中國(guó)網(wǎng)站品牌欄目（頻道）
格林尼治時(shí)間以英國(guó)首都倫敦市郊格林尼治天文臺(tái)命名，作為全球通用的時(shí)間參考標(biāo)準(zhǔn)已使用120多年。如今，這一以地球自轉(zhuǎn)為依據(jù)的“世界時(shí)”可能由以原子振蕩周期為依據(jù)的“原子時(shí)”徹底取代。上世紀(jì)70年代一項(xiàng)國(guó)際協(xié)議確定世界時(shí)和原子時(shí)兩種時(shí)間計(jì)量系統(tǒng)。世界時(shí)受地球自轉(zhuǎn)速度減緩影響，有一定誤差；原子時(shí)用原子能級(jí)躍遷振動(dòng)頻率計(jì)時(shí)，1000萬(wàn)年誤差1秒，相對(duì)精準(zhǔn)。一些研究人員呼吁廢除時(shí)間計(jì)量系統(tǒng)的“雙軌制”，以原子時(shí)作為單一計(jì)時(shí)標(biāo)準(zhǔn)。50多名研究人員11月3日至4日在倫敦市郊開會(huì)，討論相關(guān)議題。國(guó)際電信聯(lián)盟定于明年1月在瑞士日內(nèi)瓦表決是否以原子時(shí)替代世界時(shí)。不過(guò)，這一提議無(wú)疑會(huì)傷害英國(guó)人的“國(guó)家自豪感”。英國(guó)有官員表示，我們應(yīng)該以地球自轉(zhuǎn)為依據(jù)，依照人們所感知的真實(shí)時(shí)間來(lái)計(jì)時(shí)。
 |
|
Royal Greenwich Observatory. |
For more than 120 years, Greenwich Mean Time (GMT) has been the international standard for timekeeping, but it is now under threat from a new definition of time itself based not on the rotation of the Earth, but on atomic clocks.
In January the International Telecommunication Union will meet in Geneva to vote on whether to adopt the new measure, despite protests from Britain.
The two-day meeting of about 50 experts at a country house north-west of London, under the aegis of the prestigious Royal Society, on Thursday and Friday will look at some of the issues involved.
Predictably the question has hurt Britain's national pride - particularly when the British believe their old rivals France are leading the push to change from GMT to the new time standard.
"We understand that in Britain they have a sense of loss for GMT," said Elisa Felicitas Arias, director of the time department at the France-based International Bureau of Weights and Measures (BIPM), which pushed for the change.
GMT is based on the passage of the Sun over the zero meridian line at the Greenwich Observatory in southeast London, and became the world standard for time at a conference in Washington in 1884.
France had lobbied for Paris Mean Time at the same conference.
In 1972 it was replaced in name by Universal Coordinated Time (UTC) but that essentially remained the same as GMT.
UTC is based on about 400 atomic clocks at laboratories around the world but then corrected with "leap seconds" to align itself with the Earth's rotational speed, which fluctuates.
Tiny variations
But the tiny variations between Earth speed and atomic speed have become a problem for GPS, the global positioning systems and mobile phone networks on which the modern world relies.
"These networks need to be synchronised to the millisecond," Dr Arias said.
"We are starting to have parallel definitions of time. Imagine a world where there were two or three definitions of a kilogram."
The meeting in London will look at the implications of abolishing the leap seconds and moving fully to atomic time.
That would see atomic time slowly diverge from GMT, by about one minute every 60 to 90 years, or by an hour every 600 years, and there would need to be "leap minutes" a couple of times a century to bring the two in line.
The proposal would then formally be voted on in Geneva.
Damaged pride
The potential loss of GMT has prompted soul searching in the British press, particularly at a time when the country is itself considering switching to British Summer Time, one hour ahead of GMT, on a permanent basis.
The Sunday Times said GMT had "symbolised Britain's role as a Victorian superpower" but that "just as that role has inexorably diminished, so GMT itself could in effect disappear".
British science minister David Willetts has opposed the plan, saying it has become more than just a scientific row.
"This is primarily a finely balanced scientific argument but I do detect undercurrents of nationalism," he said.
"Britain's position is that we should stick to real time as experienced by humans, which is based on the Earth's rotation, not atomic clocks.
"Without leap seconds we will lose contact with the reality of Earth's rotation. Eventually our midnight would happen at noon."
China meanwhile is said to oppose the change on the grounds that its astronomers want to retain Earth-rotation-based time.
相關(guān)閱讀
(Agencies)
（中國(guó)日?qǐng)?bào)網(wǎng)英語(yǔ)點(diǎn)津 Helen ）
 |
 |
 |
 |
 |
 |
久久久无码人妻精品无码_6080YYY午夜理论片中无码_性无码专区_无码人妻品一区二区三区精99
