Does scientific knowledge have borders?

We are able to measure black holes, but we are not able to cure a cold.

Albert Einstein said that "the most incomprehensible property of the universe is that it is comprehensible." And he was surprised not in vain. The human brain as a result of evolution has developed a system of adaptation, but its basic neural architecture has hardly changed since our ancestors dissected savannas and coped with the difficulties of life. And in fact, it is striking that this same brain allows us to find meaning in the quantum world and in space, in concepts that are extremely far from the “common sense” of the everyday world where our evolution took place.



But I think that at some point science will hit the brakes. And this can happen for two reasons. Optimistic - we clean up and schematically outline certain areas (for example, atomic physics) so that there is nothing left to add. Another, more disturbing, we will reach the limits of our brain's ability. There may be concepts necessary for a complete understanding of physical reality, about which we will have no more understanding than a monkey about Darwinism or meteorology. And some discoveries will have to wait for posthuman intelligence.



In general, scientific knowledge is surprisingly fragmented - and the deepest riddles are often somewhere nearby. Today we can convincingly interpret the results of measurements showing the collision of two black holes located more than a billion light years from Earth. In the meantime, we have achieved little in the treatment of rhinitis, despite the enormous advances in epidemiology. The fact that we can be sure of the existence of a mysterious and distant cosmic phenomenon, while at the same time finding ourselves in a quandary because of everyday things, is not as paradoxical as it first seems. Astronomy is much simpler than biology and other sciences about man. Black holes, which seem exotic to us, are one of the simplest objects of nature. They can be accurately described by simple equations.



How do we determine the complexity? The question of how far science can go is partly dependent on the answer. Something consisting of only a few atoms cannot be too complicated. Large things also do not have to be complicated. Despite its huge size, the star is a fairly simple object. Its core is so hot that complex molecules are destroyed and there are no chemical compounds there, so what remains is, in fact, an amorphous gas of atomic nuclei and electrons. And you can consider a salt crystal consisting of sodium and chlorine atoms, packed together very tightly so as to create a repeating cubic lattice. If you take a large crystal and chop it up, then its structure practically does not change until you disassemble it to individual atoms. Even if it is large, a piece of salt is not difficult.



Atoms and astronomical phenomena — very large and very small — can be quite simple. But between them begin the difficulty. The most difficult of all is living things. An animal has internal structures on all scales, from proteins in individual cells to limbs and main organs. It cannot exist chopped into pieces as the salt crystal continues to exist when it is cut. It dies.



Scientific understanding is sometimes presented in the form of a hierarchy arranged in the manner of the floors of a building. Everything connected with more complex systems is higher, and everything that is simpler is lower. Mathematics sits in the basement, particle physics goes above it, then the rest of physics, then chemistry, then biology, then botany and zoology, and finally, behaviorism and social sciences (economics, for sure, claim the rights to the penthouse).



The sorting of sciences is not disputed, but the question arises whether the sciences of the ground floor - in particular, particle physics - are deeper or more comprehensive than others. In a sense, it is. As physicist Stephen Weinberg explains in his book Dreams of a Final Theory (1992) [Dreams of a Final Theory], all explanatory answers point down. If you, as a stubborn child, repeat “why, why, why?”, You find yourself at the level of particles. From the point of view of Weinberg all scientists are reductionists . They are sure that everything, however complex it may be, is a solution to the Schrödinger equation — the basic equation that governs the behavior of the system according to quantum theory.



But the explanation of the reductionists is not always the best or the most useful. “More means differently,” as the physicist Philip Anderson said. Anything as complex as possible - tropical forests, hurricanes, human communities - consists of atoms and obeys the laws of quantum physics. But even if these equations could be solved for huge clusters of atoms, they would not give us the kind of enlightenment that scientists are looking for.



Macroscopic systems containing a huge number of particles demonstrate emerging properties that are best understood in terms of new, undiminished concepts suitable for a given level of the system. Valence, gastrulation (differentiation of cells during embryo development), imprinting , natural selection are examples of such phenomena. Even so not a mysterious phenomenon as the flow of water in pipes or rivers is better understood in terms of viscosity and turbulence than in the form of relations of individual atoms. Specialists in fluid mechanics do not pay attention to the fact that water consists of H ₂ O molecules; they can understand how waves break down and when turning leads to churning of a stream just because they represent a liquid as a continuous substance.



New concepts are especially important for our understanding of particularly complex things - for example, the migration of birds or the human brain. The brain is a collection of cells; The picture is a set of chemical pigments. But it is important and interesting how structures and patterns emerge when we move up the levels - something that can be called manifest complexity.



So reductionism is true in some sense. But he is rarely true in the useful sense. Only 1% of scientists study particle physics or cosmology. The remaining 99% work at higher levels of the hierarchy. They are constrained by the complexity of their topic, and not by the lack of understanding of subnuclear physics.



So in fact, it turns out that the analogy between science and building is bad. A weak foundation endangers the structure of the building. Conversely, higher-level sciences working with complex systems do not suffer from unreliable fundamentals. Each level of science has its own, separate explanations. The phenomena of different levels of complexity must be understood in terms of different, undiminished concepts.



We can expect major breakthroughs on three fronts: very small, very large, and very difficult. Nevertheless, I venture to suggest that there are limits to our understanding. The first to reach these limits can be attempts to understand very complex systems, such as our brain. Perhaps complex clusters of atoms, whether brain or electronic machines, are unable to find out everything about themselves. And we can face another barrier if we try to follow Weinberg’s arrows even lower: if they lead to the geometry of many dimensions, which experts in string theory draw themselves. Physicists may never understand the basics of space and time because their mathematics will be too complicated.



My statement about the limitations of human knowledge was challenged by David Deutsch , an eminent theoretical physicist who invented the concept of "quantum computers." In his provocative and beautiful book "Beginning of Infinity" (2011) [The Beginning of Infinity], it says that we can basically calculate any process. This is true. However, the ability to calculate something is not equal to the ability to understand it. A beautiful fractal pattern, the Mandelbrot set , is described by an algorithm in several lines. Its form can even be built on a computer of modest power.







But no one person, having only one algorithm in front of him, can imagine this extremely complex pattern as he can imagine a square or a circle.



World chess champion Garry Kasparov writes in his book “Deep Thought” (2017) that “a person with a machine” can do more than individually. Perhaps the new discoveries will be made using the reinforcing symbiosis of these two entities. For example, in the development of drugs and materials science research, the use of computer simulations gives more and more opportunities than laboratory experiments. Whether the cars will eventually outperform us — and become reasonable — is a moot point.



Abstract thinking available to the biological brain predetermined the emergence of culture and science. But this activity, which has been going on for no more than a few tens of millennia, may serve as a brief precursor of more powerful posthuman minds, which appeared due not to Darwinian selection, but to “intelligent design.” One can argue about whether the future belongs to organic postmen or electronic superhuman machines. But we will be inappropriately anthropocentric, considering that a comprehensive understanding of physical reality is subject to man, and that there will be no secrets left to our distant descendants.