The simulation hypothesis, the holographic principle and other hypotheses about the unreality of what is happening around us, perhaps, originate from the assumption put forward by the brilliant Austrian scientist of the 19th century - Ludwig Boltzmann.
As entertaining and surprising as the experiments carried out in the laboratory are, the most interesting are the thought experiments of scientists. Boltzmann's brain is just one such thought experiment related to consciousness, intelligence, entropy, and probability.
The entropy paradox
We live in a world that, in theory, should not exist. The second law of thermodynamics says that entropy should increase over time. That is, sooner or later, everything becomes less orderly. However, in some areas of the Universe, it can become more organized as a result of random fluctuations, if at the same time its other areas become less and less ordered.
We live in an incredibly orderly part of the universe. For example, even a short segment of a DNA molecule is arranged so neatly that the probability of its appearance as a result of "random fluctuations" of physical material is unimaginably small. But how did it happen that there are billions of basic compounds in one cell, trillions of cells in complex organisms, and millions of species of living beings on Earth?
It's all about the so-called anthropic principle, which many consider to be an extreme form of selection criterion. It states that the reason we can observe something as complex as the human brain is because only something as complex as the human brain can observe.
This principle is also used to explain why universal physical constants, such as the force of gravity, seem to be fine-tuned for the existence of life on Earth. And this explanation sounds something like this: if these constants were slightly different, life could not exist and we could not be here and now, thinking about why the physical constants seem to be fine-tuned for the existence of life on Earth.
It turns out that there are slightly more ordered areas in the Universe, but there is no one nearby who could notice them. Then a fluctuation occurs - and an area of the Universe appears so ordered that intelligent life is born there, which, in turn, looks around and notices that it lives in an almost impossible ordered world.
You can recall the standard analogy. Imagine a network of a billion monkeys pounding typewriters endlessly. Now imagine that one of these typewriters printed a Shakespearean work that came to consciousness. What is the bottom line? After an incredibly long time, "Hamlet" will appear, look around and think about why it is - a brilliant play - and everything around it is an incomprehensible gibberish.
However, not all so simple. Ludwig Boltzmann, the 19th century Austrian theoretical physicist often referred to as the genius of entropy, suggested that the brain and other complex ordered objects on Earth were formed by random fluctuations like Hamlet, which we talked about above. But then why do we see billions of other complex and ordered objects around us? Why are we not akin to the lonely "Hamlet" in a sea of nonsense?
Boltzmann suggested that if random fluctuations can create a brain like ours, then brains should fly in space or sit alone in one place on uninhabited planets many light years away. This is the Boltzmann brain. Moreover, these brains must be more commonplace than all those crowds of complex ordered objects that we can see on Earth.
So we have another paradox. If the only condition for consciousness is a brain like the one in your head, then how can you be sure that you yourself are not such a Boltzmann brain? If you were experiencing a random consciousness, you would rather find yourself alone in the depths of the cosmos than surrounded by such consciousnesses. Why should Hamlet look around and find Midsummer Night's Dream to his left, The Tempest to his right, Twelfth Night in front of him, and Romeo and Juliet behind?
Simple answers seem to require some kind of magic. Perhaps consciousness does not arise naturally in the brain - like the brain - but requires metaphysical intervention. Or, perhaps, we were not random fluctuations in the thermodynamic soup and were placed here by an intelligent being?
The program "Laska"
Of course, none of the above answers are definitive. The basic idea is that the process of natural selection promotes the development of complex ordered objects, rather than just allowing them to appear randomly. As soon as a self-replicating molecule appeared on Earth about 3.5 billion years ago, a non-stop process began, which eventually led to an extreme concentration of the order that we see around us.
Richard Dawkins illustrated this in his book The Blind Watchmaker with the Weasel (or Ferret) program. The program starts with a line of randomly generated nonsense. It then creates 100 copies of the string with the same probability of mutating each letter into a different letter. Then, out of 101 lines, only one survives, the most similar to the phrase from Hamlet - “I think it looks like a ferret” (Methinks it is like a weasel), and the other 100 die. The next generation is created from the remaining line in the same way. As many generations pass, the surviving line will become more and more like a quote.
In real life, a similar situation occurs. Objects that are more capable of self-replication and less prone to destruction have the ability to self-replicate, while others are destroyed. Over the course of many, many, many generations, objects became more resilient and less likely to be destroyed before they could be reproduced. It turns out that intelligence is a very useful property for an object that can survive and self-replicate.
In short, the solution to the Boltzmann paradox lies in the fact that building one brain is much more difficult than creating an Earth filled with these brains. The random fluctuations required to trigger the natural selection process are much simpler and less accurate than those required to create a Boltzmann brain in the depths of space.
So the next time you feel small and insignificant, remember that you are much more complicated than the 4.5 billion years of history that led to your birth (and this is if you take into account not the age of the entire Universe, but only the Earth).