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How do you say “Life” in physics? New theory clarifies rise of life’s complexity

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http://nautil.us/issue/34/adaptation/how...in-physics

EXCERPTS: “To imagine a language is to imagine a form of life.”
 —Ludwig Wittgenstein, Tractatus Logico-Philosophicus (1921)

Jeremy England is concerned about words—about what they mean, about the universes they contain. He avoids ones like “consciousness” and “information”; too loaded, he says. Too treacherous.

[...] His caution is understandable. The 34-year-old assistant professor of physics at the Massachusetts Institute of Technology is the architect of a new theory called “dissipative adaption,” which has helped to explain how complex, life-like function can self-organize and emerge from simpler things, including inanimate matter. This proposition has earned England a somewhat unwelcome nickname: the next Charles Darwin. But England’s story is just as much about language as it is about biology.

There are some 6,800 unique languages in use today. Not every word translates perfectly, and meaning sometimes falls through the cracks. [...] Different fields of science, too, are languages unto themselves, and scientific explanations are sometimes just translations. “Red,” for instance, is a translation of the phrase “620-750 nanometer wavelength.” “Temperature” is a translation of “the average speed of a group of particles.” The more complex a translation, the more meaning it imparts. “Gravity” means “the geometry of spacetime.”

What about life? We think we know life when we see it. Darwin’s theory even explains how one form of life evolves into another. But what is the difference between a robin and a rock, when both obey the same physical laws? In other words, how do you say “life” in physics? Some have argued that the word is untranslatable. But maybe it simply needed the right translator.

[...] England saw more of the same as an undergraduate at Harvard University, where he studied protein folding with the biophysicist Eugene Shakhnovich. [...] “Amino acids are not going to write you a sonnet,” England says. “But when you string a few hundred of them together, suddenly you get this machine that looks like it is made for a particular purpose.”

Somehow, from the churning of blind gears, something like purpose emerges. The pieces, individually obeying nothing more than the basic laws of physics, collectively accrue function. Function seems absent from the world of physics: Time and space don’t exist for any express reason, but just are. In biology, systems are fine-tuned to act. To move, catalyze, and construct. The word “function” trapezes between life and not-life. Is it a word we bestow on things that merely seem life-like, or is it something more inherent? As England would tell an audience at Sweden’s Karolinska Institutet in 2014, physics doesn’t make a distinction between life and not-life. But biology does.

After his Ph.D. [...] His friend took England to some of his favorite Lower East Side haunts and engaged him in long conversations about the Austrian-British philosopher Ludwig Wittgenstein. [...] In the Jewish tradition, “miracles” don’t necessarily defy the laws of nature. They’re a bit less grandiose than that—instead, a miracle is a phenomenon that was previously considered unimaginable. Witnesses to that miracle are called upon to reframe their assumptions and resolve contradictions. In short, they must start to think about their world in a new light.

[...] To the physicist steeped in statistical mechanics, life can, in this sense, appear miraculous. The second law of thermodynamics demands that for a closed system—like a gas in a box, or the universe as a whole—disorder must increase over time. [...] The arrow of time points in the direction of disorder. The arrow of life, however, points the opposite way. [...] How is it that the rules governing those atoms we call “life” could be so drastically different from those that govern the rest of the atoms in the universe? In 1944, physicist Erwin Schrödinger tackled this question [...] He recognized that living organisms, unlike a gas in a box, are open systems. That is, they admit the transfer of energy between themselves and a larger environment. [...] At the same time, Schrödinger pointed to a second mystery. The mechanism that gives rise to the arrow of time, he said, cannot be the same mechanism that gives rise to the arrow of life. Time’s arrow arises from the statistics of large numbers—when you have enough atoms milling about, there are simply so many more disordered configurations than ordered ones that the chance of their stumbling into a more ordered state is nil. But when it comes to life, order and irreversibility must reign even at the microscopic scale, with far fewer atoms in play. At this scale, atoms don’t come in large enough numbers for their statistics to yield regularities like the second law.

[...] Of course, a system of atoms isn’t trying to do anything—it’s just blindly, randomly, shuffling itself around. And yet, through its journey from one shape to another, a constellation of chemical stories, it self-organizes into something that looks to us like it has adapted. “Language is a labyrinth of paths,” said Wittgenstein. To England, the translation felt right. How do you say “life” in physics? He called it “dissipative adaption.”

It may sound as though dissipative adaptation reduces us to mere cooling towers for the sun. But the theory means much more than that. Darwinian natural selection could be recast as a special case of the more generalized phenomenon of dissipative adaptation, a dialect of a more fundamental language. Whereas dissipative adaptation occurs on the micro-scale, natural selection takes place in the world of macroscopic self-replicators. And self-replication is an excellent way to consume and dissipate energy. In the language of dissipative adaptation, words like “fitness” take on new meaning. “Fitness is defined here not in terms of a set of optimal functionalities, but rather as its ‘give and take’ relationship with available energy from the environment,” says Meni Wanunu, assistant professor of physics at Northeastern University. As systems dissipate energy, they drift in an irreversible direction and by doing so become “exceptional,” as England puts it, not perfect or ideal. “A bird is not a global optimum for flying,” England says, “It’s just much better at flying than rocks or worms.”

The theory challenges us to rethink the remarkable functions that make life special: “We have more flexibility in the places we look for function,” says England. The emergence of complex function from a collection of weakly interacting particles, without any strong coordination, is now a process that can be broken down into many small irreversible transformations driven by an external drive. It could be easier for things like proteins and enzymes to emerge than we’d thought. “It might not be an issue of exquisitely selecting the amino acid sequences over eons of self-replication,” says England. “There may be faster time scales on which you can self-organize things. If we can convince ourselves that the very beginning of life looks a bit more like a ramp or stairway with lots of smaller incremental changes that point in the right direction, then that may at least reset our notion of what kinds of scenarios we should be imagining.”...
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