Stephen Hawking is dying. He has a progressive neurological disease that will kill him in three years.
At least, that’s what the doctors told Hawking’s wife-to-be thirteen years ago. The Hawkings now have two children and Stephen is the world’s foremost theoretical physicist. He’s still dying.
Slumped in his motorized wheelchair, Hawking looks like a well-loved Raggedy Andy doll. His useless hands lie flopped across each other on his lap, and a thatch of thick red hair surrounds his worn but pleasant face. He speaks in a faint gravelly quaver that becomes harder to understand as his disease advances.
With tireless diligence, Hawking works out long calculations in his mind, dictates what his hands can no longer write and pores over books and papers while his friends and students turn the pages.
Hawking’s colleagues marvel that while his body becomes weaker, his work becomes stronger. Indeed, Hawking’s latest work is more than strong. Some think it is the most profound thinking to come out of physics in fifty years. Perhaps ever.
Ironic as well is Hawking’s subject matter. While Hawking struggles against the pull of physical death, he studies black holes — places where matter is squeezed out of existence by gravitational forces so strong that not even light can escape.
There is an amazing story in all this. It is a Hatfield-McCoy tale in the world of physics, involving contrary theories that have been feuding almost since birth. It is a tale of grand reconciliation, a marriage of beautiful thoughts. It is the story of a crippled genius performing feats of surpassing intellect and gentle mending.
There’s something Tolstoyian about it — something that requires grandeur, gothic grace and doily-like detail in the telling. It’s a long story, too. One can easily imagine a 30-page introduction and a glossary half the size of a pocket dictionary. And appendices. And a big bibliography. And some tasteful dawn-of-the-cosmos art on the cover.
That’s my cop-out for not explaining it all here, though it’s damned interesting. I’ve tried. This is my umpteenth draft. And our editor, known for his way with Deep Things, gets all squinty and confused in the heavy parts, so they’re blue-penciled to the out-take file. This means I have to write well instead, performing a feat of condensation something like Reader’s Digest crushing War and Peace to a few pages in the back of a couple of summer issues.
In the beginning — which peaked in the nineteenth century — was the Mechanistic World View. This started with Aristotle and was elaborated over time by folks like the Scholasticists and the Rationalists. The Heavy was Isaac Newton, known to the public for comprehending the falling of apples and known to science for formulating some important and very enduring ideas about motion and gravity.
Another biggie was Pierre Laplace. He had the notion that if one very bright and well-informed mind could know where every particle was, and what it was doing, and how it got along with every other particle then this mind could predict the future. All of it, forever. He hypothesized a devil, thereafter known as Laplace’s devil, as the possessor of this important information. Naturally, religious thinkers figured that God was on to the same thing. Thus the determinism which Laplace gave to science and philosophy had its counterpart in the predestination found in Protestant Christianity.
The mechanistic model is still with us, although modern physics blew it out of the water fifty years ago. We are still predisposed to think of matter as solid and force as material and time as steady. They aren’t. But that fussy old mechanistic thinking is still with us in places like Psychology 201. Freud teaches us to blame our parents and our primal urges, while Watson and Skinner describe life as a kind of animated meat; not thinking and doing, but behaving. Ah, but that’s another gripe and we have some physics to cover.
Since the turn of the century, several theoretical systems have evolved in physics. Each explains different aspects of reality in different ways. In other words, each has its own territory, and its own way of doing things, thank you. Of course, there is the problem of staking claims. These theories overlap somewhat, and some territory is in dispute. Diplomats in the physics world have invented words like “complementarity” to sweeten the disagreements, but unresolved problems persist. Like with particles and waves. One explanation insists that “things” on the subatomic scale act like waves. Another says they act like particles. They can both prove their point. “Complementarity” says they’re both right.
Meanwhile, black holes are sucking in everything around them and crunching it all to nothingness. Particles or waves, they all go down the hole and don’t come back. Or at least nobody thought so until Stephen Hawking came along and explained it differently.
Now this is going to get a little dense, but bear with me. Black holes are one of those territories that have been in dispute. General Relativity, which Einstein thought up (Remember E=MC2? This is the one.), was the first on the scene. In the universe of relativity, time and space are related. If you go faster, time slows down. In fact, atomic clocks have confirmed that time is slower at the equator than at the poles, because the equator moves relatively faster than the poles. If you move near the speed of light, time goes really slow. You could cross the galaxy at near-light speed, travelling 100,000 years, and hardly age at all. But what happens when you meet or exceed the speed of light? We can’t say for sure. But we do know this happens in black holes.
