Friday, February 24, 2006

Time out of mind

BBC NEWS | Magazine | Time out of mind: "We can't touch time, or smell it. Yet it is utterly inescapable. But, research shows, time is - at least partly - something we control in our heads.

Only recently did Clay discover there was a biological explanation for his and Bethany's unusual behaviour, known as ASPS, or Advanced Sleep Phase Syndrome - a disorder of the body clock that shifts their day forward.

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.

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.

If the anecdotes are correct, Jesse's perception of time would be slowed by the terrifying experience. But how could one monitor such a thing?

Mr Eagleman came up with a cunning device: the "perceptual chronometer", a wristwatch-like device which flicked blindingly fast between two LED screens.

Normally the flicker would be so fast Jesse could only see a blur. But if time slowed down for him, he might be able to discern the two different screens and read a random number on one of them.

When Jesse landed, he noted he had seen "98". Dr Eagleman checked. In fact the number was 96. Not quite spot-on, but the two numbers look very similar on a digital screen.

Further jumps got similar results - all suggesting that time did seem to slow down for Jesse during the jump.

So while time on the clock may be constant, the time in one's brain is elastic and personal - something to remember in a boring meeting when time seems to grind to a halt. Time is not simply a fourth dimension in which we exist. It's something we, at least partly, create in our minds. "

Time, a four-part series, starts on BBC Four on Sunday 26 February, at 2000 GMT.

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