Beyond Star Trek

by Lawrence M. Krauss

  Alternatively, while there are some new types of elementary particles predicted to be produced in radioactive decays of ordinary matter, the (average) lifetimes before such decays occur are unimaginably long, because the forces involved are so weak. One current suggestion is that the constituents of normal matter, like diamonds, are not forever, and that all protons and neutrons in the universe will eventually decay, leaving nothing heavy enough to serve as the nuclei of atoms. But you don’t have to worry about watching various parts of your body disappear. The predicted lifetime for such decays exceeds a million million billion times the age of the present universe. What is even more fantastical, I think, is that we can build—and, indeed, are building—large underground detectors that might be sensitive enough to catch one such rare decay.

  So much for new weakly interacting particles. Any such new form of matter roped into service as a carrier of ESP will suffer from the Curse of Newton’s Third Law: If you interact with me, I must interact with you. Neglect of this law is responsible for a ton of silly errors in science fiction. I discussed the infamous “ghost” error in my last book, wherein a ghost is seen to be too incorporeal to lift anything or to embrace its loved ones, but for some reason whenever it walks, it walks on the floor, and whenever it sits down on a chair, its butt manages to stay put. Here is another one: Every now and then in science fiction, including (frequently) in Star Trek, humans are briefly rendered incorporeal and can pass through walls, and so forth; sometimes this happens when they “inhabit” some other dimension, so that they don’t interact with our 4-dimensional universe, and sometimes it happens just because they have been transformed into some form of non-interacting matter. However, in this case, how do they breathe? Presumably the oxygen in the air surrounding them, which is necessary for their survival, is as impervious to their existence as anything else.

  There is rock left to turn over, though. We can’t use the weak force because it is short-range, but what about some new long-range force in nature, beyond the four known fundamental forces. What about the fourth force, gravity, for that matter? It does, after all, literally make the world go round.

  No one, to my knowledge, has suggested that gravity itself is the carrier of ESP signals—perhaps because gravity is so universal. Any old chunk of matter will do the job, and exactly the same job, apparently. There is nothing special about the gravitational properties of the brain, as far as we can tell. And even if there were, it’s hard to see how even a brain as big as a dolphin’s could produce a gravitational force on a nearby object big enough to do much of anything.

  But is there a fifth force, so nearly invisible that we have so far been unable to detect it? This leads me to the pioneering work of the Hungarian baron Lóránt Eötvös. In Budapest in 1889, Eötvös began a series of remarkable experiments on the nature of gravity which he carried on over a 30-year period until his death in 1919. (Actually, his most famous paper appeared 3 years after his death, indicative of the pace of publication at the time and not of any afterlife experience.) The question Eötvös addressed is one that later formed the heart of Einstein’s general theory of relativity: Does gravity attract all materials in the same way, regardless of their composition? If gravity represents the curvature of space itself, then clearly all objects should respond to this curvature in the same way. If they do not, then either general relativity is incorrect or a new force must exist beyond gravity which is sensitive to the composition of certain materials.

  Now, you might think that since gravity itself is so weak, trying to distinguish small variations in the gravitational attraction between different materials would be impossible. However, if you are clever, it isn’t. Eötvös performed an experiment in which plumb bobs made of various materials were allowed to hang freely, and the angle these made with the vertical were compared. Absent Earth’s rotation, they would point directly down toward the Earth’s center because of the force of gravity, but the rotation of the Earth pulls them a little off center. If the gravitational force on the plumb bobs was different because of the difference in the materials making up the plumb bobs, then the relative magnitude of the downward force and the sidewise force would be different, and the plumb bobs would make different angles with the vertical. By carefully comparing their angles, Eötvös claimed to put an upper limit on the difference in the gravitational force on different materials of less than 1 part in 100 million!

  What does this mean? It means that if there were a fifth force that was material-dependent, its strength, compared to the strength of gravity, would be less than 1 part in 100 million! But things got worse.

  In 1964, a modern experimental wizard, Robert Dicke (who helped develop the maser, the laser, the lock-in amplifier, the microwave radiometer, and atomic clocks, measured the solar oblateness, and devised a way of measuring the cosmic microwave background radiation from the Big Bang), performed an experiment using a sensitive balance and laser beams to measure the possible difference between the gravitational pull of the Sun on objects made of different materials. Dicke’s experiments have put an upper limit of 1 part in a trillion on such a difference! The experiment was so sensitive that the gravitational force on the balance due to the mass of an experimenter anywhere in the room would have produced an effect orders of magnitude bigger than the quoted upper limit. It was so sensitive that a fragment of iron 10-millionths of a meter on a side on either arm of the balance would have experienced a force in the Earth’s magnetic field 100 times greater than the limit. A difference in temperature between the two balance arms of 1/100,000 of a degree would have ruined the sensitivity of the experiment. And so on. As a theoretical physicist, I am always in awe of such technological masterpieces, but the significance of these results from our point of view is that at scales for which the experimental sensitivity is the greatest, any new long-range force would have to be less than 1 billionth the strength of gravity. And I urge you to recall the arguments of the last chapter: Gravity is very very weak!

