How to Build a Time Machine

For the season finale of Star Trails, we’re building a “time machine” the only way we know how: with physics, not plot holes. Drew takes a tour through the time-travel stories that shaped his 80s childhood—Back to the Future, Star Trek IV, The Time Machine, Bill & Ted, and even Disney’s wonderfully unhinged The Black Hole—and then sets them beside the actual rules of our universe. We’ll look at the real ways you can travel into the future using speed and gravity.

Along the way we’ll ride with nuclear-pulse starships, bust the myth of the Bussard ramjet, and imagine skimming just outside the maw of Sagittarius A*, the supermassive black hole at the center of the Milky Way. We’ll talk about why time only runs forward, what it really means to “move through spacetime,” why black holes make clocks crawl, and how modern quantum ideas try, and ...