Trespassing on Einstein's Lawn (14 page)

Descartes had struggled with the same question. Of course, there weren't computers back then, but there were evil demons, and Descartes wondered if one might be tricking his senses into perceiving a false reality. He worried that everything around him, including his own body, might be a fraud. But in a sea of demonic doubt, he could say one thing for certain: He was perceiving. He was thinking. He was real. Even if everything that presented itself to his consciousness were an illusion, the very fact of his consciousness would remain true. He was thinking, therefore he existed.
Cogito ergo sum.

That was it? The one thing I could say for sure? I exist. Game over.

It was a depressing thought. Descartes never really clawed his way out of the cogito, not using reason anyway. He had to take a leap of faith and invoke a benevolent God who wouldn't be so cruel as to fool us with a fake world. But if you're willing to take a leap of faith, I thought, why add a middleman? Why not just believe in reality and call it a day?

I wasn't particularly worried about evil demons, but Bostrom's computer simulations seemed like a more viable threat. Flipping through an issue of
New Scientist
, I came across an article by cosmologist John Barrow arguing that if we are in a simulation, we ought to see glitches in reality.
“If we live in a simulated reality, we should expect to come across scientific phenomena, such as occasional glitches in experimental results that we cannot repeat, or very small drifts in the supposed constants and laws of nature that we cannot explain,” Barrow wrote. “Tantalisingly, we do have a few such results: the apparent astronomical variation in the fine structure constant by a few parts in a million, for example. Clearly, finding explanations for these phenomena is something of a priority. If we can't, then the flaws of nature may turn out to be at least as significant as the laws of nature for our understanding of true reality.”

It was tantalizing, but even if we observed glitches, how would we know they were evidence of a simulation? Couldn't they just be flaws in reality itself? Barrow seemed to be assuming that the true reality must be flawless, a pristine specimen of logical consistency. And if that's the case, perhaps there's only one possible reality anyway, one unique ideal of logical perfection. After all, physicists have yet to stumble upon a single complete and logically consistent model of a physical universe, and they've really been trying. If we can't even come up with one, what are the odds that the simulation's programmers can come up with several, even infinite variations? If there's just one possible world, it might be knowable—demons and programmers be damned.

Then again, maybe human brains aren't up for the task. Maybe the programmers have no trouble inventing universes. And if this is a simulation, who's to say it's not a simulation simulated by simulated beings, and who's to say that their reality isn't just a simulation from within another simulation, which in turn is just … When you start questioning the reality of reality, it's easy to spin out. My mind was racing. Was reality unknowable? Was this whole mission flawed from the start?
Cogito ergo panic.

I was spiraling when I landed on a strange thought: if reality is not a simulation, what is it? Simulation is an unnerving word as an antonym for something else—but what? Simulation is all we know. Our
brains are our sole portals to so-called reality. There is nothing in the universe that we can access without first filtering through the labyrinthine lumps of gray matter in our heads. We are literally, hopelessly, eternally trapped inside our minds. All the things we see, hear, touch, smell, and taste are nothing other than perceptions generated by our brains. Cats, dogs, trees, other people … all astonishingly realistic neural simulacra. Then again, who's to say they're astonishingly realistic? Compared to what?

Our eyes are not transparent windows to the outside world, despite evolution's brilliant illusion. When we think we're walking the streets of a city, we're really strolling the neural paths of our brains. Everything that appears to be outside is really inside. For all intents and purposes, there is no outside. The brain is a universe unto itself: billions of twinkling neurons, dendrites splayed like fingers reaching for the beginning of time, chemical messengers leaping across the mindless darkness of deep intracranial space. As the cosmologist James Jeans said, “The universe begins to look more like a great thought than a great machine.”

Of course, it's tempting to think that our brains' simulations are simulating
something
, some external reality that impinges on our senses, nudging our neural cogs and gears to churn up a trusty illusion. But who knows? We hallucinate, we dream. Chuang-tzu dreamed he was a butterfly, then awoke to find he was a butterfly dreaming he was a man. I suddenly understood the moral of that story: we're all screwed.

