Beyond Star Trek

by Lawrence M. Krauss

  From the moment Newton discovered the universal law of gravity, he and others were puzzled by the question, How does the Moon know the Earth is there in order to be attracted by its gravitational pull? That is, what exactly is it that communicates the force of gravity? Is that force instantaneous, or does it take time to reach the Moon?

  Newton never resolved these thorny questions, and preferred to move on to other things, including becoming head of the British Mint. Some 200 years later, however, Faraday pondered the same questions, but this time in the context of the electric forces between particles. To help himself understand why the electric force behaves the way it does, he imagined that emanating from every charged particle was an electric “field.” He pictured this field as a set of lines radiating outward in space from the particle in every direction. If he imagined the number of lines as proportional to the magnitude of the electric charge on the particle, Faraday could then understand why the electric force dropped off in strength with the square of the distance between charged objects. If I start out with a certain number of field lines emanating from a charge, and each one heads out in a straight line to infinity, the field lines will diverge. Therefore, the number of field lines that cross any given area at a certain distance will decrease with the square of the distance.

  Now, this is a nice picture, but is it more than just a metaphor? Often physicists create pictures to give themselves a clearer understanding of how the laws of nature work, but are these pictures ever the image of the reality itself? Sometimes the answer is a surprising yes. Faraday’s fields are such an example, and soon took on a life of their own. It was shortly understood that under certain conditions electric and magnetic fields could be generated simply by the presence of other electric and magnetic fields, without the presence of the electric charges that caused one to invent the fields in the first place.

  When physicists nowadays think of empty space—space devoid of matter—they realize that it’s not necessarily empty. We now think of the electric force, and also the gravitational force, as follows: A charged particle creates an electric field around itself, and a massive particle creates a gravitational field around itself. These fields propagate at the speed of light, and a far distant object can interact with them and be attracted or repelled. Because it takes some time for the fields to propagate, the Moon, for example, will be gravitationally attracted to where the Earth was at the time the field with which the Moon is interacting was created. If the Earth moves in the meantime, the Moon will nevertheless move toward the original place—that is, until the field created by the now moved Earth propagates out to the position of the Moon. Because these fields propagate at the speed of light, we don’t normally notice the delay on a human timescale. However, when cosmic distances are involved, the effects of the finite propagation speed of gravity can be dramatic. For example, the Milky Way is falling toward a huge galactic group some 50 million light-years away. In the time it has taken for the gravitational field of the huge cluster of galaxies to propagate to the region of our own galaxy, the cluster has moved from the position to which our galaxy is being attracted by perhaps 100,000 light-years, a distance comparable to the Milky Way’s diameter!

  Empty space is full of fields. A million years after I jiggle an electric charge here on Earth, the changing magnetic and electric fields have propagated a million light-years away, where they can cause an electric charge in an antenna attached to a radio receiver to jiggle up and down, producing a response in the receiver. The opening sequence of Contact, in which we pass slowly out through space, following the stream of electromagnetic waves emanating from our radio and TV broadcasts as they make their way through the universe, is a wonderful illustration of this idea.

  We sense directly only a small part of all the electromagnetic waves out there. This spectrum includes waves with frequencies to which the electrons in the atoms in our eyes can respond, sending signals to our brain which we interpret as one or another color. Waves of slightly lower frequency are invisible to us, but we nevertheless feel them as heat. Waves of slightly higher frequency are invisible—to us, though not to, say, bees—and we don’t feel them at all, but they damage our skin and produce dangerous but apparently appealing suntans.

  What could be more New Age than this? An invisible world full of electromagnetic fields all around us, some of which we generate by our own thought processes. How cosmic… ! Why couldn’t our thoughts generate weak fields that might be sensed by individuals with just the right kind of antennas built into their brains?

  But this is a case of too much of a good thing. Electromagnetic fields are remarkably good at propagating and producing effects. But if they produce effects, they are by definition observable. That’s the way the world works. If I think very hard—whatever that means—and try to produce a response in your mind, that means I must induce some chemical or electric response in the neurons in your brain. But unless you think your brain behaves differently from any other sort of antenna in the universe, then the signal I send to your brain should be detectable by radios or other types of electromagnetic receivers in the vicinity.

  There’s no doubt that the most sensible carrier for telepathic messages would be electromagnetic waves. There’s no doubt that they are directly associated with the operation of your thought processes. We have detected “brain waves” and can even measure the external electromagnetic signal they produce. But electromagnetic waves from the other end of the universe are detectable by receivers here on Earth. Why should such receivers be less efficient at receiving telepathic messages than your brain is? The fact that no one has ever detected electromagnetic waves associated with ESP is pretty damning, don’t you think?

