This 1948 graphic shows sound traveling on an axis 700 fathoms down in the Atlantic.

Something unusual happens about a half mile under the sea. Ocean physics create a special zone where sound travels for hundreds, even thousands of miles. Whales use it, and cold warriors plumbed its secrets. Listen in:

This story was produced by David Schulman in 2014. It was hosted for Transistor by Genevieve Sponsler and mixed for Transistor by Josh Swartz.