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 mostly fail, to sneak backward time travel in through the side door without breaking causality.

In the second half of the episode, we park the starship and focus on the actual sky. December is one of the richest observing months of the year, so while the podcast takes a short holiday break, you’ll have a clear roadmap: the final Cold Supermoon of the year, the Geminid and Ursid meteor showers, Mercury’s dawn cameo, Jupiter and Saturn in the evening, and the full cast of winter constellations. We’ll lay out a simple three-session observing plan to carry you through the month: supermoon and giants, Geminid weekend, and a quiet solstice night under the Ursids.

It’s an episode about time travel that ends with the most accessible time machine we have: walking outside, looking up, and catching ancient photons from the deep past on a cold December night.

Connect with us on Bluesky @startrails.bsky.social, or if you prefer listening on YouTube, visit our channel @TheStarTrailsPodcast.

If you're enjoying the show, consider sharing it with a friend! Want to help? Buy us a coffee!

Podcasting is better with RSS.com! If you're planning to start your own podcast, use our RSS.com affiliate link for a discount, and to help support Star Trails.