Brains from a vacuum: the science of the impossible

Our Universe by seven tenths consists of dark energy, a specific vacuum field with negative pressure, which forces it to swell with increasing speed. According to the standard cosmological model based on the theory of inflation, this expansion will continue until the end of time, reducing to zero the density of both ordinary and dark matter.

So, is there a universal emptiness ahead? Do not rush to conclusions. Dark energy has an extremely low temperature, of the order of 10-30 K, but still not zero. Therefore, quantum fluctuations must occur in it, leading to the spontaneous appearance and disappearance of a variety of structures. For example, an electron and a positron can be born from a vacuum, which, due to the expansion of the Universe, will fly apart over a large distance and gain independent existence. But an exact copy of the solar system in its current state may appear - even with all spacecraft. Of course, the probability of such an event is unimaginably small, but it still exists. And since the expanding cosmos is doomed to infinite life, this will certainly happen, and by no means more than once. However, the same fluctuations can give rise to disembodied human brains with any interneuronal connections. One can imagine the emergence of a brain that will consider itself an inhabitant of the Earth, for example, a biologist working with stem cells, or an astronomer studying the Universe, or even a reader reading "PM". These “vacuum thinkers” are named after one of the fathers of statistical mechanics, Ludwig Boltzmann, who studied the theory of thermal fluctuations.

Copy or original?

“The logic of quantum field theory and inflationary cosmology forces me to admit that in the infinitely distant future in a vacuum more and more copies of myself, or rather, my current consciousness, will be born, ” says Stanford University physics professor Andrei Linde. “But if this is so, why should I believe that I am the present - is this the original, and not one of the copies?” Moreover, since the number of copies is infinite, such a probability is greater than the probability of being the original source. Of course, this paradox can be circumvented. For example, it can be assumed that the dark energy causing the exponential expansion of the Universe will decay before at least some chance of having just one of my copies appears. In this case, I have the right to consider myself an original, but I have to predict that the Universe is doomed to disappear. ”

In the cerebral cortex, which, in fact, is responsible for higher nervous activity - personality, behavior, thinking and consciousness - there are, according to various estimates, from 10 to 25 billion neurons. Nerve impulses are transmitted chemically through special sections of the membranes - synapses. Each neuron has more than a thousand synaptic connections (and there are those in which this number reaches 10, 000) with other neurons, and thus the neurons are connected to each other in a huge branched network.

Many worlds

However, according to Andrei Linde, there is another way out of this situation. Inflationary cosmology insists on the constant birth of new universes with different physical laws. This is a complex network of an infinite number of worlds, a fractal structure of ever new universes. Then the possibility arises that in each of the new worlds many new originals are born. If it is possible to show that their number greatly exceeds the number of copies that are born from a vacuum, then it will become clear why we are real people, not Boltzmann brains.

“In fact, we are talking about, ” Andrey continues, “how to compare the probabilities of various processes in the ever-renewing fractal universe. This is a very real and very serious problem of cosmology. In principle, such a comparison can be done in a variety of ways. However, if we want the results to meet our intuitive belief in our own reality, so many comparison algorithms will have to be discarded. So it turns out that the seemingly purely fantastic idea of ​​the Boltzmann brain plays a very serious role in cosmology.

And we are talking about even more. Now we are starting to discuss quite rationally problems that had never occurred to us before. For example, what is consciousness and can it evolve from a vacuum? Is it necessary to consider that for this a vacuum must certainly create high molecular weight biostructures, or can it be dispensed with electronic computers? Moreover, it can be shown that it is most advantageous for a vacuum to give birth not to big people, but to computers the size of a small black hole. So maybe we are such computers and only think that we are people? We believe that this is not so, and we are trying to build a picture of the world in which such an opportunity would be excluded. But in order to understand this seriously, you need not be afraid to get into issues that border on physics, psychology, and philosophy. Previously, such discussions would be considered unworthy of scientists, but now they are gradually becoming a part of science. ”

The article was published in the journal Popular Mechanics (No. 9, September 2010). Do you like the article?

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