by Adam Frank
In a very real sense, Albrecht’s issues arose when he tried to undo Einstein’s unification of time and space. “In quantum cosmology you have to decide which part of the equations describes time”, explains Albrecht. “That choice turns out to be arbitrary.” Space, time, matter—all the pieces of reality we are familiar with—do not appear in the equations as separate entities but are expected to “emerge” from a quantum cosmological model of the universe’s birth. But Albrecht found that peeling time apart appeared to unwind the whole project of physics.
“I called it the clock ambiguity”, says Albrecht. “Basically, different choices of a clock lead to different kinds of physics.” It was as if the fundamental laws describing something as essential as a proton depend on whether you use a digital watch or a grandfather clock to tell time. The ambiguities in the laws of physics arise because everything physical is defined by time. “What is a ball?” asks Albrecht. “It’s a thing that bounces, and that involves time. What is a ruler? It’s an object that doesn’t change its length. That involves time. Even elementary particles have their properties defined in terms of how they do or do not change in time.”
In essence, the descriptions of “things” such as balls, rulers and elementary particles are exactly what scientists call the laws of nature. To his surprise and horror, Albrecht found that both time and the laws of physics rested on an ambiguous and arbitrary choice. “It sounds ridiculous”, he explains, “but choosing which part of the equations represented ‘time’ turned the maths describing electrons into the maths describing photons.” The physics changed. The laws changed. “I got entirely different kinds of universes depending on the clock I chose”, he says.
This was not what Albrecht was expecting. “As physicists, we like to think of ourselves as hard-nosed people who stick to the facts. What I was finding seemed crazy.” It was the implications that were really crazy. “It meant that the fundamental physical laws were not fundamental!”
Albrecht and his colleagues expected quantum cosmology to tell them exactly why the universe we live in looks the way it does. The clock ambiguity blocked their path. If Albrecht is right, then quantum cosmology can never fully predict the course of cosmic history because the laws determining that history can never be specified beforehand.
The idea that the laws of physics are somehow determined as the universe evolves is not entirely new. John Wheeler, a man many would consider one of the greatest physicists of the last half century, proposed something like it in a 1983 article called “Law Without Law”.11 Wheeler was looking for a way in which the laws of nature themselves are not eternal and independent of the universe but are somehow part of its evolution. While the idea has been considered intriguing, most researchers have not taken Wheeler seriously on this point. “So many times when Wheeler talked about ‘Law Without Law’ I thought, That’s nuts!” explains Albrecht. “But now I am not so willing to dismiss it.”
Reflecting on his dilemma, Albrecht realized that the problem he’d stumbled upon was special because he was trying to describe the universe as a whole. “This puzzle can only occur when you are thinking about cosmology”, he says. “The choice of what part of the universe ‘represents’ time is not a problem for laboratory experiments because in that case it’s easy to say, ‘This is the clock’ and ‘That is everything else.’” But because cosmology describes all creation at once, there is a natural problem defining “inside” and “outside”, including which subsystem represents time for everything else.
Realizing that the clock ambiguity occurred only when the universe was encountered at its most basic and all-encompassing level, Albrecht did not reject the strange direction of arbitrary law in which his research was leading him. “We could leave well enough alone and not go down this road”, says Albrecht, “but as physicists, we seek a complete description of the universe. That means we have to go further than just what we expect from a laboratory perspective.”
For Albrecht, the transition to this new way of thinking meant that what we call the universe may be just one patch of reality with one set of randomly determined laws. There can be other patches or other universes with other sets of laws, all equally random. In this way, Albrecht’s view may connect to multiverse ideas now routinely discussed at cosmology conferences. There is, however, an important difference that puts Albrecht at odds with many of his colleagues. “When most people think about a multiverse and lots of different universes existing alongside each other, they believe they already have a foundation to build on”, says Albrecht. “They believe they can, in principle, know the laws that govern all these different universes at once.” Eternal inflation, as practised by Vilenkin, Carroll and others, uses exactly this approach by developing the mathematical physics machinery that describes the multiverse as a whole. It’s a path Albrecht believes may no longer be possible. “The clock ambiguity”, he explains, “implies that the concrete set of physical laws we were all hoping for is just not there. You can’t know what kind of laws will occur in any given universe until you sit in the middle of it and see what happens.”
FIGURE 11.3. The clock ambiguity. When quantum cosmologists seek to split time from space in their “wave function of the universe”, they confront a paradox. The arbitrary choice of time leads to radically different physics. Here choice A leads to our universe. Choice B leads to a very different set of physical laws and a universe with (for example) floating mountains.
These are all startling and radical possibilities, but Albrecht has resolved to pursue them to their conclusion. Determined to keep an eye on the consequences that could appear in data from astronomy or particle physics, Albrecht is unapologetic about his research. “Maybe all this will fail, but I do think nature is forcing us to go beyond our immediate experience. Getting past my metaphysical preconceptions was the hardest part of this work”, he says. “A lot of people would ask, ‘How do we fix this?’ meaning, ‘How do we find a way around the clock ambiguity?’ The longer I work with this, the more I don’t think we can. I think it’s very basic to any formulation of quantum cosmology. We may have to assume this is the way things are and figure out how it all comes together.”
