I can’t be the only one here displeased by our current timeline. It’s pretty hard to experience endless COVID, debates about whether it’s genocide or just a little ethnic cleansing, and climate change conferences headed by oil executives, without feeling we would all do better in a different reality.

And like all of you, I’ve been brainwashed with sci-fi concept of multiple universes — in execrable series like "Loki" and umpteen Marvel creations of varying degrees of coherence, or cool versions like the totally bonkers and tender movie “Everything Everywhere All at Once” or the atmospheric TV series version of Philip K. Dick’s “The Man in the High Tower,” or literary fiction like Jorge Luis Borges’ 1941 short story, "The Garden of Forking Paths."

The idea of multiple universes actually dates back to the Ancient Greeks like Democritus, or even earlier to pre-Socratic philosopher Anaximander and his idea of infinite worlds, but today, science fiction creations are mostly inspired by cosmology and quantum mechanics.

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In cosmology, the study of the universe and how it came to be this way, the idea is that after the Big Bang, the early universe grew very quickly — increasing in volume by a factor of around 1078 in the first very tiny fraction of a second. And it could have done so unevenly, birthing patches of universe that behave differently than our own

“A little piece of spacetime could have grown really far away out here really, really quickly, while another piece of spacetime grew way out here, really really quickly. So they would become causally disconnected,” Dr. Nicole Yunger Halpern, a Harvard-trained physicist who now works at the Joint Institute for Quantum Information and Computer Science in Maryland, told Salon.

“It’s possible that even across the entire history of the universe so far, light would have not had enough time to reach us from the other patch [of spacetime]. So the other patch could essentially be its own little universe.”

"An atom can in some respects act as though it were simultaneously in multiple locations."

The separate patch, or bubble of spacetime (each constituting its own universe) could, in theory, feature its own physical laws. Science fiction writers tend to borrow the term “multiverse” from cosmology but apply it to concepts of multiple universes that are more directly inspired by quantum mechanics, with the universes being different branches of what’s called the wave function, which will come in handy later.

Yunger Halpern is actually a specialist in quantum information, not cosmology. In her 2022 book, “Quantum Steampunk: The Physics of Yesterday’s Tomorrow,” she looks back at the engines and motors that powered the Industrial Revolution — then understood in terms of classical thermodynamics — through the framework of quantum mechanics and quantum information, getting down to the level of the smallest particle and the nature of reality itself.

“In quantum physics, we can have quantum objects that can be in superposition of different states, for instance, an atom can in some respects act as though it were simultaneously in multiple locations.”

It’s not just that we don’t know where the atom is when it’s in this state, but that its position is technically not well defined — it’s neither here nor there. Or it’s both here and there. The wave function, mentioned above, is a mathematical description of the quantum state of this confusing bit of universe.

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This leads to the idea that our world kind of splits, or branches: there’s one world, or branch, in which the atom is over here, and another where it’s over there. This is called the Many Worlds Theory, (or Proposal, or Interpretation) of quantum mechanics, which American physicist (and avid science fiction reader) Hugh Everett came up with mid-last century, leading an adherent of........

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