The Strange (But Appealing) Idea That Life Is A Consequence Of Entropy

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"You start with a random clump of atoms, and if you shine light on it for long enough, it should not be so surprising that you get a plant."

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Could entropy be a driver behind life?

Image credit: ivan_kislitsin/shutterstock.com

How life first began on Earth remains a huge question - scientists have ideas of how it kicked off, perhaps near a hydrothermal vent providing the energy needed for the chemical reaction to take place that eventually led to the first living organisms. It's sometimes spoken about like an unlikely event, where the right mix of chemicals coalesced by chance and random collisions into life. But what if it was physics underlying these reactions, guiding life into existence?

That is part of an idea presented by American physicist Jeremy England, who believes that life may be a consequence of entropy.

Entropy is a measure of the disorder of a system. When something is in a state of high entropy (or high disorder) you could could switch around the components of the system and it would pretty much be the same.

But within the universe there are things, like life, which exist in a state of low entropy. This may seem like it violates the second law of thermodynamics (that entropy in a closed system always increases, or everything tends towards disorder) but that is not the case. Life does not violate the second law as it draws on energy from the environment, expending energy in order to temporarily decrease its own entropy, like how you can expend energy to temporarily push snow into the shape of a snowman and create temporary order, until entropy draws it back into disorder once more. When the overall system (including the energy source for life, and the heat expended by life) is taken into account, the overall system continues to tend towards entropy.

This statistical law of the universe were first discovered by Rudolf Clausius, who noticed that heat flows from bodies with higher temperatures towards one at a lower temperature, and not the other way around. According to England, life and life-like structures may arise in complex, chaotic environments in ways which better distribute heat to the environment. In other words, life and life-like structures arise as a consequence of entropy, for its ability to distribute heat.

In one paper, England simulated a complex soup of 25 chemicals at varied concentrations with various levels of energy applied to the system to "force" chemical reactions to take place, just as sunlight can trigger the production of ozone in our atmosphere (thank you, entropy).

"As anticipated in previous theoretical works, our central finding was that kinetically stable behaviors of such a system are indeed biased toward appearing to be finely tuned to the external drive," England and co-author Jordan M. Horowitz wrote in their paper. "In other words, the long-time behavior of the system is enriched in outcomes that would be observed only with small likelihood in a random and uniform sampling of the whole space of possibilities."

While some soups moved towards equilibrium as expected, more extreme systems experienced "spontaneous fine-tuning", rearranging themselves into more complex structures better able to cope with the complex environment and better distribute heat.

In a second paper, the team found more "lifelike patterns of collective molecular behavior" as well as a "statistical tendency of the system to adopt structures with higher-than-equilibrium rates of work absorption [...], whereby the highly irreversible transitions that sustain the system's nonequilibrium bias towards resonant structures occur because the resonance helps them harvest more work from the external [source of energy]."

Though this is an analogue for life and not nearly replicating its complexity - the theory is controversial and more work, as always, needs to be done - the results are intriguing, and suggest that life could arise as a result of the laws of physics. If correct, it would suggest that life is likely ubiquitous throughout the universe, arising in complex systems such as our own planet.

"You start with a random clump of atoms, and if you shine light on it for long enough," as England told Quanta Magazine in 2014, "it should not be so surprising that you get a plant."