  Maybe the electromagnetic waves associated with telepathy are so weak that existing detectors are insensitive to them? But they can’t be too weak to generate some physical disturbance in the brain of the recipient. This would entail carrying enough energy to cause an electron to jiggle, or an atomic spin to wobble, or something. But this same something can be used as the basis of some detection apparatus or other. Existing detectors of visible light can detect, for example, individual photons. We can build X-ray detectors to see through what we cannot see through with the naked eye, infrared-sensitive cameras to spy on our neighbors in the dark. The bottom line is that there is nothing more detectable in the universe than electromagnetic waves, as hidden as they seem.

  No, this is another case where Fox Mulder’s maxim, “The easiest explanation is also the most implausible,” holds true. If ESP is to work, there’s gotta be another way—something not quite so easy.

  CHAPTER TEN

  MAD, BAD, AND DANGEROUS TO KNOW

  Thinking is very far from knowing.

  —Proverb

  Stare deeply into the eyes of someone you love, and you are sure to feel that you know what they are thinking. Their thoughts are as real to you as your own. Everything about this person seems tuned to your own visions and desires. You send out the signals, and wait.

  Indeed, if you know someone well enough, you often do know what they are thinking! I recently had lunch with a physicist who said he read his daughter’s mind on occasion. This statement surprised me considerably, but later on in our discussion it became clear that he really meant something more along the lines of what I stated above: He knew her so well that he often was able to anticipate what was going on in her mind.

  Still, the lesson of the past century is that the universe is full of invisible fields—so many that Faraday himself would have been surprised. As you walk across the room, the number of invisible items impinging upon your body is staggering. Besides the complete spectrum of electromagnetic waves—the radio waves from nearby broadcasting stations or from distant galaxies, the infrared waves radiated by the heat of the walls or the bodies of other people in the room—we are bombarded by invisible neutrinos from the Big Bang, gravitational waves from collapsing stars in our galaxy, neutrons emitted by radioactive materials decaying in the c
eiling and walls, not to mention the invisible Higgs field that many elementary particle physicists believe permeates space giving mass to all matter, or a possible invisible field associated with the mysterious “dark matter” that is thought to make up the greater part of the mass of the universe that I described earlier. As one gets to smaller and smaller scales, the presence of the various fields becomes more and more evident, so that on subatomic scales the elementary particles themselves can be thought of as manifestations of the fields which can create and destroy them.

  There are a host of other phenomena out there as well, which, while invisible to the eye, can be detected by our other senses. A few molecules of perfume evaporating off the nape of a nearby female induce a flood of sensations and memories in your average male.

  So who cares if electromagnetic fields don’t fit the bill for ESP? The world seems full of senses and sensibilities beyond the five we know. If a bee can detect the invisible (to us) ultraviolet pattern on the petals of a flower, or a dog can hear the high-pitched squeal of a whistle in the distance while we hear nothing but silence, why cannot some of us detect at a distance the otherwise undetectable intense emotions of our loved ones, or even the more prosaic musings of our neighbors?

  Extrasensory perception seems so palpable, so tempting, that it’s hard to believe it doesn’t exist. Psychologists and parapsychologists of varying degrees of eminence have advanced ideas with varying degrees of vagueness over the years. Carl Jung, in a leap of imagination unfettered by empirical evidence, posited the existence of a “collective unconscious” shared by all minds (not unlike the Borg of Star Trek). Others have argued that as humans developed language they lost the need for their innate ESP sense, much as our senses of hearing and smell, so essential to life in the wild, have been suppressed by our urban experience. Luther Boggs, a death row inmate on The X-Files who possesses ESP, goes a step beyond Jung and claims that “the dead, living… all souls are connected.” Others have adopted jargon with a more scientific ring, like “morphogenetic fields,” a term meant to describe energy emanating from all sources—animal, vegetable, and mineral—and carrying ESP signals.

  Alas, the statement of Groucho Marx that he would not want to belong to any club that would have him as a member comes to mind. As noted in the last chapter, for a field to carry signals from one person’s brain to another it has to (a) transport enough energy to make something happen, and (b) interact strongly enough so that in a brain’s “ESP antenna” a signal can be received. One can imagine how both these things can be done, but such a field would not be undetectable by our present instruments.

  We know of long-range fields in the universe, from electromagnetism, the strongest macroscopic field, to gravity, the weakest. Having dispensed with the former, let us work our way down to the latter. Let’s consider a carrier somewhere in the range between gravity and electromagnetism: for example, the so-called weak force. The interactions mediated by this force between different particles in the nuclei of atoms are responsible for the reactions that power the solar furnace. This may not sound particularly “weak,” but that’s because while the reactions mediated by the weak force allow nuclei to change their identity, another nuclear force, called the strong force, is responsible for the large energies released when they do.

