nature, which needed our senses for their perception, were of merely subjective reality. This reality was considered very inferior to the objective reality of the divine world, which of course was beyond the direct perception of our ordinary senses and thus also beyond the need of our human presence to exist. This divine world was not just a world of religious belief in these philosophies. It was a world of real existence and the realm of all “true” knowledge. It could be accessed by people specially trained for such contact, such as oracles, seers and mystics.
Galileo’s revolutionary thinking can now be fully appreciated. He had the audacity to take the concept of objective reality, as a property of the divine world only, and tack it on to his two primary qualities of matter and motion, which were properties of the lowly world of nature. Matter and motion were now the exclusive subjects of his new science, physics. They formed the basis of all Newton’s great synthesis of natural laws. They were the foundation concepts of a philosophy, scientific determinism, and of a model of the world that ruled physics until the 1920s, when it had to be abandoned.
The consequences of Galileo’s actions in these matters were quite extraordinary and have lasted to this day. While he himself was careful to limit objective reality to only his two primary qualities of matter and motion, as time went on scientists began to treat all natural phenomena, perceived by all our senses, as having an independent existence of their own. This allowed them to postulate that the history of nature was quite independent of the history of man, so that it could be extrapolated to the earliest periods of this earth’s existence, long before the appearance on the scene of man. It may seem extraordinary to us today, but this method of perceiving the geological history of the world is no older than Galileo. Before him, at least in Christian times, the world started in 4004 BC. There was also another consequence. This independent matter was now perceived as the primal substance, from which everything else that has appeared on earth, such as life, feeling and consciousness, has evolved by means of purely natural, random processes.
Objective reality disappeared from physics in the 1920s, when scientific determinism, based on the total predictability of cause and effect, had to be abandoned as it no longer represented the facts discovered by the new branches of physics, especially quantum mechanics, which required the inclusion of Heisenberg’s Principle of Uncertainty. For the last eighty or more years, therefore, physics has operated on the basis of subjective reality only. It no longer recognizes Galileo’s division of natural phenomena into two classes: for modern physics, all perceived natural phenomena are of a subjective nature, because they require the apparatus of our senses. Galileo’s attempt to make some “qualities” of matter objective has simply been ignored by modern physics, which is not interested in philosophical errors of hundreds of years ago. As the divine world was eliminated by science, so its objective reality has also been removed. In this, modern physics has recognized that Galileo made a fundamental error when saying that his primary qualities did not need the presence of a person. Matter and motion still had to be perceived in order to be dealt with by science. The sense of sight was therefore involved and the sense of sight is still a physical sense and thus subjective.
All these developments in physics have left loose ends dangling about. If matter is now no longer considered objective, must we not alter our assumptions about the very early eons of the earth’s existence, before the appearance of man? Philosophically speaking, how does the absence of objective reality affect us in our relationship with nature? If we only accept subjective reality now in our science, does this not mean that we must regard ourselves as the creators of the world? Only to the creator is everything around him subjective, because he himself has created everything! Then again, if matter is merely a subjective appearance, of which we are aware only through our sense perceptions, can it really be the primal, independent substance from which everything else has been derived?
All these musings about the nature of reality are beginning to be important because of recent developments in particle physics. What, for instance, can be said about the reality of a string particle? This particle is defined as the ultimate, irreducible matter particle. It is also defined as having only one dimension, length. Our sense structure is not built to perceive an object of only one dimension anywhere in our physical world. So we cannot call the string particle subjectively real, like other physical phenomena. But if matter is considered to be subjectively real, should not the origin of matter, the ultimate, irreducible particle of matter, also be real? Here again, the absence of objective reality in physics today is becoming a problem.
Subjective reality is becoming interesting to physics in another line of investigation being followed. The old question, posed by Bishop Berkeley and others, about the existence of the world if we are not there to perceive it, can now be investigated scientifically. The results of two such investigations have recently been published, one conducted in Japan and the other in Canada. Both used photons as the particles being observed and then not observed. The last part was achieved mathematically by not completing the procedures under observation. The results in both cases indicate that the world does indeed continue to exist when we are not observing it, but some of the results were nevertheless startling. Some of these photons, which should have been somewhere, simply disappeared. The Japanese experimenter called this result “preposterous”.
Galileo’s Shadow is a book that deals with these conflicting concepts of reality within physics. It suggests a way to reincorporate objective reality back into science, as well as many other problems in physics that are becoming increasingly urgent. One of the aims of the book is to make physics accessible again to a broader audience, where it used to be in the age of Newton, when ordinary educated people could understand its broad concepts even if they were not mathematical geniuses.