The Bedtime Scientist

Episode guide

The Chunnel: A Train Ride Beneath the Sea

Under the water between England and France runs a tunnel where trains hum through the chalk. This episode rides it end to end, slowly, with the sea resting overhead.

The science, gently

  • The Channel Tunnel runs about fifty kilometers, most of it under the seafloor.
  • It was bored through soft chalk, and the two digging teams met in the middle within centimeters.
  • Trains cross beneath the sea in about half an hour, dry and calm the whole way.

Wonder together

  • What do you think the diggers said when the two tunnels met?
  • Is it stranger to fly over the sea or to ride under it?
  • What would you hum to match a train's rhythm?

Tonight's calm-down

A train under the sea cannot rush; it just holds its steady hum. Hum one low note in your head, feel it in your chest, and ride it, station by station, into sleep.