Bill Nye, Neil DeGrasse Tyson, doctor turned actor Ken Jeong, science fiction director James Cameron, former NASA astronaut Scott Kelly and neuroscientist Anil Seth answer the most interesting science questions from Twitter. Do your guts float in space? How do you know if you're an alien? Can you punch specific memories out of your brain? What exactly is a tractor beam? If humans evolved from monkeys, why are there still monkeys?