Space is not empty. The planets are only the most obvious of the millions of bodies circling the sun, all bathed in the streaming particles of the solar wind. Beyond the reach of the wind, an immense invisible cloud of small icy bodies called the Oort Cloud circles in the darkness. Beyond that the density drops off dramatically into the cold dark voids of interstellar space. But even that is populated with drifting clouds of dust and gas, millions of times the mass of our solar system, the ashes of long-dead stars and the materials of stars yet unborn. Throughout the galaxy these nebulae float like vast unseen reefs of matter, revealed only when they are heated to incandescence by a hot star within them.
Beyond the dense disk of stars, dust, and gas that make up the spiral arms of the Milky Way, huge balls of stars drift in distant orbits around the center of the galaxy. And there is growing evidence that even far beyond the last visible outlying stars there is matter slowly being drawn into the collective gravity well of all the stars in the galaxy. And beyond that? Intergalactic space makes the voids between the stars look as dense as lead by comparison. And yet even here, there are slowly drifting clouds of gas, galaxies that died unborn, wheeling in perpetual and eternal darkness.
But what of the spaces between these inconceivably tenuous clouds? Surely there at least there are volumes that are truly empty?
Not even there, the physicists tell us. In fact, they say it is impossible for any space to be totally empty. The reason for this requires dipping into the strange worlds of quantum reality. These worlds are bizarre and alien beyond our comprehension, so hold onto your hat - but not your "common sense."
We are used to visualizing atoms as tiny balls circling a cluster of other balls. Most of us have heard that the electrons and protons have been found to be made up of even smaller things called quarks, and we can imagine them as assemblages of teeny-weeny balls. This model is completely and fundamentally incorrect.
A quark is not a teeny-weeny ball, nor even an infinitesimal point. The point is that a quark doesn't have a point at all. It does not exist as we do, or even as the invisible atomic world exists. In normal terms, a quark is not anything real at all. A quark is a wave, like a graph of the likelihood of something existing in a particular place. It is not a physical object, it is a potential object; it contains the possibility of existing - more precisely, it is the possibility of existing. But just what it is that might exist is a meaningless question. It begins to sound like something out of a zen koan: it is that which cannot be known; not that which is, but that which might be. When they are quarks, nothing physical exists. When the wave of possibility collapses to one and they become manifest, they are matter. They are us.
Don't shake your head and say, "That's too weird for me; what have those physics guys been smoking?" They don't like it any more than you do. They're scientists whose careers depend on being hard- nosed, no-nonsense mathematicians trying to reduce our complex world into rigid equations. They really hate to present papers saying the audience is made out of nothing but probabilities. Physicists have been dragged kicking and screaming to this absurd conclusion only because it is the only theory that accurately predicts the results of experiments. It has solved all the problems that Newtonian and Einsteinian mechanics solved, and some that they could not. There are not even any seriously contending theories any more. So it is not smoke and mirrors. It is as close as we have ever gotten in our quest to understand what everything is made of. It behooves us all to try to understand the concept.
Quantum objects do not really exist anyplace, but they have the potential, some calculable probability of existing in many places. Scientists can work out what those probabilities are. In fact, we all do these calculations unwittingly every day. If two billiard balls collide with a particular angle and velocity, we can predict that one will drop into the corner pocket. We have learned through countless experiments that these results can be expected. They have to, because the balls must obey physical laws. It is only common sense.
But common sense is wrong. These objects do not have to obey any physical laws. Instead of falling into the corner pocket, the nine ball could suddenly disintegrate or rush off to Neptune. There is nothing at all to stop it. Why then would we find such a result surprising? Because it is unlikely.
Each of the trillions of quarks that make up that billiard ball has the potential to manifest itself anyplace in the universe. But scientists have learned how to map the probabilities of its appearing at each of those points. Countless experiments have shown that the vast majority of the quarks will travel forward along a straight line at a speed proportional to the impact the ball received, constrained to a level roll by the surface of the table until they reach the edge, then gravity will tug them down into the net. Probably they will do this, but not certainly. The probability maps show a very strong likelihood of this result, but nowhere does the probability become nil. Some of those quarks may in fact have gone to Neptune.
Our universe is knowable, indeed inhabitable, only because quarks obey the laws of probability. It is more accurate to say that scientists have observed what quarks are likely to do next and have named the collective data the laws of probability. The technological advances throughout our history are memorials to the steady refining of our understanding of the probabilities of where a quark will next manifest itself as matter.