Here is the story of classic black hole formation. When a big star gets old, it blows up. Every star explodes eventually, but the big ones are especially dramatic. Not only do they create a brilliant flash and an expanding cloud of glowing debris, but the leftover matter collapses in on itself. It does this faster and faster, getting smaller and smaller and denser and denser. With an ordinary star like the sun, this process results in a glowing remnant called a white dwarf. Others become neutron stars — wads of chargeless particles held together by gravity alone. But a big star ends up collapsing so quickly and completely that it simply disappears into itself. This leaves a black hole. Hole status is reached when the infalling matter becomes so small and dense that not even light can escape its gravitation.
It still doesn’t end there. All this matter goes on collapsing until it is nothing but a point of pure mass. This point has no size, shape or time. It is called a singularity, a place where time and space have become one. But singularity isn’t a black hole. The mass of a singularity determines the size of a larger “surface” surrounding it. This “surface” is only a boundary, a sphere of space from which nothing can escape but into which anything can enter. It’s called the event horizon, and it’s important because it represents the edge of the universe we know, or can know.
Unfortunately, that’s about all General Relativity has to say about black holes. This big theory has delivered to physics a kind of apocalyptic enigma — the notion of ex-stars that suck in everything, send out nothing and look like an unpleasant model for the end of the universe.
“Structure” of a black hole — There is nothing in the finite world to compare with a black hole. A black hole is simply an infinite nothing surrounded by a finite sphere of black space. The border of a black hole is called the event horizon. It is the area within which gravity is too strong for light to escape. At the center of a black hole is a mystery called singularity. This is the “spot” where collapsing matter has reached infinite density. Here space and time are squashed into a single dimension about which the laws of physics have nothing to say.
What we need, some physicists said back in the sixties when black holes were still bleak, is a “quantum theory of gravitation.”
Quantum theory is an interesting business, too. We owe the Atomic Age largely to quantum mechanics. It doesn’t say much about gravity, but it goes on for libraries about particles. And it’s nearly impossible for anyone but a talented fanatic to understand. As a fanatic I’m only half-qualified at all this, so right now I won’t try to explain anymore about quantum mechanics than Werner Heisenberg’s uncertainty principle. This was the discovery that put an end to the Mechanistic World View, at least in physics. What it said was this: It isn’t possible to specify both where a particle is and where it’s going. One can say only one or the other, but not both. And beyond this, the very act of measurement affects the results. So Laplace’s idea of a devil intelligence that could know where everything is and what it’s doing is simply wrong. There is no certainty, Heisenberg says. There are only probabilities. And the observer is a part of what he or she studies.
Einstein didn’t like this at all. He was schooled in the old mechanistic world, and even though he contributed much to the development of quantum mechanics, he never bought the theory. A world of chance annoyed him. So he is often remembered for his statement: “God does not play dice.”
Anyway, before Hawking, the call for a quantum theory of gravitation met with shaking heads. Gravity was relativity territory, and black holes were gravity places. Meanwhile, quantum researchers stuck with blowing up ever-smaller particles in billion dollar “accelerators” (that’s what they call atom-smashers now). No word about black holes from this quarter — at least until recently.
The Thermal Claim
Thermodynamics, or heat theory, also deals with particles. It describes the state of an object or system in terms of the rates at which molecules spend energy. Molecules are never supposed to stop. As long as molecules move around, energy is spent disorganizing things. This energy is called entropy. It can be described as “lack of knowledge about a system’s precise state.” The conversion of energy to entropy is called heat, and is measured as temperature. Now you know where they come from. Thermodynamics had some confusing things to say about black holes. First, there was the problem of temperature. According to relativity, a black hole would absorb everything and radiate nothing, including a temperature. So, presumably, the temperature of a black hole was absolute zero.
This was a bit uncomfortable for thermodynamics, which likes to use absolute zero only as an idea. Achieving it seemed out of the question, since it would describe something thought impossible: a state in pure organization. Dis-organization is what thermodynamics describes best — energy decaying to entropy. In fact, for a long while physicists thought that the universe was going entropic, decaying into a quietly disorganized cloud of entropy. Then it was discovered that this only applies to closed systems. The universe is an open system, so the Entropic End isn’t anything to worry about. Back to our story.
Hawking and others noticed some interesting things about the way black holes grow. When they took a pair of hypothetical black holes and put them together, surprise! — they got a new black hole bigger than the first two combined. This looked like a thermodynamic effect, and more research revealed other connections.
One was with the no-hair theorem. This was a clever idea that physics thought up. It comes from the simple statement “a black hole has no hair.” Physicists know this for sure, because just about all information about any configuration of matter, including hair, is lost when it enters a black hole. All you can say about black hole “stuff” (the singularity within) is mass, charge, and something called angular momentum, a term which, for the sake of our editor, I won’t repeat. No hair, anyway, on a black hole.
Well, if a black hole is a case of information (hair) going down the drain, it sounds like entropy to thermodynamics. That’s what Jacob Bekenstein noticed back when he was a graduate student at Princeton in 1972. So he did some mathematics and came up with a lawfully thermodynamic way for black holes to act by describing the entropy of black holes.
