Beyond Star Trek

by Lawrence M. Krauss

  The fact that empty space is filled with a boiling mess of virtual particle-antiparticle pairs that spontaneously appear and then disappear before you can say “Rumpelstiltskin” suggests that empty space may, in the quantum world, actually carry energy. In fact, in general it should. We know, for example, that as the universe evolved and cooled, the energy of empty space—or the vacuum, as it is usually called—changed as the temperature changed, and various so-called phase transitions took place to make the universe look the way it does now. So it is natural to suspect that even today the vacuum carries significant energy.

  Which is a puzzle. If empty space carries significant energy, then this energy would produce gravitational effects that would change the way the universe expands. But observations of the expansion put an incredibly tight upper limit on the amount of energy that can be associated with empty space—an unbelievably tight limit, in fact: a billion billion billion billion billion billion billion billion billion billion billion billion billion billion times smaller than most theoretical physicists would have predicted, given our ideas from fundamental particle physics.

  This puzzle—why empty space doesn’t have a whole lot more energy associated with it than the observations allow—has become known as the Cosmological Constant Problem, and it is probably the most severe numerical conundrum in all of physics. There is no doubt that trying to resolve it will take us to the very deepest understanding of the fundamental laws governing the universe.

  The name for this vacuum energy—the cosmological constant—refers to a theoretical speculation of Albert Einstein’s, which he later discarded. In 1916, when he was developing his general theory of relativity, he realized that if it was to be a theory of gravity, it should be applicable to the universe as a whole. Current wisdom suggested that the universe was static; however, there was no solution of the general relativity equations that allowed for a static universe, if normal matter was all there was. The reason is simple. Normal matter attracts other matter gravitationally. If you lay out matter randomly in the form of stars and galaxies at rest throughout the universe, slowly and inexorably the gravitational attraction between these systems will begin to cause the whole system to collapse inward. Einstein soon realized that a way out of this problem was to add a term to his equations, the cosmological constant, which represented a kind of cosmic repulsion between matter on large scales. By balancing this repulsion with the standard gravitational attraction, one could arrive at a static solution of Einstein’s equations—a solution that Einstein hoped would describe the universe we live in.

  Within little more than a decade of this proposal, however, Edwin Hubble and others had convincingly demonstrated that the universe was expanding. In an expanding universe, there is no need for a cosmological constant, because attractive gravity can simply slow the expansion. As soon as Einstein became aware of the expansion, he dispensed with the cosmological constant, calling it one of his worst theoretical blunders. The only problem is that we now realize it was not his to dispense with. The vacuum energy associated with the virtual particles I have described would produce exactly the kind of term that Einstein added by hand to his equations. So the problem becomes trying to understand why this term in Einstein’s equations, which we now understand should be there, must be (because of observation) 125 orders of magnitude smaller than arguments based on particle physics suggest.

  Now, you might say, and some physicists do, that since the upper limit on the allowed energy is so small, why not just assume that the actual value is zero, and that some as-yet-unknown law of physics sets it so. This may be the solution to the problem. However, no one to date has come up with a convincing argument as to why this energy in the vacuum should be zero. Moreover—and more significant to me, at least—there is growing cosmological evidence that perhaps the energy density of the vacuum is not exactly zero. Along with my colleague Michael Turner at the University of Chicago, I have been championing this once completely heretical idea for over a decade. Who knows? It might even be true. If it is, a number of fundamental puzzles in modern cosmology might be resolved.

  But although we might resolve cosmological paradoxes, we will have raised new problems for particle physics. It might be that no one has any really good understanding of why the cosmological constant should be zero, but at least one can imagine plausible new physics arguments for its being zero. If the cosmological constant is instead very small, we all will have a lot of homework to do.

  As I mentioned earlier, while preparing this book I queried a group of the most prominent theoretical physicists working in particle theory and general relativity as follows: If there were one question about the universe you could receive an answer to, what would that be? The responses were remarkable in their variety and depth. One of the people I contacted was Edward Witten, a brilliant mathematical physicist currently at the Institute for Advanced Study, in Princeton. Witten works on string theory, an area of physics originally designed to address the fundamental paradoxes arising when one tries to reconcile quantum mechanics and gravity, but which many people hope will provide a unified theory underlying all the known forces in nature. His answer caught me by surprise. I had expected he might want to know if string theory described the real world; instead, he indicated that he would like to know if the cosmological constant was zero, and if it was, why, and if it wasn’t, why not. In retrospect, this is understandable: any Theory of Everything worth its salt must address this fundamental issue.

  Be that as it may, let us finally return to the issue at hand for John Travolta and Luke Skywalker. Could the vacuum, if it indeed carries energy, and if that energy were properly tapped, provide a power source of the type envisaged by old Obi Wan? I had never thought of the Cosmological Constant Problem in this context before now, but one can do a simple estimate, based on the maximum allowed energy which could be stored in the vacuum as a cosmological constant consistent with the observed expansion of the universe. If one were somehow able to release the energy stored in 1 cubic meter of the vacuum, it would amount to 1 ten-billionth of a joule.