What then is matter? It is only an apparition of something much more mysterious and tenuous than any ghost. The motions of quarks are forever unknowable. Quarks are like dancers in a strobe- lit room. Each instant is a motionless image: we see their current positions, but we cannot guess at the motions of the dancers between the flashes. But as quarks are only virtual particles, they do not have to travel between the positions in which each flash finds them. They do not persist as physical entities in the darkness.
Where do these mysterious quarks come from? Nowhere. They arise out of nothingness. In even the hardest vacuum out there between the clusters of galaxies, potential matter is constantly bubbling away, coming in and going out of existence. Quarks are spontaneously appearing. No ingredients go into the recipe to create them, nor is there any reason or cause that makes a particular quark suddenly appear at a particular point. It simply does, and for that instant it is no longer merely potential: it is matter. Most such particles return to the potential froth a trillionth of a second later. But some interact with other new-born matter to form more complex structures that persist longer: perhaps a photon that goes whistling off through space; or perhaps a blue-green planet full of people.
What we consider solid matter is constantly winking in and out of existence. There is no way to predict what will appear next, or where. The observable universe contains countless common particles: electrons and protons and neutrinos and such. But there is no certainty that these are the only particles that arise from the froth of potentiality - they are only the most likely. It is highly unlikely, but not impossible, that a maroon 1947 Cadillac will spontaneously materialize in the Small Magellanic Cloud .
In fact, any kind of particle could appear, with any properties of mass or energy. Because the probability never fully reaches zero, given enough time, that Cadillac has to appear. But what if something even stranger materializes: a particle infinitely small, but almost infinitely massive? The precise laws of probability show what would most likely happen, just as they can guess that the pool ball will probably go in the pocket.
If such a massive particle appeared, the interactions of its component quarks would immediately tear it apart in a titanic explosion. Its vast mass would warp space and time around itself, sealing it off forever from whatever previous surroundings it might have had. It would then rush outward, not into space, but creating space as it expanded. It would become a new universe. Such an event has been called a big bang.
An extremely unlikely event? Definitely. An impossible event? Definitely not. In fact, we know it happened at least once, to form our universe. When? About fifteen billion years ago, though there is still a great deal of debate about the figure. Where? Right here. You were there. We all were. Every atom of your body was there, as was everything else in the universe. We were all at ground zero when the thing went off. We are the outrushing fragments of that one event.
But why is this universe the way it is? Why does an electron have a specific mass and charge and spin as opposed to some other figures? A minute difference in any of hundreds of so-called physical "constants" would result in a universe in which we could not exist. Perhaps the universe has to be the way it is because if it were not, we would not be here to wonder about it.
If another identical particle sprang into existence again, would another you be sitting here reading this essay fifteen billion years later? No. One thing we do know about quarks is that we cannot predict with perfect accuracy what they are going to do next. A different big bang would produce a different universe. But would it be a little different, with blue trees and green sky, or would it be unimaginably different, perhaps without matter, or without time, or without space? Perhaps there are many universes, each radically different. We can never know the truth, for each universe would be wrapped in its own event horizon, all information beyond it forever unknowable. We cannot know what is beyond our universe, or where is beyond.
And what went before that particle? Did it happen in "empty" space, or in somebody's closet? Again, such information is outside our universe. It is not that scientists haven't yet found the answer, for they think they have. The answer is, the questions have no meaning. Our space nor time did not exist before our big bang.
How should we feel about this new knowledge we have gained? It depends on our personality types. Pragmatists reject it, saying that physics has left the real world and gone off into flights of fancy. They deny that stuff is at some level not made of other stuff, and that universes can appear out of nothing and for no reason.
Many mystics embrace it, saying that at last science has caught up with religion. They see the change from "First there was the word" to "First there was the probability" as a linguistic quibble. God still created the universe, but He did it with a big bang.
For myself, I am very happy with the vague and simplistic knowledge that I have of these strange matters. I enjoy both puzzles and zen koans, so I like having such a strange and paradoxical truth at the heart of existence. It increases my wonder as I look up at the night sky. And I feel proud that my species, my generation even, has parted this far the many veils of mysterious Nature herself. I am pleased to think that if and when we do finally pull away the last veil, we will find that She is, like all of us, both beautiful and born of a miracle.
copyright 1996 by Brian K. Crawford