Written by Dr. Sten Odenwald
Copyright (C) 1995.
To escape the latest run-in with hostile aliens, Captain Kirk of the starship Enterprise orders Engineer Scotty to take the ship to 'warp factor 6'. The mighty engines open a doorway into the magical world of 'hyperspace' and in an instant, the Enterprise is taking a short cut through space. A trip to the nearest star now takes only a minute or so, not centuries, and Captain Kirk survives to continue his 'five year' mission.
Science fantasy has always delt with fantastic ideas at the very limits of believability, but sometimes the distinction between science fact and science fiction can become murky indeed. "Space...the final frontier" is a truism that takes-on a very different meaning in light of what is now known or suspected about space. Today, physicists and astronomers are exploring exciting new ideas that may be the basis for a future at least as exciting as Captain Kirk's 23rd century.
Of course 'outer space' is filled with planets, stars and galaxies. Without these ingredients space would be a sterile 'nothingness'. But a simple glance at the infinite blackness of the night sky shows that this intangeable ingredient is one of the most common in the physical world; It is also the least understood. Unlike most things that can be directly experienced, it is difficult to speak critically about something you can neither touch nor see. Fortunatly, when it comes to pure, empty space, the situation is not quite so bleak.
As we all learned in high school, one of the most basic properties of space is its extension, also called its dimensionality. The world in which we work, pay taxes and take vacations is a three-dimensional one. In it, we are free to move forward and backward, side-to-side, and to a limited extent, up and down. The intricate gyrations of a ballerina or a gymnast tell us that no matter how we might move, we never 'turn a fourth corner' and find ourselves moving along a new direction through space. This tells you right away that Captain Kirk's world of hyperspace is not going to be an easy one to break into, especially by something as big as a human or a starship!
And then there's Time.
A strictly three-dimensional world is pretty boring. Nothing happens in it. Suppose you tell your friend that you will meet her at the entrance to the Washington Monument. Your well intentioned instructions will help her narrow your location in the universe to a six foot cube of space at a particular point on the surface of the earth. But unless you also say when to be there, the instructions are useless. Time is a vital fourth coordinate or dimension to our world. Without it, we would all be trapped in a perpetual Now, much like the frozen images captured on a photograph. Space and Time taken together define the complete arena in which we live. They form such an integral, cohesive framework for our existence that physicists since Albert Einstein refer to their combination as simply 'spacetime'.
Spacetime is vast. It extends well beyond the earth and solar system, encompassing the entire universe out to the farthest galaxy. Its indivisable time-like aspect also extends from the instant that the universe flashed into existence, through the present moment, and on into the future.
Where did spacetime come from? Astronomers who study the universe have developed a detailed model of its evolution called the Big Bang Theory. About 15 to 20 billion years ago, everything in the universe came into existence in an awesome explosion. The feeble light from the fireball of creation can still be detected by sensitive instruments as they peer into the depths of space. The magnitude of this event is truely mind boggeling. Earthbound explosions begin with a bomb whose detonation sends debris flying out into space. But in the Big Bang, not only did matter come into existence, but space and time as well!
According to some recent theories, before the Big Bang, our particular spacetime simply did not exist. Anywhere. Anywhen. In the distant future if gravity wins the upper hand, this universe may finally recollapse under its own weight, once again vanishing into the absolute nothingness of no-time and no- place. It is difficult and somewhat troubling to imagine that time and space had a beginning and may someday come to an end. Even among religeous cosmologies, both ancient and modern, this has been a common theme. Science may, in the next few decades, prove true what humans have long suspected, and perhaps even feared, about the fate of the universe.
More amazing and profound than its scope and possible transcience are new discoveries that may portend even more remarkable revelations about the nature of spacetime. These discoveries have come not from the study of the grand design of the universe, but from a meticulous investigation of the composition of matter spanning over 300 years of experimental and theoretical work. From this intense human activity has emerged a detailed understanding of just how matter and force come together in spacetime to build-up the complex structures in our world.
