This Explains Everything

by Mr. John Brockman

  SUBJECTIVE ENVIRONMENT

  ANDRIAN KREYE

  Editor, The Feuilleton (arts and essays) of the German daily Süddeutsche Zeitung, Munich

  Explanations tend to be at their most elegant when science distills the meanderings of philosophy into fact. I was looking for explanations for an observation when I came across the theory of Umwelt vs. Umfeld (loosely, “environment” vs. “surroundings”) by the Estonian biologist and founding father of biosemiotics Jakob von Uexküll. According to his definition, Umwelt is the subjective environment, as perceived and acted on by an organism, whereas Umfeld is the objective environment, which encompasses and acts on all organisms within it.

  My observation had been a mere notion of the major difference between my native Europe and America, my adopted continent for a couple of decades. In Europe, the present is perceived as the endpoint of history. In America, the present is perceived as the beginning of the future. Philosophy or history, I hoped, would have an explanation for such a fundamental yet simple difference. Both can deliver parts of an explanation, of course. The different paths the histories of ideas and the histories of the countries have taken just in the past 200 years are astounding.

  Uexküll’s definition of the subjective environment as published in his book Umwelt und Innnenwelt der Tiere (Environments and Inner Worlds of Animals, published in 1909 in the language of his German exile) puts both philosophy and history into perspective and context. Distrusting theories, he wanted ideas to persist in nature, putting his notion of the subjective environment to the test in the Indian Ocean, the Atlantic, and the Mediterranean. He observed simple creatures like sea anemones, sea urchins, and crustaceans, but the famous example illustrating his theory was the tick. Here he found a creature whose perception and actions could be defined by three parameters. Ticks perceive their surroundings by the directions of up and down, by warm and cold, and by the presence or absence of butyric acid. Their actions to survive and procreate are crawling, waiting, and gripping.

  This model led him to define not just environment but also time as a subjective notion. He found any organism’s perception of time as subjective as its perception of space, and defined by the very perceptions and actions that create the organism’s subjective environment.

  If subjective time is defined by the experiences and actions of an organism, the context of a continent’s history, with its myriads of parameters, turns philosophy and history into mere factors in a complex environment of collective perception. Now, here was an elegant explanation for a rather simple observation. Making it even more elegant is the notion that in the context of a continent’s evolution, such factors as geography, climate, food, and culture will figure in the perception of both the subjective environment and the subjective time, making it impossible to prove or disprove the explanation scientifically. Having rendered philosophy to just one of many parameters, it thus reduces its efforts to discredit Jakob von Uexküll’s definition of the subjective environment to mere meanderings.

  MY FAVORITE ANNOYING ELEGANT EXPLANATION: QUANTUM THEORY

  RAPHAEL BOUSSO

  Professor of theoretical physics, University of California–Berkeley

  My favorite elegant explanations will already have been picked by others who turned in their homework early. Although I am a theoretical physicist, my choice could easily be Darwin. Closer to my area of expertise there is general relativity: Einstein’s realization that free fall is a property of spacetime itself, which readily resolved a great mystery (why gravity acts in the same way on all bodies). So, in the interest of diversity, I will add a modifier and discuss my favorite annoying elegant explanation: quantum theory.

  As explanations go, few are broader in applicability than the revolutionary framework of quantum mechanics, which was assembled in the first quarter of the 20th century. Why are atoms stable? Why do hot things glow? Why can I move my hand through air but not through a wall? What powers the sun? The strange workings of quantum mechanics are at the core of our remarkably precise and quantitative understanding of these and many other phenomena.

  And strange they certainly are. An electron takes all paths between the two points at which it is observed, and it is meaningless to ask which path it actually took. We must accept that its momentum and position cannot both be known with arbitrary precision. For a while, we were even expected to believe that there are two different laws for time evolution: Schrödinger’s equation governs unobserved systems, but the mysterious “collapse of the wave function” kicks in when a measurement is performed. The latter, with its unsettling implication that conscious observers might play a role in fundamental theory, has been supplanted, belatedly, by the notion of decoherence. The air and light in a room, which in classical theory would have little effect on a measuring apparatus, fundamentally alter the quantum-mechanical description of any object that is not carefully insulated from its environment. This, too, is strange. But do the calculation and you will find that what we used to call wave-function collapse need not be postulated as a separate phenomenon. Rather, it emerges from Schrödinger’s equation, once we take the role of the environment into account.

  Just because quantum mechanics is strange doesn’t mean it’s wrong. The arbiter is nature, and experiments have confirmed many of the most bizarre properties of this theory. Nor does quantum mechanics lack elegance: It’s a rather simple framework with enormous explanatory power. What annoys me is this: We do not know for sure that quantum mechanics is wrong.

  Many great theories in physics carry within them a seed of their demise. This seed is a beautiful thing. It hints at profound discoveries and conceptual revolutions still to come. One day, the beautiful explanation that has just transformed our view of the universe will be supplanted by another, even deeper insight. Quantitatively, the new theory must reproduce all the experimental successes of the old one. But qualitatively, it is likely to rest on novel concepts, allowing for hitherto unimaginable questions to be asked and knowledge to be gained.

