What If? by Randall Munroe Review: Science Meets Absurdity With Rigorous Delight

Published by Dey Street Books on September 2, 2014, What If?: Serious Scientific Answers to Absurd Hypothetical Questions grew out of Randall Munroe's xkcd science question-and-answer blog, where fans of the webcomic began submitting increasingly strange hypotheticals. The book collects the most popular answers from that blog alongside entirely new questions, and Munroe treats each one with full analytical seriousness: running computer simulations, working through differential equations, poring over declassified military research memos, and consulting nuclear reactor operators. The result is a structured Q&A reference work in which the questions are absurd — What if you tried to hit a baseball pitched at 90 percent the speed of light? If everyone on Earth jumped simultaneously, what would happen? What if every human had exactly one soul mate? — and the answers are grounded in real physics, chemistry, biology, and mathematics. Chapters include explorations of topics ranging from draining the world's oceans to constructing a periodic table out of actual elements, and the answers are accompanied by Munroe's signature xkcd-style comics throughout. The book also features recurring "Weird (and Worrying) Questions from the What If? Inbox" interludes, dedicated to questions too strange or alarming even for a full treatment.

Munroe's credentials are not decorative. He studied physics at Christopher Newport University, then built robots at NASA Langley Research Center before leaving in 2006 to produce xkcd full-time. That background shapes what distinguishes What If? from lookalike popular-science titles: the methodology is the joke and the substance simultaneously. Where many science-communication books explain phenomena and then invite wonder, Munroe inverts the process — the absurdity of the premise forces the reader through the actual underlying mechanics of lightning, orbital mechanics, thermodynamics, and relativistic physics in order to arrive at an answer. The results, as the publisher's description notes, "often predict the complete annihilation of humankind, or at least a really big explosion," which is both accurate and part of the appeal.

One published reviewer, writing at length about the book's approach, observed that "Munroe's drawing style is like his intellectual style — spare, efficient, and winning," and that the answers collectively demonstrate "how to break down a problem, use assumptions and data, model out an answer, and contemplate consequences." That same reviewer described the experience as "one of my favorite journeys… from the ridiculous to the sublime," a characterization that captures how the chapters illuminate specific scientific phenomena — why temperature in space is a fraught concept, how to calculate momentum for a rocket engine turned inward on a submarine — as a byproduct of chasing a silly premise to its logical end. The xkcd comics integrated throughout are not supplementary decoration; they are credited in the publisher's materials as central to how the book communicates. A 10th-anniversary edition, featuring new two-color annotations and expanded illustrations, later extended the book's reach, suggesting sustained demand well beyond the initial publication.

The book's format is episodic by design — each chapter is largely self-contained — which makes it excellent for dipping in and out, but means there is no cumulative narrative or structured curriculum for readers hoping to build knowledge systematically. Someone seeking a conventional popular-science book with a linear argument or progressive depth will find the chapter-to-chapter structure deliberately loose. Additionally, the "Weird (and Worrying) Questions" interludes, while comedic, deliberately sidestep full scientific treatment; readers drawn in by the rigorous chapters may find those sections a tonal detour rather than a payoff. The book is also anchored in questions generated by xkcd's audience, which skews toward readers already comfortable with a certain flavor of internet-native, physics-adjacent humor — readers who do not share that sensibility may find the comedic register less accessible than the science itself.

What If? occupies a well-earned position as a New York Times bestseller and a recurring recommendation across popular-science reading lists. It is designed for curious general readers, science enthusiasts, and fans of Munroe's webcomic, but its accessible framing of real scientific concepts — from how lightning propagates to the mechanics of relativistic collisions — also makes it a credible gateway for younger readers developing an interest in physics and quantitative reasoning. The bibliographical references (pages 299–303) indicate that the humor never came at the cost of sourcing. For readers who want popular science that is neither dumbed down nor self-serious, and who are drawn to the question of what genuine scientific thinking actually looks like when applied without restraint, this is one of the more distinctive titles in the genre.