53 pages • 1 hour read
Randall MunroeWhat If?: Serious Scientific Answers to Absurd Hypothetical Questions
Nonfiction | Book | Adult | Published in 2014A modern alternative to SparkNotes and CliffsNotes, SuperSummary offers high-quality Study Guides with detailed chapter summaries and analysis of major themes, characters, and more.
Themes
Absurd Questions and Useful Answers
Most questions about science sound relatively normal: “How can a submarine crew stay underwater for weeks?” “Why do helium balloons rise?” “What causes rainfall?” Scientists can straightforwardly answer these questions. The questions are sometimes downright weird: “How long could a nuclear submarine last in orbit?” (78). “How long of a fall would I need in order for [a helium] balloon to slow me enough that I could land safely?” (150). “What if a rainstorm dropped all of its water in a single giant drop?” (274). The author of What If? specializes in these questions; his answers take advantage of their weirdness to demonstrate interesting aspects of the world that ordinary questions and answers might not reveal.
Chapter 67 answers a question about a bullet made of solid neutrons—a material found only in super-dense neutron stars—saying it would be as heavy as the entire Empire State Building and, within inches of it, would have such concentrated gravity that it would capture a person and not let go. The weird question permits the author to describe the forces involved in neutron stars by describing the effects a thimble-full of the stuff would have on Earth.
A question about daring to swim in a pool containing spent nuclear fuel, asked in Chapter 3, opens up an opportunity for the author to explain that water is an excellent filter for radiation and that a swimming pool keeps a swimmer safer from radiation harm than when she stands next to the pool. The same safety applies to someone swimming at the top of a spent-fuel pool, which makes clear, with an odd example, just how safe water is: “You may actually receive a lower dose of radiation treading water in a spent fuel pool than walking around on the street” (11-12).
Nearly every chapter contains an example of some weird property of nature that helps readers understand the world around us. The very weirdness of these facts helps us better understand the universe's breadth and depth. Thus, though the questions are extreme, the answers are surprising in ways that improve our understanding of the physical world.
Extending Things to Their Limits
The primary explanatory technique used in What If? involves multiplying the size of things to show the range of possibilities for matter and energy in the universe. By doing this, the author adds perspective to readers’ understanding of physics.
Scale is multiplying the size of something; in thought problems, spatial scale increases or decreases the size of an object to consider its properties at various sizes. The author, trained in math and physics, is handy with the arithmetic of scale, and he uses it to vary tremendously the size of the phenomena he describes. He then lists what would happen at that scale, demonstrating the effects of size changes in physical objects or processes. This gives readers a sense of how things behave differently when very large or small.
Scale helps the author explain the reasons for his answers to odd questions about physics. He imagines, for example, a hair dryer switched on inside a one-meter-square box and describes how hot the box would get as the power running through the dryer scales up. Increasing the dryer’s wattage millions of times quickly puts the entire thought experiment well past human technology’s known abilities with materials; this, by itself, is instructive, as it sets practical limits on what people might be able to accomplish with electric power and materials.
Scaling illustrates the effects of enormous amounts of power when focused on small areas; this, in turn, provides readers with analogies for specific events, like nuclear-bomb detonations, that loom as possibilities in the background of their lives. A baseball traveling inside a stadium at 90% of the speed of light, for example, would destroy much of the surrounding city, while “a growing fireball would rise into a mushroom cloud” (9).
Chapter 39 uses two extremes to illustrate the strangeness of neutrinos: their infinitesimally small chances of interacting with anyone or anything and the enormous size of an event that would cause those interactions to prove lethal. Millions of trillions of neutrinos pass through a person over several years before a single one interacts with an atom in their body. Only a supernova, the most violent event in the universe, going off at the distance of our sun, would release enough neutrinos to kill a person who’d already be dead from the explosion. The upshot is that neutrinos are everywhere but have almost no effect and, on their own, perhaps never will.
By describing ordinary things at extraordinary scales, the author vividly depicts the range of the possible in our universe. This gives readers a better perspective on how things work at different sizes; with that knowledge, they also improve their intuitive grasp of the basic principles on which ordinary objects behave.
The Strangeness of Things
People are good at gauging things in their local world: the weather, distances walked, the number of houses on their block. They’re poor at imagining things well outside their everyday experiences, such as the vacuum of space or the gravitational pull of extremely dense matter. Because they’re so unusual, such facts tend to amaze us with their strangeness. Part of What If?’s purpose is to bring out the weirdly astounding nature of the wider universe.
Airplanes seem to fly effortlessly in the sky, but without air—for instance, on a planet with no atmosphere, as described in Chapter 30—planes would be unable to fly at all. Even with atmospheres, most planets would quickly crush or freeze an airplane. Knowing this reminds us that mechanical flight depends on certain particular aspects of the environment around us, and we’re struck by how rare such conditions actually are in the solar system.
It's hard to imagine the closeness of outer space to our lives. On the other hand, it’s easy, on a clear day, to look across a valley 62 miles wide, yet that’s how close outer space is. The author points out that outer space is closer than the sea for many major cities near the coast (188-89). Knowing this provides a stunning sense of how thin our oasis of life is and how immense the realm is beyond it.
When he imagines, for example, laser pointers that emit light with the intensity of the sun—or describes how a thimbleful of a neutron star would behave on Earth—the author offers a glimpse into the nature of the gigantic processes churning away, all around us, in the universe at large.
It’s not enough merely to take an inventory of amazing facts about reality beyond Earth. Even the ordinary, everyday world contains, here and there, astonishing things. For example, Chapter 39 describes neutrinos—the ghostly particles that are everywhere yet rarely interact with the rest of the universe—pouring daily through our bodies, tens of trillions of them every second, while we work and talk and sleep, yet they almost never touch us. Elsewhere, he describes how much water there is in a common thunderstorm, an amount that, were it released all at once, would destroy miles of the Earth’s surface.
Not only do the unusual facts presented in the book stun the imagination, but some also go far beyond our ability to imagine them at all. That, in itself, is the most amazing realization readers can derive from a book made of amazing information about the world we live in.