  Newton, for instance, was troubled by the fact that his theory of gravitation allowed for instant communication across arbitrarily large distances. Einstein’s general theory of relativity fixed this problem, and as a by-product gave us dynamical spacetime, black holes, and an expanding universe that probably had a beginning.

  General relativity, in turn, is only a classical theory. It rests on a demonstrably false premise: that position and momentum can be known simultaneously. This may be a good approximation for apples, planets, and galaxies—large objects, for which gravitational interactions tend to be much more important than they are for the tiny particles of the quantum world. But as a matter of principle, the theory is wrong. The seed is there. General relativity cannot be the final word; it can only be an approximation to a more general quantum theory of gravity.

  But what about quantum mechanics itself? Where is its seed of destruction? Amazingly, it’s not obvious that there is one. The very name of the great quest of theoretical physics—quantizing general relativity—betrays an expectation that quantum theory will remain untouched by the unification we seek. String theory—in my view, by far the most successful, if incomplete, result of this quest—is strictly quantum mechanical, with no modifications whatsoever to the framework that was completed by Heisenberg, Schrödinger, and Dirac. In fact, the mathematical rigidity of quantum mechanics makes it difficult to conceive of any modifications, whether or not they are called for by observation.

  Yet there are subtle hints that quantum mechanics, too, will suffer the fate of its predecessors. The most intriguing, in my mind, is the role of time. In quantum mechanics, time is an essential evolution parameter. But in general relativity, time is just one aspect of spacetime, a concept that we know breaks down at the singularity deep inside a black hole. Where time no longer makes sense, it is hard to see how quantum mechanics could still reign. As quantum mechanics surely spells trouble for general relativity, the existence of singularities suggests that general relativi
ty may also spell trouble for quantum mechanics. It will be fascinating to watch this battle play out.

  EINSTEIN’S REVENGE: THE NEW GEOMETRIC QUANTUM

  ERIC R. WEINSTEIN

  Mathematician and economist; principal, Natron Group

  The modern theory of the quantum has only recently come to be understood to be far more exquisitely geometric than Einstein’s general relativity. How this came to be discovered over the last forty years is a fascinating story that has, to the best of my knowledge, never been fully told, as it is not particularly popular with the people who created this stunning achievement.

  The story begins at some point around 1973–74, when our consensus picture of fundamental particle theory stopped advancing. This stasis, known as the Standard Model of Particle Physics, seemed initially little more than a temporary resting place on the relentless path toward progress in fundamental physics, and theorists wasted no time proposing new theories in the expectation that they would be quickly confirmed by experimentalists looking for novel phenomena. But that expected entry into the promised land of new physics turned into a forty-year period of half-mad tribal wandering in an arid desert, all but devoid of new phenomena.

  Yet just as particle theory was failing to advance in the mid-1970s, something amazing was quietly happening over lunch at the State University of New York at Stony Brook. There, Nobel physics laureate C. N. Yang and geometer (and soon to be billionaire) Jim Simons had started an informal seminar to understand what, if anything, modern geometry had to do with quantum field theory. Their shocking discovery was that both geometers and quantum theorists had independently got hold of different collections of insights into a common structure that each group had discovered for themselves. A Rosetta stone of sorts called the Wu-Yang dictionary was quickly assembled by the physicists, and Isadore Singer of MIT took these results from Stony Brook to his collaborator Michael Atiyah in Oxford, where their research with Nigel Hitchin began a geometric renaissance in physics-inspired geometry that continues to this day.

  While the Stony Brook story is less discussed by today’s younger mathematicians and physicists, it is not a point of contention between the various members of the community. The controversial part of this story, however, is that a hoped-for golden era of theoretical physics did not materialize or produce a new consensus theory of elementary particles. Instead the interaction highlighted the strange idea that, just possibly, quantum theory was actually a natural and elegant body of pure geometry that had fallen into an abysmal state of dilapidation putting it beyond mathematical recognition. By this reasoning, the mathematical train wreck of modern quantum field theory was able to cling to life by its fingernails and survive numerous near-death experiences, confronting mathematical rigor only because it was being held together by a natural infinite-dimensional geometry which is, to this day, only partially understood.

  In short, most physicists were trying and failing to quantize Einstein’s geometric theory of gravity because they were first meant to go in the opposite and less glamorous direction of geometrizing the quantum instead. Unfortunately for physics, mathematicians had dropped the ball and not sufficiently developed the geometry of infinite-dimensional systems (such as the Standard Model), which would have been analogous to the four-dimensional Riemannian geometry appropriated from mathematics by Einstein.

  This reversal could well be thought of as Einstein’s revenge on the excesses of quantum triumphalism, served ice-cold decades after his death: The more researchers dreamed of becoming the Nobel-winning physicists to quantize geometric gravity, the more they were rewarded only as mathematicians for the relatively remedial task of geometrizing the quantum. The more they claimed that the “power and glory” of string theory (a failed piece of 1970s subatomic physics which has mysteriously lingered into the 21st century) was the “only game in town,” the more it looked like strings-based unification, lacking testable predictions, was itself sinking with a glug to the bottom of the sea.