  About 70 years after Eötvös’s death, some desperate soul decided to reanalyze the baron’s data and claimed to find evidence for a material-dependent force. This newfound fifth force dominated the physics literature for a few months. Of course, as any experimentalist will tell you, it is particularly worrisome to analyze the fine details of experimental data if you have not been a part of the experiment yourself—much less the details of data from an experiment performed 70 years earlier. The new “fifth force” quickly went the way of many other sensational but incorrect discoveries. Nevertheless, although the claim was disproved, it served a useful purpose. Many experimentalists realized that they had the technology to search for new forces that might act on a variety of scales, from meters to miles. Within a couple of years, experimental results began to appear constraining a new material-dependent force on various scales, always at levels well below the strength of gravity, the weakest known force in nature.

  Now, it is true that no one has ever put two people, one thinking and one ready to receive, on a Dicke-type balance, but given the plethora of experiments, I find it difficult to believe that any new force strong enough to tweak the atoms in another person’s mind across the room can have escaped the attention of all those researchers. As long as one subscribes to the notion that our brains are made of the same stuff as everything else, then much as we would love to read another’s mind, there seems to be no light to read it by.

  With all this talk about gravity and new weak forces between mind and matter, I can’t help but return to an idea far older than ESP. The Force in Star Wars, which led off this discussion, is in fact much closer in spirit to a notion originally at the basis of astrology, which in turn had its roots in ancient Greece. Suspecting that four elements—air, earth, fire, and water—were not enough to keep the universe going, Greek natural philosophers decided that there must be something else out there. This material, dubbed the “quintessence” (fifth essence) by Aristotle, was the material of the heavens, permeating all things—the funda
mental essence of creation. It was of course invisible, and for two millennia—until it was shown not to exist in an experiment by A. A. Michelson and Edward Morley at Case Western Reserve University—it went by its more familiar name: the aether.

  The aether, being universal, connected the world of the stars with the world of humanity. This idea took on new life in the mystical world of ancient Alexandria. Here it was woven with various forms of Eastern mysticism into a new religion, astrology. The aether was the medium that linked the human drama to the regular motions of the planets around the Sun, and astrology explained what the planets were up there for. In yet another example of our profound ability to imagine ourselves at the center of the universe, the Alexandrian astrologers determined that the planets governed human affairs. The idea was not unique. In Rome, after all, the planets were gods, and mortals were subject to their caprice.

  Twenty centuries ago, the notion that the aether should exist was a good enough hook on which to hang a new philosophy like astrology. However (except perhaps in the Reagan White House), that is not supposed to be good enough today: Astrology is neither internally consistent nor supported by experiment. (In my favorite example of the acuity of astrology, several people were provided with a horoscope, which was actually that of a famous serial killer. They mistook it as their own, confident of its characterization of their own personalities and experiences.) Still, most newspapers in this country carry a column on astrology, the annual sales of astrology books in the United States is about 20 million, and presidents and their wives find nothing particularly strange about determining their actions using the predictions of a “science” based on a material that was shown more than 100 years ago not to exist.

  As myth gave way to science, the aether took on a more scientific cast. Newton and his contemporary the Dutch physicist and astronomer Christiaan Huygens had already established in the seventeenth century that light was a wave. This presented a problem, however, because a wave needs some medium to travel in. Remove the air surrounding a buzzer in a jar, and the sound disappears. There is no sound in space (as Gene Roddenberry knew but ignored). But what about light? The light that carries the image of the buzzer still reaches you even if the sound waves don’t. There had to be some material, other than air, that light traveled in. What better choice than the aether?

  So, from the seventeenth century to near the end of the nineteenth, the aether flourished for a scientific and not a mystical reason. In 1887, when Michelson and Morley demonstrated that there was no evidence for aether, they did not suspect that within 20 years a young theoretical physicist, Albert Einstein, would show that not only did experiment provide no evidence for the aether but theory now rendered the existence of such a material impossible. As far as science fiction writers were concerned, Einstein may have dispensed once and for all with the aether, but he gave them something much richer, a universe in which space and time themselves were relative.

  One might say that the dark matter of modern cosmology is our modern-day aether, and in some general philosophical sense it is. It seems to permeate the universe, and it is (thus far, anyway) undetectable. There is one big difference, though: Dark matter is inconsequential on the human scale. It does nothing for us. Its gravitational attraction may determine the very expansion rate of the universe, but as far as day-to-day human activity is concerned, it may as well not exist. It is invisible precisely because it does not interact with stars or other forms of normal matter. It could no more tell us whether Mars was rising in the house of Aquarius than it could write a sonata.

