Trespassing on Einstein's Lawn (9 page)

In general relativity, observers have to be inside the system—since “the system” is all of spacetime—and the theory accounts for every quirk that arises as a result of their differing perspectives. It's a closed, self-contained whole. Quantum mechanics, on the other hand, is about open systems—the observer has to be outside the system in order to make a measurement, to transform possibility into reality. If you want to unite them into a single theory, you have to figure out where the observer goes: inside or out? Quantum gravity was going to have to negotiate a perilous catch-22: stick the observer outside the universe and you violate general covariance; keep the observer inside and the universe's wavefunction can never be collapsed.

It seemed obvious that the first option was barely an option at all: you can't have an observer standing outside space and time. So the question seemed to be, how do you do quantum mechanics in a closed system? Then again, maybe quantum mechanics wasn't the culprit. Maybe quantum cosmology was trying to tell us that there
is
no closed system. After all, in Markopoulou's model, the universe was just a collection of open systems, each defined by its own observer. But if there's no single closed system, what happens to reality? To the universe as a whole?

Did it even make sense to talk about the universe as a whole, or did that very notion require an impossible God's-eye view? Maybe we had all gone wrong in thinking of the universe as a thing, a noun, an object replete with all the properties that objects normally have, like an outside.
But if the universe isn't a “thing,” what is it? A loose assortment of points of view? And if that's the case, points of view
of what
?

The question reminded me of a late-night conversation with my father back when I was in high school. We were talking about curved spacetime. “Wait a second,” I had said. “If spacetime is all there is, how can it be curved? It would have to be curved relative to something outside; it would have to be embedded in a higher-dimensional space.” I had smiled proudly, sure that at fifteen years old I had just spotted the long-overlooked flaw in Einstein's theory.

My father had laughed. “The math allows you to talk about intrinsic curvature, so you can measure curvature from within the spacetime. It doesn't have to refer to anything outside it. Curvature is just the warping of the metric.”

Now I wondered if something similar could save the universe. Was there some way to continue talking about the universe while only referring to it from the inside? Markopoulou seemed to think so, but it came at a serious price. It meant tossing aside ordinary Boolean logic and replacing it with a kind of logic that depended on the observer. It meant redefining what we mean by “true.” It meant stripping physics of the ability to make absolute statements about ultimate reality. Propositions were no longer true or false. They were true or false
according to some particular observer.

I laughed to myself, thinking about how much some of my old classmates at the New School, who were constantly spouting some kind of postmodern bullshit, would have loved to hear that truth was relative to observers. Of course, what Markopoulou was saying didn't fit their agenda at all—truth and falsity were relative to observers as dictated by the geometry of their reference frames and the objective laws of physics. It wasn't like you could will a star into exploding or render the Earth flat with sheer multicultural tolerance. “Observers” didn't mean people, and “observer-dependent” didn't mean subjective. But I could imagine how easily it could all be misconstrued.

After talking with Markopoulou, one thing was clear: the old way of thinking about cosmology wasn't going to cut it. We couldn't keep pretending that we can describe the universe from the outside, from an impossible God's-eye view. There had to be some accounting for
what individual observers, shackled to their light cones, could see from the inside.

As I walked through the sweltering New York streets, the heat rising up from the pavement, I felt as though I had been let in on a secret, as though the city I had left behind when I entered the lobby of the Tribeca Grand was not the same city in front of me now. I watched all the people hurry past me on the sidewalk, rushing through their day like it was any other, as if concepts like “true” and “false” and “space” and “time” meant anything at all. That's right, I thought, keep sipping your Frappuccinos and gazing at the world through your Boolean-colored glasses. Binary logic is bliss.

A man being walked by several dogs bumped me as he passed, a knot of leashes lurching in his hand. It's okay, I told myself when he didn't bother to apologize, we don't even live in the same universe. For someone like me who was a bit crowd-phobic, it was an oddly comforting thought. Lonely, maybe, but beautiful: we each have our own universe. We just don't notice because there's so much overlap.

