What if you built a billion-story building?

Get a copy of What If? 2 and Randall’s other books at: https://xkcd.com/books
More serious answers to absurd questions at: https://what-if.xkcd.com/

This question came from Keira, who at age four and a half wanted to build a billion-story building. Actually, it came from Keira’s dad, who wanted to help Keira appreciate how big and difficult such a project would be.


Credits
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Randall Munroe | Narrator
Henry Reich | Writer & Director
Lizah van der Aart | Illustration and Video Editing
Ever Salazar | Chief Chaos Controller
Know Art Studios | Music & Sound Effects

What If? The Video Series is the official adaptation of the What If? books by Randall Munroe and is produced by Neptune Studios LLC.

Randall Munroe is the author of the New York Times bestsellers What If? 2, How To, What If?, and Thing Explainer; the science question-and-answer blog What If?; and the popular web comic xkcd (https://xkcd.com). A former NASA roboticist, he left the agency in 2006 to draw comics on the internet full time.

Henry Reich is the creator of MinutePhysics and executive producer of MinuteEarth and MinuteFood and founder of Neptune Studios LLC (the parent company for all three youtube channels).

©2025 xkcd, inc.