  What we learned from this episode was profound. If the physicists failed, it was only in their own terms that they went down to defeat. Just as in an earlier era, in which a number of physicists retooled to become the first generation of molecular biologists, physicists came to dominate much of modern geometry in the last four decades, scoring numerous successes that will stand the tests of time. Likewise their quest to quantize geometry backfired in the most romantic and elegant way possible, by instead geometrizing the quantum which, in hindsight, was needed to fill in a gaping hole left by the mathematical geometers. This lacuna would have been discovered sooner or later by mathematicians, as it is by now seen as an entirely natural piece of pure mathematics. Quantum field theory, despite its name, turns out really to be a piece of pure mathematics developed by ingenious amateurs out of the need to unpack the consequences of the fundamental equations representing the true physical content.

  But the most important lesson is that, at a minimum, Einstein’s minor dream has already been realized as something of a group effort. All known physical phenomena can now be recognized as fashioned from the pure marble of geometry, through the efforts of a pantheon of new giants with less familiar names, like Quillen, Singer, Simons, Atiyah, Witten, Penrose, Yang, Schwartz, Seiberg, Segal, Hitchin, and Jackiw. This explains, in advance of unification, that the source code of the universe is likely to be a purely geometric operating system written in a single programming language. While that leaves the quest for the unifying physics unfinished and the marble something of a motley patchwork of colors, it suggests that the leaders during the years of the Standard Model have put this period of stasis to good use for the benefit of those of us who hope to follow.

  WHAT TIME IS IT?

  DAVE WINER

  Software developer; founder, UserLand Software; editor, Scripting News weblog

  A few years ago, I heard it said that only old-fashioned folk wear watches. But I thought I would always wear a watch. Today I don’t wear a watch.

  How do I find the time? Either I do without or I keep my eyes fixed on a screen that has the time in the upper-right corner. It’s gotten so that I resent that reality doesn’t display the time in the upper-right corner.

  REALISM AND OTHER METAPHYSICAL HALF-TRUTHS

  TANIA LOMBROZO

  Assistant professor of psychology, University of California–Berkeley

  The deepest, most elegant, and most beautiful explanations are the ones we find so overwhelmingly compelling that we don’t even realize they’re there. It can take years of philosophical training to recognize their presence and evaluate their merits. Consider the following three examples:

  Realism.

  We explain the success of our scientific theories by an appeal to what philosophers call realism—the idea that they are more or less true. In other words, chemistry “works” because atoms actually exist, and hand-washing prevents disease because there really are loitering pathogens.

  Other minds.

  We explain why people act the way they do by positing that they have minds more or less like our own. We assume they have feelings, beliefs, and desires, and that they are not (for instance) zombie automata that convincingly act as if they have minds. This requires an intuitive leap.

  Causation.

  We explain the predictable relationship between some events we call causes and others we call effects by an appeal to a mysterious power called causation. Yet, as noted by 18th-century philosopher David Hume, we never “discover anything but one event following another,” and we never directly observe “a force or power by which the cause operates, or any connection between it and its supposed effect.”*

  These explanations are at the core of humans’ understanding of the world—of our intuitive metaphysics. They also illustrate the hallmarks of a satisfying explanation: They unify many disparate phenomena by appealing to a small number of core principles. In other words, they are broad but simple. Realism can explain the success of chemistry, but also of physics, zoology, and d
eep-sea ecology. A belief in other minds can help someone understand politics, their family, and Middlemarch. And assuming a world governed by orderly, causal relationships helps explain the predictable associations between the moon and the tides as well as that between caffeine consumption and sleeplessness.

  Nonetheless, each explanation has been seriously attacked at one point or another. Take realism, for example. While many of our current scientific theories are admittedly impressive, they come at the end of a long succession of failures: Every past theory has been wrong. Ptolemy’s astronomy had a good run, but then came the Copernican revolution. Newtonian mechanics is truly impressive, but it was ultimately superseded by contemporary physics. Modesty and common sense suggest that, like their predecessors, our current theories will eventually be overturned. But if they aren’t true, why are they so effective? Intuitive realism is at best a metaphysical half-truth, albeit a fairly harmless one.

  From these examples I draw two important lessons. First, the depth, elegance, and beauty of our intuitive metaphysical explanations can be a liability. These explanations are so broad and so simple that we let them operate in the background, constantly invoked but rarely scrutinized. As a result, most of us can’t defend them and don’t revise them. Metaphysical half-truths find a safe and happy home in most human minds.

  Second, the depth, elegance, and beauty of our intuitive metaphysical explanations can make us appreciate them less rather than more. Like a constant hum, we forget that they are there. It follows that the explanations most often celebrated for their virtues—explanations such as natural selection and relativity—are importantly different from those that form the bedrock of intuitive beliefs. Celebrated explanations have the characteristics of the solution to a good murder mystery. Where intuitive metaphysical explanations are easy to generate but hard to evaluate, scientific superstars like evolution are typically the reverse: hard to generate but easy to evaluate. We need philosophers like Hume to nudge us from complacency in the first case and scientists like Darwin to advance science in the second.