Trespassing on Einstein's Lawn (52 page)

“So it'll be like a memoir?” my mother asked.

I smiled, exuberant. “Exactly.”

It was the only logical possibility: a book that contained its author on the inside, a maze so convoluted that what appears from one standpoint to be author is from another point of view character. A top-down, self-excited, first-person, Gödelian gonzo cosmology. A fucking memoir.

My mother was eyeing me warily. “Am I going to be in it?”

“If you're lucky,” I said.

She shot me a stern look. “You better not make me look bad.”

When we returned to the hotel, I nervously told my father about my idea to write a physics book that was also a memoir, and I watched as the logical necessity of the thing washed over his face.

“That's it,” he said fervently, grinning. “
That's
the real book.”

He said it as if that were the book we had been talking about the whole time, only we didn't know it. Or as if
he
had known it and was just sitting around waiting for me to see the light. I was seized by a momentary paranoia. Had he planned this all along? Was he teaching me some kind of
lesson
? Maybe it was the passing of the kidney stone, but he even seemed a little relieved, as if he was more comfortable in the role of character than author. I was more than a little relieved myself, knowing that he was happy and on board and that I had found a way to try to be that other kind of writer, the one he had once worried I hadn't become.

Thirty thousand feet above the Earth, heading back toward the East Coast, I began to sense the enormousness of what we had encountered on the road. Cosmology was truly on the cusp of a radical paradigm shift. Although it had yet to fully permeate the physics community, let
alone the wider public, it was on its way and there was no stopping it now. As Bousso said, it was inevitable.

Paradigm shifts in cosmology are few and far between. There was Copernicus's
De Revolutionibus
, published in 1543, which sparked the so-called scientific revolution and sent the Aristotelian worldview, which had reigned for more than a millennium, into crisis. Aristotle had argued that the universe was a finite set of nested crystal spheres that carried the Moon, Sun, planets, and stars in perfect circles around the Earth, which sat at the center of it all, unmoving. Objects, Aristotle said, moved up or down according to their relative abundances of nature's four elements—air, fire, earth, water—then settled into absolute rest. Copernicus, however, suggested that the Sun sat at the center of the solar system and that the Earth itself was moving, a claim that pushed what we now call science beyond the bounds of common sense toward something more like ultimate reality. It also blurred the division between celestial and terrestrial, introducing a relativity of motion that could no longer support Aristotle's physics of absolute up and absolute down. By attributing the apparent motion of the stars to the motion of the Earth, Copernicus freed the stars from their fixed sphere and scattered them at various distances throughout space, opening up the possibility of an infinite universe. Tycho Brahe's observations of the paths of comets shortly after obliterated the existence of the spheres altogether, leaving the planets and stars to wander on their own, untethered, through vast stretches of unnervingly empty space.

These developments raised difficult questions. For example, if the Earth is moving, how can we ever say that an object is at rest? What makes the planets move? If there's nothing but space where the crystal spheres used to be, what mysterious force keeps the planets in their orbits? Galileo answered the first question: Aristotle's defunct distinction between invariant motion and rest was replaced by Galilean relativity, which showed that there is no difference between rest and inertial motion. Newton answered the next two: the same force that had an apple fall toward the Earth had the Earth fall toward the Sun. Gravity. But Newton's theory raised a question of its own: what the hell is gravity? That question hung in the air for three hundred years, weightless.

Einstein's general relativity unveiled the true nature of gravity and sparked the possibility of a dynamic spacetime, a changing cosmos, one that could expand and contract and begin in a big bang. But the big bang wasn't complete until 1980, when inflation filled in the missing pieces of the puzzle. Unexpectedly, inflation had brought a paradigm shift of its own. It went eternal, swapping our single universe for an endless multiverse. At the same time, it wrought a new crisis, the measure problem, which undermined the basic predictability of science.

