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Why Time Stands Still
By HENRY FOUNTAIN
Why Time Stands Still
Time marches on ‹ except when you turn your gaze toward a clock with a
second hand. Then, in what is a common illusion, the hand can appear to
have stopped, momentarily, before it moves again.
Researchers in Britain have now shown why this illusion occurs, and say
it is related to what happens when the eyes move from one fixed point to
another, known as a saccade. Vision is blurred during the hundred
milliseconds or so of a saccade, so the brain is unable to determine with
certainty whether any objects in the field of view have changed
positions. So the brain extends the perception of the target ‹ the clock,
with its second hand in a specific position ‹ back in time to the
beginning of the eye movement. This can make it seem as if the second
hand were in that position for longer than it actually is.
The researchers performed experiments using human subjects who focused on
one point on a computer screen, moved their eyes to focus on a numeric
counter that changed every second (the digital equivalent of a second
hand) and then estimated how long the first digit was on the screen
compared with the succeeding ones. The subjects consistently
overestimated the duration of the first digit.
When the experiment was altered so the counter changed position while the
eyes were moving, no time illusion was experienced. This, the researchers
wrote in the journal Nature, shows that the phenomenon is linked to the
brain's assuming that the target is fixed during the eye movement.
There's no word on whether the researchers are now turning their
attention to the question of why a watched pot never boils.
It's a fact of life in the animal world: males sometimes imitate females.
The behavior is usually seen as a mating strategy ‹ a male that mimics a
female's appearance, say, may avoid aggression by larger males and
eventually get the partner of its dreams.
But a study of male garter snakes suggests another reason for female
mimicry, and love's got nothing to do with it. It's all about staying
Biologists at the University of Sydney in Australia and the University of
Oregon studied red-sided garter snakes in Manitoba. These snakes mate in
large groups in their dens, with as many as 100 males writhing around one
or just a few females in what is known as a mating ball.
In the first day or two after emerging from hibernation, when they are
cold and slow, male snakes produce femalelike pheromones. This attracts
already warm males who form a mating ball around the just-emerged snake.
The ball, the researchers suggest in Nature, protects the weak snake from
potential predators like crows. But more important, all that pressing the
flesh warms the snake up quickly.
By attaching tiny thermal sensors to the snakes, the researchers found
that a garter could go from about 40 degrees Fahrenheit to about 70
degrees in half an hour. And when you're coldblooded, every bit of heat
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