Trespassing on Einstein's Lawn (19 page)

According to Worrall, I didn't have to lend any ontological credence to the individual rats—all I had to worry about were the structural relations among them. That made me feel slightly better, but I still wished I had it in me to be a social constructionist. Then I could get rid of the damn things just by refusing to believe they were there—philosophical extermination. Unfortunately, I believed that physics was what made planes fly and rats scurry. Given the data points of shuffling noises, motion in my peripheral vision, falling books, apocalyptic messages, and London, I had to face facts: the existence of rats, quantum or otherwise, was the simplest explanation.

If I couldn't excise them with Occam's razor, I was going to have to resort to more conventional methods. “Okay,” I told the hardware guy, “give me the traps that will kill them. But kill them quick, so they don't suffer.”

He helped me load my basket with rat traps—standard spring-loaded mousetraps, only bigger. I bought seven.

I went home and rigged the traps. It wasn't as easy as it looked. They're supposed to be this perfect, impossible-to-improve-upon invention, but I nearly lost a finger. Eventually I got them all set up and baited them with peanut butter. I had read somewhere that rats love peanut butter. Then I grabbed my suitcase and got the hell out of there.

I was sitting in a Japanese restaurant in Holborn, in central London, waiting for Michael Brooks.

After laying the traps, I had checked in to a hotel a few blocks down the road on Notting Hill Gate. I didn't want to be around when the rats discovered the peanut butter and I figured I'd enjoy a few extra square feet. After settling in, I had emailed Brooks about a
New Scientist
article and mentioned that I was now living on his side of the pond. “Since you are here in London,” he had replied, “why don't we meet for lunch?”

Brooks arrived at the restaurant along with Valerie Jamieson, another physics editor from
New Scientist
, who introduced herself with a melodic Scottish brogue. We ordered drinks and sushi, which arrived at our table on a large wooden boat. As we plucked fish from the deck with our chopsticks, we chatted about life in London and in the universe at large.

“What's your view of inflation?” Brooks asked me.

Having just shoved a piece of salmon into my mouth, I had a moment to think. Inflation. On one hand, I understood the appeal. As Guth liked to say, it was the ultimate free lunch: a universe that blossoms from some primordial seed and just keeps on growing, gravity's negative energy offsetting the limitless creation of infinite space, which stretches quantum ripples into astronomical veins, the gravitational lifeblood of stars and galaxies.

On the other, inflation couldn't explain why the universe exists at all. From whence the primordial seed? It assumed the existence of the inflaton from the start, not to mention the very laws of physics, and in
its heart it wasn't quantum. It didn't account for what internal observers could see or explain why nothing looks like something. Its logic was Boolean, its view God's-eye, its approach bottom-up; it was helpless in the face of quantum dragons. Besides, there was that disturbing low quadrupole. WMAP hadn't found any large-scale temperature fluctuations—not what you'd expect from an inflated universe.

I swallowed the salmon. “I think it has more problems than people admit.”

I felt weird offering my opinion, as if maybe I wasn't supposed to have one, and as the conversation continued, I couldn't help feeling a little guilty. Brooks and Jamieson had PhDs in physics, and they were real journalists to boot. I was nothing but a poseur trying my best to fit in. But the strange part was, I felt like I
did
fit in. As we compared views of inflation and its discontents and swapped stories about our run-ins with quirky cosmologists, it dawned on me that there was a whole community of people out there—
writers
—who actually wanted to talk about physics over sushi. Science journalism was supposed to be my disguise, but the mask fit a little too perfectly today.

As I snagged a piece of port-side tuna, I couldn't help but wonder what my father was doing now, on the other side of the ocean. It was morning there. He was probably getting ready for work.

One … two … three. Turn the key. Take a deep breath. Open the door.

