Conceptually, hope feels big, amorphous, hard to define exactly. But for the past few months, "To The Best Of Our Knowledge" producers have been trying anyway. Scientists, activists, futurists, theologians, artists, authors all weighed in on what they think when they hear the word "hope."
Fear about the future of the planet keeping you up at night? Aerospace engineer Robert Zubrin has a solution: it’s time to settle Mars.