Bishop Berkeley embraced the dilemma and ran with it, claiming that the world was mind-dependent—a physical reality built of abstract thought. To Descartes's
cogito ergo sum
, Berkeley replied,
esse est percipi:
to be is to be perceived. The world stops at perceptions—beyond them, there's nothing. Perceptions, he said, are the be-all and end-all of existence, not representations of external, physical things. This didn't go over well. Outraged by Berkeley's idealist philosophy, Samuel Johnson famously kicked a rock, declaring, “I refute it thus.” How can we refute Bostrom? I wondered. Who was going to kick him?

Berkeleyan idealism had one fatal—and, frankly, kind of obvious—flaw: the bishop's mind-dependent world was dependent upon minds. Minds that were somehow separate from the world they perceived.
There was a categorical dualism: observer and observed. Two fundamentally different kinds of things. But what are our brains if not physical objects conceived of the same stuff they simulate? After all, we are just pieces of the universe looking at itself, and if we are a simulation, then we are a simulation simulating itself. So was it all just a cosmic hall of mirrors? Mirrors reflecting mirrors, infinite regress of images of … nothing? Was that what Wheeler meant when he talked about a self-excited circuit? Or my dad, imparting his lotus-style wisdom?
You think there's you
,
and then the rest of the world outside you. But it's all just one thing.

I was ready to resign myself to life in Plato's cave, mistaking shadows for reality, when it dawned on me:
The brain is a universe unto itself. For all intents and purposes
,
there is no outside. One-sided coin
,
the side of things …

Smolin had said that the first principle of cosmology must be that there is nothing outside the universe. Maybe we were in need of an analogous slogan here: there is nothing outside reality. Suddenly the simulation problem looked an awful lot like quantum cosmology's observer problem in a different guise. You can't step outside the universe, you can't step outside your brain, and you can't step outside reality. If I'm a simulation, there's no way I can step outside the simulation and look down on it from a higher level of reality, nor could I then step outside that level to the next level up. And if I'm not a simulation, I likewise can't step outside reality and look back to confirm that it's real. There is simply no vantage point from which we can assess the reality of the reality we're inside. The simulation argument begs for an impossible God's-eye view. Does that mean we'll never know the truth? Or is the truth that reality is a one-sided coin?

Leibniz once said, “Although the whole of life were said to be nothing but a dream and the physical world nothing but a phantasm, I should call this dream or phantasm real enough if, using reason well, we were never deceived by it.” Well, sorry, Leibniz, but I was looking for something a little better than “real enough.” I wanted ultimate reality and I wasn't going to settle for anything less.

* * *

Several months later, I got a call from
New Scientist.
They wanted me to write an article about a group of physicists in Long Island who had created some kind of fireball. I had already written one article for them—a story about loop quantum gravity, which I had pitched to Michael Brooks, the editor whom I had met on the bus. Despite his warning of nearly inevitable rejection, he had not only accepted it, he had put it on the cover. Now they were calling me for a story? It seemed too good to be true.

“It's got a lot of complicated particle physics,” explained the editor, one whom I had never met. “We all agreed that you were one of the few writers who could handle the difficulty. Are you up for it?”

We all agreed?

I cleared my throat to stifle my excitement. “Of course.”

“They suspect they've created the quark-gluon plasma,” she continued.

“Ah, yes, the quark-gluon plasma,” I said. “Fascinating.”

When I hung up the phone, I immediately set to work on the story. I needed to call the physicists in Long Island and ask them about the details of their experiment. And I had to call other physicists in the field to discuss the implications of the discovery for our understanding of the universe. But first things first—I needed to find out what the hell a quark-gluon plasma was.

“I just had the most surreal night.”

I had been curled up in bed with a book about quarks when the phone rang. It was my father calling from a hotel room in Chicago, where he was attending a radiological society conference.

