PHOTOGRAPHY and ILLUSTRATION CREDITS

♥ heavy object rising to top, illustrations by The New York Times.

♥ census taker, photo by Cheryl Gerber.

♥ elderly man, illustration by Stuart Goldenberg.

♥ charts, illustrations by Jessica Hagy.

♥ rabbit, illustration by Xianfeng David Gu and Shing-Tung Yau.

♥ fingers, number sets, and subsets, illustrations by The New York Times.

♥ knots, illustration by Joan S. Birman.

♥ bubbles, photo by Tony Cenicola.

♥ Nick Patterson, photo by Jonathan Player.

♥ Ali Shamir, photo by Gabriel Bouys/AFP/Getty Images.

♥, ♠, ♣, ♦, and ♥, illustrations by Charles E. McDonnell.

♥ Terence Tao, photo by Monica Almeida Monica.

♥ treasure chest, Frank O’Connell.