時(shí)間和磁場史詩般的巧合

For the first time in centuries, compasses in Greenwich are about to point directly at true north: an epic coincidence of time and magnetism that hasn't taken place for some 360 years.

幾個(gè)世紀(jì)以來，格林威治的羅盤第一次將指向真北:一個(gè)360年來從未發(fā)生過的時(shí)間和磁場的史詩般的巧合。

This serendipitous occurrence – which is set to occur within the next fortnight – serves as a startling reminder of how Earth's magnetic north pole is constantly wandering, unlike the fixed 'true north' of Earth's geographic north pole.

這一意外事件——預(yù)計(jì)將在未來兩周內(nèi)發(fā)生——令人吃驚地提醒人們，地球的磁北極與地球地理北極固定的“真北極”不同，是如何不斷地漂移的。

The angular difference between those two different points is called magnetic declination, and while the gap might not be something ordinary people spend a great deal of time thinking about, it's a disparity that can last for centuries at a time.

這兩個(gè)不同點(diǎn)之間的角差被稱為磁偏角，雖然這種差距可能不是普通人花大量時(shí)間思考的問題，但這種差距一次可以持續(xù)數(shù)百年。

For hundreds of years now in the UK, due to Earth's shifting magnetic north pole, declination has been negative, meaning compass needles have been pointing west of true north.

幾百年來，由于地球磁極的移動，英國的磁偏角一直是負(fù)的，這意味著指南針一直指向正北的西面。

But nothing lasts forever. The agonic – an invisible line that connects Earth's north and south magnetic poles (and which represents zero declination wherever it passes through) – has been moving westward at approximately 20 kilometres (about 12 miles) per year.

但沒有什么是永恒的。條不可見的線連接著地球的南北磁極(在它經(jīng)過的任何地方都代表零赤緯)，一直以每年約20公里(約12英里)的速度向西移動。

(British Geological Survey/Twitter)

At that rate, it's set to pass through Greenwich this month – the historic site of the Greenwich Royal Observatory – making history in the process.

按照這個(gè)速度，它將于本月通過格林威治——格林威治皇家天文臺的歷史遺址——在這個(gè)過程中創(chuàng)造歷史。

"At some point in September, the agonic will meet zero longitude at Greenwich," says geomagnetism researcher Ciaran Beggan from the British Geological Survey (BGS).

英國地質(zhì)調(diào)查局(BGS)的地磁研究人員西蘭·貝根(Ciaran Beggan)說：“在9月份的某個(gè)時(shí)候，阿戈尼奇將在格林威治遭遇零經(jīng)度。”

"This marks the first time since the Observatory's creation that the geographic and geomagnetic coordinate systems have coincided at this location."

“這標(biāo)志著自天文臺成立以來，地理和地磁坐標(biāo)系首次在這個(gè)位置重合。”

As fate would have it, it was a coincidence that when the Royal Observatory was founded in the late 17th century – at the decree of King Charles II – compasses in Greenwich also pointed directly at true north, due to zero declination.

巧合的是，當(dāng)皇家天文臺在17世紀(jì)晚期根據(jù)查理二世國王的命令建立時(shí)，格林威治的羅盤也由于零赤緯而直接指向真北。

Ever since then, constant variations in the position of Earth's magnetic north pole due to changes in the composition of Earth's molten outer core have seen the agonic keep shifting.

從那時(shí)起，由于地球熔化的外核成分的變化，地球磁北極的位置不斷變化，導(dǎo)致了電子的不斷移動。

It's a phenomenon that's expected to endure well past this September's circumstantial synchronicity (from the perspective of compass users in Greenwich, at least).

這種現(xiàn)象預(yù)計(jì)將在今年9月的間接同步之后繼續(xù)存在(至少從格林威治羅盤用戶的角度來看)。

"By 2040, all compasses will probably point eastwards of true north."

“到2040年，所有圓規(guī)都可能指向正北的東方。”

As for the more distant future beyond that, scientists' ability to foresee the magnetic movements are limited.

至于更遙遠(yuǎn)的未來，科學(xué)家們預(yù)測磁場運(yùn)動的能力是有限的。

"It is, at present, impossible to predict how the magnetic field will change over decades to centuries," Beggan says, "so the compass may well point east of true north for another 360 years in the UK."

貝根說:“目前還無法預(yù)測磁場將如何在幾十年到幾百年的時(shí)間里發(fā)生變化。因此，在未來360年里，英國的羅盤很可能指向正北以東。”