  The weak force has an extremely short range (less than the size of a single atom) and therefore does not qualify as a direct carrier of ESP, but particles that interact only via this force may themselves travel long distances and thus transmit signals. It turns out that all known elementary particles in nature interact via forces stronger than the weak force, except one: the neutrino. For this reason, neutrinos are almost completely undetectable and can propagate over long distances unaffected. Neutrinos are streaming through your body as you read this. Over a trillion neutrinos from the Sun stream through your body at near the speed of light every single second of every single day. These solar neutrinos not only pass through your body without interacting with the matter in it, they pass through the whole planet without any appreciable interaction. In fact, they could pass through a billion billion Earths lined up in a row without any such interaction. In spite of their cosmic impotence, we have detected solar neutrinos by feats of technological prowess that few science fiction writers would have dared to propose—for example, we have noted the effect of the occasional rogue neutrino on a single chlorine atom in a tank containing 100,000 gallons of cleaning fluid. There remains the neutrino background from the birth of the universe, however, which no one yet has any idea how to detect.

  In the earliest moments of the Big Bang, the temperatures and densities everywhere were incredibly high. At these levels of density and temperature (exceeding 10 billion degrees), even neutrinos could not sneak through matter unaffected. They would have remained in thermal equilibrium with the environment; if the surrounding gas was hot and dense, so too would have been the neutrinos. As the universe expanded and cooled, normal matter emerged—protons, neutrons, and electrons—and then formed atoms of the very lightest elements. Using straightforward calculations based on laboratory measurements of nuclear reactions, we have been able to predict that most of the protons and neutrons should have coalesced into the lightest element, hydrogen; about a quarter of them into the second lightest, helium; and a mere trace into the third lightest, lithium. And the cosmic abundance of these elements today fits the prediction: The universe is roughly 75 percent hydrogen and 25 percent helium, while the abundance of primordial lithium is only about 1 part in 10 billion. This agreement between theoretical prediction and observation is one of the triumphs of Bang theory and gives us confidence that another prediction of the theory—one that cannot be directly verified—is also true.

  The same reactions that determine the ratio of protons to neutrons in the universe and explain the observed ratio of hydrogen to helium also suggest that a background of neutrinos from the Big Bang must exist, which permeates all of space. At any time, in a volume of material as big as a teaspoon, there should be roughly 100 neutrinos left over from the Big Bang. Like the solar neutrinos, these neutrinos are not actually sitting still in the teaspoon but streaming through it at or near the speed of light. Unlike solar neutrinos, however, these neutrinos carry a much smaller energy—a cosmic background neutrino has less than a millionth of the energy of a solar neutrino. Therefore, no one has ever been able to figure out a way to detect the neutrino background, even though physicists are persuaded of its existence. The discovery in the mid-1960s of the universal background of microwave radiation from the Big Bang—radiation produced by the same reactions that should have resulted in the invisible neutrino sea—gives us additional confidence that it exists.

  So, here is a genuine candidate for a truly invisible background “field” that permeates the universe. But it gets better. Elementary particle physicists believe that other, even more weakly interacting particles might have been produced in the Big Bang. These particles are purely hypothetical, and they have strange names—neutralinos, axions, dilatons, and so on. Nevertheless, there are various fundamental puzzles about the nature of matter and the nature of the known interactions which can be solved only if such (as yet undetected) particles exist.

  Better still, when we attempt to measure the total amount of matter in the universe—both within galaxies and between them—all indications are that there is far, far more than meets the eye. As I noted in chapter 6, over 90 percent of the mass of the universe seems to be invisible; it doesn’t shine by emitting electromagnetic radiation. Could some exotic form of “dark matter” thus be the carrier of ESP signals?

  No.

  And neither could neutrinos, even the ghostly sort from the Big Bang. In fact, neutrinos illustrate perfectly the problems involved in positing any physical mechanism for ESP. For one thing, the fact that neutrinos are weakly interacting also means that they are very hard to produce. The processes that create them either happen very rarely or require enormously high energies. For example, neutr
inos released in nuclear decays (such as solar neutrinos) generally carry energies over a million times higher than are carried by radio waves. This means, first of all, that if they did manage to interact in your body, the energy they deposited would be far greater than that required just to lightly jiggle an atom; rather, the energy deposited would be characteristic of other radioactivity and would not be particularly healthy. The cosmic neutrino background, on the other hand, is not energetic today because it has cooled considerably since it was produced. And the production of enough neutrinos via nuclear decays so that, say, 1 neutrino per second would interact with an atom in your brain, calls for a source at least 10 times as energetic as the Sun but contained in a volume the size of a breadbox and situated no more than about 1 foot from your head. I think any such neutrino-generated mental messages coming at you from, say, your lover or your dog would be irrelevant in this case!

  These problems are even greater when it comes to particles more weakly interacting than neutrinos, like the purported dark-matter particles. One needs either the Big Bang or very-high-energy particle accelerators, like the 26-kilometer machine currently under construction at CERN (the U.S. Congress unfortunately canceled a more powerful machine, which was under construction in Texas), to produce very weakly interacting particles. To detect such particles one requires either very large detectors, occupying most of a city block, or else a tremendous amount of patience. I once worked out that even if one could build a detector capable of detecting a cosmic background of axions or neutralinos, the rate of energy deposited in the detector would be less than a millionth of a millionth of the energy produced by the residual radioactivity that exists in your big toe.