Meanwhile, Einstein's theory of gravity had come into deep conflict with quantum mechanics, the theory of matter. When Hawking pitted the two against each other, the result was the black hole information-loss paradox, which looked to be a lose-lose situation until Susskind's epiphany—
restrict to a single observer's point of view—
provided an escape. That, in turn, brought with it yet another shift, one that would further shatter our notions of invariance and ultimate reality, a shift too young to have a name but would likely sound something like “holographic,” one that swaps the multiverse back for a single universe.

Gazing out the window and down into the clouds, it dawned on me how amazingly unlikely our own story was turning out to be. For fifteen years my father and I had been running around trying to answer our own questions about the universe, living in the small, surreal world we had created for ourselves, as if it were all just our own private little game. We had come to California to hang out with Bousso and Susskind and Banks thanks to a conversation we once had in a Chinese restaurant, and somehow we had been wrenched out of our little world and into something so much bigger. It was as if we had bumped into Galileo just as he turned his telescope to the sky or brought Hubble his coffee as he calculated the distances and redshifts of the galaxies. As we stupidly carried out our personal mission, we had stumbled, Forrest Gump style, into the trenches of history.

If Max Born thought that the notion of reality had become problematic by the 1950s, I thought, he'd be freaking out now. M-theory's dualities had undermined the reality of size, dimensionality, geometry, topology, particles, and strings. What looks like spacetime in one view
looks like an object in another. High energy becomes low energy. Elementary becomes composite. Big becomes small.

Personally, I was relieved to be an ontic structural realist. An ordinary realist would lose her shit. Nearly every remaining shred of ontology was vanishing before our eyes. But dualities preserve structure. All of those drastically different physical pictures are descriptions of the same mathematics. Structure is safe in the face of ontological underdetermination, and the universe had never seemed so underdetermined as it did now. Jesus, as far as the world's leading physicists are concerned, there is
no ontology.
Which is to say, the world isn't made of anything at all.

Now I understood what Susskind and Gross had meant when they said that they didn't know what string theory was. It wasn't because there were some holes in the mathematics or a lack of plausible experiments or even a missing principle or two. It was because they literally didn't know what the theory was describing. Particle physics is the theory of particles. Quantum field theory is a theory of quantum fields. General relativity is a theory of gravity and spacetime. String theory is a theory of … 
what
? Not strings. Not particles, either, or even branes. So many physicists had been working so hard constructing the mathematical edifice of the theory, but they had no idea what it was supposed to be describing. “I can't even guess,” Polchinski had said. If strings looked like branes at low energy, and branes looked like strings in extra dimensions, and particles looked like strings in different geometries, then none of them could be invariant. None of them could be real.

Adding to Born's anxiety, Banks had taken any remaining hope for invariance and sent it packing across the horizon. Taking the lessons of the holographic principle and horizon complementarity to their logical conclusions, Banks argued that information couldn't be lost across de Sitter horizons. Each observer's universe, though finite and bounded, was the whole show. If no observer was missing information—if all of reality was contained completely within an observer's light cone—then anything beyond the observer's horizon couldn't be new information. It had to be a redundant copy of information the observer already had. Another description of the same elephant. A new it from the same bit. An isomorphic element of the same structure. A gauge copy. Unreal.

To Susskind's deepest question in cosmology, Banks answered firmly in the negative. Objects on the other side of the cosmic horizon are not real. Which, ultimately, meant that
nothing
was real. After all, horizons are observer-dependent. My de Sitter horizon was not the same as my father's, which meant that an object outside my universe could be inside his. If objects outside horizons aren't real, then something that wasn't real according to me could be real according to my father, and vice versa. Reality is no longer observer-independent.

Thanks to Banks, we could cross the universe off the ultimate reality list. Individual, observer-dependent universes were all that remained, along with the cardinal rule of the new cosmology: you can't talk about more than one universe at a time. It was the kind of solipsism that Wheeler had tried so hard to avoid. Still, there had to be some kind of consistency conditions to relate what different observers see. If each observer's universe is another complementary, redundant description, what exactly is it a description
of
? Banks said it was a homogeneous black hole fluid. My father said it was nothing.