Fine, Hawking said. “But what could be meant by the entropy of a black hole?” The problem was that conversion of energy to entropy meant heat radiation, and black holes didn’t radiate. So it looked like a false claim for the Thermo folks.
Settling The Score
So by 1973 the black hole territorial stakes looked looked like this: General relativity had discovered the place, thermodynamics had a false idea about it and quantum mechanics was still mystified.
Then Hawking started putting it all together. He did it by taking the descriptions of black holes supplied by relativity and thermodynamics, and planting them both in the ground of quantum reality.
This was a neat trick, because quantum mechanics describes a pretty weird reality. According to quantum mechanics, all space is filled with little items called “virtual” particles. These are massless pairs of matter and antimatter that pop into existence, separate, then rejoin in mutual annihilation. This goes on everywhere, all the time.
Hawking wondered what the immense gravitation in a black hole would do to all these virtual goings-on. He figured that one half of a particle-antiparticle pair could be sucked into a hole, allowing the other to escape, radiating to infinity. Like one lover dying to release the other. An alternative explanation showed one member of a pair falling backward in time through the event horizon, then “tunneling out” forward in time, becoming its opposite and radiating off into space, kicked (instead of pulled) by the gravitational field.
Either way, Hawking described black hole radiation through a gravitational field interacting with a quantum process. Lo, relativity and quantum theory now had a joint claim on the black hole, with thermodynamics still somewhat out in the cold.
Then, in 1976, Hawking came through again. When he checked how this quantum radiation ought to measure, it started looking thermal. Black hole temperature wasn’t absolute zero, after all. Here’s what Hawking says: “The black hole creates and emits particles just as if it were an ordinary hot body with a temperature that is proportional to the surface gravity and inversely proportional to the mass. This makes Bekenstein’s suggestion that a black hole had finite entropy fully consistent . . .” And when Hawking played out the calculations, most quantum radiation from black holes fell into what’s known as a “thermal spectrum.” Put Thermo back. We’ve got three good claims there now.
Hot Little Holes
An interesting fact: The biggest black holes are the the coldest, and hardly radiate at all. They have gravitational fields that extend too far for freed particles to “tunnel” out. So a black hole the mass of the sun would have a temperature of only a ten-millionth degree above Zero. But the smaller ones look dangerous. A black hole the mass of an asteroid (the volume of a mountain range) is the size of a proton. It has an extremely strong but small gravitational field that extends only a few yards from its tiny surface. The temperature here is about 120 billion degrees Kelvin, with a thermal radiation of 10 million electron volts. Since asteroids haven’t the ability to implode and become black holes, these tiny hot holes would have to date back 12 billion years to the Big Bang, which most physicists agree was the way everything we know began. With lifespans in the billions of years, such “primordial” black holes ought to be blowing up every now and then, after wasting away from all that quantum de-pairing.
Interpretations of satellite data somehow shows that this is happening. In fact, the universe may be so full of hot little black holes that there is an even chance of at least one in our own solar system system.
A lot of little primordial black holes means that the universe could be much more massive than we’re accustomed to thinking (at least for the few of us who think about the mass of the universe). It also means that we could collide with one. Near as I can figure (remember I’m a fanatic, not an expert), such a collision would yield a flash of light, a huge boom, and a small hole drilled to the center of the earth. According to Isaac Asimov (making a case on TV for the impossibility of a black hole lurking in the Bermuda Triangle), such a black hole would “oscillate about, eating the inside of the planet like a worm eats an apple.” Some people have already speculated that a black hole may be responsible for something that happened in Siberia early this century. A giant explosion, heard thousands of miles away, literally flattened a large area of forest. There was no trace of impact, no meteor crater, no atom bomb-type damage, nothing man-made. Nobody reported a 3000-mile-deep hole either, but the damaged area was pretty big, so a narrow hole would be hard to find. If that Thing is down in middle earth now, the paranoids may have something to worry about. When a black hole explodes, it’s quite a show.
The size of a black hole explosion would depend on the real number of elementary particles. Ordinary protons, neutrons and electrons are made of “quarks.” These come with names like “up,” “down,” “strange,” and “charm.” As a primordial black hole evaporates, it radiates an increasing number of particle combinations. With the known number of quarks (16), a black hole explosion would be equivalent to 10 million one-megaton hydrogen bombs. An alternative theory suggests an unlimited number of basic particles with higher and higher mass. So if this is the case, multiply that explosion by 100,000. Scientists think a black hole explosion could tell us something about the real number of elementary particles. Meanwhile, I think about that little black hole that came in through Siberia, and then about what happened to the planet Alderaan in “Star Wars.”