ACT III: THE END OF LAW
While Andy Albrecht might not be metaphysically predisposed to challenge the existence of timeless laws, others would say metaphysics and philosophy are exactly where the problem started. For physicist Lee Smolin of the Perimeter Institute and philosopher Roberto Mangabeira Unger of Harvard, the real challenge in moving forward is getting past an unspoken metaphysics that is leading the whole enterprise of fundamental physics and cosmology astray. In a move that is either courageous or foolhardy, Unger and Smolin are willing to challenge the philosophical limits of thinking that lead to multiverses and higher dimensions. In their eyes, these fantastical worlds are just that—fantasies—and progress forward may demand that we re-examine our most cherished beliefs in the eternal physical laws.
Smolin and Unger are an odd couple. Smolin is a highly regarded theoretical physicist who has worked in a wide range of fields, from particle physics to string theory to loop quantum gravity.12 A popular author in his own right, Smolin has become a reluctant critic of string theory and the culture of present-day theoretical physics. He argues that a wider array of ideas and options must be explored. Unger is a well-known Brazilian philosopher and a professor at Harvard Law School.13 He has written widely on the dynamic evolution of law in societies. Turning from the realm of philosophy to the pragmatics of politics, Unger has also served as Brazil’s Minister for Strategic Affairs.
Both men, working from separate starting points, have found common ground in rejecting the idea of eternal, timeless laws as well as in the construction of a radically new starting point for physics.
Like most physicists, Lee Smolin began as a true believer in timeless law, but developments in cosmology forced him to rethink the unthinkable. “Thirty years ago, talk of other universes was not seen to be part of science”, he says. “But t
here has been a gradual shift during which it became acceptable to work on theories that described possible other worlds, universes with a different number of dimensions than ours, or with different kinds of particles and forces.”14 According to Smolin, only over the last few years have these other worlds gone from being “just possible” to “hypothetically actual”. “In certain circles”, he says, “it’s fashionable to talk of a cosmos containing a vast number of other universes with different dimensions, different fundamental particles and different laws. Some of the best young cosmologists now do most of their work on the details of such multiverse scenarios.”
While Smolin has worked on his own version of a multiverse in the past, he now sees these theories as indicative of a wider problem in physics and is convinced that it needs to change on a fundamental philosophical level.15 According to Smolin, hiding behind recent developments is an unspoken metaphysics that has two troubling features. First is the claim that our universe is just one of many. Second is the claim that time is not fundamental to reality but emerges from some deeper set of laws such as the quantum cosmological equations. Smolin argues that the equations themselves and the metaphysical approach they embody must now be considered suspect. In raising these deep objections to the way physics and cosmology are carried out, Smolin and Unger find common ground.
FIGURE 11.4. Lee Smolin’s The Trouble with Physics. Theoretical physicist Lee Smolin has become a critic of string theory and (with philosopher Roberto Unger) multiverse cosmologies, claiming they stray too far from concerns with the one universe we observe.
“The treasures of a scientist are his riddles”, says Unger, speaking sadly of the modern history of physics, which led scientists to embrace theories with hidden dimensions and alternate universes. For Unger, these kinds of theoretical constructions are “allegories” because they are, essentially, fictions. As he points out, no one has observed another universe or an extra, hidden dimension of space. That fundamental fact constitutes the shaky ground on which entire fields of research in modern cosmology have been built. “The scientist should treasure the riddles he can’t solve”, continues Unger, “not explain them away at the outset.”
According to Smolin and Unger, the invisible “fictions” of the new theories are created in response to some challenge posed by the world we directly observe. Physicists want a theory of quantum gravity, for example, and string theory looks like an attractive possibility. But string theory’s project of exchanging point particles for microscopic strings could not be made to work if the world was only three-dimensional. In response, string theorists “added more space”, allowing the world to include seven extra dimensions that are hidden from us. With this move, researchers built a working framework for quantum gravity in terms of vibrating strings, but the price they paid was the need to add seven invisible dimensions to reality.
In Unger’s eyes, the multiverse counts as another fiction. Multiverse cosmologies do away with the dilemma posed by the twenty finely tuned constants of the standard model. In a universe of universes, the values of the constants we see in our cosmos are just an accident. Instead of being fundamental physics, the values of the constants become merely a matter of statistics occurring across many incarnations of the standard model in the many pocket universes that make up the multiverse.
In both these cases—the multiverse and string theory’s hidden dimensions—Unger says the theories don’t explain; rather, they explain away. For Unger, these unseen universes or dimensions drain the reality out of what we actually experience. “When we imagine our universe to be just one of a multitude of possible worlds, we devalue this world, the one we see, the one we should be trying to explain”, he says. Both Unger and Smolin want to shift emphasis in physics away from these possible worlds back to the one real world. That world, they say, is saturated with time and free of timeless law.
