Breeding Ethereal Cosmological Monsters: The Unavoidable Resurrection of the Boltzmann Brains

Boltzmann Brains are a metaphor for observers of the universe that may appear spontaneously in the space void, check out its surroundings, and disappear back into the quantum foam. They are theoretical monsters that emerge from equations. They were proposed in the late 20th century to test the limits of Ludwig Boltzmann’s statistical mechanics definition of entropy. Even when Boltzmann himself only speculated about the unlikely event of the spontaneous fluctuation of a universe which starts with low entropy (such as ours), the hypothetical entities were named after him because he reformulated the Second Law of Thermodynamics to define entropy statistically. In the early 21rst century the Boltzmann Brains metaphor was used also to address issues with theories that predicted an infinite and eternal universe, such as eternal inflation, which in fact predicts infinite multiverses with these characteristics. It was also linked to the anthropic principle and the so-called measurement problem in cosmology. In this last case, the entities were an instrument to discriminate between cosmological models. The consensus is that theories predicting Boltzmann Brains as the more likely observers of the universe are “bad” or wrong ones. In this conference paper I reviewed the development of these disembodied entities in cosmology and explored its uses in popular science and other disciplines. I l also presented my own creative reinterpretation of Boltzmann Brains in a novel that also deals with two big 21rst century monsters: climate change and general artificial intelligence.