Posts Tagged ‘rotation’
“You may delay, but time will not”*…
It turns out that our feeling that things are speeding up has some basis in science…
Earth’s changing spin is threatening to toy with our sense of time, clocks and computerized society in an unprecedented way — but only for a second.
For the first time in history, world timekeepers may have to consider subtracting a second from our clocks in a few years because the planet is rotating a tad faster than it used to. Clocks may have to skip a second — called a “negative leap second” — around 2029, a study in the journal Nature said Wednesday.
“This is an unprecedented situation and a big deal,” said study lead author Duncan Agnew, a geophysicist at the Scripps Institution of Oceanography at the University of California, San Diego. “It’s not a huge change in the Earth’s rotation that’s going to lead to some catastrophe or anything, but it is something notable. It’s yet another indication that we’re in a very unusual time.”
Ice melting at both of Earth’s poles has been counteracting the planet’s burst of speed and is likely to have delayed this global second of reckoning by about three years, Agnew said.
“We are headed toward a negative leap second,” said Dennis McCarthy, retired director of time for the U.S. Naval Observatory who wasn’t part of the study. “It’s a matter of when.”…
The full story: “A faster spinning Earth may cause timekeepers to subtract a second from world clocks,” from @AP.
For (even) more on leap seconds on their history, see “Will We Have a Negative Leap Second?“, by Demetrios Matsakis (also a retired director of time for the U.S. Naval Observatory).
See also: “Climate change is altering Earth’s rotation enough to mess with our clocks” (gift article): “in that one second, the Earth rotated about four football fields”
* Benjamin Franklin
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As we muse on measurement, we might send carefully-observed birthday greetings to Sir Harold Spencer Jones; he was born on this date in 1890. An astronomer (indeed, for 23 years the tenth Astronomer Royal), he specialized in positional astronomy, particularly the motion and orientation of the Earth in space… a focus that helped him contribute to knowledge of the Earth’s rotation and improved timekeeping– efforts that led to Spencer Jones’ election (in 1947) as the first President of the Royal Institute of Navigation (which, In 1951, named its highest award, the Gold Medal, in his honor).
“Iteration, like friction, is likely to generate heat instead of progress”*…
A word of caution from the wondrous Randall Munroe (@xkcd): “Rotatation.”
* George Eliot, The Mill on the Floss
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As we resist repetition, we might send perpetual birthday greetings to Jean Bernard Léon Foucault; he was born on this date in 1819. A physicist who made an early measurement of the speed of light, discovered eddy currents, and is credited with naming the gyroscope (although he did not invent it), Foucault is best remembered for the (eponymously-named) Foucault’s Pendulum– suspended from the roof of the Panthéon in Paris– demonstrating the effects of the Earth’s rotation. Using a long pendulum with a heavy bob, he showed its plane was not static, but rotated at a rate related to Earth’s angular velocity and the latitude of the site.
In fact, essentially the same experimental approach had been used by Vincenzo Viviani as early as 1661; but it was Foucault’s work that caught the public imagination: within years of his 1851 experiment, the were “Foucault’s Pendulums” hanging– and attracting crowds–in major cities across Europe and America.
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