Pages 18 and 19, left to right: Stars: NASA, ESA, and A.
El Caracol) The Great Conch () photo (,‎ Mayan / ​ Chichen Itza ,‎ Yucatan ,‎ Mexico / ​ Giraudon / ​ The Bridgeman Art Library :‏ Copley / ​ age fotostock; Mayan observatory .‏