  This allows me a brief jab at the Transcendental Meditation movement of the Maharishi Mahesh Yogi. This group, which started out as a rather innocuous bunch claiming that meditation could help you feel and work better (probably true), has proceeded over the years to increase its promises. Now it is claimed that not only can TM help you “fly” momentarily but it can also help slow the aging process, and if enough people perform it, it can reduce the crime rate. I certainly believe that if a fair fraction of the Earth’s population meditated regularly, the crime rate would decrease, because presumably a portion of the criminal population would be meditating some of the time instead of preying on the public. But flying is another matter. The TM movement is the only group I know of that pins its claims so thoroughly on modern physics. TM literature is full of explanations couched in the jargon of string theory and quantum mechanics. A theoretical physicist I have known since his student days is now head of the Physics Department at Maharishi University, in Iowa, and is a leading adviser to the Maharishi himself. On the side, he has run twice as a candidate for president of the United States, on the Natural Law ticket.

  In any case, I have read somewhere the claim that it is by tapping the energy from the vacuum of the universe that TM devotees can momentarily fly. Using the maximum-vacuum-energy estimate above, I have calculated that to momentarily raise the Maharishi a meter off the ground would require tapping into a cubic volume larger on each side than the island of Manhattan. (Perhaps they should call it the Unnatural Law Party?)

  To lift in this way the pen that began this discussion is not much easier, requiring us to tap a mere 10 billion cubic meters of vacuum, or the space inside a cube 3 kilometers on a side.

  The Force may be with us, all right—but don’t hold your breath!

  CHAPTER THIRTEEN

  THE MEASURE OF A MAN

  There once was a man who said, “Damn,

  It is borne in upon
me I am

  An engine that moves

  In predestinate grooves,

  I’m not even a bus, I’m a tram.”

  —Maurice Evan Hare

  In spite of popular notions to the contrary, art and science will be forever intertwined. The limerick above was penned in the year 1905. In the popular consciousness, this was the dawn of a new century of progress and material success, based on the nineteenth-century mechanistic ideal. A well-managed world would run like a well-oiled clock. To many a scholar, and poet, the universe was a cosmic game of billiards, initiated by a master billiards shark and continuing indefinitely on its own, wherein the trajectory of history was as predetermined as the trajectory of the balls on the cosmic table.

  This picture of the universe could not have been farther off the mark. That year would witness the birth of the two great revolutions in twentieth-century science, relativity and quantum mechanics—revolutions that would forever change the way we think about the world and our place in it. Paralleling these developments, within a generation the world would live through the unraveling of the great nineteenth-century European order, a World War, and a Great Depression.

  As a new millennium approaches, the world is a much more uncertain place than it was at the last turn of the century. For one thing, our experience with the physical world at the various extremes of scale has taught us to expect the unexpected.

  How is this change reflected in our literature—in particular, in our science fiction? Maurice Hare’s tram has been replaced by the likes of HAL, the overzealous computer in 2001: A Space Odyssey, and Data, the near-human android in Star Trek, and The X-Files’ homicidal computer COS. The question no longer seems to be “How much like a predestinate machine is Man?” but “How much like a human being can a machine be?”

  I am writing this shortly after a watershed moment in the history of the man-machine debate. The IBM computer Deep Blue recently defeated world (human) chess champion Gary Kasparov, marking the first time the best human chess player on the planet has been defeated in a tournament series by a computer. This defeat was particularly notable because Kasparov had predicted publicly before the contest that a computer would never beat a human world champion. After his defeat, he suggested to reporters that the machine showed signs of “intelligence.” This highly publicized matchup has spawned a batch of articles in the popular press addressing the question: Can computers think?

  This is not the first time, of course, that this question has been raised. Since digital computers first appeared on the scene, people have been wondering whether they might possess attributes heretofore thought of as exclusively human. The logician and computer scientist Alan Turing laid out the issues in a 1950 essay titled “Can a Machine Think?” and Star Trek’s Data has pondered them in more than one episode, particularly after his emotion chip was installed.

  Each time a computer has crossed a new threshold, disproving yet another claim that “a machine will never be able to X,” the debate has been reinvigorated. To some, the suggestion that computers may one day develop consciousness is heretical. These people link the concept of consciousness to their belief in the existence of a human soul, a nonmaterial entity supposed to embody our intellectual, emotional, and moral being—and thus, presumably, our consciousness. In many religions, the soul is viewed as immutable and indestructible, continuing to exist long after our material bodies have turned to dust. I have always had a hard time with this logic, since one’s consciousness, or self-awareness—and thus, it would seem, one’s soul—develops gradually after birth (or, if you are a stickler for embryonic rights, after conception). If a consciousness can be created where none existed before, then why should it not die with the body? (This is where the Enterprise’s transporter, as I indicated in my last book, would come in handy: If every atomic configuration in your body can be transported to another locale, and you end up as the same person, that circumstance would appear to dispense with the idea that a nonmaterial soul perfuses the body. That is, of course, unless you imagine that the soul can find the body wherever it may be located in space; that might explain why there are so many souls in Star Trek that get disconnected from their bodies only to find their way home eventually.)