At some time in our schooling we are told that matter consists of atoms; one for each element like oxygen or iron. The atoms themselves are built from even more elementary particles called electrons, protons and neutrons of which the latter reside in the dense atomic nucleus. Since the 1960's, gigantic machines commonly called 'atom smashers' have uncovered an even finer structure to matter. Neutrons and protons are, themselves, made from minute particles called quarks. All common forms of matter can now be represented by the combination of just three particles: one electron and two kinds of quarks.
But there is more to Nature than matter. Without forces such as gravity, the world would be formless and devoid of living matter. Once again, although the dynamics of the world seem bewilderingly complex, there are only four distinct types of forces in Nature, each playing its own crucil role in orchestrating the universe.
The force of gravity acting over billions of years assembles matter into galaxies and stars, choreographs the dance of the planets around the sun, and keeps our feet planted firmly on the ground. The electro- magnetic force holds electrons captive inside atoms and allows matter to give off light for us to see. The strong nuclear force binds atomic nuclei together, and its release in nuclear fusion keeps the sun and stars shining. Last but not least is the weak nuclear force which causes matter to decay, and stars to detonate as supernovae in devastating explosions.
Detailed mathematical descriptions are available for each of these phenomena which allow anyone interested in such matters to comprehend and perceive the physical world with unprecedented clarity. Basic phenomena in the world, from the color of a sunset to the birth a star, are no longer regarded as capricious and mysterious, but can actually be predicted with fair accuracy. Physicists, however, want to do more than merely describe how each separate force acts upon matter. Physics is more than merely the passive 'high-tech' bookkeeping of Nature's comings and goings. It is a search, guided by experiment, for the basic, universal principles that underlie how the physical world operates at every imaginable scale, from the most distant galaxy to the innermost workings of the atom. In creating such a comprehensive 'Theory of Everything', somewhere along the way one of the greatest remaining challenges to our understanding of the physical world must be faced. A glimpse of this challenge can be seen by thinking about a simple electron.
If you were to draw an imaginary line through space, piercing the center of an electron, why is it that you single out one of these points as an electron but call all of its neighbors 'empty' space? It is easy to semantically define them as being different, "This one is the electron, that one over there is space", but how do you go about handeling this difference quantitatively?
Many schemes for describing the essential difference between matter and empty space have been tried over the decades; many have failed. The electron was at first thought to be a tiny sphere of matter whirling around the nucleus of an atom like a mineature planet. As intuitively seductive as it was, this idea fell into disrepute once Albert Einstein developed the Theory of Relativity. Then the revolution of Quantum Mechanics showed that all matter had wave-like properties; electrons at a particular instant were not located at fixed positions in space, but seemed to be in many places at once. For the last 50 years, electrons and other elementary particles like quarks are routinely thought of as small dots of pure energy whose boundaries vanish into the undefined fabric of space itself. It isn't that physicists have directly measured this to be the case, only that this is the only remaining working model for the electron that has survived, and is consistent with all that we know about electrons, both theoretically and experimentally.
Theoreticians since Einstein have speculated about the geometric features of spacetime, and the structure of electrons and matter for decades. The growing opinion now seems to be that, ultimately, only the properties of space such as its geometry or dimensionality can play a fundamental role in the defining what matter really is. In a word, matter may be just another form of space. If the essence of matter is to be found in the geometric properties of 'empty' space, our current understanding of space will not be sufficient to describe all of matter's possible aspects.
Remember, you needed to specify four coordinates in order to meet your friend at the Washington Monument at the right time and place. For most things in the world, including the motions of the planets, stars and galaxies, four dimensions is enough. But to describe the world of elementary particles, physicists have to add some additional coordinates to spacetime to keep track of the properties of subatomic particles. There does not seem to be enough room in a strictly four-dimensional universe to explain why matter looks and acts the way it does. Some of the most promissing theories require that the universe exists in as many as 7, 10 or even 26 dimensions at once!
These added dimensions do much more than just tell where a particle is located in the universe. They actually determine how that particle will look! According to Superstring Theory which was developed by physicists John Schwartz and Michael Green in 1982, every point in spacetime is represented by its usual four coordinates, along with up to 22 more 'stunted' coordinates. Every particle, on the other hand, is given an address in this 26-dimensional universe; an address telling whether the particle is located in a star or in the paper you are reading. The additional coordinates tell us what kind of a particle it is. Depending on how a particle 'moves' in these other directions it might, for example, be seen as an electron, a quark, or even 'empty' space.
