Imagine an infinite number of unobservable parallel universes, each with different laws of nature. While this idea has captured imaginations for millennia — the latest example being Marvel movies — the theory of the multiverse has recently skyrocketed in popularity, even among serious scientists. Many top physicists truly believe in an infinite multiverse and consider it the best scientific alternative for explaining the fine-tuned constants of nature without an intelligent cause (or, as it is more commonly stated, without God).

The idea of the multiverse is not new. Over 2,000 years ago, the Roman philosopher Lucretius theorized that over an infinite expanse of time, atoms randomly assemble themselves into all possible arrangements — including a universe like our own. This idea was revived over a hundred years ago in 1895 by physicist Ludwig Boltzmann; only this time it was described in the more modern language of random fluctuations in the state of thermal equilibrium.

Despite its various iterations, few philosophers or scientists had taken the multiverse seriously — until 1998. Cosmologists discovered that the expansion rate of our universe is accelerating due to the extremely fine-tuned cosmological constant. Because of the clear theological implications of fine-tuning, this discovery forced modern scientists to reconsider the ancient theory of the multiverse. 

After introducing the idea of fine-tuning, this essay lays out the three basic features needed for a multiverse theory to successfully explain fine-tuning. It then analyzes and evaluates the scientific supports that multiverse scientists offer for each of its three premises. Finally, it shows why proper scientific methodology leads to the devastating measure problem and necessitates rejecting the multiverse as a viable scientific theory.

Author’s note: For the entire essay, visit our Physics to God website here. We wrote this piece as a summary of the core arguments of Season 2 of the Physics to God podcast about the multiverse.