What We Can Never, Ever Know: Does Science Have Limits?
by ROBERT KRULWICH
September 06, 201311:52 AM
I got two books in the mail that, if they could have, would've poked, scratched and ripped each others' pages out. I don't know if Martin Gardner and Patricia Churchland ever met, but their books show that there are radically, even ferociously, different ways to think about science. Gardner died last year. He was a science writer whose monthly "Mathematical Games" column in Scientific American was wildly popular. Patricia Churchland is a philosopher who teaches at U.C. San Diego.
The issue between them is: How much can we know about the universe?
"I am a mysterian," says Gardner, in his new (posthumously published) autobiography. Mysterians, he writes, believe that some things — how life began, the nature of time, what consciousness is, whether there is free will — are so inherently complex that they will forever elude human understanding. Not only does "no philosopher or scientist living today [have] the foggiest notion" of how mind or time or consciousness work, "we believe" he wrote, "it is the height of hubris" to suppose those things will ever be understood completely.
Forever Unintelligible
Gardner allows that humans have wonderful brains, that we can invent thinking machines, microscopes and any number of intelligence-enhancers, but he says there are still limits, hard limits.
Just as "there is no way to teach calculus to a chimp, or even make it understand the square root of 2," he writes, "surely there are truths as far beyond our grasp as our grasp is beyond that of a cow." He concedes that once upon a time humans were chimp-like and over time developed brains that cracked the "square root of 2" problem — but that doesn't faze him. There are properties of our universe so profoundly complex that no sentient mind, no matter how enhanced, will ever understand them fully.
It's not clear from his book whether this is a scaling problem (that our brains are too small and the universe too, too big) or if the universe has been deeply designed to stay mysterious to its inhabitants. Either way, in his book he insists that some mysteries are permanent.
Gardner was a fine science writer, fearless, imaginative, daring. But he pushes his argument very far. Because some scientific questions are unanswerable, he says, maybe we shouldn't investigate them, that "[t]hese questions are so far above our natural human prowess that to fret about them seems as ridiculous as insisting that a dog understand general relativity."
Ignorance Is Just Ignorance
Patricia Churchland hates this notion. "Ignorance is just ignorance," she says. If you don't know something that doesn't mean you will never know it. In her new book, she writes, "There is something smugly arrogant about thinking, 'If I, with my great and wondrous brain, cannot imagine a solution to explain a phenomenon, then obviously the phenomenon cannot be explained at all. ... What I can and cannot imagine is a psychological fact about me. It is not a deep metaphysical fact about the nature of the universe.' "
For centuries, she says, authority figures have argued that we will never understand germs or earthquakes or atoms or volcanoes — that even to try was to trespass on divine territory. But we trespassed. We asked. We probed. And we learned. People who say we will never fathom the nature of consciousness are just doing what previous authorities did — they are choosing to hide from knowledge; they're cowards.
Yay, Brain
When a friend of hers, another philosophy professor, jumped out of his seat at a conference and yelled, "I hate the brain, I hate the brain!" because all this attention to brain science was taking attention away from philosophical pursuits, she smelled his fear. "Does he worry that neuro-knowledge is forbidden fruit, a Promethean fire, a Pandora's box, ... an evil genie released from a rightly sealed bottle?"
Patricia Churchland calls people like Martin Gardner "anti-enlightenment." She's proud of the human brain, its reasoning ability, its resourcefulness, and given enough time, she suspects, no question is unanswerable, there are no permanent mysteries. In the end (and the end is a long, long time away), we will know it all.
Asking, Asking, Asking
And, then, a third book fell into my lap, not from a scientist, but from a poet, Stanley Kunitz. His views on this subject, casually mentioned at the end of a chapter, are my own. He wrote that he finds his life, his being here, deeply mystifying. He loses friends to diseases and doesn't know why. He loves deeply, but doesn't know how. "Can there be any possibility of completely understanding who we are and why we're here and where we're going? These are questions that can never be answered completely," Kunitz says, contradicting Patricia. But then, contradicting Martin, he takes the crucial next step, "But you have to keep on asking ..."
