St Elmo's Fire
During storms at sea, sailors saw blue-white flames dancing on the tops of their masts. They took it as a sign their patron saint was watching over them.
What was reported
Since ancient times, sailors have reported a strange glow during thunderstorms: flickering blue or violet flames on the tips of masts and rigging, sometimes with a hissing sound. Ancient Greek sailors saw it as a sign of the twins Castor and Pollux.
Later, Mediterranean sailors named it after St Erasmus, or Elmo, their patron saint, whose shrine was at Gaeta in Italy. Its appearance was often taken as a sign of protection. Magellan's crew reported it on their voyage around the world.
Explanations offered
St Elmo's fire is a kind of glowing electrical discharge, known as a corona discharge. In thunderstorms, the electric field in the air becomes strong enough to make pointed objects like masts and aircraft wings glow. It is harmless in itself, but shows that the air is highly charged.
- When
- Reported since ancient times
- Where
- Gaeta and the Mediterranean, Italy
- Witnesses
- Sailors through the ages
- Status
- Explained
Famous cases are real, widely reported events. Each file sets out what witnesses said and the explanations that have been offered, without taking a side.