After a week living it up in a hotel, it was time to return to my miniature flat and dive back into ultimate reality. But as I stood frozen outside my door it occurred to me that when I had set up the traps, I hadn't fully considered the end result. I had wanted the rats gone, but they weren't gone. They were right there on the other side of the door, possibly seven of them, with snapped necks and shocked faces, the traps sprung and sated like bottomed-out guillotines, the morbid remains of a rodent revolution, a noble troop brought down by Sainsbury's peanut butter. And what exactly was I supposed to do with them? Hold a mass funeral? Fire twenty-one shots from a tiny, tiny cannon? Run?

One … two … three …

Fuck.

Is there anything in there I can't live without?

After several more failed attempts, I finally turned the key, cringing as I pushed open the door. Inside, I surveyed the gruesome scene. It was even more horrifying than I had imagined. Every last lick of peanut butter was gone, and the traps, still rigged, were empty.

Worrall's structural realist philosophy had struck a chord in me. If I wanted to find the truth about ultimate reality and the nature of the something that allegedly came from nothing, it was going to be crucial to separate our descriptions of the world from the world itself, what physics really says from the meanings we ascribe to it. But I was confused. Worrall had said that theories talk about mathematical structure, and not about objects. Did that mean that objects don't exist at all, or merely that our scientific theories can never tell us which objects are the real ones? Was it a claim about what we can know or about what actually exists? Was it epistemological or ontological?

“Epistemological,” Worrall answered definitively when I asked him. “I have a lot of trouble with the idea of relations without relata. And anyway, I feel that we should generally be silent about metaphysical issues. We think about what reality is probably made of via physics. All structural realism does is insist that we should not think that we have any grasp of reality over and above what our current theories tell us.”

At first, Worrall's objections to an ontological structural realism seemed fair enough. After all, what
could
it mean to talk about relations without relata? If the world is made of mathematical relationships, mathematical relationships among
what
?

Maybe they're not among anything. Maybe the relationships are all that exist. Maybe the world is
made
of math. At first that sounded nuts, but when I thought about it I had to wonder, what exactly is the other option? That the world is made of “things”? What the hell is a “thing”? It was one of those concepts that fold under the slightest interrogation. Look closely at any object and you find it's an amalgamation of particles. But look closely at the particles and you find that they are irreducible
representations of the Poincaré symmetry group—whatever that meant. The point is, particles, at bottom, look a lot like math.

If structure is all that our theories can ever tell us about the world, forever veiling some unknowable ontology beneath, then our pursuit of ultimate reality was completely hopeless. Accepting Worrall's epistemological structural realism was like retreating right back into Bostrom's computer waving a simulated white flag.

On the other hand, if structure is all that exists—if the world really is made of math rather than things—then physics
can
tell us everything there is to know about ultimate reality. Ontic structural realism was our only hope. My father's and my mission hung in the balance.

“Does
anyone
think that structural realism is ontological?” I asked my philosophy professor after class one day.

He thought a moment, then nodded. “You ought to talk to James Ladyman.”

The fact that all the peanut butter was gone was pretty damning evidence that the rats were ontologically valid, but I knew that I couldn't logically defend my inference to the best explanation. Sure, it seemed the most likely conclusion, but blunting Occam's razor was the undeniable fact that there were an infinite number of possible unobservables that could explain the peanut butter's disappearance—though I was having trouble imagining what the hell they might be. Was British peanut butter especially prone to rapid evaporation? Had seven dollops of anti–peanut butter spontaneously sprung from the vacuum, annihilating the store-bought stuff in a sudden burst of light? This underdetermination of theory by the data was bolstered by the null results of the traps, which just sat there, empty, rigged, full of potential energy, itching to go kinetic. I had learned in philosophy class that inductive reasoning was totally indefensible; all the clues in the world just wouldn't amount to much. The only way to claim that the rats were categorically real was to logically deduce their existence from some set of self-evident axioms, to render them necessary and not merely contingent. Of course, by those standards, a rat could be sitting in front of
me waving its paw and my existence claims still wouldn't hold water. I could hear the contingent bastards scratching at the walls, scurrying in the ceiling two feet above my head.

