12 min · 11 chaptersNarrated in your voice
What it's about
Randall Munroe takes ordinary tasks — jumping, digging a hole, crossing a river, mailing a package — and answers them with the most technically extreme, often absurd method possible, then works out whether it would actually work. The book argues that pushing a simple problem to its outer physical limits teaches more real science than following sensible advice, because the extremes expose exactly which constraints — energy, materials, biology — are doing the real work all along.
Read a little every day
15 min a day
1 days · done Sat, Oct 31
Read together
Start a circle and share the code — everyone sees everyone's honest place in the book. Accountability, not leaderboards.
Who it's for
- Readers who loved Munroe's xkcd or What If? and want more of his mix of physics and absurdity - Curious non-scientists who want an entry point into engineering reasoning without a textbook - Parents and teachers looking for accessible ways to make back-of-envelope science fun for kids and teens
What’s inside
- 1The Method: Worst Possible Advice as a Teaching Tool1 min
Deliberately overengineering a simple task teaches more real science than giving sensible advice, because the extremes expose exactly which constraints actually govern the problem.
- 2Jumping and the Ceiling on Human Power1 min
The limit on how high a person can jump is set by muscle biomechanics rather than effort or technique, and no amount of clever engineering around the body changes that ceiling much.
- 3Digging a Hole Is a Heat Problem Before It's a Labor Problem1 min
Digging deep is limited by rising underground temperature long before it's limited by how hard or how long you can dig.
- 4Crossing a River Is a Question of Scale, Not Cleverness1 min
The size of a body of water determines which physical trick is even possible, so a method that works on a puddle is often thousands of times too weak to work on a river.
- 5The Reactor Pool and the Gap Between Fear and Risk1 min
A nuclear reactor's cooling pool is, by the numbers, one of the cleanest and safest bodies of water to swim near, which shows how badly instinctive fear can diverge from measured risk.
- 6Tag, Surveillance, and What Perfect Information Destroys1 min
Giving a game like tag perfect real-time tracking information doesn't make it more fun, it collapses the asymmetry of uncertainty that made the game a game.
- 7Mailing a Package Is an Energy and Infrastructure Trade-off1 min
Faster shipping is fundamentally bought with more energy and more built infrastructure, so 'just make it faster' proposals like mail cannons reveal how well-optimized ordinary postal networks already are.
- 8Charging a Phone Reveals the Hidden Scale of the Power Grid1 min
The tiny amount of energy needed to charge a phone is trivial by itself, but the infrastructure required to generate, transmit, and deliver that energy reliably to billions of devices is enormous and mostly invisible.
About Randall Munroe
Randall Munroe is a former NASA robotics contractor and the creator of the webcomic xkcd. He built a following answering absurd hypothetical questions with real physics and engineering, first in the blog and book What If?, then in Thing Explainer and How To. He is known for pairing rigorous calculation with deliberately impractical conclusions.
