(This is the third post in the series on The Big Picture by Sean Carroll based on the physicist’s book of that title. In the previous posts we considered his arguments for the reality of human choices and then his broadest arguments for the possibility of growing complexity in a universe that is running down. In this post, the more specific case of the creation of Life on our planet will be reviewed. Life is an amazing thing, often; if we can understand it, it may become even better and this more often. I must admit that this kind of ‘hard science’ is not my forte. I hope to briefly and accurately represent Carroll’s theories in the plainest language. First published 11/24/2019)
The Earth is a special place. By comparison to the other planets in our solar system, life exists here and is complex enough to write and read about itself. To have gained this kind of Complexity, it is necessary for it to have ‘built up’, evolved from simpler states of life. ‘But how does this square with the Second Law of Thermodynamics?’, I have often been asked. True, the universe is ‘running down’ not ‘building up!’, we know this.
In the previous post, Things Emerge in a Universe that is Running Down, the answer was in the most general terms. Complex structures emerge as the universe moves from low entropy to high entropy(1), but a more specific answer is possible for our planet.
On other occasions, I have always answered, ‘the Earth is an open system, we receive
energy from the sun…This input forestalls the inevitable and allows our forms of complexity.’ After all, disorder (entropy), says the Second Law, increases in closed systems.
Our physicist for the day, Sean Carroll, argues that though this answer is true, it misses the main underlying point. If your bedroom is a mess and you clean it, order has been ‘built up’ but it took work and especially work by an intelligent worker. Your bedroom did not “spontaneously organize itself.”(2)
So, life and eventually human life are the great organizers here on planet Earth. Where did they come from? Carroll sees life on Earth not as a luxury nor as having an intelligent source, but as the solution to a problem. The “problem” of available “free” energy.(3)
Sunlight as “Free” Energy
What is “free” energy? That is a term I had not heard until I read Carroll’s The Big Picture. But “free” has nothing to do with cost. Free energy is “useful” energy; it is “energy with low entropy” An “amount of energy is ‘free’…(depending) on its environment”, says Carroll.(4) “A piston full of hot gas…(does) work…but that is
assuming that the piston isn’t surrounded by gas of an equal temperature and density.” (Carroll) It is the disparity of temperature and density inside and out of the piston that gives the exploding gas its push. It is the disparity in the evolution of the universe’s entropy that has resulted in an opportunity for complexity.
It is worth remembering, at this point, that Carroll also describes our “vocabularies about emergent phenomena” — like talk of living things and persons — as not only the “poetic” part of his “Poetic Naturalism”, but also “useful to us” (see previous post). This usefulness to us makes emergent objects real to us, though not as “deep” or “fundamental” as the objects of physics. So now we have in addition to “useful” objects (like the solidity of a table, the growth of a zinnia in my garden, the ‘redness’ I see in red); we have “useful” energy — “free energy”. This, too, has its reality importantly tied to us and complexity; I think this is Carroll’s point.
And our planet is in the right spot. Our setting has the kind of disparity discussed above: there are low entropy objects in an environment that is of higher entropy. From our previous post, Complexity is like the brief complex swirls of cream as they mix into the surrounding coffee.
A lack of disparity would be, if we had no sun, or the sun was much farther away. “The entire sky would look like the night sky does now”, Carroll says. The earth would adjust (toward entropy equilibrium, a kind of ‘smoothness’) with dropping temperatures and complexity on Earth. The light that reached us would have little to no free energy. Conversely, he tells us, if “the whole sky was raining photons down on us as bright as the sun does now” the Earth would, again, “equilibrate” and become as hot as “the surface of the sun.”(5) Again, there would be no contrast and no “free” energy useful to do the work of building complexity.
“The sun is a hot spot in a cold sky”, says Carroll, and for this reason “the energy
we receive in the form of solar photons is almost entirely free energy to be turned into useful work.”(6) For us and our planet of life, that is just what we need. It is very useful. It is part of the mechanism by which energy is “funneled to us” and can be said ‘is for us’. This is the way Carroll attempts to reconcile, within Poetic Naturalism, the difficult position of having a ‘deepest level’ of reality and less fundamental, almost less real, levels.(7) It’s somewhat awkward, it seems to me, but it’s a difficult area for any philosophy that argues for “levels” of reality or existence.
