Continuing from the previous part, we examine the lineage of gradient science and the gradients nature shows (river, star, ecosystem). The cited references follow the original manuscript.
Onsager and Scheffer: Two Supporting Discoveries
The last two of the six masters are the discoverers we briefly met earlier. In 1931, the Norwegian-born American physical chemist Onsager formalized the mathematical relationship that flux is proportional to gradient. The intuition that flow cannot exist without a gradient has now been rigorously proven mathematically. This work led to the 1968 Nobel Prize in Chemistry.
In 2009, the Dutch ecologist Scheffer, together with nine colleagues, comprehensively organized the statistical signals that a system commonly shows when it comes close to a critical point. Slowing of recovery speed, increase of variability, rise of autocorrelation. These signals appear in the same form across domains, from ecosystems, climate systems, and even the electrocardiogram just before myocardial infarction. This research showed for the first time comprehensively that early warning of system crisis is possible.
[Figure 3] The Masters of Gradient Science: A 200-Year Flow
| Discoverer | Year | Core discovery | One-line meaning |
|---|---|---|---|
| Poiseuille | 1846 | Flow rate is proportional to the fourth power of the tube radius | A slight narrowing, and the flow plunges |
| Clausius | 1865 | Entropy and the second law of thermodynamics | Equilibrium is death |
| Onsager | 1931 | Flux = transport coefficient × gradient | Without a gradient there is no flow |
| Mitchell | 1961 | Chemiosmosis: the proton gradient makes ATP | To be alive is to maintain a gradient |
| Prigogine | 1977 | Dissipative structures: order maintenance of an open system | Flow creates order |
| Scheffer et al. | 2009 | Early-warning signals of critical transition | The critical point sends a signal in advance |
Placing the trajectories of the six masters together, one fact becomes clear. Every physical law needed to explain how the aging and chronic disease of our body progresses has already been discovered. That there must be a difference for there to be flow, that flow is proportional to gradient, that when the pathway narrows the flow plunges nonlinearly, that to be alive is to ceaselessly receive energy and maintain a gradient, and that when a system comes close to a critical point a signal appears in advance. All of this is the established theory of physics and chemistry over 200 years.
Now one final confirmation remains. Only by seeing exactly how the same laws operate in the nature outside our body (the river and the star and the ecosystem) does it become clear that this law has cosmic universality.
The Gradient Nature Shows: River, Star, Ecosystem
Now finally we confirm one thing. If the five words and the discoveries of the six masters addressed so far are all general laws of the universe, then before entering the human body it is necessary to briefly note where in nature the same law operates. Once we see that the same law repeats from the river to the star, from the star to the ecosystem, and into our body, changing only the medium, the landscape of the human body comes to us more familiarly.
Here we briefly look into three natural sites. The river, the star, and the ecosystem.
River: When the Altitude Gradient Vanishes, the River Dies
The reason the river flows is simple. It is because the altitude of the upstream is higher than the downstream. It is not because the water itself has a will to flow. The difference of altitude, that is, the gradient of gravitational potential energy, pushes the water in one direction. If this gradient is lost in any section of the river, the flow stops at that point and the river changes into a lake or a marsh.
The most shocking case of a river's death in the 20th century is the Aral Sea. Once the fourth-largest inland lake in the world, this place began to shrink rapidly as the water of two major rivers was drawn out in large quantities for irrigation projects for cotton cultivation in the 1960s. According to data from the U.S. National Aeronautics and Space Administration's Earth Observatory, the Aral Sea lost 88 percent of its area and 92 percent of its water volume after 1960, and by 2007 it had shrunk to about 10 percent of its original size. The fishing villages that once flourished on fishing were left in the desert tens of kilometers inland from the vanished lakeshore.
Rereading what happened at the Aral Sea in the language of flow makes it clear. The amount of inflow decreased over decades, but the system maintained its outward form for a while. Then the moment it crossed a certain critical point, evaporation began to exceed inflow, and the lake rapidly shrank. A lake that has once shrunk did not return spontaneously. The change that had progressed slowly crossed irreversibly at a certain moment.