Principle Of Ignorance
Ignoring that creepy possibility, what happens to a black hole after it explodes? Quite literally, nothing. All that remains is a naked singularity — a spaceless, timeless point of oneness. Hawking has a theory about singularities and the strange radiation that comes from black holes which surround them. He does Heisenberg one better. While Heisenberg’s uncertainty principle says that a particle can be specified by either location or velocity, but not both, Hawking says that with black hole emissions, neither location nor velocity can be specified. He calls this the Principle of Ignorance. It says, among other things, that we don’t know what will come out of a black hole. The range of particle configurations is infinite. He jokes: “Indeed, it is possible that the black hole could emit a television set or the works of Proust in ten leather-bound volumes.”
Then Hawking takes on Einstein directly: “It therefore seems that Einstein was doubly wrong when he said ‘God does not play dice.’ Consideration of particle emission from black holes would seem to suggest that God not only plays dice but sometimes throws them where they cannot be seen.” Where they can’t be seen is black holes, where singularities dwell. The Ignorance principle says that physics simply breaks down at singularities. Physical theory, all of it, is formulated against the background of space and time. There is is no more space or time in a singularity. So physics can say nothing more about one.
It’s Our (W)Hole
So what have we got to do with it? Maybe more than we think. Here is an interesting observation from Dennis Overbye’s excellent article in the August, 1977 Sky and Telescope:
“The most powerful constraint we can set on the Big Bang is that it must result in our present universe. Hawking, for example, suggests that we, ourselves, could only appear in a universe composed entirely of matter. This view verges on the speculations of some cosmologists that our role as observers in the universe is more fundamental than we think. As in the quantum-mechanical microcosm, does our participation somehow influence the properties of the whole universe?”
The answer may be yes. This is our universe. We not only use science to explain it, but we participate in it. And we usually aren’t uncertain or ignorant either, despite those important principles in physics. This is because we exist in skilled flow with our environment. And this flow involves a lot more than intellectualizing about the minute mechanics of how it all happens.
Science is far from concluding its foray into apparent reality. But the ignorance principle and the infinite mystery of singularities may have brought us to the dark at the end of a tunnel.
The pursuit of science is an adventure in theories. And theories, of course, are explanations. Each new successful theory is adopted because it works, or appears to work, better than those which it replaces.
Why do theories work? Some scientists wonder about that. Math is the main tool of theoretical science, especially the kind of far-out physics we’ve just covered. Eugene Wigner, a Nobel Prize-winning physicist, finds something eerie in the appropriateness of math to the development of new theories. Math has a way of turning up new and and unexpected connections, as it did for Hawking when he discovered links between thermodynamics, quantum mechanics and relativity — all in black hole studies. Wigner commented in 1959: “We are in a position similar to that of a man who was provided with a bunch of keys and who, having to open several doors in succession, always hit on the right key on the first or second trial. He became skeptical concerning the uniqueness of the coordination between keys and doors.”
He goes on to point out that “the enormous usefulness of mathematics in the natural sciences is something bordering on the mysterious and there is no rational explanation for it (and), it is just this uncanny usefulness of mathematical concepts that raises the question of the uniqueness of our physical theories.”
Mind Vs. Theory
Does mathematical soundness give us theories that offer honest descriptions of reality? Or does it just flesh out vague constructs with a lot of equations and numbers? Wigner urges caution: There’s something spooky, something loaded, in the way math leads theory. Are we getting a more accurate view of the world this way? Or are we just getting another interesting point of view?
Wigner worries that modern physics, built on a great edifice of math, may be a false description, a dead end. He fears a possible theory of consciousness “that would be as coherent and convincing as our present theories of the inanimate world” — especially if such a theory disagreed with physics. It would be even worse if such a conflict could not be resolved experimentally. “The reason that such a situation is conceivable,” he says, “is that, fundamentally, we do not know why our theories work so well. Hence their accuracy may not prove their truth and consistency.”
Trust The Man Who Knows
With this in mind, what can we really say about black holes? Except for a few strange x-ray sources and some data from satellites, all the evidence for black holes is mathematical. Could it be that black holes are simply mathematical artifacts that have little or nothing to do with reality? Or does our powerful role as observers help create black holes through the agency of math-supported theory?
Why has Stephen Hawking, for years near death, had so much to say about the ultimate in our physical universe? Hawking, who lives in proximity to the singular mystery of death, has come up with the most profound ideas about singularities in physics. He has provided us with a view towards a place about which nothing more can be said. Perhaps it can only be known.
Physics approaches a singularity, a place of total oneness, and goes mute. Singularity, on the other hand, can say whatever it pleases about physics.
Maybe, like Stephen Hawking, we should listen a little more closely to the singularity.
For the accompanying poem “Black Holes” by Sy Safransky, click here.