  In fact, there are a number of ways to wiggle out of the immutable-individual-soul idea. For example, one can invoke the notion of reincarnation, wherein the soul exists before birth. There is a huge numerical anomaly, however: there are more people alive at the present time than have been alive in the planet’s previous history, so where have all the extra souls come from?

  Well, one can argue—as do some religions and at least one X-Files episode—that some souls migrate from animals to humans, thus taking up the slack. But some might find this idea more offensive than the idea that computers possess a consciousness and with it a soul. Aside from that consideration, what about evolution? What about when all that was here on Earth was algae? Do algae have souls? Well, I suppose one can get around this by appealing to the cosmos—that is, perhaps our souls have transmigrated from others long dead, in other solar systems? One now must suspend disbelief about how the souls got here and wonder whether there is some cosmic Law of Spiritual Conservation, so that the number of souls present in the universe at any one time is constant.

  Or perhaps one can appeal to a kind of “collective consciousness,” in which all our souls are part of one coherent whole that exists everywhere at once and can be divided up into as many pieces as necessary. Avoiding the issue of where this reservoir would actually exist and how such an arrangement would be made consistent with a causal universe, we must conclude that a collective consciousness would certainly allow for such phenomena as ESP, channeling, and so forth—and it has a nice New Age flair to it. But, as I discussed in chapters 9 and 10, this requires one to believe that the mechanism of consciousness is nonphysical, since there appears to be no physical mechanism to mediate ESP in a way not easily detectable. However, the fact that the actual process of thinking can be observed using sensitive magnetometers suggests that at least some aspects of conscious thought—and thus perhaps consciousness itself—are physical.

  One may then appeal to the last refuge (literally) of religion—namely, that souls reside in Heaven, a place inaccessible on a human plane—and hold that, like God and Heaven, the soul exists beyond physical law and cannot even be discussed in terms of physical law. There’s no argument to be posed against this point of view, because it is deliberately untestable; one must accept it or reject it on the basis of faith. But it’s worth emphasizing that reliance on faith is probably the only way to avoid the various logical pitfalls that confront the advocates of an immutable soul grafted onto human consciousness.

  Now, if we can demonstrate that the source of consciousness is completely biophysical, is that the end of the human soul? No, I expect not. Fundamental religious tenets must evolve as science evolves, in order to remain viable. When the Earth was shown not to be the center of the universe, the Catholic Church survived the blow and moved on. Faith is not easily shed. Fox Mulder’s motto “I want to believe!” applies just as well to conventional religion as it does to UFOlogy. I suspect that once we understand the physiological basis of consciousness, the theological realm of the soul will retreat, to avoid conflict with experiment.

  Even for some of those who believe that the mind is physical, it is not easy to accept the notion that a computer might one day think in just the way a human being does. The mathematical physicist Roger Penrose is one of the most prominent believers in a fundamental irrevocable physical difference between man and machine. Penrose is convinced that digital computers can never achieve human intelligence and self-awareness. He has written at least two books on the subject, with slightly different premises. Lest what I am about to say be misunderstood, let me affirm the fact that Penrose is a far more brilliant mathematician than I am, and that he has clearly thought about and researched this issue at much greater length than I have. Many of his descriptions of mode
rn physics are incisive and beautiful, but I find his arguments on the subject of human vs. machine intelligence completely unconvincing. The premise of his first book on the subject, The Emperor’s New Mind, is that some as yet undiscovered law of physics operating in the shadowy realm where quantum mechanics and gravity meet, differentiates between the processes of human intelligence and those of a digital computer. Most physicists think that what happens on this minuscule scale is completely irrelevant to an understanding of what goes on at the scale of the human brain—or even at the atomic scales relevant to chemical processes, which are themselves orders of magnitude larger than the scale where quantum effects become significant in gravity.

  Penrose has slightly modified—or, at least, clarified—his arguments somewhat in his next book. Here he makes it clear that he believes that computational machines cannot think as humans do because of the mathematical theorems (proposed by, among others, Kurt Gödel and Alan Turing) proving that computational systems are necessarily incomplete. In other words, there are certain assertions that are true but can never be proved true within the context of any particular system of mathematical or computational logical rules. Since humans can understand the truth of such assertions through human intuition and insight, then human intuition and insight cannot be reduced to any set of rules. And therefore human understanding (read “consciousness” or “self-awareness” ) can never be replicated by computing machines.