Trespassing on Einstein's Lawn (24 page)

“Yup,” I said. “It's only conserved when you put it together with parity and time translation. But CPT invariance is really just Lorentz invariance, and Lorentz invariance conserves spacetime intervals. So we have to keep spacetime on the list.”

“We can cross off spin,” my father said. “Supersymmetry shows that what looks like a boson in one frame looks like a fermion in another.”

That was a good point. Usually it's easy to tell the difference between a force-carrying boson, which has an integer spin, and a fermion, or matter particle, which carries a half-integer spin: just rotate the particle by 360 degrees, and if it looks exactly the same as when it started, it's a boson. If, instead, the amplitude of its wavefunction comes out inverted and you have to rotate it a second time—720 degrees in total—before it goes back to the way it started, it's a fermion.

To transform a fermion into a boson, and vice versa, you need some way to flip the amplitude of its wavefunction. And you can do that if you add a few extra dimensions. Not spatial dimensions, but mathematical ones. Rotate the particle through the extra dimensions and a positive amplitude will come out negative, and a negative amplitude positive, interchanging whole- and half-integer spins. In the higher-dimensional “superspace,” bosons and fermions are identical. In ordinary space, they are different shadows of the same piece of cardboard, their distinction based only on the reference frame from which they're viewed.

“
Should
we assume supersymmetry?” I asked.

No experimental evidence for it had turned up yet. If reality were really supersymmetric, every boson would have a fermion partner and vice versa, a particle that is perfectly identical to its partner except that the amplitude of its wavefunction is inverted. Physicists were gearing up to start hunting for supersymmetric particles at the Large Hadron Collider in Geneva, but the accelerator hadn't been turned on yet. Supersymmetry remained theory.

My father shrugged. “There are good theoretical reasons to believe in it.”

That was true. For one, in a supersymmetric vacuum, the forces can be unified. From our cool, low-energy perspective, the strong force appears 100 times stronger than electromagnetism, and the weak force 100 billion times weaker than that. But heat up the vacuum and their strengths begin to change. As the vacuum loosens its grip on quarks, the strong force weakens. At the same time, the electromagnetic and weak forces grow stronger. Keep cranking up the heat and soon all three forces are approaching the exact same strength. At around 10
¹⁶
billion electron volts, the electromagnetic and weak forces merge into a single electroweak force, but the strong force is still a little too strong. But not when there's supersymmetry involved. In a supersymmetric world, the three forces are revealed to be broken facets of a single, unified, fictitious superforce.

It wasn't the only theoretical motivation. Supersymmetric particles don't interact with electromagnetism or the strong nuclear force, but they do interact with gravity. Just like dark matter.

“Besides, there's no reason to expect that experimentalists would
have seen supersymmetric particles yet,” he said. “They could well be out of reach, at higher energies than we can measure.”

“Okay,” I said. “Let's assume supersymmetry and cross off spin.”

“So what's left?”

I grinned with excitement, picking up the napkin and reading from it as if it contained the Gettysburg Address and the overweight sweatpant-clad patrons of IHOP were brave soldiers in the Union Army. “The potential ingredients of ultimate reality are—”

“More coffee?”

My father laughed, and we both gave the waitress an appreciative nod. Our mugs full and steaming, I began again. “The potential ingredients of ultimate reality are: spacetime, dimensionality, particles/​fields/​vacuum, strings, the universe, the multiverse, and the speed of light.”

“You know, my suspicion is that none of those is really invariant,” my dad said, smiling mischievously.

“Then nothing would be real.”

“Exactly. ‘Nothing' would be real. If everything is ultimately nothing—and, really, it
has
to be—and we're defining ultimate reality as what's invariant, then the only invariant should be nothing. Which makes sense because it's the most symmetric thing there is.”

“But we've got lots of invariants on the list here. Can it really all be nothing?”

“Well, look at how many things that physicists once thought were invariant have already been crossed off. Born said that's how physics progresses. I doubt it ends there.”

“So if everything is ultimately nothing, then every remaining ingredient on this list should turn out to be observer-dependent.”

“That's right. They'd have to.”

I smiled, intrigued. “Well, I guess we'll see!”

I was rummaging through a drawer in my childhood bedroom, looking for a pen, eager to write down my racing thoughts about invariance and symmetry and reality, when I saw, sticking out from beneath a stack of papers, a blue folder. I slid it out, sat down on the bed, and opened it.

I grinned. It was the Beat poem my father had written for me in honor of my high school graduation all those years ago. I had always thought it was sweet. But as I read it now, it finally dawned on me what he had done to write the thing. It wasn't just that he had paid attention to the books I loved and to the ideas I cared about.

It was that he had read the words. He had noted which books meant the most to me, and he had—in his exceedingly spare time between saving lives and marking nipples and reverse-engineering the fucking universe—read them, just so he could write me a poem in a voice that I would hear, a poem to send me off to New York City, to send me off into the world, only it wasn't
the
world, or even
his
world. It was
my
world. As if my world mattered. As if my words mattered.

I closed the folder and placed it carefully back in the drawer. A nagging sadness pooled in my stomach. Like nostalgia, only counter-factual. Like the world was still big and still blank. Like I was still waiting, waiting.

