At age 23, Michel Siffre descended into the underground glacier of Scarasson in the French Alps. His two month experiment, conducted in sub-zero temperatures and 100% humidity, was a landmark on chronobiological research: isolated from any external influence or timepiece, he found upon resurfacing that it was not August 20, as he had calculated, but September 17. Exhaustive replications of thse conditions establish that, left to one's own devices, a human being will derail from the circadian rhythm and adapt to a 26 hour day. Explanations for this anomaly remain speculative.

Similar experiments have been held in the permanent darkness of Greenland's winter and the endless summer dayling of Tromso, Norway. The sleep lab at Stanfor University is temperature-controlled, soundproofed, pitch black with the lights off, and isolated from the earth's magnetic pull. Somewhat less exotic than a glacier, it is decorated like the guest room of a country house, with electrodes kept tastefully in the corner.

-- Scott Howard, night in practice