Trespassing on Einstein's Lawn (51 page)

“Relativity tells us that no observers are special. There has to be a gauge equivalence between causal diamonds, so everything outside my horizon is a gauge copy of the physics I can observe right here. So if you think of every possible causal diamond, you have an infinitely redundant description of the same quantum system seen by different observers.”

Banks was taking the holographic principle to its logical conclusion, but the conclusion was pretty astounding. Susskind had taught me that no observer can see both elephants—or, more accurately, that there's only one elephant. There only
seems
to be two when you mistake a copy for the real thing. Not that there was a “real thing.” There were only copies of copies, each as illusory as the next. But if redundant elephants seemed fucked up, what exactly were we to make of redundant
universes
?

“So you have infinitely redundant descriptions of the same quantum system, and spacetime emerges when you put all these descriptions together,” Banks continued.

“Spacetime is emergent?” That made sense, given everything Polchinski had told us about M-theory.

“Well, time isn't emergent, but it is observer-dependent. Space arises from the quantum mechanical relations between different observers. The key is that where two observers' causal diamonds overlap, there has to be consistency between what they both see. And that's actually a very, very strong constraint.”

“What would satisfy that constraint?” I asked. What could possibly remain invariant from causal diamond to casual diamond? If all observers had different views of the same underlying reality—what's the reality?

“It doesn't have many solutions,” Banks said. “The one Willy Fischler and I found is what we call a black hole fluid. It's a state that doesn't look like anything we're used to. There are no particles. There's not even spacetime. There's just a quantum system in which all the degrees of freedom are interacting constantly. It's a homogeneous and isotropic state with maximal entropy.”

No particles, no spacetime? Perfectly homogeneous? It sounded an awful lot like my father's nothing to me.

“We believe that the black hole fluid existed at the very beginning of the big bang,” Banks said. “Inflationary cosmology was created to explain why the universe started off so homogeneous and isotropic, which is such an improbable or low-entropy state. But the black hole fluid is homogeneous and isotropic, but it's also at maximum entropy. So then the question becomes, why doesn't the world look like the black hole fluid now? And the answer is, you can't have life or biology or any kind of complexity in that state. But if the black hole fluid only has a finite number of states, you could imagine that it eventually finds itself in an improbable low-entropy state. That idea goes back to Boltzmann. He said, if a system has finite entropy and it's in equilibrium, so it's cycling through every possible state, if you wait long enough it will happen to find itself in a low-entropy state where complexity can emerge. Willy and I are working on that idea—how can we start with the black hole fluid and yet explain how you get low enough entropy for something complex and interesting, like life, to happen? That's our goal, but we haven't gotten there yet.”

“I was reading LuboÅ¡ Motl's blog and he said that you are
‘building physics from scratch,' ” I said. “Do you feel that way?”

“LuboÅ¡ is partly right. However, none of the ideas that went into holographic spacetime could have existed without the work of all the people who contributed to our understanding of string theory. So, in the unlikely event that it turns out I'm right, then ‘if I've seen further than others, it's because I stood on the shoulders of giants.' I assume
you know that Newton said that as a concealed dig at Hooke, who was a dwarf.”

I had heard that, but it still made me laugh. Everyone thinks Newton was being eloquently modest, when really he was just being a dick.

“There seems to be a kind of paradigm shift under way in thinking about cosmology—from a God's-eye point of view to saying that you have to think about it from the point of view of a single observer,” I said.

“Yes, but I don't think it has permeated the community yet. The people at Stanford think that way, but they're thinking differently from me. They're trying to put everything that was done in the God's-eye point of view, like eternal inflation and the string landscape, into this new framework, whereas I think those things were just misconceptions. They want to take the observer's view of the world and try to squeeze the God's-eye view into it. I think they're wrong, but at least it's an idea for an idea,” Banks said, quoting Wheeler.

