Podcast Summary

Podcast: Short Wave (NPR)
Episode: "Interstellar: Time Dilation And Wormholes Explained"
Date: September 9, 2025
Hosts: Emily Kwong & Regina Barber
Guest: Dr. Erin MacDonald (Astrophysicist, Scientific Advisor for Star Trek)

Overview of the Episode

This episode takes a deep dive into the science behind Christopher Nolan’s film Interstellar, focusing on its portrayal of concepts like spacetime, wormholes, time dilation, and black holes. Hosts Emily Kwong and Regina Barber are joined by astrophysicist Dr. Erin MacDonald, who helps disentangle the film’s fact from fiction while highlighting notable scientific achievements and missteps. The conversation covers the film’s realism, the real-world physics it drew from, and its impact on science communication.

Key Discussion Points & Insights

1. Environmental Catastrophe and Science Fiction Set-up

• [04:15–05:49] The film’s opening, depicting a worldwide crop blight and dust bowl, is lauded for its realism and subtle (perhaps too subtle) reference to climate change.
• Emily notes the use of actual Dust Bowl survivor footage for realism.
  • "They're showing what the Dust bowl of the 30s might have been like..." (Emily, 04:32)

2. Realism in Scientific Advisory & Black Hole Depiction

• [01:17–02:21] The role of physicist Kip Thorne as scientific consultant is spotlighted.
  • Regina highlights Thorne’s gravity research and how even her physics students were obsessed with the movie’s accuracy.
• [12:07–12:33] The film’s rendering of black holes, especially “Gargantua,” is celebrated for its accuracy.
  • "It was basically the most accurate black hole depicted by Hollywood in its time." (Emily, 12:07)
  • Dr. MacDonald emphasizes how the look aligns with real black hole images received after the film’s release.
    • "You can actually kind of see how the Interstellar black hole...would look the same, which is really, really cool." (Erin, 12:25)

3. Explaining Spacetime and Wormholes

• [06:16–08:16] Erin breaks down the concept of spacetime (four dimensions) and the visualization of wormholes.
  • The classic "folding paper" analogy from the film is discussed, emphasizing why a wormhole would look spherical in three dimensions, not just like a “hole” or “tunnel.”
    • "It's...really hard for us to conceptualize...but it would look something spherical, basically. And that's how they portrayed it in the film. Brilliantly." (Erin, 08:09)
• The concept of gravitational lensing is praised in the film’s visual effects.

4. Time Dilation: The Science Behind “One Hour = Seven Years”

• [09:15–11:15] The mechanics of time dilation, as shown in the infamous “Miller’s planet” sequence, are dissected.
  • Erin clarifies that time dilation is due to gravitational effects (general relativity), not just planetary conditions.
    • "Gravitational time dilation is...the most practical application of general relativity we have right now. Our GPS system uses this..." (Erin, 09:37)
  • GPS satellites experience time at a different rate than people on Earth due to varying depths in the planet’s gravity well.

5. Special vs. General Relativity

• [11:15–11:51] Time dilation via high speeds vs. high gravity is explained.
  • Special relativity (high speed): "as you're moving really fast...you're experiencing it [time] differently...That's special relativity."
  • General relativity (gravity/mass): "has to do with gravity and mass and the distortion of space."
  • Erin admits the movie blurs this distinction:
    • "I never understood the difference. Got it." (Emily, 11:47)
    • "Neither did the movie." (Erin, 11:51)

6. The “Spaghettification" Conundrum

• [12:56–13:42] In the final act, the film’s protagonist survives entering a black hole, defying the science of “spaghettification” (being stretched by gravity).
  • "Spaghettification should have happened...you're going to get stretched apart, much like his ship got torn apart. But then also, he should have been torn apart, and he wasn't." (Erin, 13:09)

7. Science Communication & Trust in Scientists

• [13:47–14:59] Erin shares a “hot take” on the film’s legacy in science communication.
  • "People were curious about relativity...they had never understood before. [But] it made people distrust scientists more..." (Erin, 13:59)
  • The portrayal of scientists as duplicitous is criticized, with only a few exceptions (notably Murph).

Memorable Quotes

• On the value of the film’s science:

  • "Like the most accurate depiction of a black hole in Hollywood history. That was in this film."
    — Regina Barber, 02:20

• On spacetime:

  • "We live in a four dimensional universe of space and time...we also move forward in time at 1 second per second..."
    — Erin MacDonald, 06:26

• On time dilation’s real-world application:

  • "Our GPS system uses this idea of time dilation... GPS satellites experience time slightly faster than we do, but it's like fractions of a nanosecond."
    — Erin MacDonald, 09:37

• On the film’s impact on trust in scientists:

  • "Where the film fails epically...I think it made people distrust scientists more. And that's because the scientists in the film...was duplicitous or had some weird motivation."
    — Erin MacDonald, 13:59

Notable Timestamps

• 01:05 — Introduction of Dr. Erin MacDonald
• 06:26 — Erin explains spacetime and wormholes
• 09:37 — Time dilation explained via GPS analogy
• 12:07 — Discussion of Gargantua’s visual accuracy
• 13:09 — Erin evaluates the scientific accuracy of “spaghettification”
• 13:59 — Erin critiques the film’s portrayal of scientists

Conclusion

The hosts and their guest strike a balance between playful fan discourse and serious science. Interstellar is lauded for getting many physics concepts right, thanks to real scientific consultation, but also critiqued for missed opportunities in accuracy and science communication, especially regarding representation of scientists. The episode supplies both fans and newcomers to the science behind Interstellar a welcoming, accessible entry point into complex theories, while inviting reflection on media portrayals of science.