The physics of life

Jeremy England writes: Living things are so impressive that they’ve earned their own branch of the natural sciences, called biology. From the perspective of a physicist, though, life isn’t different from non-life in any fundamental sense. Rocks and trees, cities and jungles, are all just collections of matter that move and change shape over time while exchanging energy with their surroundings. Does that mean physics has nothing to tell us about what life is and when it will appear? Or should we look forward to the day that an equation will finally leap off the page like a mathematical Frankenstein’s monster, and say, once and for all, that this is what it takes to make something live and breathe?

As a physicist, I prefer to chart a course between reductionism and defeat by thinking about the probability of matter becoming more life-like. The starting point is to see that there are many separate behaviours that seem to distinguish living things. They harvest energy from their surroundings and use it as fuel to make copies of themselves, for example. They also sense, and even predict things about the world they live in. Each of these behaviours is distinctive, yes, but also limited enough to be able to conceive of a non-living thing that accomplishes the same task. Although fire is not alive, it might be called a primitive self-replicator that ‘copies’ itself by spreading. Now the question becomes: can physics improve our understanding of these life-like behaviours? And, more intriguingly, can it tell us when and under what conditions we should expect them to emerge?

Increasingly, there’s reason to hope the answer might be yes. The theoretical research I do with my colleagues tries to comprehend a new aspect of life’s evolution by thinking of it in thermodynamic terms. When we conceive of an organism as just a bunch of molecules, which energy flows into, through and out of, we can use this information to build a probabilistic model of its behaviour. From this perspective, the extraordinary abilities of living things might turn out to be extreme outcomes of a much more widespread process going on all over the place, from turbulent fluids to vibrating crystals – a process by which dynamic, energy-consuming structures become fine-tuned or adapted to their environments. Far from being a freak event, finding something akin to evolving lifeforms might be quite likely in the kind of universe we inhabit – especially if we know how to look for it. [Continue reading…]

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