To me, that's the beauty of science: to know that you will never know everything, but you never stop wanting to, that when you learn something, for a second you feel crazy smart, and then stupid all over again as new questions come tumbling in. It's an urge that never dies, a game that never ends. Science is a rough trade, played, I hope, forever — and, sorry Patricia, sorry Martin, that's how I think of it, not limited, not unlimited, just an itch that always needs scratching.
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Patricia Churchland's new book is called Touching a Nerve: The Self As Brain. Martin Gardner's upcoming autobiography, to be released next month is Undiluted Hocus-Pocus, The Autobiography of Martin Gardner. I found Stanley Kunitz's thoughts in Wild Braid: A Poet Reflects on a Century in the Garden.
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Physicists Take a New Approach to Unify Quantum Theory and Theory of Relativity
Physicists from the Max Planck Institute and the Perimeter Institute in Canada have developed a new approach to the unification of the general theory of relativity and quantum theory.
For almost a century, the two major theories of physics have coexisted but have been irreconcilable: while Einstein’s General Theory of Relativity describes gravity and thus the world at large, quantum physics describes the world of atoms and elementary particles. Both theories work extremely well within their own boundaries; however, they break down, as currently formulated, in certain extreme regions, at extremely tiny distances, the so-called Planck scale, for example. Space and time thus have no meaning in black holes or, most notably, during the Big Bang.
Daniele Oriti from the Albert Einstein Institute uses a fluid to illustrate this situation: “We can describe the behavior of flowing water with the long-known classical theory of hydrodynamics. But if we advance to smaller and smaller scales and eventually come across individual atoms, it no longer applies. Then we need quantum physics.” Just as a liquid consists of atoms, Oriti imagines space to be made up of tiny cells or “atoms of space”, and a new theory is required to describe them: quantum gravity.
Continuous space is broken down into elementary cell
In Einstein’s relativity theory, space is a continuum. Oriti now breaks down this space into tiny elementary cells and applies the principles of quantum physics to them, thus to space itself and to the theory of relativity describing it. This is the unification idea.
A fundamental problem of all approaches to quantum gravity consists in bridging the huge dimensional scales from the space atoms to the dimensions of the universe. This is where Oriti, his colleague Lorenzo Sindoni and Steffen Gielen, a former postdoc at the AEI who is now a researcher at the Perimeter Institute in Canada, have succeeded. Their approach is based on so-called group field theory. This is closely related to loop quantum gravity, which the AEI has been developing for some time.
The task now consisted in describing how the space of the universe evolves from the elementary cells. Staying with the idea of fluids: How can the hydrodynamics for the flowing water be derived from a theory for the atoms?
This extremely demanding mathematical task recently led to a surprising success. “Under special assumptions, space is created from these building blocks, and evolves like an expanding universe,” explains Oriti. “For the first time, we were thus able to derive the Friedmann equation directly as part of our complete theory of the structure of space,” he adds. This fundamental equation, which describes the expanding universe, was derived by the Russian mathematician Alexander Friedman in the 1920s on the basis of the General Theory of Relativity. The scientists have therefore succeeded in bridging the gap from the microworld to the macroworld, and thus from quantum mechanics to the General Theory of Relativity: they show that space emerges as the condensate of these elementary cells and evolves into a universe which resembles our own.
Quantum gravity could now answer questions regarding the Big Bang
Oriti and his colleagues thus see themselves at the start of a difficult but promising journey. Their current solution is valid only for a homogeneous universe – but our real world is much more complex. It contains inhomogeneities, such as planets, stars and galaxies. The physicists are currently working on including them in their theory.
And they have planned something really big as their ultimate goal. On the one hand, they want to investigate whether it is possible to describe space even during the Big Bang. A few years ago, former AEI researcher Martin Bojowald found clues, as part of a simplified version of loop quantum gravity, that time and space can possibly be traced back through the Big Bang. With their theory, Oriti and his colleagues are hoping to confirm or improve this result.
If it continues to prove successful, the researchers could perhaps use it to explain also the assumed inflationary expansion of the universe shortly after the Big Bang as well, and the nature of the mysterious dark energy. This energy field causes the universe to expand at an ever-increasing rate.
Oriti’s colleague Lorenzo Sindoni therefore adds: “We will only be able to really understand the evolution of the universe when we have a theory of quantum gravity.” The AEI researchers are in good company here: Einstein and his successors, who have been searching for this for almost one hundred years.
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