Boltzmann Brains: Out of Sight, Out of Mind

Bultzmann Brains

Contemporary physics consists of more philosophy than it does science. Whether it be multiple universes, the wave/particle duality of light or the spooky nature of quantum entanglement, the paradoxes that accompany physics seems to fall within the purview of philosophy rather than science. Perhaps the most eminent example of where science meets philosophy in the magnitude of the multiple-verse are Boltzmann Brains.

No one believes the implications of Boltzmann Brains. Rather, Boltzmann Brains illustrate the paradoxes that occur when contemporary cosmological theories are pushed to their limits. Yet to understand Boltzmann Brains requires a brief background into the nature of entropy and infinity.

The basic idea behind entropy is that a closed system increases in complexity over time. The Earth is an open system, meaning it gets its energy from the sun. Assuming the universe is a closed system, we would expect its entropy to increase with time. This being the case, the most likely state of the universe is one that consists of thermo equilibrium. Yet the universe, being sprinkled with a conglomeration of stars, is surprisingly low.

An explanation for the universe’s low entropy is that the cosmos emerged out of an improbable quantum fluctuation adrift in a mega universe consisting of thermo equilibrium. Our universe occupies a pocket within this mega universe that, when lumped together with the whole, consists of more order than disorder.

Within the magnitude of the mega universe, unlikely events are bound to occur. Some improbable events are more likely to occur than others; just as it is easier to assemble a single word by shaking a box of Scrabble letters than assembling an entire sentence. Likewise, it is more likely to assemble complex part of a universe than an entire universe, since the former is less complex than the latter.

One aspect of our universe is that it consists of bodies endowed with complex brains. Fluctuating a complex brain into existence is more probable than fluctuating an entire universe with complex brains into existence. Therefore, it is more likely that the reader of this article is a brain floating in space endowed with memories, than an actual organism that emerged through 4.5 billion years of evolution. In other words, quantum fluctuations coupled with entropy implies solipsism (the view that the world is an illusion that exists only a single mind).

In another scenario, our universe expands indefinitely, eventually reaching a state of thermo equilibrium. However, this false vacuum of space is churning with tiny quantum fluctuation. In the chaos of eternity, one of these fluctuation will eventually sprout an improbable event. One of these fluctuations could generate a Boltzmann Brain. Thus, the Boltzmann Brains paradox still prevails.

As highlighted earlier, no one actually believes the Botlzmann Brains hypothesis. Yet pinpointing where exactly the hypothesis goes awry is surprisingly difficult. The Boltzmann Brains hypothesis remains a paradox. Yet a paradox is by definition, a paradigm of the impossible. This being the case, the Boltzmann Brain paradox pushes our best cosmological theories into an abyss best deemed “the absurd.”

By Nathan Cranford


New York Times
New Scientist

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