A few days later I boarded a plane headed back for London. No matter how often I traveled, I couldn't seem to get through a flight without an
anxiety attack. Takeoff was the worst. I forced myself to breathe deeply as the plane readied itself on the runway.
Physics works
,
physics works
, I repeated in my mind, my standard mantra. Suddenly the girl from philosophy class popped into my head.
Airplanes only fly because we all agree they do.
I rolled my eyes in disgust. We picked up speed, accelerating down the runway. A few rows behind me, a baby started to scream. The cabin shuddered violently. Suitcases banged about in the overhead compartments, the tray tables rattled on their hinges. Then the wheels were off the ground, the plane wobbling as it rose.
I agree that planes can fly
,
I agree that planes can fly
, I silently chanted. Anxiety trumps realism. Pascal's postmodern wager.

Soon we were cruising smoothly above the clouds. I unclenched my fists and reaffirmed my philosophy. Thirty thousand feet above the Atlantic Ocean, at rest relative to the obese man spilling over the seat next to mine, in 500-mile-per-hour motion relative to the slowly turning planet below, I thought about my mission to understand the universe.
Find the invariants
,
and you'll find reality.
I pulled the crumpled IHOP napkin from my pocket and stared at the handful of items that had survived the first round of cuts, the remaining candidates for the ingredients of ultimate reality.
Spacetime. Dimensionality. Particles/​fields/​vacuum. Strings. The universe. The multiverse. The speed of light.
They were good leads, and I felt a new surge of motivation now that we had a solid plan. A strategy.

Still, I couldn't help but think that it would be anticlimactic if any one of those ingredients turned out to be invariant.
Reality has ten dimensions and is made of tiny strings
would be a valid conclusion, but I was pretty sure I'd be left unsatisfied. The truth was, any ontology would seem awkward and arbitrary.
Reality is shaped like a trombone and is made of goldfish crackers.
I thought of Wheeler's words:
“One therefore suspects it is wrong to think that as one penetrates deeper and deeper into the structure of physics he will find it terminating at some nth level … in some smallest object or in some most basic field.” He seemed to think that the only ultimate reality was the observer. That when we look closely enough at the universe, we'll find ourselves staring back. But were observers any less arbitrary than goldfish crackers? I found myself asking the same old question: where do the observers
come from?
The universe is a self-excited circuit.
We really needed to figure out what the hell that meant.

My father, meanwhile, seemed pretty convinced that nothing would be invariant. That is, that Nothing would be invariant. It did seem more satisfying. Questions stop at nothing. You don't have to ask, “But where did
that
come from?” Nothing doesn't come from anywhere. It's nothing. It needs no explanation. At the same time, I found it nearly impossible to imagine how this whole crazy universe, obese airline passengers and bottles of Xanax, press passes and Panama hats, oceans and rats and poems and pancakes … how it could all be just
nothing.

Back on solid ground, in my shrunken flat, I grabbed a tiny soda from my tiny fridge and sat down to check my email. There in my inbox I found one with the subject
New Scientist.

Seriously? A job on staff as an editor at
New Scientist
? We had just figured out our reality-hunting strategy, and now I was being handed
the ultimate press pass? Hell, yes, I was interested! I began composing my reply. As I typed, I spotted something out of the corner of my eye. There on the lovely wooden floor, between the one-seater couch and the miniature sink, was a glue trap, and on the glue trap, a single, solitary, silvery tail.

My work visa came through and I began my six-month stint as an editor at
New Scientist.
The timing couldn't have been better. By the end of April I had finished up my classes, leaving me the next several months to work exclusively on my thesis.

On my first day at work, I made the rounds, introducing myself to all the editors and reporters. I grew increasingly intimidated with each person I met. At twenty-five years old, I was noticeably the youngest editor there. All of them had graduate degrees in science or science journalism, often both, not to mention British accents that made everything they said sound smarter. They had held internships at major newspapers and scientific journals; they had worked alongside scientists in the field and in labs. They had paid their dues, worked their way up. I had faked my way into a conference or two and written a handful of articles. I was going to have to prove myself quick.

Everything seemed to be going great, but each morning when I'd stroll confidently into the office, the receptionist would invariably take one look at me and ask, “Are you all right?” He seemed friendly enough, but I couldn't pinpoint his cause for concern, so I'd respond with “Yes,” then add, “Well, maybe I didn't get quite enough sleep,” or “The commute was a little rough today,” or “I'm being stalked by this troop of
invisible rats.” He'd give a polite but awkward smile, and I'd head over to my desk wondering if the color of my shirt made me look ill.

After
many
weeks of this, I was walking in one morning just a few steps behind another editor. “Are you all right?” I heard the receptionist ask her. She replied, “Are you all right?”

I quickened my pace until I was walking alongside her. “Sorry, what just happened there?” I asked.

“Where?”

“He asked if you were all right, and then you said, ‘Are you all right?' ”

She laughed. “It's an expression. A greeting. It's like …” She searched her mind for an American analogue. “It's like ‘What's up?' ”

“Ohhh.”

“Is that not what it means in America?”

“No,” I said. “ ‘Are you all right?' is something you'd say to someone who just tripped on her high heels and spilled a purseful of tampons on the sidewalk. ‘Are you all right?' means ‘You absolutely do not look all right.' ”