Red Herring

Episode Summary

Executive Summary: Radiolab recounts a Cold War-era Swedish naval panic: repeated detections of “Soviet submarine” sounds and sightings were eventually traced not to espionage, but to massive schools of herring releasing air bubbles from their swim bladders. The story blends military paranoia, scientific sleuthing, and the dangers of assumption, showing how secrecy and authority can harden a false theory into official truth.

Main Topics: Cold War anxiety in Sweden: The episode opens with 1981 Sweden, a neutral country living in fear of Soviet incursions across the Baltic Sea, where a stranded Russian submarine became a national shock and symbol of vulnerability. The mystery of the “typical sound”: Swedish hydrophones repeatedly picked up a classified underwater noise labeled as a definitive submarine signature, driving years of alarms and military responses despite no physical proof. Science enters the investigation: Biologist Magnus Wahlberg and colleague Håkon Westerberg were brought into a secret navy inquiry and quickly suspected a biological source rather than a military one. Herring as the culprit: The team hypothesized that herring release air from a swim bladder canal through their butts, producing bubble streams that sounded like the mysterious signal; testing eventually confirmed this in large schools of fish. Failure of institutional assumptions: The military’s top-down, secretive culture helped sustain the submarine theory for over a decade, even when evidence was weak and the sonar signatures were inconsistent with submarines. Humor and humility in science: The ending reframes the Cold War drama as a giant misunderstanding and a reminder that humans can become overconfident in their explanations, especially under pressure.

Key Arguments: The Swedish military mistook a biological underwater noise for a Soviet submarine signature for years because the data were filtered through Cold War fear and secrecy. Magnus and Håkon recognized the sound as potentially biological by comparing it to air bubbles, not machinery, and by using underwater acoustics to test herring behavior. Single-fish experiments were insufficient; only when they recorded schools of herring did the sound match the military’s observations. Institutional hierarchy and secrecy discouraged open scientific skepticism, allowing the submarine narrative to persist despite weak evidence. The sonar visuals the navy interpreted as a hidden advanced sub could plausibly have been schools of fish splitting and regrouping. The story serves as a broader caution about confirmation bias: people will gather evidence for a theory once authority and fear have already defined the conclusion.

Data Points: Year of first major incident: 1981 - A Soviet submarine ran aground/beached on the Swedish coast, triggering national alarm. Age of Magnus during first incident: 13 - Magnus recalls being a schoolboy in Stockholm when the 1981 submarine event occurred. Distance across Baltic Sea: about 140 miles - Used to describe the separation between Sweden and the Soviet Union. Year of major harbor incident: 1982 - Periscopes were reported near a Swedish naval base, leading to an extended anti-submarine operation. Duration of classified sound: 15 years - The navy’s “typical sound” remained top secret for this period before scientists heard it. Length of Swedish coastline: over 1,000 miles - Explains why coastal defense and sonar monitoring were difficult. Frequency of later incidents: 20–30 incidents every year - Even after the Cold War changed, the Swedish military kept reporting submarine sounds annually. Year the truth became official: 1999 - The navy officially accepted that the typical sound was made by herring, not submarines. Fisheries/schooling scale: square kilometer-sized schools; sometimes billions of fish - Explains why the biological sound only matched when many herring were present.

Pivotal Quotes: "The typical sound." — Magnus / narration: The classified label for the underwater signal the Swedish military believed came from Soviet submarines. "It sounds a bit like a few Donald Ducks at a very long distance." — Magnus Wahlberg: His description of the mysterious recorded sound after first hearing it at the naval base. "This is definitely not the sum." — Magnus and Håkon (internal reaction): Their immediate private conclusion after hearing the “typical sound” for the first time.

Implications: The episode shows how fear, secrecy, and authority can distort interpretation of evidence. It’s a reminder to test assumptions openly—especially when claims carry military or political consequences.