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Star Trails: A Weekly Astronomy Podcast · Single Malt Sky

How to Build a Time Machine

·29 min·1 clip
Near a black hole, one hour for me might equal days, weeks, or even years back home.
A night-sky guide becomes a thought experiment. Drew starts with familiar time-travel stories, then points to relativity as the closest thing physics has to real clock-bending machinery. First, the hard limit: nothing with mass reaches light speed, so the episode hangs out just below it. Proxima gives the math somewhere to land. At 99 percent of light speed, the ship still takes 4.28 years by Earth's clock, while the travelers feel roughly seven months. Push to 99.999 percent and Earth waits just over four years for one leg, but the crew gets about a week. That is forward time travel, just without the shiny machine. A round trip leaves Earth about 8.5 years older while the travelers age only about two weeks. Then gravity gets its turn. Drew explains that clocks run slower deeper in a gravitational well, which means your feet age a tiny bit slower than your head. The solar system is not much help. A close solar orbit might buy a couple seconds and a serious frying; Jupiter offers only a few microseconds. For real leverage, the episode needs black holes and neutron stars, where a day could mean minutes or hours of dilation. Sagittarius A is the big example, with four million times the mass of the Sun at the Milky Way's center. After all that, the show comes back down to December observing, holiday wishes, and a quiet look at the actual sky.

As heard by us

A steady walk from time travel and relativity into extreme gravity and practical skywatching.

The season finale keeps the time machine question in view, but it spends most of its time on the physics behind it. Drew moves from pop culture time travel into Einstein's two theories of relativity, then into the equations and limits that make the idea feel at once distant and…

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Why you'd press play

Time travel, relativity, and a December sky preview in one patient listen.

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