The same pattern is seen on a larger scale. A short paper published by Milly and others in the journal Science in 2008 shocked academia. The title was as follows. "Stationarity Is Dead." Throughout the 20th century, water-resource engineering was built on the assumption that the flow rate of a river varies within a constant probability distribution. Under this assumption the size of dams, the height of embankments, and the water-supply capacity of cities were designed. What this research group declared was the fact that that assumption is no longer valid. It is that the river has entered a section of change that does not return.
Star: When the Fusion Gradient Goes Out, the Star Dies
The reason a star shines is because of the nuclear fusion reaction occurring inside it. But for that reaction to occur, one condition is needed. It is the enormous energy gradient between the high-temperature, high-density core of the star and the low-temperature, low-density surface. Along this gradient, heat flows by radiation and convection and is released from the surface in the form of light, and this flow keeps the star alive. A star is also one form of a non-equilibrium flow system, and the difference, if any, is only that it does not receive energy from outside but makes it inside. When the gradient is maintained the star gives light, and when the gradient bends the star dies.
This process progresses over billions of years. As the hydrogen of the core is depleted, the nuclear fusion reaction rate decreases and the cost of maintaining the energy gradient rises. When gravity begins to win again, the core contracts and the temperature rises higher, and now a more extreme reaction in which helium fuses into carbon begins. A sufficiently heavy star fuses in turn through carbon, oxygen, neon, and silicon up to iron. Upon reaching iron, further fusion no longer releases energy but only absorbs it. It is the moment the fuel gradient is physically exhausted. At this moment the core of the star loses pressure support and gravitational collapse begins, and as a result the outer layers are violently expelled and a supernova explosion occurs.
There is one fact to note. Among the heavy elements that the supernova explosion scattered into the universe is calcium, and that calcium, over billions of years of time, has now entered our body. It is, in effect, that the medium scattered as one enormous gradient collapsed enters another small gradient system and becomes the medium of a new flow. What role this calcium plays within the human body and how it operates as the most decisive medium of aging and chronic disease is unraveled in earnest in the next chapter.
Ecosystem: When Resilience Is Exhausted, the Regime Transitions
An ecosystem is a web of interaction in which numerous biological species eat and are eaten, compete, and coexist with one another. The secret by which this web is maintained is the complex balance of gradients. The gradient of the number of predators and prey, the spatial gradient of nutrient concentration, and the temporal gradient of photosynthetic efficiency interlock with one another to form the stable state of the whole system. This stable state is not static. It is a state that dynamically finds balance under ceaseless disturbance.
Another paper that Scheffer, whom we met earlier, published together with other colleagues in the journal Nature in 2001 comprehensively organized how this balance breaks. The core observation is as follows. Different ecosystems such as lakes, coral reefs, forests, and semi-arid regions commonly have multiple stable states, and under gradual stress, when they cross a critical point at a certain moment, they suddenly transition to an entirely different state. For example, a shallow lake maintains one of a transparent state with abundant aquatic plants and a turbid state with an algal bloom, and when nutrient inflow is below the threshold the clear state, and when it exceeds the threshold the turbid state, becomes the stable state.
The decisive thing is the fact that this transition is not gradual. While the stress grows slowly, the ecosystem is maintained with almost no change. Then the moment it crosses the critical point it transitions sharply, and thereafter, even if the stress is returned to the original level, the system does not return. The case in which, after the coral reef of the Caribbean transitioned to an algae-dominant state, the coral reef did not recover even when the nutrient concentration improved, and the case in which, after the southern Sahara transitioned sharply from a green grassland thousands of years ago to a desert, it did not return even when the climate conditions improved, are all the same pattern.
The core concept this research group emphasized is resilience. Even if the outward form of an ecosystem looks fine, its internal resilience may already be almost bottomed out. When a single ordinary disturbance enters in this state, the system crosses the critical point and drops into another state. To our eyes it looks "sudden," but physically it is only that the simultaneous vanishing of the gradient and the resilience, which had progressed from long ago, surfaced at that moment.
