One of the most remarkable astrophysical facts I know of is that essentially every atom inside our bodies was once inside an exploding star. The carbon that permeates our bodies, the oxygen and nitrogen we breathe, were not around when matter first formed. These elements were created in the nuclear furnaces of stars. In order for us to exist, it was necessary for generations of massive stars to live and die. During the fiery supernovae that marked the death of such objects, all the heavy elements that make up everything we see around us were spewed out into the cosmic nothingness. Eventually, some of this material merged with the collapsing cloud of hydrogen gas and dust that would form our own solar system. Some sort of life-forms may well have been sacrificed in these explosions, providing a part of the necessary raw materials, so that we might one day evolve and flourish. Perhaps, in one way or another, we may someday return the favor.
SECTION TWO
MADONNA’S UNIVERSE
We are living in a material world, and I am a material girl.
—Madonna
CHAPTER NINE
MAY THE FORCE BE WITH YOU
You gotta love this place. Every day is like Halloween!
—Fox Mulder
Early in the first film of the Star Wars trilogy, Obi Wan Kenobi urges Luke Skywalker to “feel the Force!” To no one’s surprise, Luke does, eventually, and it is very very good to him. It was also very very good to George Lucas. A billion dollars and 20 years later, the Force is still with us.
Tell me that you have not, at some time in your life, looked up at the night sky and shuddered at the vast loneliness of our existence. Or sitting alone in a darkening room, perhaps in a remote cabin in the woods, have you never, as a barely perceptible chill breeze brushed your skin, had an idea that there might be some “thing” in the room with you, which you cannot see? What are the things that go bump in the night?
Dark side or not, there’s something particularly cozy about an invisible Force that ties the universe together and gives it meaning, coherence, legitimacy. Pondering the existence of aliens may be how we ease our innate human loneliness nowadays, but pondering the existence of invisible forces is nothing new. Such musings are, after all, at the heart of most of the world’s religions, whose annual gross stretches back for millennia and makes Lucas’s look like chicken feed.
In fact, invisible forces are not merely the stuff of revelation: they are everywhere! Turn on your radio, and suddenly there is music, borne by invisible radio waves. Leap into the air, and the force of gravity pulls you back to Earth. Pluck a couple of magnets off the refrigerator and feel them push away from each other. As a matter of fact, there is almost no such thing as a visible force! I say “almost” because, of course, if a piano falls on your head, the source of the force you feel (before you feel nothing anymore) is eminently visible! Or is it? What is it about the piano that makes it “material”? Why does it crush your skull?
This might seem like a silly question; after all, what could be more solid than wood, ivory, metal, all the things from which a piano is fabricated? Well, a piano, at the fundamental level, is made of billions and billions of atoms. You can therefore reasonably assume that the particles in the atoms in the piano smack up against the atoms in your head and the multiple collisions are what cause one of these atomic aggregates to spatter.
Ah, nothing could be farther from the truth. No particle in any atom in the piano—no proton, neutron, or even electron—ever gets close, on an atomic scale, to any particle in any atom in your skull. Most of what we like to think of as “matter” is actually empty space. The region in which electrons orbit an atomic nucleus is more than 10,000 times as large as the nucleus itself. It’s the invisible electric forces emanating from the charged particles in the atoms in the piano that repel the charged particles in the atoms in your head and do such a good job of making both your head and the piano seem solid.
The physicist Richard Feynman used this idea to relate the strength of the electric force to the gravitational force. I will repeat his argument here, changing it slightly so we can continue to speak in terms of your head and the piano. But instead of dropping a piano on your head, let’s drop your head on a piano from, say, 100 floors up. Let’s assume you are at the top of the Empire State Building, which I seem to remember from my youth has 102 stories. And say that you manage to climb over the high fence around the observation deck and do a swan dive toward the ground below. At the same instant, some piano movers have taken a union-required break from their chore of moving a new concert grand into the lobby of the building. The piano is still in several pieces, which are lying on mats on the sidewalk. Suddenly the movers look up, and to their horror they see you hurtling earthward. You land on the instrument’s elegant, polished wooden lid, which is lying flat on the ground.
Now, says Feynman, gravity has been accelerating you for 102 stories, but you don’t continue your descent toward the center of the Earth: The electrical force—in this case between the atoms in the lid (in turn supported firmly by the sidewalk) and the atoms in your head—stops you cold in a fraction of an inch! Despite its spectacularly noticeable effects, gravity is the weakest force in nature.
Even this example doesn’t do justice to how weak gravity really is compared to the electric force. Here’s another one: Take a single electron, which has a small electric charge associated with it. If I put another electron near it, they are repelled by the electric force between them. In empty space, where no other forces were around to balance this force, they would fly apart. Now, say I wanted to pin the second electron down by putting a large mass on top of it, so that the gravitational attraction of the large mass (plus the electron) toward the original electron would exactly balance out the electric repulsion between the two electrons. How big a mass would I need?
When I asked my wife this question, she asked how far apart the two electrons were, which is a good question. However, in this case it is irrelevant, because both the electric force and the gravitational force vary the same way with distance, so if they balance out at one distance, they will balance out at all distances.