I dog-eared my page and closed the book. “What happened?”

“I was invited to a reception at the Field Museum tonight,” he said. “Everyone was at the cocktail party in the atrium, but I just sort of wandered off into the museum. It was after hours so it was completely empty. But it turns out the current exhibit is the Einstein exhibit! So there I found myself alone in a room surrounded by all of Einstein's things—his handwritten manuscripts, photographs, and letters. It was so strange. It was completely silent and I was alone with all of his stuff.
And for some reason I just kept staring at his compass. I wanted to grab it and run.”

“You should have!” I said.

When we hung up the phone I giggled as I pictured my father busting open the glass case, snatching the compass, and sprinting through the crowd of confused radiologists as a growing swarm of museum guards followed in close pursuit, shouting, “Stop that man!” I pictured him clutching it on the plane as he flew back to the East Coast. And then, since it was my imagination, I pictured him placing it in a small box, wrapping it with a bow, and giving it to me.

Einstein had been only four or five years old when his father gave him that compass. It was one of those small tokens that somehow change the world. Watching the way an invisible force always guided the compass needle north had convinced Einstein that
“something deeply hidden had to be behind things.” He spent the rest of his life trying to find it.

My father, too, had offered me my first clue that reality is not what it seems. Only in my case the clue wasn't an object but an idea, and instead of turning out to be Einstein I grew up to be a counterfeit journalist with more questions than answers. Still, it occurred to me now that the best gift a parent can give a child is a mystery.

Quantum chromodynamics, or QCD, was the theory that described how gluons bind quarks together in groups of three to form the protons and neutrons deep in the core of every atom. Quarks, I learned, come with three possible charges, known metaphorically as red, blue, and green. If you combine all three, the colors cancel to neutral. In fact, the quarks
have
to remain color neutral, which means that they are stuck living in groups, bound together by the gluons. Never can a lone quark venture out on its own. Unless, that is, you turn up the heat. In extreme temperatures, such as those following the big bang, the gluons' grip loosens, the quarks wander freely, and matter dissolves into a primordial plasma.

To achieve such extreme temperatures, physicists at the Relativistic Heavy Ion Collider, or RHIC, at Brookhaven National Lab had
taken gold nuclei, steered them around a 2.4-mile track at nearly the speed of light, and then crashed them together, releasing 100 billion electron volts' worth of energy and creating said fireball, 300 million times hotter than the surface of the Sun. A good 10
^-23
second later, it was gone. But in that fraction of a fraction of a second, the quarks roamed free.

It was an exciting discovery, but the plasma didn't look quite like what physicists had expected. Contrary to their calculations, the quarks and gluons seemed to be moving around in a coherent way. It wasn't the chaotic free-for-all motion of a gas-like plasma, but the synchronized swim characteristic of a liquid. In fact, its viscosity made it the most ideal liquid ever observed—nearly twenty times more liquid than water.

That was pretty weird, but what really grabbed my attention was something Johann Rafelski said. Rafelski was a quark-gluon plasma expert; I had phoned him to discuss the implications of the discovery. “The structure of the vacuum is the origin of quark confinement,” he told me. “So the idea was to melt the vacuum and dissolve the binding, allowing the quarks to move freely.”

Melt the vacuum?
I couldn't get that phrase out of my head. It was so awesomely bizarre—you can
melt nothing
? Okay, I knew that the vacuum wasn't really “nothing.” Nothing, presumably, would be a state of zero energy, and zero was way too precise a number for quantum mechanics. Quantum nothing seethes with activity, thanks to the uncertainty relation between energy and time—the shorter the time period, the larger the energy that can spontaneously spring from the depths of the vacuum only to disappear again in far less than the blink of an eye. This energy can take the form of fleeting pairs of virtual particles and antiparticles that boil up from the vacuum, then meet and annihilate. But how did those virtual vacuum fluctuations bind quarks together? I had to do a lot more research—quickly.