“I've been trying to find out what the most fundamental ingredients of the universe might be,” I said. “It's becoming clear that strings aren't the answer.”

“That's right,” Banks said. “We have these models, and in some extreme range of parameters where everything becomes calculable, they look like they are describing strings. But the real theory doesn't have strings in it in any fundamental way. I think a lot of people would agree that we don't really understand what's fundamental. My view is that the fundamental principle is the holographic principle, this relationship between geometry and quantum mechanics.”

When our conversation ended, I called the cab company for a ride back to the hotel. Fifteen minutes later the same cab driver who had dropped me off pulled up in front of the institute.

“Are you a scientist?” he asked me as we headed back down the coast.

“No,” I said. “A writer. I was just doing some research.”

“What kind of research?” he asked.

“Physics,” I said. “The nature of reality.”

“I was watching a show on TV the other day and they were talking about the smallest things that exist. The
smallest
things! Some kind of little atoms. You know something about that?”

“Quarks?” I ventured. I didn't bother explaining that “small” didn't mean anything anymore. That what looked like the smallest thing in one reference frame could look like the biggest thing in another. I figured it wasn't a good idea to blow someone's mind while he was driving.

“That's it, quarks!” he said, satisfied. “Interesting stuff.”

“They might be holographic encryptions of gravity in ten dimensions,” I mumbled.

“What's that now?” he asked.

“I said they're interesting,” I yelled up to the front seat. “So
small
!”

Back at the hotel I was grateful to find my father sitting up in a chair reading. With a particularly bad bout of pain-induced vomiting, the stone had lurched farther down its route, where it now sat comfortably, his pain temporarily subsided. My mother, looking exhausted and relieved, was on the bed, knitting.

“How was Banks?” my father asked.

“Completely fascinating.”

I recounted what Banks had told me about holographic cosmology. It wasn't like Markopoulou's universe, I explained, in which we were all looking at finite chunks of the same larger universe. No, according to Banks, every observer's finite chunk was
the
universe. The whole thing. Self-consistent and complete. “Your universe is all there is,” I told my father.

He looked thoughtful. “Does that mean that you are just a copy of me?”

“Well, we already knew
that
,” my mother said.

“I'm pretty sure this is my universe and you are all copies of me,” I said.

“Please,” my mother said, rolling her eyes. “We were here way before you.”

I laughed, but the question of exactly whose universe this was, was
a legit one. Banks had taken Smolin's slogan to a whole new level. The first principle of holographic cosmology must be that there is nothing outside
my
universe.

That evening, while my father rested in bed, I took a walk with my mother. We wandered aimlessly through the quaint Santa Barbara streets and eventually made our way to the harbor. The air was warm, the sky a soft pink; the boats rocked gently at their moorings.

“I can't stand seeing Dad in pain,” I said as we looked out over the marina.

“Tell me about it,” she said. “You should have seen him in the middle of the night. It was awful.”

“But he'll be okay?”

She offered me a reassuring smile. “Of course he will.”

“I keep thinking about the book,” I said. “And about Brockman and Matson. They don't think coauthorship can work. Neither does physics. Banks says we each have our own universe and you can't talk about more than one at a time. I guess part of me wants to try to write a book on my own, and another part of me can't handle the thought of it. Do you think he would be upset? Do you think he would hate me?”

I wasn't sure what had brought on my sudden confession. Something about seeing him lying in bed in agony—I felt guilty. Like his kidney stone was a direct manifestation of my betrayal. Like my secret consideration of sole authorship had calcified and lodged itself in his urinary tract. Like if I didn't get it out in the open, here and now, it would lodge itself somewhere inside me. Like it would keep on amassing until it formed a black hole in my center and sucked me in. Like I was Screwed.

My mother laughed. “He could never hate you! Working on physics with you and being your partner in crime mean the world to him. I think he would be terribly disappointed to not have that anymore. But I don't think it's about authorship. The writing part was always for you. He's a thinker. You're the writer.”

