If you buy a clock like this, one that says “radio controlled”,
如果你买一个这种“无线电控制”的电波钟表
you just put a battery in, and it sets itself to the correct time.
只要装上电池 它就可以自动校对时间
And it stays there, automatically, for a year or more.
然后自动运行长达一年或者更久的时间
So it can’t be receiving signals from satellites,
它不能接收卫星信号
there’s no wifi connection,
和wifi信号
there’s nowhere near enough power in here for any of that.
因为它的动力不足以支持这两种授时方式
Instead, it uses much older technology.
相反 它用到了非常古老的技术
Here at the radio transmission station in Anthorn,
这是Anthorn无线电通信站
the National Physical Laboratory, NPL, broadcasts a time signal out for the UK
国家物理实验所 简称NPL 从这里向英国发布了
in a simple enough format that
一种简单编程的时码信号
the cheap electronics inside this clock can understand it,
让电波钟表内部便宜的电子器件也能解调
and run accurately for over a year on a single double-A battery.
并且只需要一节五号电池 就可以精准运行
And at NPL’s base in London, I asked their team how it all works.
在伦敦的NPL基地 我询问了工作人员它的原理
– What we have in Anthorn are some very high-end cesium atomic clocks,
在Anthorn无线电通信站有一些高端的铯原子钟
like the ones we have down here.
比如我们放在这里的这些
We broadcast from there, we monitor the signals at NPL
我们从这里发布信号 然后在NPL监测
and accordingly put out steers to those clocks to correct for any any change.
如果有任何改变 我们就会向这些铯原子钟发出相应的指示进行修正
It’s a very low frequency, 60 kilohertz,
它利用低频（60千赫）载波方式发射信号
it has very low susceptibility to atmospheric effects.
并且对大气效应的敏感性很低
We steer from NPL based on measuring what Anthorn is broadcasting
基于对Anthorn无线电通信站发出的纳秒级信号的考量
at the level of nanoseconds.
我们在NPL做出控制
That is a nanosecond, the distance light travels in one nanosecond, 30 centimeters.
这就是1纳秒 30厘米 即光在1纳秒传播的距离
All that is taken into account.
所有这些都需要经过计算
– So that seemed simple enough. The official timescale is kept in London.
这样似乎就简单明了了 伦敦持有官方时间
I wasn’t allowed anywhere near the official atomic clocks,
我不被允许出现在这些官方原子钟的附近
I don’t even know if they’re actually at NPL’s headquarters or not,
我甚至不知道原子钟是不是真的在NPL的总部
they might be somewhere else. They told me nothing!
它们可能在别的地方 但工作人员没告诉我
But up north here, this transmitter has separate atomic clocks,
但在北边这里 这个发射台有独立的原子钟
about four hundred kilometres away from the base.
它离基地大约400千米远
Or 1.4 light-milli-seconds away.
相当于光传播 1.4毫秒的距离
There’s a light-speed delay, a latency, of about a thousandth of a second
这个发射台和伦敦的基地之间有光速延迟
between the transmitter here and the base in London.
大概千分之一秒的时延
Because the team at NPL know exactly what that delay should be,
因为NPL的工作人员精准地了解这种延迟
they can issue corrections if these clocks start to drift,
所以如果这些原子钟即使出现纳秒 也就是十亿分之一秒的偏离
even by nanoseconds, billionths of seconds.
他们也可以着手校对
Officially, the accuracy is much lower than that, of course,
正常情况下 电波钟表的准确率当然要低很多
partly because they keep a very wide safety margin,
部分原因是它们保留了较高的安全波动范围
and partly because I can introduce a one-nanosecond drift to this clock
还有一部分原因是 我做这种动作
by doing that.
就可以导致一纳秒的偏离
– What is really important when you’re transferring time is not about the latency,
当发布时码信号时 真正重要的不是时延
but understanding the latency.
而是理解这种延迟的存在
So you can take that out of the equation.
所以在用方程计算时你可以不考虑它
From the NPL, we disseminate to the UK over radio broadcast.
通过NPL发射的无线电波 我们向英国发布时码信号
Essentially that offers the entire UK mainland
本质上来说 这个信号遍布整个英国大陆
several milliseconds of traceability to UTC.
