What exactly is a Boltzmann Brain, you might ask?
Well, it all started when scientists realized that empty space wasn’t empty. There are random quantum fluctuations that occur in empty space that spontaneously pop particles in and out of existence. As the universe evolves into a more complex and high entropic version of itself, these spontaneous fluctuations could become more and more complex and resemble a hypothetical entity that is complex enough to be self-aware.
Go a little bit further into this rabbit hole, and this hypothetical entity could have false memories, false motivations and delirious dreams about being a human finding themselves living in a planet no so different the one we live in. Who is to say that you and I are not Boltzmann brains?
Some scientists, like the eminent Sean Carroll, argue such arguments are “cognitively unstable”. Some philosophers say that you can’t really be sure. The one thing that we can do is engage with reality, collect more data, make better models of the Universe, and hope that we can rule out possible versions of Boltzmann brains that we are not. That after all is what we call the scientific process.