So, overall, from the point of the universe, growing disorder remains the rule. “For every one visible photon (Earth) receives from the Sun, (it) radiates approximately twenty infrared photons back into space, with approximately one-twentieth of the energy each.(Carroll). An infrared photon is a “degraded”, higher entropy, form of radiation compared to visible light. Here on Earth, we get energy that works; the universe (at least immediately beyond us) gets energy with much less to offer. “The Earth gives back the same amount of energy as it gets, but we increase the entropy of the solar radiation by twenty times before returning it to the universe.”(8)
The Practical Biology
When we consider “levels” of what exists, Carroll tells us, each is “a way of talking” with objects specific to them and consistent ways these objects interact. Each level has its “domain of applicability” which is the setting in which we find it appropriate to talk that way.(9) So, not only does talk of living things occupy ‘regular’ people, it also forms the science of biology.
The preceding sections were my attempt to relate to you the interface between biology and physics as understood by Carroll. One of the ‘rules’ of Poetic Naturalism, and really any serious talk of ‘levels’, is that all the layers must be “compatible” and that especially with the areas of science for which ‘many competent people’ are most assured.(10) Of course, this is open to interpretation, but for Carroll physics is sure knowledge. We, here at NatieRel, agree with this but will ourselves have some issues of disagreement with Carroll in the end. The above sections attempted to ‘square’ complexity with the reality of rising entropy. Now let us briefly get to some of the biological mechanisms for “funneling” and using energy to facilitate the complexity of life on Earth.
It starts with Photosynthesis, of course. Free energy, in the form of a photon of visible light, “knocks loose” an electron from a molecule of chlorophyll in a leaf, for example. This creates “an electrical gradient” in which “protons push each other apart” with some “escaping through an enzyme called ATP synthase” which “winds up” and synthesizes ATP from ADP (adinosine diphosphate).(11) ATP (adinosine triphosphate) is the “battery of life”, says Carroll, but in the sense of “energy storage” more similar to “a compressed spring.”(12) ATP then powers all “the vital biochemical functions”: muscle contraction, synthesizing DNA and proteins, nerve cell signaling, etc.
“The Origin and Purpose of Life”
The story we have been telling thus far leads Carroll to “the metabolism-first” camp in the debate on the origins of life.(13) The availability of “free energy”, the ‘knocking loose” of an electron in photosynthesis, the layers of complexity above physics as “useful” views of existence, lead him to thinking of life and its origin as basically all about eating. Who am I to disagree with that, especially as Thanksgiving and the Winter Holidays approach? The purpose of life is to eat up the free energy available here on Earth and send it back out into the universe as rising entropy or disorder. The contrasting ‘camp’ is “the replication-first” approach; the purpose of life is to replicate with the emphasis on information and the DNA molecule.
“There is free energy locked up in certain chemical configurations, and life is one way it can be released”, says Carroll, and this is “a good summary of the metabolism-first view.” Of course, it all starts with the useful energy of photons in our higher entropy environment. That free energy was not capable of release through photosynthesis until life originated. Original life had to receive its energy differently and that leads us to the vents deep in some of the seas. Here, electrons could have been “knocked loose” and their protons forced apart to “wind up” ATP for the first time, and without chlorophyll.
If I understand Carroll correctly, these deep vents of the mid-Atlantic Ocean provide several advantages for the appearance of these vital chemical processes without all the equipment of the modern cell. Interestingly, a geochemist named Michael Russell hypothesized the existence of something like these vents as far back as 1988(14) and the possible advantages they could offer. Vents that “were alkaline, warm (but not too hot), highly porous (riddles with tiny pockets, like a sponge), and relatively stable and long-lasting.” The pockets would act as cell walls before there were cell walls and the alkaline in the vents created a disequilibrium with “the proton-rich acidic ocean water beyond them, creating the proton movement similar to that which “winds up” ATP today.
It was not until the year 2000 that vents of this type were actually discovered in the Atlantic. They are 30,000 years old and vast enough to have been dubbed The Lost City. Older such vents are certainly possible on the Earth’s ocean floors that remains largely unexplored.
Our Crazy, Mixed Up World
So, our world is a crazy mixed up place, and that’s a good thing. “The expansion of the universe draws things apart; mutual gravitational forces pulls them together; magnetic fields push them sideways; collisions between atoms shove matter around and allow it to cool down”, writes Carroll.(15) Entropy started low but is moving toward high. In this swirl of forces and objects, “all of the pieces matter, and they matter all at once”, for complex objects.(16) According to him, it’s the only kind of place complex objects could exist. And, “That’s us…Ephemeral patterns of complexity, riding a wave of increasing entropy…We should enjoy the ride.”
Notes: are provided in this series to allow the reader access to the points being made in Carroll’s test. 1. page 234 2. 228 3. 263 4. 242 5. 242 6.242 7. 235-6 8. 243 9. 103 10. 104 11. 245-6 12. 244 13. 263 14. 262 15. 234 16. 236