A Fortuitous Planet (Part 2)
From matter to life
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How can life emerge from non-life? And what do possible answers to this question hold for the future of humanity? The deeper we look into the origins of life here on Earth, the more we must confront a troubling reality; biology holds fewer and fewer answers. Instead, we must turn to physics to understand why life may have sprung on the ‘fortuitous planet.’ The same laws of physics, it turns out, constrain and direct humanity and progress today.
Biology Falls Short
In a prior essay, A Fortuitous Planet, I walked through an extremely brief history of the universe, beginning at the ‘gravitational singularity’ from which everything, including the laws of physics, arose, to the formation of an early fortuitous Earth. But how exactly did life emerge from non-life? To answer this, it may help to first understand what separates that which we call “living” from raw matter in the form of elements and molecules that we consider to be “nonliving.”
Interestingly, separating matter from life is a surprisingly difficult endeavor. In the words of physicist Chet Raymo, “We recognize life when we see it, but it is devilishly hard to say what it is.” Biologists turn to describing some key characteristics of life. For example, most biologists agree that organisms that have the following seven characteristics are alive or animate: the ability to grow, respire, excrete, reproduce, move, metabolize, and respond to the environment.
The problem is, that while a characteristics approach may be a useful shorthand, there are exceptions to the rules. A mule, for example, cannot reproduce, yet nobody would doubt that it is alive. A virus, on the other hand, can reproduce, but most biologists consider it to be non-living because it depends on other species to do so. We wouldn’t argue that a crystal is alive, yet it grows. On the other hand, there are bacteria that go through dormant periods where they do not grow or metabolize, yet we still consider them to be living.
What is going on here? The more we attempt to tighten our grasp around a succinct definition of “life,” the more organisms that slip through our fingers as outliers and exceptions. It might simply be the case that no such universal definition or defining characteristic can be found. Instead, what we call life could be merely a human construct, a mental heuristic that we have developed to better explain the world around us. Perhaps we humans have drawn an arbitrary line between simple and complex matter and have decided that all matter on one side of this line is “alive” and the other side is not.
The Second Law
Or perhaps the answer doesn’t lie in biology, but rather in physics. Here, we find scientists attempting to define life not by its characteristics but on a higher level, the “why,” not the “what.” Jeremy England, an MIT physicist, proposed that the key difference between life and non-life is that the former is better at the dissipation of energy in accordance with the Second Law of Thermodynamics.
To understand this, we must return to the first seconds of the Big Bang where the laws of physics were initially written. Chief among those laws is the Second Law of Thermodynamics or the law of increasing entropy; hot objects must cool down, concentrated gases must diffuse, eggs can scramble but never spontaneously unscramble…etc. The law of entropy holds that in our universe, energy tends to disperse as time moves forward.
This all comes back to raw probabilities. There are far more ways for energy to spread out than there are for it to concentrate. A cup of coffee will release its heat to the surrounding room until the room reaches equilibrium because that is what is more likely to happen. The probability of the reverse happening, the room releasing and concentrating its heat into a cup of coffee, on the other hand, is unimaginably small.
But what of life? Life is certainly capable of concentrating energy from its surroundings…surely this is a violation of the law of entropy? On the contrary, life is an “open” system capable of receiving energy from an external source and can use this energy only to lower the entropy within itself. It does, however, by increasing the entropy of the universe around it. Thus, life does not violate the laws of the universe at all…it speeds the process of energy dispersion up.
What better way to speed up this process further than to be able to replicate itself and create yet more life? Life’s ultimate goal is the reproduction and survival of its species. We know this because Darwinian evolution tells us; life does all it can to adapt to changing environments. But the underlying force behind this motivation to survive and thrive is the dispersion of energy in accordance with the laws of physics. From this view, life is here to accelerate the inevitable course of increasing entropy.
To put this more simply, recall a common middle-school science experiment of taping two water bottles together, end to end, with water inside. If I flip the bottle, the entropy of the system increases as the water slowly works its way downward, specifically the gravitational potential energy of the water is dispersed. But if I were to shake the bottles in the right way, I could create a vortex that drains the water faster…accelerating the rate of increasing entropy. The vortex itself is an ordered, low-entropy phenomenon, but its creation accelerates the transition to higher entropy for the system as a whole.
Perhaps we cannot neatly distinguish life from matter because life is merely a special form of matter whose purpose is to accelerate the dissipation of energy. From this basis, it was an inevitability that some matter would eventually acquire at least some of the defining characteristics of what we call ‘life.’ Such a suggestion is not entirely new, Jeremy England’s 'dissipation-driven adaptation' theory is building upon decades of research before him. Nor does his theory replace Darwinian evolution. Rather, it attempts to explain the underlying force as to why Darwinian evolution occurs at all.
From this perspective, the current thinking of how life emerged on an early Earth is wrong. Life did not arise because of a rare chance event of molecules coming together in precisely the right way and being struck by lightning. Rather, the abundance of Carbon on an early Earth, an element that bonds readily with itself and other elements, soaking in a “heat bath” of free-moving water, located under a source of concentrated energy (the Sun), the emergence of life was almost inevitable.
Within this “heat bath,” of water and organic molecules, it is very difficult to dissipate heat. The law of entropy saw some molecules combine and arrange themselves in a fashion that would better disperse this energy, and some of that matter took on some of the characteristics we call life. Thus, counterintuitively, life was more likely to form under these conditions than not, as stated by England, “...if you shine light on it for long enough, it should not be so surprising that you get a plant.”
A Fortuitous Earth
In some sense, should this theory be correct, the conclusion is a bit frightening. Knowing the age of the universe and just how many planets must conceivably be out there, the fact that we have not detected a universe teeming with life is concerning. Sure, simple life forms like plants and animals may not be detectable with our current technology, but intelligent life that had at least a rudimentary understanding of radio signals certainly should be. Why is it that when we point a radio telescope at the sky…all we “hear” is silence?
Known as the Fermi Paradox, this mystery is a topic that I will visit in an upcoming essay, but it opens the possibility that while life itself may not be particularly rare, something about human civilization very well could be. Perhaps most life dies out long before it can control and direct radio waves. Or maybe civilized life inherently perishes under its own weight soon after gaining such capability. Both explanations could explain why the night sky is eerily quiet and both highlight the importance and uniqueness of the progress that humans have achieved here on Earth.
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