We have every reason to believe that the universe is infinite. Also, the universe is filled with matter and energy: galaxies, stars, gas and dust clouds, nebulae, etc.
In connection with this, the assumption arose that objects that are aware of their existence can arise in an infinite universe. But arising not like you and me - as a result of evolution, but spontaneously organizing from atoms, as a result of the chaotic movement of atoms. Such a hypothetical object is called the "Boltzmann brain".
Some scientists even estimate the likelihood of spontaneous formation of a Boltzmann brain is higher than the likelihood of the formation of the solar system and the origin of life through evolution.
In science fiction, an example of the Boltzmann brain is the intelligent ocean in Solaris by Polish science fiction writer Stanislaw Lem.
A still from the film "Solaris" by A. Tarkovsky.
A paradox arises: why we see less probable objects, but do not see Boltzmann's brain. It has several explanations: either Boltzmann's brains do not exist and the prediction of their spontaneous formation is erroneous, or the conditions for their formation are now inappropriate in the Universe, and they will appear in later epochs, or Boltzmann's brain has a huge scale, comparable to the size of the visible universe, and we are inside it, and we cannot notice.
The latter is one of the hypotheses about the Universe as a giant self-conscious being, of which humanity is a part.