Unexplainable: "A Strange Signal from Space" – Detailed Summary

Introduction

In the March 5, 2025 episode of Unexplainable, hosted by Vox, the team welcomes Julia Longoria as a special guest. Julia, known for her work on acclaimed series like More Perfect, Rabbit Hole, and Radiolab, is set to launch her new series, All About AI, and will soon join the Unexplainable team permanently. The episode adopts a game show format where Julia engages with the hosts to unravel scientific mysteries.

Game Show Format

The episode features the game show segment "Unexplainable or Not," where Julia is presented with three scientific mysteries. Two remain unsolved, while one has recently been deciphered. Her task is to guess which mystery has been solved. The team comprises Meredith Hodna, Bird Pinkerton, and Ann, each bringing unique insights to the mysteries at hand.

Mystery One: Weird Ocean Holes (Presented by Bird Pinkerton)

Bird introduces the first mystery, focusing on enigmatic holes discovered on the ocean floor by the National Oceanic and Atmospheric Administration (NOAA). In 2022, a NOAA ship exploring the Mid Atlantic Ridge at a depth of 2,500 meters (1.5 miles) encountered a series of almost rectangular holes aligned in a straight row, reminiscent of "a row of stitches" (03:50). These formations, also observed in 2004, bear similarity to fossilized rock holes, suggesting a natural, possibly tectonic origin.

Despite theories ranging from gas bubble activity to the actions of unknown burrowing organisms, environmental DNA analyses yielded no matches in existing databases, leaving the phenomenon unexplained (05:31). Julia expresses skepticism about theories like gas bubbles forming such precise shapes, indicating the mystery remains unresolved (07:15).

Mystery Two: Roman Concrete Durability (Presented by Meredith Hodna)

Meredith delves into the second mystery concerning the extraordinary longevity of Roman concrete. Structures like the Pantheon’s unreinforced dome have withstood the test of time and harsh marine environments, puzzling modern scientists. Contemporary concrete typically has a lifespan of 50 to 150 years, whereas Roman concrete has lasted over two millennia (08:35).

The mystery extends beyond mere material composition; it involves understanding the unique chemical processes employed by the Romans. Factors such as the use of specific volcanic ash and unconventional mixing techniques have been hypothesized but not fully explained. Julia humorously remarks on the precariousness of modern infrastructure built on "shaky foundations," highlighting the contrast with ancient Roman engineering (12:55).

Mystery Three: The Wow Signal (Presented by Host)

Inspired by Julia’s experience with Radiolab, the host introduces the third mystery: The Wow Signal. Detected in Ohio in the 1970s by the Big Ear Radio Telescope, the signal was a single, narrow-frequency spike that has never been replicated or fully explained (13:00). Its frequency coincides with hydrogen emissions, a universal constant that made it a candidate for extraterrestrial communication (14:05).

Despite excitement, Dr. Yvette Sendis, a radio astronomer from the University of Oregon, remains unconvinced by the alien hypothesis. She suggests potential terrestrial causes such as satellite interference, though these explanations don't perfectly account for the signal's characteristics (16:32). The mystery persists, leaving Julia uncertain about its resolution (18:06).

Guessing Session and Revelation

Post-commercial break, Julia attempts to guess which mystery has been solved. She opts for The Wow Signal, influenced by her intrigue with space phenomena. However, the reveal comes that Roman concrete is the solved mystery. Despite her incorrect guess, Julia receives an engaging explanation of how Roman concrete's durability was uncovered (23:02).

Solution to Roman Concrete Mystery

Meredith Hodna elucidates the breakthrough discovery by Professor Admir Macšic of MIT. Analysis of ancient Roman concrete revealed millimeter-scale calcium-rich nuggets distributed throughout the material (24:25). Unlike modern homogeneous concrete, these heterogeneous nuggets enable a self-healing process: when cracks form and water infiltrates, the calcium dissolves and recrystallizes, effectively sealing the cracks and preventing further degradation (27:31).

This chemical ingenuity explains the unparalleled resilience of Roman structures and offers a pathway to enhancing modern concrete by introducing self-healing properties, potentially reducing environmental impact and extending infrastructure lifespans (28:07).

Unexplainable Series Trailer: "Good Robot"

In anticipation of her new series, Julia shares a trailer for "Good Robot," which explores the multifaceted implications of artificial intelligence. The trailer features imaginative perspectives from experts, portraying AI as both a potential savior and a harbinger of apocalypse, reflecting the complex emotions surrounding AI advancements (31:35).

Conclusion

The episode wraps up with accolades to Julia for her contributions and a teaser for her upcoming series. The team credits the production crew, acknowledges departing members, and invites listeners to engage with future mysteries and episodes.

Notable Quotes:

• Julia on emotions while tackling mysteries: “I am shaking in my boots. I'm terrified.” (01:37)

• Meredith on the significance of Roman concrete: “Roman concrete is literally healing itself.” (27:44)

• Julia's humorous reflection on modern infrastructure: “I didn't quite realize we were building our societies on like such shaky foundations.” (12:27)

• Host on the Wow Signal’s potential extraterrestrial origin: “I'm convinced that the wow. Signal certainly has the potential of being the first signal from extraterrestrial intelligence.” (15:41)

Key Takeaways:

• Ocean Holes: Mysterious, intentional-looking rectangular holes on the ocean floor remain unexplained, with current hypotheses failing to provide definitive answers.

• Roman Concrete: The ancient Roman technique involved calcium-rich nuggets that enable self-healing, offering insights to revolutionize modern concrete durability and environmental sustainability.

• Wow Signal: An enigmatic radio signal from the 1970s continues to elude conclusive explanations, maintaining its status as a tantalizing prospect for extraterrestrial communication.

Final Thoughts

This episode of Unexplainable seamlessly blends scientific inquiry with engaging storytelling, inviting listeners to ponder some of the most intriguing mysteries of our time. Julia Longoria's participation adds depth and anticipation for her forthcoming contributions to the series.