The Allure of the Multiverse: Extra Dimensions, Other Worlds, and Parallel Universes by Paul HalpernThe Allure of the Multiverse: Extra Dimensions, Other Worlds, and Parallel Universes by Paul Halpern

The Allure of the Multiverse: Extra Dimensions, Other Worlds, and Parallel Universes by Paul HalpernThe Allure of the Multiverse by Paul Halpern delves into the scientific history of the theory that seems to have taken over pop culture. Admittedly difficult at time thanks to the relatively esoteric nature of some of the theories such as string theory or M-brane theory, and also perhaps a bit mistitled, it remains a mostly clear exploration of 20th and 21st century physics.

The book opens with what might come as a surprise to some readers who have steeped in the multiverse concept via film, TV, and books for some time now: the theory is far from universally accepted by scientists thanks to “the stark disadvantage of a lack of direct detectability.” Scientists prefer theories that can be tested, and so, as Halpern puts it, while “many theorists are willing to accept unobservable components … if it supports a promising way of explaining the basic facts of the reality we experience … there is a wide range of opinions and tastes about how seriously to take multiverse schemes.” Halpern’s own stance is to “remain cautiously open-minded about various multiverse schemes — rather than dismissing them outright,” pointing out how “what is fringe sometimes slips into vogue”, such as the concept of the fourth dimension which was once considered mystical nonsense and now is “standardly applied” in space-time calculations.

From there it’s a relatively deep dive into classical physics, particle physics and the weird world of quantum physics, with all the usual stop-offs at Newton, Einstein, Schrödinger’s Cat, the Standard Model, Bohr, Heisenberg’s Uncertainty Principle, the Big Bang, Hawking, String theory, black holes, the Higgs boson, and more. Halpern methodically lays out the questions all these are supposed to answer, then more importantly for the book’s subject, all the questions they don’t answer, which leads to the origination of Hugh Everett’s Many Worlds Interpretation, one of several multiverse theories.

One of the better elements of the book is in fact how Halpern makes clear there is more than one way to skin Schrödinger’s Cat and get to the multiverse: there’s Everett’s theory, the argument that in an infinite universe filled with finite material it’s inevitable to have multiple Earths, the theory of eternal inflation (meant to explain things like the uniformity of the observable universe), and even Nietzsche’s concept of a never-ending cycle of repeating lives and events. Another point I appreciated was how he made clear that the pop culture view of Everett’s theory doesn’t actually align with the actuality of the theory, which is far more prosaic than the idea that every decision creates another “you” out there somewhere. As Halpern notes, “the MWI would not produce dueling Kirks, bearded versus clean-shaven Spocks … battling Lokis … Rather it might distinguish between near-identical versions of a scientist witnessing one type of blip versus another type of blip.” Hardly “Avengers Assemble!”

For the most part Halpern does a good job of making this all understandable, employing the usual tools of popular science: analogy, metaphor, and of course clear, easy-to-follow language and syntax. That said, it does at times get a little hard to follow, as with this passage:

The Randall-Sundrum model attempts to resolve the cosmological constant problem by adding a large positive value to a slightly smaller negative value to produce a tiny positive value for the overall cosmological constant. The large positive value is the vacuum energy of our brane due to the baseline of quantum interactions in the Standard Model. The slightly smaller negative value is the negative cosmological constant of the higher dimensional anti-de Sitter space in which our brane resides.

The reality of course is these are abstruse concepts and lots of times writers will go too far in oversimplifying them. So this is less a criticism than simply an observation that readers may face some difficulties. That said, passages like this one are rare; for the most part the book simply requires some readerly attention.

A bit more of a criticism is the titling, which I’d say implies a more far-ranging, in-depth exploration of the multiverse in pop culture than what we get, which is mostly limited to a single chapter. So those coming for that book may be a bit disappointed. But as an exploration of modern-day physics, Halpern more than satisfies.

Published in January 2024. Our books, our movies—our imaginations—are obsessed with extra dimensions, alternate timelines, and the sense that all we see might not be all there is. In short, we can’t stop thinking about the multiverse. As it turns out, physicists are similarly captivated. In The Allure of the Multiverse, physicist Paul Halpern tells the epic story of how science became besotted with the multiverse, and the controversies that ensued. The questions that brought scientists to this point are big and deep: Is reality such that anything can happen, must happen? How does quantum mechanics “choose” the outcomes of its apparently random processes? And why is the universe habitable? Each question quickly leads to the multiverse. Drawing on centuries of disputation and deep vision, from luminaries like Nietzsche, Einstein, and the creators of the Marvel Cinematic Universe, Halpern reveals the multiplicity of multiverses that scientists have imagined to make sense of our reality. Whether we live in one of many different possible universes, or simply the only one there is, might never be certain. But Halpern shows one thing for sure: how stimulating it can be to try to find out.


  • Bill Capossere

    BILL CAPOSSERE, who's been with us since June 2007, lives in Rochester NY, where he is an English adjunct by day and a writer by night. His essays and stories have appeared in Colorado Review, Rosebud, Alaska Quarterly, and other literary journals, along with a few anthologies, and been recognized in the "Notable Essays" section of Best American Essays. His children's work has appeared in several magazines, while his plays have been given stage readings at GEVA Theatre and Bristol Valley Playhouse. When he's not writing, reading, reviewing, or teaching, he can usually be found with his wife and son on the frisbee golf course or the ultimate frisbee field.

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