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Leap second to keep us in sync with Earth
By Yang Jian |
March 19, 2012, Monday
|
Print Edition
Print Edition
PEOPLE in China will gain an extra second at 7:59:59am on July 1, the country's time service authority announced over the weekend, to keep official time in line with the Earth.
A leap second will occur after 7:59:59am Beijing time across the world before it's 8am, according to the Coordinated Universal Time, the National Time Service Center said.
The time on computers and mobile phones can be adjusted automatically as the center will send signals to all the electronic terminals to adjust the time, while the stock exchanges and financial institutes will also add a second automatically.
"The leap second will have no impact on our daily lives," said Dong Shaowu, director of the time frequency reference laboratory office of the center affiliated to the Chinese Academy of Sciences.
Leap seconds can prevent atomic clocks from speeding ahead of solar time. They were introduced in 1972 to keep modern timekeepers - atomic clocks, which rely on the vibrations in atoms to provide a very accurate measurement of time - in line with the Earth.
Sometimes a leap second is added every year, sometimes not for several, with six-month's notice provided before action needs to be taken. There have been 24 leap seconds added to time. The previous one was on December 30, 2008.
The time of China's satellites, including the Tiangong-1, a module of the country's planned space station, will be adjusted by ground-control centers to pull them into sync, said Dong.
"The launch of Shenzhou-9 spacecraft that is scheduled between June and August to dock with the 8.5-ton orbiting Tiangong-1 module will also be unaffected as long as the launch would not be set on the leap second," he said.
After that, China will launch Shenzhou-10 spacecraft next year to send two or three astronauts into the module, the China Aerospace and Technology Corporation has said.
Some countries, including the United States and France, have been pushing to abolish the leap second because it might cause problems, especially for navigation systems. They say machines shouldn't any longer be tethered to the imprecise cycle of sunrise and sunset.
But critics warn that scrapping the leap second would break the last link between the passing of time and the course of the sun across the sky.
A leap second will occur after 7:59:59am Beijing time across the world before it's 8am, according to the Coordinated Universal Time, the National Time Service Center said.
The time on computers and mobile phones can be adjusted automatically as the center will send signals to all the electronic terminals to adjust the time, while the stock exchanges and financial institutes will also add a second automatically.
"The leap second will have no impact on our daily lives," said Dong Shaowu, director of the time frequency reference laboratory office of the center affiliated to the Chinese Academy of Sciences.
Leap seconds can prevent atomic clocks from speeding ahead of solar time. They were introduced in 1972 to keep modern timekeepers - atomic clocks, which rely on the vibrations in atoms to provide a very accurate measurement of time - in line with the Earth.
Sometimes a leap second is added every year, sometimes not for several, with six-month's notice provided before action needs to be taken. There have been 24 leap seconds added to time. The previous one was on December 30, 2008.
The time of China's satellites, including the Tiangong-1, a module of the country's planned space station, will be adjusted by ground-control centers to pull them into sync, said Dong.
"The launch of Shenzhou-9 spacecraft that is scheduled between June and August to dock with the 8.5-ton orbiting Tiangong-1 module will also be unaffected as long as the launch would not be set on the leap second," he said.
After that, China will launch Shenzhou-10 spacecraft next year to send two or three astronauts into the module, the China Aerospace and Technology Corporation has said.
Some countries, including the United States and France, have been pushing to abolish the leap second because it might cause problems, especially for navigation systems. They say machines shouldn't any longer be tethered to the imprecise cycle of sunrise and sunset.
But critics warn that scrapping the leap second would break the last link between the passing of time and the course of the sun across the sky.
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