This insight repeats identically in the understanding of aging and chronic disease from the next chapter on. The very moment one is diagnosed with essential hypertension is not the starting point of the onset. It is only that the decades of accumulation, in which the microvascular gradient of our body slowly vanished and the resilience was gradually whittled away, surfaced at a certain critical point. The landscape nature shows is, in effect, repeated exactly within the human body.
[Figure 4] The Gradient of Natural Landscapes: The Same Law, Different Media
| Natural system | Gradient | Medium | Result of gradient collapse |
|---|---|---|---|
| River | Difference of altitude between upstream and downstream | Water | Irreversible transition to lake or marsh (Aral Sea) |
| Star | Difference of temperature between core and surface | Light, radiant heat | Red giant, supernova explosion |
| Ecosystem | Balance of interaction between species | Biological species | Irreversible transition to another stable state |
| Climate | Difference of energy between equator and pole | Atmosphere, ocean currents | Passage of tipping elements through a critical point |
That the climate also follows the same pattern was organized in a review that Lenton and others published in the Proceedings of the National Academy of Sciences, and it is known that several tipping elements such as the loss of the Greenland ice sheet, the summer disappearance of Arctic sea ice, and the savannization of the Amazon rainforest each have a critical point. The phenomenon we call "climate change" in everyday life is, on the surface, a rise in temperature, but physically it is a process in which the energy gradient distribution of the Earth system itself is reorganized.
What we saw in the three natural landscapes (and the climate) are not different events. It is the same law manifesting on different media at different time scales. The medium of the river is water, the medium of the star is light and heat, and the medium of the ecosystem is living biological species, but all of these flow on top of a gradient, and when the gradient collapses they transition irreversibly in the same way.
It becomes clear that this cosmic landscape seen this way is placed on top of exactly the same law as the landscape within our body, that is, the landscape of that microvasculature seen in the previous chapter. The diagnostic name essential hypertension and the irreversible shrinkage of the Aral Sea are the same kind of event, microvascular calcification and the fusion exhaustion of the star are the same kind of irreversible deposition, and the critical point of the manifestation of aging and chronic disease and the critical point of ecosystem transition are the same kind of branch point. Since our body is placed within the universe, that the law our body follows is the same as the law of the universe is in fact a natural consequence.
In this chapter we met one universal law. The simple law that there must be a difference for there to be flow. We followed this law in four stages. In the earlier part we confirmed the definition of gradient, that there must be a difference to move, and the ternary structure of energy, gradient, and medium that runs through every flow system. Next we learned the five words for handling this law precisely (flux, deposition, nonlinear sensitivity, dual blockade, critical point). Then we confirmed, through the footsteps of the six masters, that this law is not a new discovery but the result that physics and chemistry formalized in stages over the past 200 years. Finally we saw that this law is operating in the same way at every scale of the universe, the river and the star and the ecosystem and the climate.
Now one thing has become clear. Gradient is one higher physical law that is everywhere in nature. The reason the river flows, the reason the star shines, the reason the ecosystem is alive, and the reason we breathe and our blood circulates each moment are all one and the same law. There is energy, that energy has a non-uniform distribution so that a gradient is made, and along that gradient some medium flows in one direction. While this flow is maintained the system is alive. The moment the flow stops the system converges to an equilibrium state, and in nature equilibrium is death.
Now one question remains. When the flow within our body collapses on top of this cosmic law, what is the substance that operates as the most decisive medium at its very center? It is one mineral most familiar to us, known to make bone hard. But the moment this mineral is placed in the wrong place in the wrong amount, it becomes the most decisive deposition that cuts off the entire flow. The next chapter is the story of that calcium. It is the story of the single medium that is most decisively involved in every flow of the human body, but that operates as the underlying reality of aging and chronic disease when it is placed in the wrong place.
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