“But that's just it. I'm not. I'm
pretending
to be a writer.”

“Maybe it's time to stop pretending,” she said.

I sighed. “I guess I'm afraid that I won't know how to do that. Matson said I need to write with my own voice. I'm just not sure where to start. I'm not even sure I
want
to start. Not without Dad.”

Every way I looked at it, it looked wrong. How could I write a physics book without him? If it hadn't been for him, I would never have learned a word about physics in the first place. I would never have done any of it—not only because he roped me in with his question about nothing, but also because without him there to share my excitement at every turn, none of it would have mattered anyway. I guess that was the thing about invariance. I guess that was the thing about other people. Even though they have minds we can never verify, let alone know, even though they sit on the other side of an unbridgeable abyss, even though their irreducible otherness is exactly what makes us so fucking lonely, it's also the only thing that makes us feel like we are real. Like life is real. Not even the answer to the universe would have made it all seem worthwhile without my father there, echoing it back to me.

I looked at her pleadingly. “Tell me what to do.”

“I can't,” she said.

I pouted. “Since when?”

“He'll be proud of you no matter what,” she said. “And so will I. I'm sure you'll make the right decision.”

I gazed out across the harbor, my eyes following the calm water until it met the mountains, which looked small off in the distance under the now fuchsia sky. I knew that coauthoring a book committed the mortal sin against holography, that cutting across horizons was bound to produce something voiceless and untrue. Then again, I wasn't entirely sure that my father and I counted as two separate observers, like Safe and Screwed. We always knew what the other was thinking. We spoke in half-uttered thoughts, we easily finished each other's sentences, and there had been more than one occasion on which I had called him to share some new revelation and reached his voicemail only to find out moments later that it was because he had been calling
me
at precisely the same moment to share
precisely the same revelation.
If I hadn't been one of the telepathic parties in question, I never would have believed it. Such preternatural events occurred with enough frequency
that those who knew us best, like my mother, were convinced that we were two halves of a single brain.

On the other hand, we had our differences. Where he was eternally patient, I was impetuous. Where he was unflappably kind, I was moody and cynical. He was laid back and intuitive; I was anxious and logic-bound. He refused to cross the street against a Don't Walk sign, even if the road was empty for miles, while I felt more comfortable breaking rules than following them. And when he had a brilliant idea, like the H-state, he preferred to sit on it awhile, as if it were an egg in need of incubation, while I preferred to grab hold of it and strap it to our chests like dynamite, then send us running for the highway into oncoming traffic.

I wanted to listen to Matson. I wanted to find my voice, to venture outside the justified line and head for the margin. I needed to find a way to write from inside my own reference frame, but here in my frame I didn't know what it meant to talk about physics without talking about my father. For me, from the beginning, growing up and discovering the nature of the universe had always been one and the same, though I suppose that's true for everyone. My world had always been a strange hybrid of life and physics, and if reality was my Snark, I thought, perhaps my book would have to be a strange hybrid, too.

“Holy shit,” I muttered.

“What?” my mother asked.

“I think I know what to do.”

It was all hitting me now. Horizon complementarity demanded more than sole authorship. It demanded
first-person narration.

“I'm going to write the whole thing,” I said. “The whole story. About Dad and the H-state and Princeton and Wheeler … about all of it.”

My father and I might not live in the same universe, I thought, but he appeared in mine as convincingly as I did in his. His name didn't have to be on the cover—he could be
in
the book. He would be my sidekick, or maybe I'd be his. We'd be like Don Quixote and … Don Quixote's equally delusional father. I would write the book in the first person according to the mandate of Brockman and Matson and the laws of physics, and, most important, we would still be in it together,
partners in crime. Our book had started off as an idea, a symbol, the answer to the universe. But I realized now that growing up meant recognizing the book for what it really was: a story. No, my story.
Smash the glass, reach in.