With the occasional nod to his greatest achievements, his exploration of the cosmos is at times a challenging, daunting ...

Carl Sagan had a bone-chilling prediction about America in 1995. A passage from his book, The Demon-Haunted World, is now trending online a day after Donald Trump’s presidential inauguration.

This story appears in the August 2017 issue of National Geographic magazine. Carl Sagan spent his childhood immersed in Mars. The future scientist, an avid reader of Edgar Rice Burroughs’s ...