In 1962, three inmates at Alcatraz Federal Penitentiary attempted one of the most daring and ingenious escapes of all time. They got out of Alcatraz, but where they ended up is still a mystery. The FBI concluded they most likely drowned. But the inmates did have a slim chance at survival, according to a few Dutch hydrologists who have reanalysed the tides that night.
The three men, Clarence Anglin, John Anglin and Frank Morris, concocted an elaborate and famous escape plan that included a homemade periscope, a raft made out of raincoats, and even dummy heads with real human hair. Once they made it out, though, they would have been at the mercy of the tides of San Francisco Bay.
At the American Geophysical Union conference this week, a group of Dutch scientists will present a reconstruction of the tides of that fateful night. Olivier Hoes of the Delft University of Technology was studying the flood risk to industrial sites around the Bay, when he realised his simulations might have some historical relevance.
Timing would have been key. If the escapees left before 11 pm and simply floated, they would have been swept out to the ocean with the tides. If they had left after midnight, the tides would have reversed, and they would have died of hypothermia swirling all night in the cold bay.
You can see for yourself in this simulation of the worst case scenarios. A dot leaves every hour, tracking the possible trajectories of a raft leaving at that time.
But if the inmates had left between 11pm and midnight and paddled north (paddles were found on an island in the bay), they would have reached the bay's entrance just as the tide was reversing, allowing the escapees to land. Ultimately, we don't know exactly when the three inmates left Alcatraz. There's a chance they got lucky, but there's a bigger chance that all their planning was ultimately foiled by tides. [AGU, BBC]