"The American physicist John Archibald Wheeler is an outstanding scientist. Connected with his name, for instance, as well as with the names of the Danish physicist Niels Bohr and the Soviet physicist Yakov Frenkel, are the proposal and development of the liquid-drop model of the atomic nucleus. In the last decades, Wheeler has suggested some ideas with which the majority of physicists do not fully agree, but, nevertheless, admit that they are of great interest. Incidentally, if 'the viability of hypotheses depended upon the literary style used in expounding them, Wheeler, among physicists of the Western world, ought to be recognized as the greatest discoverer of new truths.
Wheeler has spent many years in advocating the idea that all of space should be considered to be empty. He has been making every effort to prove that, strictly speaking, there is nothing in the world, there never has been anything and never will be anything except absolute vacuum. He contends that the physics of the world is fully determined by its geometry, that the physical content of the universe is, in a sense, determined by the geometric shape of space.
In his time, Einstein, in developing the general theory of relativity, related gravitation with the geometry of space. According to Wheeler, "Einstein, above his work and writings, held a long term vision: There is nothing in the world except curved empty space. Geometry bent one way here described gravitation. Rippled another way somewhere else it manifests all the quantities of an electromagnetic wave. Excited at still another place, the magic material that is space shows itself as a particle. There is nothing that is foreign and 'physical' immersed in space. Everything that is, is constructed out of geometry." Einstein's long-standing dream, unrealized throughout his lifetime and to whose realization we are no closer today, can be expressed by the ancient saying: "Everything is nothing".
The picture of the geometric primordial entity of the universe proposed by Wheeler excites the imaginations of his readers.
Wheeler considers geometry to be the building material of nature. Any elementary particle, according to Wheeler, is "not a foreign and physical entity moving about within the geometry of space, but a quantum state of excitation of that geometry itself; as unimportant for the physics of the vacuum as a cloud is unimportant for the physics of the sky."? Indeed! But this statement, very likely, was made in a moment of ardent enthusiasm. Because Wheeler intends, nevertheless, not to ignore the physics of "unimportant" particles, but to explain it. This explanation is based on how space itself is organized, i.e, its purely geometric structure.
To comprehend, at least in some manner, on what Wheeler's ideas are based, it is necessary to penetrate into the "depth" of matter, deeper than to the atom, atomic nucleus or elementary particle. Wheeler contends that the scale of measurement becomes a quantity of the order of 10-33 cm. It is precisely of cells of this size that space is built at its deepest level.
What is the origin of this quantity? Max Planck, whose supreme achievement was the discovery of the "quantum of action", the minimum possible portion of energy in our universe, introduced the hypothetic concept of a "fundamental length". Distances shorter than this length, it is assumed, are simply impossible in our world, in exactly the same way that there can be no portion of energy less than a quantum of action. It is very typical, as a matter of fact, for quantum mechanics to strive to have space and time obey the same laws that govern elementary particles.
Still far in the future is the time when it will be possible to test the hypothesis of a fundamental length. But this should not and cannot stop theoretical investigations. It is worthy to recall that certain fundamental laws of quantum mechanics were discovered at a time when only a single particle - the electron - had been strictly and accurately discovered in experiments.
A thought experiment is frequently ahead of a real one, although in the final analysis it requires confirmation by actual experimental research.
Thus, a region of space with the characteristic distance of 10-33 centimeter, is, according to Wheeler "superspace". How does it look? Wheeler called it vacuum foam. Something bubbling, continuously changing shape. He writes: "The space of quantum geometrodynamics can be compared to a carpet of foam spread over a slowly undulating landscape. The continual microscopic changes in the carpet of foam as new bubbles appear and old ones disappear symbolize the quantum fluctuations in the geometry." "In other words," adds Wheeler, "geometry in submicroscopic scales, 'resonates' between one foam-like structure and another."
This conclusion, in his opinion, is inevitably reached by the consistent application of the quantum principle. Here we find ourselves in a world reduced in scale even with respect to our "customary" microscopic world by a factor of about twenty. It is assumed that the diameter of the proton is approximately 10-13 centimeter. The diameter of the earth is somewhat over 12 thousand kilometers. We shall write it as 109 centimeters (for the sake of simplicity, we sacrifice some accuracy, but in the case of elementary particles, the accuracy is still lower). With this approach, the earth is greater "in length" than the proton by a factor of 1022, and the proton is 1020 times greater than the fundamental length, the measuring device for scales in Wheeler's vacuum.? From a man's height (let us assume it to be 2X102 centimeters, or almost 6 feet 7 inches, which is quite high, even for basketball players), only less by a factor of 107 than the diameter of our planet, you cannot see the distribution of oceans and continents. But this does not imply that they cease to exist. Hence, should it surprise us that even less commensurable virtual particles with their minimal cells are unnoticeable in superspace? I repeat that Wheeler's ideas are insufficiently convincing. The images and analogies that he employs are filled with emotional, I would even say, artistic compulsion. He compares, for instance, superspace with the ocean. From a plane at a great altitude, even the roughest sea may look smooth and even. But a man in a small boat, tossed up and overwhelmed by the waves, is quite sure that he is not rowing along an even, mirror-like surface. If in such a situation the man has the courage to closely observe the foamy and churning water, he will witness this continuously changing complicated picture in its finest details and minute features.? The varying geometry of superspace is comparable to the surface of a real ocean observed by us from different distances and at various altitudes.
It is unfortunate, however, that an artistic image, no matter how convincing or persuasive it may be, is no proof in science. Other proof, so far, is clearly insufficient. But Wheeler backs his belief in superspace by one of the aphorisms that he is a past master in coining: "Moreover, the whole character of physics speaks for the theme that 'everything that can happen will happen'." But, on the other hand, he recalls, whenever necessary, that he has only proposed a hypothesis. Not without reason is the statement: "…only physics in the region of 10-33 cm can enable us to understand the physics of elementary particles", preceded by the cautious words: "It may well be that."? Also to be taken into account is that even if the picture of vacuum drawn by Wheeler turns out to be correct, the image of the stormy ocean he uses should not be taken too literally. An elementary particle in a vacuum, even in a "modern" vacuum of virtual particles, definitely does not resemble a boat rowed by a courageous observer. The waves can put the boat off its course or even over-turn it. The direction of a particle traveling in a vacuum is constant. Photons, traveling from the earth to distant stars keep on their courses for millions and thousands of millions of years.
One must have faith that the incomprehensible can be cleared up, otherwise he will not ponder over it. Johann Wolfgang von GOETHE
Thus, according to Wheeler, laws based on geometry and governing the ocean of superspace, specify the laws of the microscopic world that we are accustomed to. These latter laws are complied with by elementary particles and the Dirac Sea itself." [Something Called Nothing, pages 175-178]