Is There Evidence For a Vast Multiverse?

In 1987, Steven Weinberg wrote a cute little paper entitled “Anthropic Bound on the Cosmological Constant”. I say cute little paper because it feels minor in comparison to, say, electroweak unification theory that won him the Nobel Prize. Weinberg was foundational in establishing the standard model of particle physics, and represented an enormous leap in understanding how this universe works. But his little 1987 paper, though more obscure, may tell us something about how the multiverse works, and can even be thought of as evidence for the existence of an enormous number of other universes.