What if the search for life in the universe is really a search for how the cosmos computes? That’s the intriguing, and perhaps unsettling, possibility that we are exploring as a part of our quest to find out whether or not we are alone.
Since the beginnings of our scientific understanding of genetic inheritance in the 1800s and our discovery of molecules like DNA and RNA in the 1900s, we’ve seen that life is informational in nature. There is a “code” of sorts at the heart of living things. It’s a hugely complex code for sure, a code that constantly rewrites itself on the fly and isn’t structured like our digital inventions, but we see it running across the wet, carbon-based biochemistry that pervades the Earth. And just like the manufacture and use of your power-hungry PC or game console, that biosphere reworks the planet, making it a Gaian machine of water and oxygen, nitrogen and carbon.
That planetary reworking is something we might look for with telescopes like JWST, but it’s a scientific struggle to fit all the pieces together to know what a planet and its life can become together. Critical questions revolve around how climate and geophysics provide an environment that can support life, and how life gets its energy and its essential chemical ingredients, and what it does with those.
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Seeing biology as information might offer some answers. Independently, since the 1940s and the work of scientists like Claude Shannon, we’ve learned that information theory and the physics of thermodynamics are, in essence, one and the same way to describe the world. Information is always represented in matter—by 1s and 0s, or by one molecular bond or another—and information can in turn change matter’s configurations. But it takes energy to make change, and so information and energy are endlessly swapping back and forth, all described by the laws of thermodynamics.
Pull these threads together, and life begins to look like information controlling matter to propagate. And that happens through processes that we would call computation—the shuffling and combination and recombination of information through algorithms that are themselves written in that same information. It’s a mind-blowing, weed-smoking trip to contemplate. It also provides an extraordinary way to connect life and its habitats.
One of information thermodynamics’ most important theoretical insights, drawing on 1950s work by John von Neumann and proposed by Rolf Landauer in 1961, is that there’s an absolute energy cost to irreversibly changing any bit of information, something that you can never beat. That so-called Landauer limit is thanks to entropy (and the fact that organized change pushes again a universal tendency for disorder), and depends solely on the temperature at which the information change takes place.
Remarkably it seems that biology also adheres to that limit, and can operate very, very close to it. In 2017 the biologist and complexity scientist Chris Kempes and his colleagues pointed out that when the process of RNA translation takes an amino acid and attaches it to a chain of other amino acids (making or “computing” a protein inside cells) the energy involved is within a factor of 10 of the Landauer limit—which is an absolutely tiny 10-20 joules at room temperature.
What these findings hint at is a way to rewrite how we look for life, by instead looking for the “computational zones” of the universe, whether in RNA translation or in digital 1s and 0s or something else altogether. This is what I and my colleague and artificial life expert Olaf Witkowski have recently explored. If computation is universally constrained by the Landauer limit, which depends on temperature, as well as by how much energy and matter can be given over to computing, we can begin to chart out the prospects for computation on planets and elsewhere.
Computational zones can also upend conventional thinking on life’s possibilities, or “habitable zones.” If there’s energy flow in an environment and matter to build with, we can say something about computation’s potential, whether it’s in rich hydrocarbon slush on Titan’s frigid shorelines or molecules bouncing between the flowing cloud layers of Venus. Perhaps even in the subatomic constituents of a neutron star or the dispersed organic molecules of an entire galaxy’s interstellar gases.
But we also have to figure out what parts of a living system are truly computational. DNA transcription or RNA translation look and smell like computation, and they’re explicitly informational in nature. But what about metabolic processes, or gene regulation? This is where we have to be cautious in seeing terrestrial biology as any kind of “simple” collection of computational proesses. Learning life’s complex informational hierarchies and functions is likely key to learning how life is implemented across the universe, where the same principles might have very different outcomes.
Searching for computational zones also dissolves the boundaries between what we think of as biology and technology. At the technological extremes are hypothetical concepts like Dyson structures that would capture all of a star’s energy. If these structures are for computation, then we can figure out the design options afforded by thermodynamic and informational principles. Calculations hint that abundant substellar objects—so-called brown dwarfs, weighing in at a few percent the mass of our sun and a hundred thousand times less luminous—might be better Dyson energy sources for uncomplaining technology, but not for biology with its bothersome requirements for warmth and nutrients.
Perhaps though most of the universe’s computation takes place somewhere between “pure” biology and pure technology. Humans are an example of a biology whose external machine structures now take on, and create, much of its computational needs. We’re already a blended system, and that could be the most common type of life across the cosmos, and the type of life we’re most likely to eventually detect.
It may also be the case that blended living systems are the only ones able to discover other living systems. Anything else will simply be incapable of noticing, or uninterested in what it shares the cosmos with. If that is true, we really do exist at the most exciting time for any species that has ever arisen on the Earth.
This is an opinion and analysis article, and the views expressed by the author or authors are not necessarily those of Scientific American.