In any case, the answer is nothing short of flabbergasting. Plugging in the relative strengths of gravity and the electric force, it turns out that the mass you have to put on top of the second electron to counteract the electric repulsion is—get this!—5 billion tons. This is not only more massive than either the Empire State Building or the twin towers of the World Trade Center, or any other Manhattan skyscraper, it is more massive than all of them put together!
Even though I have been for some time familiar with the relative strengths of gravity and the electric force, I was surprised by this particular result after obtaining it—so much so that I had to check my calculations three times and then ask a graduate student who happened to be walking by my office to check them to make sure I hadn’t done something foolish. This time, I hadn’t.
Why, you may naturally ask, don’t we just use small electric charges to levitate buildings or large flying saucers? The answer is that these objects, if they are at the Earth’s surface, are not merely attracted downward by the gravitational force of the single electron that one might hope to levitate them with, they are attracted by the whole Earth. And since the Earth is massive indeed, their “weight” at the Earth’s Surface is enormous compared to the force of electrostatic repulsion between electrons located any reasonable distance apart. On Earth, all these skyscrapers are extremely heavy, but in empty space they are nearly weightless. The reason that all of these skyscrapers combined are needed to balance the electric force with gravity in empty space is not that this electric repulsion is so great but that the gravitational attraction of the electron on each of these objects is so small.
Gravity is so weak that it is almost miraculous that we can detect it at all. The reason we “feel” gravity is that although the pull of each individual atom in the Earth on each individual atom in my body is unbelievably small, the effect adds up, so that the attraction of all the at
oms in the Earth on each atom in my body is substantial (most noticeably in the morning, just after my alarm goes off). We don’t “feel” the electromagnetic force in this way, because the negative charges in our body are exactly canceled by the positive charges in our body. As I suggested in chapter 4, this is a good thing; if it weren’t so, the electric forced would explode us out of existence.
As weak as gravity is, we can still measure the gravitational attraction between human-scale objects. (The attraction between single atoms is so small that there’s no hope of measuring it directly in the near future.) In fact, about 100 years after Newton’s discovery of the law of gravity based on the motions of the planets around the Sun, a fellow Englishman, Henry Cavendish, came up with a sensitive method to measure the gravitational attraction between objects the size of cannonballs by attaching two to a crossbar to form a kind of dumbbell balance and suspending it from a wire. He then moved a third cannonball close to one end of this contraption and measured the infinitesimal torque this produced on the wire. In this way, the fundamental strength of gravity itself—the so-called gravitational constant—was determined. Previously, one could use Newton’s law to calculate the strength of the gravitational force between planets and the Sun, or between the Earth and the Moon, for example. However, the mass of these objects was not independently known; one could not determine how strong the gravitational force was between objects of known mass in this way. After Cavendish’s experiment, not only was this measurement possible, but one could put the gravitational constant into Newton’s law and in this manner weigh the planets and the Sun. The current best measurement of the mass of the Sun is due to this technique.
The purpose of my discourse on gravity’s weakness, however, is not to bury gravity but to praise it. There is nothing basically wrong with imagining a universe full of invisible things, some of which are beyond our control. The universe is full of invisible things, some of which are beyond our control! We should think about gravity whenever we ponder the Big Question that has stirred our imaginations for centuries (and inspired much of modern science fiction): What invisible things are still invisible?
At the top of the list, anyone’s list, must be ESP. It’s difficult to name a major work of science fiction or fantasy that does not somewhere contain an element of telepathy. Each of the Star Trek series, for example, has had its telepaths: Spock, Deanna Troi, her mother Lwaxana, Kes—to say nothing of a host of telepathic aliens on various planets. The aliens in The X-Files perform telepathic mind scans; and even the disgusting creatures in Independence Day, whose only purpose in life seemed to be to kill other species, used telepathy as a weapon.
How many times have you felt that you knew what someone else was thinking? Certainly, as we become accustomed to reading body language and facial expressions, we can sometimes anticipate other people’s reactions, or even divine what is on their minds. Is it all that crazy to imagine that with one more step we could communicate without speech?
The term “extrasensory perception” was coined by the Duke University researcher Joseph Banks Rhine, who wrote a well-known book by this name in 1934 in which he claimed to have overwhelming evidence for telepathic communication. His popularizations, combined with the interest of the publisher of the pulp magazine Astounding Science Fiction, helped fuel public interest and inspired a raft of ESP-related science fiction. Rhine also coined the term “parapsychology,” for the study of various kinds of alleged psychic phenomena.
Alas, the invention of these two serviceable terms was probably Rhine’s greatest contribution to science, since essentially all of his ESP results that were subjected to outside scrutiny were shown to be flawed—including his first discovery, Lady Wonder, the telepathic horse. While the flawed experiments of one researcher cannot be used to dismiss a whole field, the following facts are not in dispute:
1: In the more than 60 years since Rhine created the field, there has been not a single definitive experiment broadly accepted—that is, by scientists not directly involved in similar lines of research—which unambiguously demonstrates the reality of any of the phenomena he set out to explore and promote.
