Fascinating BBC News article, Time out of mind , about the body clock and time perception.
The body clock determines our most fundamental behaviours: when we wake up, go to sleep, and eat. But it also determines our physical strength and performance over a day. However basic the clock's functions seem to us today, its existence was only proved in 1962, by a French caver. Michel Siffre had been planning to study the movement of a glacier through an underground cave, when he realised the enormous potential of his experiment for the field of biology. "I had the idea of my life: I decided not to take a watch in the cave. I decided to live without time cues," he said.
Mostly, we're pretty good at estimating durations of time - how long you've been online, for example. But people also speak of "time flying" when they're enjoying themselves, or slowing right down in perilous situations such as car crash. But is there any real distortion of perceived time here, or are people re-inventing their experiences after the event? Psychologist Dr David Eagleman, of the University of Texas, recently set out to nail this assumption, and a BBC film crew was there to record it. He asked volunteer Jesse Kallus to perform a terrifying backwards free-fall of 33 metres.
The falling experiment is interesting, perception does speed up under threat. The article starts with a father and daughter whose body clocks are stuck out of phase with daylight, like permanent jet lag. I wonder if they'd be OK on European time? It takes me at least four days to completely make the adjustment when we go over to England. Coming back is a lot easier.