As I've discussed in earlier blogs, life requires a source of exergy in order to maintain its structure. And this source of exergy must be far-from equilibrium, i.e. life can't survive solely on a linear temperature gradient. Typically, the exergy that life uses comes from chemical compositions of molecules far from their equilibrium values in the environment. For example, bacteria can convert hydrocarbons and oxygen to carbon dioxide and water because the composition of hydrocarbons (such as in the Gulf of Mexico) is greater than that which would be predicted by thermodynamic equilibrium in the presence of oxygen.
So, what was the source of exergy in the early universe?
There is a lot of debate in this area because it's really difficult to obtain information about the origins of life here on Earth.
Luckily, discussions about the source of exergy in the early universe immediately remove the discussion about whether the Earth's first life forms started here on Earth or started else where and somehow were frozen and survived the trip to Earth.
Possible sources of exergy in the early universe include: 1) sunlight 2) chemicals from underwater vents that are out-of-equilibrium with the ocean 3) chemicals produced inside of lightning bolts that are then out-of-equilibrium with their composition in the environment.
As for chemicals produced in lightning bolts, there have already been multiple experiments showing that complex chemicals (such as amino acids) can be formed in electrical discharges when the gases inside the discharge are similar to those in the early universe (perhaps CO2, CH4, N2/NH3,H2S). The Miller–Urey experiment is just one example.
Lightning is a source of exergy far-from equilibrium. Lightning on Earth today is due to charge imbalance between the solid earth and the atmosphere. Most of this charge imbalance is due to charges carried down with precipitation. Rain and snow fall are due to the non-equilibrium composition of water vapor in the atmosphere, which is in turn due to sunlight vaporizing the oceans so that the composition of water in vapor in the atmosphere can be greater than that expected from thermal equilibrium at the temperature of the atmosphere.
In order words: Sunlight (chemical/thermal exergy) -->> water vapor non-equilibrium (Gravitational potential energy) -->> charge build up (electrochemical exergy) -->> lightning (high temperature thermal exergy) -->> formation of molecules in amounts greater than expected at ambient temperature conditions(chemical exergy)
Many of the non-equilibrium molecules created in the atmosphere during a lightning strike will eventually fall into the ocean.For example, some of the radical species (such as CH3) produced in the lightning strike can combine with other gases species in the atmosphere to produce molecules (like amino acids) that prefer to be in the aqueous state in the ocean.
So, if amino acids were the building blocks for early life forms, what were the food sources? What food source was the reducing agent and which food source was the oxidizing agent? (There probably wasn't oxygen in the atmosphere when life first began.) And how did early life forms create a spatial gradient in the reducing/oxidizing chemicals in order to generate work?
If there's no spatial gradient in the oxidizing and reducing agents, then there's no way to generate power in a mitochondria (or a fuel cell for that matter.) Did the first mitochondria rely on local gradients of chemical compositions?
This leads me to one of the main questions I would like to know:
What was the first source of work? I.e. at what point in time, did a cell use stored chemical exergy (perhaps a precursor to ATP) to separate a well-mixed solution of reducing and oxidizing chemicals so that it could derive more stored chemical exergy via an electrochemical reaction across one of its membranes? Where did the ability to store chemical exergy come from?
I have yet to come across a set of differential equations that yields a solution in which chemical exergy is stored for later use to yield even more chemical exergy.
It is well known that non-linear differential equations with cubic terms have the capability of yielding solutions with limit cycles, such as Van der Pol's equation. However, life is much more complicated than just a limit cycle. Limit cycles don't have the capability of self-replication, and they most definitely don't have the capability of storing exergy for later use to derive more exergy. Neither do strange attractors.
This leads me to the conjecture: Metabolism and replication (as opposed to other forms of nonlinear behavior, such as Rayleigh-Benard convection cells or weather patterns) require that the set of differential equations has a set of symmetry generators (X1, X2, X3,...Xn) such that the algebra describing the Xn's is powerful enough that Godel's incompleteness theorem applies to the group and its algebra.
This is just a conjecture, but what I would like to do is to change the focus of the debate on the first life forms on Earth from a discussion of particular self-replicating chemicals to a discussion of: how does the set of differential equations yield solutions (or attractors) that can yield phenomena such as metabolism and replication? (i.e. can storage of exergy or information appear from the attractors found in nonlinear differential equations with sources of exergy?)
It appears to me that there must be solutions of differential equations that are even more complex that limit cycle or strange attractors. In a previous blog ("Meaning of Life..."), I suggested that the set of differential equations must have enough symmetry generators that the algebra describing the group is powerful enough that Godel's incompleteness applies. If it is powerful enough, then there's forms of recursion such as the operators/generators can map back into themselves. It's the attractors of the differential equations that are replicating...not just the molecules. And this is why I think that it's more important to find the differential equations that produce self-replicating attractors than it is to find the actual chemical species involved in replication. This way, we can solve the chicken-and-the-egg paradox of self-replicating molecules. What you need is for the differential equations to contain self-replicating attractors (and this requires both a source of exergy, the self-replicating chemical species, and perhaps some other requirements.)
(I think that the nonlinear differential equations that have such a self-replicating attractor can not be solved, i.e. they aren't integrable.)
So, the following questions remain in my mind:
What was the source of exergy in the early Earth's history?
Can life be described by a set of self-replicating attractors within nonlinear differential equations?