I was so lost in thought that I didn't notice I had walked past the subway station until I was nearly at the next one. Before descending into the ungodly heat of the subway platform, I fished my cell phone out of my bag and called my dad at his office.

“It was amazing,” I told him. “I'll send you the whole interview once I've transcribed it. But it's got me thinking—maybe it doesn't make sense to think about the nothingness from the outside, since there is no outside. By definition it's infinite and unbounded. Maybe we should be thinking about what it looks like from the inside, since that's the only possible perspective.” I paused for a moment. “Do you think light cones could be the boundaries that turn nothing into something?”

My mother says that she remembers exactly what she was doing the moment she heard John F. Kennedy had been shot. My father remembers exactly where he was when Neil Armstrong stepped onto the Moon. Me? I will never forget the day the WMAP data were released. It was the twelfth of February in 2003, I was in my Brooklyn apartment, and I was on the phone with Poison Control.

Cassidy, my black Lab, had managed to nose her way into the pantry, where she promptly ate an entire package of roach traps, box and all. When I saw the mangled remains of her snack, I panicked and called Animal Poison Control. The woman on the other end of the phone calmly asked me what brand the traps had been, then took a few minutes to search for the ingredients. As she typed away, Cassidy sprawled out on the floor at my feet looking satisfied with herself, and I flipped through the day's
New York Times.

“Holy shit!”

“Miss, is the dog all right?” the Poison Control operator asked.

“What? Oh, yes, she's fine, sorry. The cosmic microwave background data are out.”

“The what?”

“The microwave background radiation. It's the best picture they've ever taken of the early universe.”

“Huh,” she said. “You mean like outer space?”

“Sort of,” I said. “It's a picture of the universe from, like, 14 billion years ago.”

“Well,” she said, “how about that.”

I scanned the article as she continued searching.
The most detailed and precise map
yet produced of the universe just after its birth confirms the Big Bang theory in triumphant detail and opens new chapters in the early history of the cosmos … gives a first tantalizing hint at the physics of the “dynamite” behind the Big Bang …

“Your dog should be fine, miss. All the ingredients are toxic to insects but not mammals. The only thing I'm worried about is the plastic. It's cheap and it can splinter in their stomachs. Your best bet is to feed her a loaf of white bread. It will stick to the plastic and prevent it from puncturing her.”

“A whole loaf?” I asked.

“Yes.”

I thanked her, grabbed my gloves and a scarf, and headed to the corner store to pick up some bread. As I waited in line for the register, I texted my father:
WMAP!

Back in the apartment, Cassidy greeted me with her tail wagging. “This is your lucky day,” I told her, dumping the bread into her bowl. As punishment for eating roach poison, I was, apparently, giving her the biggest treat of her life. While she blissfully gobbled it down, I brought up NASA's website.

“NASA today released the best ‘baby picture' of the Universe ever taken; the image contains such stunning detail that it may be one of the most important scientific results of recent years,” their press release announced.

A decade earlier, when the COBE satellite had first snapped a picture of the nascent universe, Nobel laureate-to-be George Smoot said that it was like seeing the face of God. With thirty-five times the
sensitivity, the Wilkinson Microwave Anisotropy Probe could now make out his faintest freckles, the subtlest laugh lines. The press release explained that the data confirmed the big-bang/inflation package that constituted cosmology's standard model. If you listened carefully, you could hear the champagne corks popping.

The standard model began with the big bang. With Edwin Hubble on Mount Wilson, watching the galaxies recede into the vastness of space and time. With a horrified Einstein realizing his greatest blunder, having let his philosophical prejudices eclipse his equations and missing the opportunity to make what would have been the most extraordinary prediction ever ventured: that the universe was expanding. That spacetime was stretching, growing bigger all around us, and that we were growing smaller by comparison, an ever dimming light in an increasingly magnificent void.