“Okay,” I told the hardware guy, “I'll take the glue traps.”

“I'll tell you what reality is not. It's not made of little things.”

James Ladyman was sitting on the floor of his hotel room. “We can't help but think that way, but it's not what reality is like.”

I was swaying in a creaky swivel chair. We had met in the bar of the Holiday Inn, where Ladyman was staying while he was in town for a conference on metaphysics. Despite Worrall's warning that we should be silent on metaphysical issues, it seemed a whole slew of philosophers weren't ready to keep their mouths shut. The hotel bar had proved too noisy for a discussion of the nature of reality, so we had retreated to his room, where he was now sitting on the floor, stretching his legs. With a headful of dreadlocks spilling halfway down his back, it would be easy to mistake Ladyman for the bongo drummer in a reggae band, though his British accent carried the distinct melody of academia.

“But how do you go from saying ‘structure is all we can know' to ‘structure is all that exists'?” I asked.

“The motivation for me was looking at contemporary physics and realizing that it doesn't support an intuitive picture of unobservable objects. You could say particle physics is about mesons and quarks and baryons and electrons and neutrinos and so on, but when you get beyond the pictures they draw and just look at the theories, it's very difficult to interpret those theories as being about particles, right?” Ladyman said. “So the thing about particles is that they're not particles.… If you want to know what the ontology is, look at what the theory is saying. Don't try to overlay the mathematical structure with some kind of folky, homely imagery.”

Like
balls
?

“So physics itself steered you to interpret structural realism ontologically?” I said, grinning.

Worrall had developed structural realism to respond to a philosopher's
squabble. If Ladyman's version was driven by physics rather than pure philosophy, it stood a better chance of being true.

“Both quantum mechanics and relativity profoundly challenge our intuitive idea that the world is made of objects,” he said. “Quantum particles have all sorts of problems about their individuality: entangled states, quantum statistics. Then in general relativity, spacetime points don't seem to be the ultimate reality; the reality is something more like a metric field. In both cases we are pushed away from an ontology according to which you drill down and find little things that everything is built of.”

It was a good point. Not only were quantum statistics weird, but they made it pretty much impossible to think of particles as “things.” If you have two electrons, there's no way to distinguish between them. Electrons have no known substructure; they're defined solely by their rest mass, spin, and charge, which are the same for every electron. Electrons, by definition, are identical. Of course, you'd think you could distinguish them just by their locations in space and time—an electron
here
is not the same particle as an electron
there
, by virtue of their being in different places. That trick might have worked in classical physics, but not quantum. Quantum particles don't have well-defined positions in spacetime, only probabilities for appearing in various locations, the locations themselves smeared out by uncertainty. The result is that quantum physics renders elementary particles literally indistinguishable, a fact that becomes pretty important when you're calculating probabilities. If each of the seven rats in my flat inevitably ended up stuck to a glue trap, then I'd say there was a one in seven chance of finding a given rat on a given trap. But if the rats really were quantum, there would be a 100 percent chance of finding any rat on any given trap. If you're placing bets, knowing whether you're dealing with classical or quantum statistics makes a pretty big difference. And what would it even mean to call a rat a “thing” if it has no individuality on which to pin its “thingness”?

General relativity only exacerbated the situation. My father had taught me that to keep accelerated and inertial reference frames on equal footing—to turn a curve into a line—you have to bend the paper. The problem is that you can bend it in endlessly different ways and
produce the same results, a fact made possible by Einstein's central principle, general covariance. Different configurations of the paper can all correspond to the exact same physics, a kind of underdetermination that led not only Ladyman but also Einstein himself to believe that the paper itself—the “thingness” of spacetime—wasn't ultimately real. The only reality lay in the spatiotemporal relationships traced by the paper's curves. The metric. The structure.