[time-nuts] Gentlemen: Synchronize Your Watches!
sandeenpa at yahoo.com
Sat Nov 5 00:19:08 EDT 2016
Time may be relative, but physicists are a stickler for accuracy.
While many of us may give a few minutes’ grace to the timepieces in our homes, one group of scientists has successfully synchronized a pair of optical clocks to within a million billionths of a second.
By measuring time to such a fine point of accuracy, physicists could ultimately change the length of a second.
Scientists have managed to synchronize two optical clocks 12 km apart to within a quintillionth of a second. By measuring time to such a fine point of accuracy, physicists could ultimately change our longstanding units for how time is measured
World's most accurate clocks are synchronised to a quadrillionth of a second - and it could change how we define time
SUPER ACCURACTE CLOCKS
Physicists in the US fired a laser beam between two buildings more than seven miles (12 km) apart.
At either end they used optical clocks to detect regular laser pulses every five nanoseconds – five billionths of a second – just like ticking of a clock.
The two clocks send the pulses to each other, with the arrival time measured at each clock.
The measurements were so fine that they even took the swaying of the buildings and air turbulence into account, to account for tiny changes which could affect the arrival times of the pulses.
Once the tiny differences were taken into account, the clocks could be synchronized to within a quadrillionth of a second.
In order to make such precise measurements, a team led by physicists at the US National Institutes of Standards and Technology (NIST) in Colorado fired a laser beam from one building to another, more than seven miles (12 km) away.
At either end they used optical clocks, which work in a similar way to microwave clocks, using atoms or ions which oscillate about 100,000 times higher than microwave frequencies, in the optical, or visible, part of the electromagnetic spectrum.
Using a specialized laser tool called a frequency comb, they were able to detect regular laser pulses every five nanoseconds – five billionths of a second – just like ticking of a clock.The two clocks send the pulses to each other, with the arrival time measured at each clock.The team’s measurements were so minute that they even took the swaying of the buildings and air turbulence into account, to account for tiny changes which could affect the arrival times of the pulses.
Accounting for these differences meant they could be subtracted from any difference in arrival times to synchronize the two to within a quadrillionth of a second.
Once we measure the difference of the clock times, we can speed up or slow down the clock at site B so that it agrees with the clock at site A to within femtoseconds,’ explained Laura Sinclair, a physicist at the NIST.
Writing in the journal Applied Physical Letters, the team reports the how they were able to maintain such a fine degree of accuracy in spite of such large distances.More accurately keeping would enable financial networks to use more precise time stamps, so handle even more transactions in shorter amounts of time. It would also allow GPS and other satellite-based navigation systems to provide even more precise location information
‘The 12 km of turbulent air results in massive distortions of the laser beams, yet the two clocks agree in time to 20 digits,’ said Sinclair.
The physicist added: ‘How far, in distance, can we really go?
‘If we want to someday redefine the second so that it’s based on an optical standard instead of a microwave standard, we’ll need to be able to link up the world’s best clocks and then distribute that time information.’
Earlier this year, researchers in Germany devised the method to measure precisely how long a second is with far more accuracy.
It could mean the definition for what a second actually is will change by an incomprehensibly tiny amount - just a fraction of a quadrilltionth of a second.
The change will see the amount of error in estimating the length of a second reducing from 0.25 quadrilliionths of a second - that is 0.25 with 15 zeros in front of it - by a factor of ten.Reducing the amount of uncertainty in how long a second is means physicists will be able to make much more accurate estimates of how long events take.
In context, it means such clocks would only have lost about 100 seconds since the universe began, 14 billion years ago.
Read more: http://www.dailymail.co.uk/sciencetech/article-3834518/World-s-accurate-clocks-synchronised-quadrillionth-second-change-define-time.html#ixzz4MtN7WvBJ
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