My father, of course, was thrilled with these developments. All of them seemed to support his intuition that everything had to be nothing, the H-state, which meant that nothing other than nothing itself could be invariant or real. I was a bit thrilled myself, because I knew that a universe with any ontology at all would be impossible to explain. A universe made of nothing, however, could potentially explain itself. Like a self-excited circuit.

But we weren't down to nothing just yet. One ingredient on the IHOP napkin persevered:
the speed of light.
It made sense that it would be the last one standing. Everything had been rendered observer-dependent, but observers themselves are
defined
by light cones. If all you need to turn nothing into something is a boundary, all you need to have a boundary is a finite and invariant speed of light. I couldn't imagine how we would ever cross that one off the napkin. It wasn't a new question. In fact, it now dawned on me with horror, it was exactly the same question we had started with when we confronted Wheeler in Princeton: if observers create reality, where do the observers come from?

I took hold of my laptop, subscribed to the first step taken, and began to type.

I was working in a magazine office when the lie was born. That was the idea, anyway—“working” in an “office.” In reality I was stuffing envelopes in the dusty one-bedroom apartment of a guy named Rick. The idea was that I worked for
Manhattan
magazine. The reality was that I worked for
Manhattan Bride.

I wrote about faking some press credentials to crash the Science and Ultimate Reality symposium with my father. I wrote about our cryptic conversation with Wheeler, and about loitering on Einstein's lawn. I wrote about my secret plan to become a journalist and about scoring the
Scientific American
piece. I wrote about sneaking into the photograph at the Davis conference and escaping the awkward dinner by fleeing in Timothy Ferris's car. I wrote about my father's ideas about nothing, how it was an infinite, unbounded, homogeneous state, and I wrote about my ideas about something, how it was defined by invariance and how it slips away every time you reach for it. I wrote it not as a Journalist or an Academic or an Author. I wrote it as me. Twenty pages poured out of me in what felt like an instant. I titled the proposal
“Crashing the Ultimate Reality Party,” stuck it in an email addressed to Matson and Brockman, and hit “Send.”

I arrived at the Harvard Science Center and made my way to the fifth floor, but when I got there a flood of students and professors came pouring down the hallway. “Is the Witten talk in there?” I asked a student emerging from the room where the lecture was scheduled to take place.

“Too many people,” he said. “We're changing rooms.”

In California, my father and I had learned so much about M-theory—its instantiation of the holographic principle in AdS/CFT, its radical revision of the nature of spacetime, and its suspiciously vacant ontology, all of which seemed to turn the universe inside out. But there was one thing about M-theory we still didn't know: what the hell did the
M
stand for?

Everywhere I read about it, I was told, “Nobody knows what the
M
in M-theory stands for.” Perhaps it's
magic
, they said, or
mother.
Steven Weinberg guessed that it stood for
matrix.
Sheldon Glashow wondered if it was an upside-down W, for
Witten.
Even Stephen Hawking wrote, “No one seems to know what the
M
stands for, but it may be ‘master,' ‘miracle,' or ‘mystery.' ”

How can nobody know? I thought. Ed Witten made it up and the guy's still alive. Why doesn't someone just ask him?

When I heard he'd be speaking at Harvard, I figured I'd try.

I followed the crowd to the new classroom and tried to snag a seat, but it quickly became apparent that the bigger room wasn't big enough. Whoever had organized this thing had forgotten that Witten was a fullblown superstar. Soon we were switching rooms again, this time heading to another building on campus, one with a larger auditorium. I rushed to keep up with the ever-growing crowd as they made their way outside, pushing and shoving one another out of the way in a race to score a seat. I had never seen physicists get so rowdy. As a group, they aren't exactly the most aggressive or athletic bunch, but with a Witten lecture on the line, these guys were ready to sprint, tackle, and pound anyone who got in their way. Running alongside them, I noticed a blind guy in the midst of the stampede, waving his walking stick and trying
to keep his footing as the other physicists trampled past. I momentarily slowed down and considered helping him maneuver through the crowd. But he'd probably rather do it on his own, I told myself, then charged, elbows out and full speed ahead, toward the auditorium door.
M
is for
mayhem.