2: At the same time, huge numbers of people, including a number of active workers in this field, believe that ESP exists.
I know better than to try and resolve this debate. Moreover, I have never personally tried to verify or debunk any specific set of ESP experiments. I’m skeptical, but then I try to be skeptical of everything (I don’t believe there’s any other way to learn about how the world really works). But I don’t want to directly question here the quality of current research in this area. Rather, I want to ask a question I think is more enlightening, not to mention more fun: What would be required for ESP to exist?
I find it significant that the furor over telepathy and ESP began within a few decades of the invention of the radio by Guglielmo Marconi, and less than one decade after its first widespread usage. Once wireless communication became a reality, the idea that invisible “waves” of some sort could lead to direct nonverbal communication between people probably became a lot more plausible. Until then, the only nonverbal communication that didn’t make use of some overt physical connection between source and receiver involved visible light, so that any suggestion that one might receive invisible signals was completely unprecedented. Radio waves fit the bill perfectly.
There are so many remarkable aspects of radio waves (which, like visible light, are electromagnetic waves, but of much lower frequency), that it’s hard to know where to begin talking about them. First and foremost, in spite of both the curvature of the Earth and the long distances involved, shortwave radio signals can be received on the other side of the planet. Moreover, though radio waves carry very little power, they can be precisely detected. The most striking illustration of this sensitivity is afforded by the marvelous Arecibo radio telescope in Puerto Rico. Built in a natural crater filled with tropical vegetation, the Arecibo antenna is 1,000 feet across, and viewers of the movie Contact will recognize it. It has detected radio waves from the surface of Venus, from rotating neutron stars thousands of light-years away, and from extragalactic objects hundreds of millions of light-years away. I toured the facility with the assistant director a while back along with my wife and daughter, and I remember trying to think of a way to convey how sensitive this beautiful device was. Based on the sensitivity data for the instrument, I worked out that it could easily detect a 25-watt lightbulb on Pluto, several billion miles away, if instead of generating visible light the bulb emitted its energy as a radio frequency accessible to the telescope’s receivers.
Well, if we can detect such small sources located in the outer reaches of the solar system, why shouldn’t two minds be able to communicate across a room? After all, thinking itself involves precisely the same processes as those that produce electromagnetic disturbances. Thoughts and actions are initiated by the firing of neurons in our brains, which produce electrical currents, which in turn travel to nerves and muscles elsewhere in our body. Electrical currents are precisely what generate electromagnetic waves.
On the surface, the forces of electricity and magnetism seem very different. Permanent magnets exist, but they behave quite differently than electric charges do. For example, if one cuts a magnet in half, one does not produce an isolated north pole and an isolated south pole; instead, one gets two smaller magnets, each with a north and south pole. But if I bisect an object with a positive electric charge on one side and a negative charge on the other, I will end up with one positively charged object and one negatively charged object. There is clearly some connection between electricity and magnetism, however. For example, I can create a magnet by moving charges to produce an electric current. These electromagnets are standard components in almost every electric appliance in your house.
Near the end of the nineteenth century, one of the greatest theoretical physicists of that era, the Scottish physicist James Clerk Maxwell, arrived at one of the greatest intellectual unification of
ideas that has ever taken place on this planet. He demonstrated conclusively not only that electricity and magnetism were related but that they were really just different aspects of the same thing. One person’s electricity is another person’s magnetism, depending on the reference frame.
Besides setting the stage for relativity theory, which is based on this principle, Maxwell’s theory of electromagnetism made a central prediction: Light is a wave of electricity and magnetism. The interplay between electricity and magnetism was such that whenever you jiggled an electric charge, a “wave” of electric and magnetic disturbances traveled outward at a speed that could be calculated from first principles. This speed turned out to be the same as the measured speed of light. We now understand that the frequency with which you jiggle the charge determines the measurable characteristics of the resulting wave. If you jiggle it back and forth only a million times per second, you will produce radio waves. If you jiggle it back and forth a billion times per second, you will produce microwaves. If you jiggle it back and forth a million billion times per second, you will produce visible light. And so on.
You might ask, what is it exactly that is propagating in an electromagnetic wave? What is there in the wave itself, and what will the wave do when it encounters matter? Here we have to thank another remarkable nineteenth-century British physicist, Michael Faraday. Faraday is in some ways a more romantic figure than Maxwell. Without a formal education, as a mere bookbinder’s apprentice, he attended a public lecture in 1812 at the esteemed Royal Institution, in London, given by the brilliant chemist Sir Humphry Davy. Sometime later he returned to the institution with the lecture notes he had taken, bound into a handsome volume. Davy was so impressed that he took Faraday on as an assistant. The rest is history.
The particulars of this history involve a number of seminal discoveries about the connections between electricity and magnetism which set the stage for Maxwell’s work. But the one I want to focus on here is one that changed forever the way physicists think about empty space. Faraday was an intuitive, seat-of-the-pants type of thinker, which is one reason I like him so much. Prior to Faraday, when physicists thought about forces, like gravity, they pictured the equations that governed these forces. Faraday provided a more intuitive, physical picture, which in some ways is far more valuable.
Beyond Star Trek Page 9