How can a particle's motion along a particular dimension change its character so drastically? Fortunatly, you don't have to be an expert in physics to get some idea of how this might happen. For instance, your entire life's history, stretching along the fourth dimension of time, contains versions of you that are an infant, a young adult, or a senior citizen. Now suppose that we could move freely through time, we would be able to witness your drastic physical transformation from one kind of human 'particle' to another! By knowing your position along the fourth dimension the rest of us can keep track of how to interact with you. At some point it will, of course, be better to interact with you using 'baby language' than at other times!
We know from the gyrations of ballerinas and gymnasts that, if they exist at all, these dimensons can't be very big. There is no danger of taking a walk to the store and suddenly finding yourself in the 17th dimension! Only subatomic particles like electrons are small enough to gain any benefit from such a journey. Superstring Theory and some of its predecessors say that these added dimensions are rolled up into miniscule balls one trillion trillion times smaller than an atom. An atom would have to be enlarged to the size of the Milky Way galaxy 100,000 light years across, before any signs of them would be apparent!
Just as the lumps and bumps in the geometric shape of a piece of paper will control the motion of marbles moving across them, there is also an intimate relationship between the geometry of a 26-dimensional spacetime and the behavior of matter. Since the properties of the elementary particles and forces in the universe are already known, this can be used to discover what kind of geometry a 26-dimensional universe would have to have in order to resemble the universe we are familiar with.
The answer to this question is still being searched for today. But if and when it is found, it is believed that the geometric basis for the Theory of Everything will at last have been uncovered. To say that this will be a major accomplishment is an understatement. In fact, some physicists like Stephen Hawking in 'A Brief History of Time' even predict that the discovery of the correct geometry will herald the end of physics as we know it.
It has been said that to understand the motions of the clouds in the sky, you must first study the winds and currents of the invisible atmosphere itself. Like clouds, it may well be that matter is merely a tracer of activity at a more basic level in the physical world. The deep roots that elementary particles have may reach down into the bedrock of spacetime whose geometry ultimately controls their properties and how they are destined to interact with one another. Like an oak or a maple tree, we measure and perceive only their broad canopies. Their roots remain forever hidden.
It would seem that if our modern theories are correct, Captain Kirk will have to do something else other than duck into hyperspace to escape his enemies! Because the universe may manifest these other 'hyper' dimensions at the subatomic scale, only electrons can take advantage of them. Few of us would especially enjoy being squeezed to the size of an electron to escape even the most hostile alien! Although such rapid travel through hyperspace may never be possible given the rules upon which our universe may be based, there are other even more exciting possibilities.
If matter is 'simply' twisted space, would it be possible to create matter and perhaps even entire, artificial mini-universes out of warped space? Though technically difficult, some physicists such as MIT's Alan Guth have seriously thought about these possibilities and consider them within the realm of possibility in the distant future. Although it may not be possible for humans to travel through any of the other dimensions to space as a short cut to some distant star, what about the massless particles of light called photons? Could we at least send radio messages through hyperspace almost instantaneously, and not have to wait hundreds of years to get a reply from our colonists orbiting Antares? Then again, just because the physical world may not naturally include something like hyperspace on the interstellar scale, is it possible that no injunction exists forbidding its artificial creation? Perhaps given enough raw energy focussed on a small enough region of spacetime, many natural barriers could be overcome.
The scientific exploration of the world has taught us much about the way the universe is put together. We are now familiar with nearly all of its most important rules and regulations for living in harmony with its basic phenomena. It is always difficult to predict where the next great revolution in thinking will come from. Perhaps some of the current ideas about matter and space will not even survive the end of the 20th century as new experiments are developed. Then again, the scientific advancement of the last three centuries would have been impossible had not some ideas, as far fetched as they seemed at the time, been correct in one form or another!
So, the next time you gaze at the night sky, take a moment to reflect on the nature of the vast emptiness between the stars. Even perfectly empty space, the quintessential nothingness, may be a far more sublime and complex ingredient to our universe that we have ever before imagined!