It didn't take long for physicists to run the film backward in their minds, to watch the galaxies hurtling toward one another, the universe growing smaller, denser, hotter, squeezing toward a single, infinite point.

If the universe had begun in fire, they figured, it should still be smoking. Radiation from the nascent universe should still permeate the cosmos, stretched to microwave wavelengths by 14 billion years of expansion, keeping the temperature of empty interstellar space just a nudge above absolute zero. Arno Penzias and Robert Wilson, two radio astronomers working at Bell Labs in 1965, discovered the radiation by accident while hunting the source of a persistent static in their antennae. They thought it was pigeon shit. It turned out to be a relic from the origin of time. They won a Nobel Prize.

But something about the cosmic microwave background, the CMB, didn't add up. It was the same temperature everywhere across the sky. Measure some patch of sky 12 billion light-years away in one direction and it's 2.7 Kelvin. Measure another patch 12 billion light-years in the opposite direction and, again, 2.7 Kelvin. Separated by 24 billion light-years, those two regions could never once have met in the mere 14-billion-year history of the universe. Yet they seem to be in equilibrium. It was too precise to be a coincidence. Something was missing.

The solution came late one December night in 1979 when Alan Guth, an unknown postdoc at Stanford University, had a spectacular realization. He had been thinking about monopoles. At the time, physicists believed that at extremely high temperatures, such as those near the big bang, the forces governing the interactions of particles would merge into a single superforce, one that would splinter into its constituent pieces as the universe expanded and cooled. The idea had one flaw. As temperatures plummeted, the superforce wouldn't be the only thing splitting apart—spacetime itself would suffer topological damage. Like water freezing into chunks of ice, fragments of spacetime would freeze out and form exotic particles such as the hypothetical monopole—a magnet with a single pole, north without south. Physicists searched the universe for monopoles but never caught sight of one, which was a serious problem for a theory that predicted a universe overrun with the things, monopoles more numerous than atoms.

Guth sat down, resolved to tweak the big bang in such a way that spacetime would no longer manufacture monopoles. When the solution dawned on him, he took out his notebook and wrote, “Spectacular realization.”

Guth had realized that if the universe underwent a sudden burst of expansion in the first fraction of a second, inflating at speeds faster than light, any monopoles produced in the big bang would quickly be pushed out to the far reaches of space, far beyond any region we could feasibly measure. That would explain why no one had ever seen one. As a bonus, it would also explain why the temperature of the CMB was so uniform.

The problem with far-off regions of space having the same temperature was that they didn't have time to equilibrate—but by having spacetime expand faster than the speed of light, the inflationary theory buys the universe extra time. Superluminal expansion sounds like a blatant contradiction of relativity, but it falls into a sort of cosmic loophole—while nothing
in
spacetime can travel faster than light, there's no law against spacetime
itself
exceeding the limit. That distant regions are in equilibrium seems impossible because photons wouldn't have had enough time since the big bang to travel between them, but by expanding faster than light, spacetime gives those photons a boost,
carrying them out to the far corners of the cosmos, much farther than they ever could have gotten on their own.

Of course, for the theory to work, you need some physical mechanism that will cause the universe to suddenly balloon outward like a blowfish. Guth came up with one. The newborn universe, he suggested, might have been filled with a hypothetical field called the inflaton, which found itself in a false vacuum—a momentarily stable state, but not the state of lowest energy, like a ball precariously perched on a plateau midway down a mountain. The smallest push will send that ball rolling downward until it reaches minimum energy, otherwise known as the ground. As for the inflaton, quantum fluctuations could provide the push, sending it tumbling into a lower energy state. As it plummets, spacetime takes on a negative pressure, creating a kind of antigravitational force that pushes outward and causes the universe to expand exponentially, growing a million trillion trillion times bigger in just a fraction of a second. As Guth put it, inflation explains what went bang.