In Smolin and Unger’s view, it is critical that we recognize how the metaphysics of string theory and multiverse cosmologies continues the grip of an ancient idea whose roots were laid down with Plato. The job of theoretical physics, according to this venerable notion, is to discover timeless universal laws of nature. “By definition that goal is transcendental”, says Smolin. “It requires grasping something true outside of time and beyond space.” For both Smolin and Unger, the connections with religion are obvious. “Because of this implied transcendence”, Smolin wrote in a recent article, “this goal just continues the still older metaphysical presuppositions of religion: that the world we experience is less real than a much greater and timeless reality of eternal truths.” There is no need, say Smolin and Unger, to keep physics wedded to this kind of philosophy, especially if it forces so much fiction into the domain of science.
In his own work, Unger has already mapped out some of the territory Smolin now believes is the future of physics—a future without timeless truths.16 Here the two men stand at the boundaries of science and philosophy. While Andreas Albrecht’s clock ambiguity emerged from a direct exploration of quantum cosmology’s equations, Unger and Smolin want to dig below any specific equations or physical formulations. In their view, developing equations for the new perspective will come later. For now, they want to argue broadly about the rationale for looking at those equations in the first place.
“We must try to imagine a new kind of law”, Smolin says, “which applies only one time. Such a law need not and should not have any sense in which it exists outside of time. Nor could it be conceived of as apart from the universe it describes.”17 This distinction is crucial. If time is real, then everything in the universe is part of time and subject to it. The essence of time, as every human is painfully aware, is change. That simple fact gives Smolin and Unger one way of imagining what all their philosophy will mean for the future of cosmology and fundamental physics. What we call the “laws of physics” may have a story in time—they may evolve. History may matter even for the underlying rules of physics. “We may now have to think about laws where the distinction between a one-time narration of the one universe’s history and the statement of principles governing that history weakens.” In other words, the story and the laws unfold or “become” together.
Smolin and Unger do not yet have the concept of evolving laws worked out. They consider themselves at the beginning of a journey. While their ideas may seem radical, both men feel that cosmology’s current, unspoken philosophy of invisible worlds is also a radical departure from traditional scientific practice. Given that state of affairs, their perspective must also warrant consideration. “What would it mean not to pull our punches?” says Unger, speaking of science’s long tradition of dealing with the facts that this one world presents to us, and only those facts. “What would it mean to take the insistence on dealing only with this world to the extreme?” Unger asks. “What light would that cast?”
REBEL YELL: BEYOND TIME, CLOCKS AND LAW
When confronting the questions of time and what came before the Big Bang, each of the rebel thinkers portrayed in this chapter offers a different perspective. Julian Barbour tells us that “before” the Big Bang is no problem because “before” and “after” never existed in the first place. There is no time and no change. Andreas Albrecht, one of the original leaders of inflation theory, follows his quantum cosmology equations to their logical conclusion and watches in wonder as the clock ambiguity swallows the possibility for eternal, timeless law. Lee Smolin and Roberto Unger look across the landscape of modern cosmology with its extra dimensions and other universes, declare them fictions and set off to deliberately forge another path. Each researcher is serious, sober and determined, but each is exploring a frontier that lies at the edge, or even past the edge, of what mainstream cosmological physics seems willing to consider.
In an era when mainstream cosmology offers so many strange-sounding alternatives to the standard model of the Big Bang, it may seem equally strange that any of these ideas can be considered as too much or too far. But science is, above all else, a community
of thinkers. For hundreds of years, that community has developed its own consensus about what problems it thinks are essential and, more important, what methods it considers appropriate for attacking those problems. The options offered up by mainstream cosmology now may seem like a bewildering array of strange titles to the rest of culture: string theory, loop quantum gravity, holographic universes, brane-worlds and so forth. But these theories still live within the scientific community’s shared sense of what is reasonable in terms of goals and methods. What puts something like the Anthropic Principle on the fringe is its implied demand to change the goals of science. The four rebels encountered in this chapter go even further: each one offers a much deeper critique of the assumptions underlying modern cosmological physics.
The presence of the rebels and their varied visions demonstrates the unsettled and thrilling character of this moment in cosmology building. We are clearly poised to push beyond the now sixty-year-old Big Bang model of a universe that began with a single moment of creation. Genesis is over. But what will take its place? New theories, many making strange demands of reality, are multiplying like rabbits. Observations that can settle the issue may be decades away at best. New discoveries, such as dark energy, might topple the current enterprise and send us off in a new direction at any time. With so much shifting and so much uncertainty, even the rebels must be given their due.
Chapter 12
IN THE FIELDS OF LEANING GRASS
Ending the Beginning in Human and Cosmic Time
NEW SEATTLE, THARSIS HILLS, MARS • 2256 CE