  Nevertheless, while astrology just seems silly, ESP remains a domain where one can continue to ask valid questions. While the data is discouraging—with the best candidate, electromagnetism, being too detectable and the handiest candidate (in terms of its ubiquity), gravity, being too weak—the search for new forces in nature is still an important enterprise. There is little doubt that undiscovered forces and undiscovered elementary particles exist at some level. While they play no direct role in our everyday lives, understanding them will inevitably help us to understand the processes that led to our own existence. This is the real “cosmic” connection to the stars provided by modern science, replacing the mystical renderings of astrology.

  We are far from knowing everything about the nature of matter, and while there does not seem to be room to wiggle even a single undetected thought through the maze of modern experiments, the fact that we can test a force at a level of 1 part in a billion—a force so weak that it takes something the size of Earth to bring it to your attention—provides hope that if there are any strange new things that go bump in the night to be found, we will eventually find them.

  CHAPTER ELEVEN

  IT’S ABOUT TIME

  SCULLY: Time can’t just disappear! It’s a universal invariant!

  MULDER: Not in this zip code!

  For a former physics student who was supposed to have done her undergraduate thesis on “A New Interpretation of Einstein’s Twin Paradox,” Dana Scully should have known better than to utter the above statement. Or maybe she had a really new interpretation. For at the very heart of Einstein’s special theory of relativity—at least, the relativity I know and love—is the fact that time is precisely not a universal invariant. It flows at different rates for different people in different circumstances of motion or in different gravitational fields.

  Now, what’s Einstein got to do with ESP? Well, first off, back in the early heyday of ESP research, before the results of J. B. Rhine and others had been discredited, Einstein remarked that he had an open mind on the subject but would not believe it until he saw a “distance” effect. He was alluding to the fact that all long-range forces in nature fall off with distance, gravity and electromagnetism being the prime examples. Radio waves become less intense the farther away the source, so why shouldn’t “brain waves?”

  The fall-off with distance is really just a consequence of energy conservation. A source radiates a signal with a certain energy, and if that signal later spreads out over space, the energy per unit area carried by the signal has to decrease. There is no way around this. Not only has the conservation of energy been tested to the nth decimal place, but—more important, perhaps—we now understand that energy conservation is a consequence of the fact that the laws of nature don’t change with time.

  It seems to me that Hollywood has generally caught on to this sensible idea. In Star Trek, for example, Spock has to touch the person whose mind he is reading, and Deanna Troi has to be near someone in order to sense that person’s feelings; even the perpetrator of ESP rape in the Next Generation episode “Violations” apparently had to be on the same spacecraft as his victims. The captured alien in Independence Day likewise seemed to have to be in the same room with its victims before it could kill them by psychic means. (If not, of course, why bother arriving here in spacecraft—why not just zap everyone from home?) And the spooky children in the sci-fi classic Village of the Damned could sense your malevolent thoughts only if you were nearby. Some of the wackier shows on TV have lately seemed to stray from this principle—but then, they’re wacky.

  In any case, following Einstein’s remark, some ESP researchers searched for this distance effect and never found it. But of course they never found any irrefutable evidence of ESP itself, so there was no way to tell whether or not it fell off with distance.

  More important, perhaps, than distance dependence is the relation between the ideas of time and space central to the theory of relativity, and ESP issues of clairvoyance and precognition. It is a tenet of relativity, one that has been verified over and over again, that no signal can travel faster than light. This means that instantaneous knowledge of remote events is simply impossible. Of course, the speed of light is pretty fast, so this isn’t much of a limitation on terrestrial communication; however, it would rule out psychic messages from inhabitants of a distant galaxy who were not around 10 million years ago, if 10 million years is the amount of time it would take lig
ht to reach us from that galaxy.

  More important still, this tenet of relativity defines the nature of time itself and also determines the nature of cause and effect, which is upended by some of the notions associated with ESP and precognition.

  Back to Scully. One can plausibly argue that the flow of time is not invariant in nature by recognizing relativity theory’s treatment of space and time as related aspects of the picture of the universe as 4-dimensional space-time. Therefore, what happens to distance can happen to time. And everyone knows that the distance between New York and Boston depends upon the route you take. If you go due north on the Merritt Parkway and up through Hartford and then east on the Massachusetts Turnpike, the distance that elapses on your odometer will not be the same as it would be if you had taken Interstate 95 along the coast. But two people who travel these routes can still meet for a drink at the same place in space—say, on top of the Prudential building in downtown Boston.

  Following this logic, why can’t these two people take different routes between two points in space-time, with more time having elapsed on one person’s clock than on the other’s? This is precisely what does happen, if one of them travels out on a fast rocket for a long time and then returns to Earth, while the other sits in her armchair reading this book while her friend is away. It goes without saying that for my reader the hours will fly like minutes and the days like hours—but when she eventually looks at her watch she will discover that the normal amount of time has passed. Her friend in the rocketship, who is traveling at a very high rate of speed, will have a watch, too, which will be running slow compared to the watch back on Earth. Thus—in this version of Einstein’s classic twin paradox, studied by the undergraduate Dana Scully—for the rocket traveler the days that his friend passes on Earth really can be hours for him. When they meet again, she will be several days closer to his own age than she was when he left.