并且与“协调世界时间”只相差几毫秒
We also have a fibre-delivered service
为了保证金融部门
for regulatory compliance in the finance sector,
微秒级别的执行标准
guaranteed at the microsecond.
我们也有一种光纤传输服务
And that’s fine, I can understand all that. But then that leads to another question:
好吧 我可以理解 但这也导致了另外一个问题
how does NPL know if their clocks in London start to drift?
NPL怎么知道他们在伦敦的原子钟开始出现了偏离
Sure, they’ve got many of them, they cross-check,
当然 他们有很多个原子钟可以交叉校验
and a “second” in the 21st century is defined
21世纪的一“秒”
by the number of vibrations of a cesium atom.
是由一个铯原子的无数次震动来定义的
But still, they can’t be perfect.
但它们不可能十全十美
They’re meant to show the international standad,
他们的目的是展示国际标准
UTC, coordinated universal time,
即UTC 协调世界时间
so what if NPL’s official source of timekeeping truth drifts from that standard?
那么如果NPL的官方时间和“协调世界时间”有出入怎么办呢
– UTC or coordinated universal time, as the name suggests,
正如它的名字一样 UTC或者“协调世界时间”
is coordinated globally, contributing data from multiple atomic clocks
是从大量的原子钟上采集数据 得出结论
to generate what is the global timescale, UTC.
从而协调全球的时间
What we have here at NPL is the UK’s timescale, UTC(NPL).
在NPL我们使用的是英国标准时间 即UTC(NPL)
We have a whole suite of atomic clocks,
我们有一整套的设备
cesium clocks, hydrogen masers, and a cesium fountain.
原子钟 铯原子钟 氢微波激射器和一个铯原子喷泉
The Bureau of Weights and Measures based in France
法国基地的计量局
take the data from the clocks around the globe,
在全球范围内采集原子钟的数据
and inform each of the national labs how offset it is from UTC.
然后告知各个国家实验室与UTC存在的偏离情况
– And that’s where the buck stops. In Paris.
所以巴黎是最终责任所在
Unless you start getting into physics and relativity and light cones,
除非你很懂物理 相对论和光锥（才能够理解这一系列操作）
and that’s way beyond me.
但这远远超出我的能力范围
Why does it matter?
为什么这很重要
Well, first of all, finance and high-frequency trading.
呃 首先 金融以及高频交易的需要
But also: science.
其次是科学的需要
Things like the Square Kilometre Array, a planet-wide array of radio telescopes
比如“平方公里阵列”作为一种全球性的射电望远镜阵列
that’s being planned and built now.
正在筹建当中
When they’re listening for incredibly faint radio waves from space,
当观测来自太空的极其微弱的无线电波时
all the telescopes around the globe have to be synchronised
所有的射电望远镜都必须保持同步一致的精准性
with that level of precision, or the whole experiment could fall apart.
否则整个实验就会分崩离析
So then, I had a final question:
那么 我有最后一个问题
when accurate timecode is being sent from so many places,
当精确的时码信号从这么多地方传来
when the public can get time that’s more than accurate enough
与太空中的导航卫星信号授时方式相比 无论从哪一方面来说
for almost every purpose from navigation satellites in space:
大众得到的时间都远不那么精确时
why is this signal still important?
这种无线电波信号授时方式为什么仍然具有重要性?
And the team from NPL had a rather serious answer.
NPL的工作人员给出了更加严肃的回答
– Time really is an invisible utility.
时间是一种看不见的资源
It underpins our digital infrastructure.
它是我国数字基础设施的基石
Whether it’s the synchronization of the energy grid,
无论是能源网 电信网
or the telecom networks, or finance,
还是金融网的同步
we are so dependent on GPS and other constellations.
我们都太过于依赖GPS和其他人造卫星
One of the problems we face is those signals are easily disrupted.
我们面对的问题之一就是这些信号很容易被干扰
It’s the equivalent of a light bulb on the moon.
就相当于月球上的一颗灯泡
One of the things we’re doing at the NPL
我们在NPL做的事情之一
is to ensure that the UK is resilient for the future.
就是确保英国的未来富有活力
– Standing by the ocean with a domestic appliance.
拿着这个家用电器站在海边
The weird thing is, it’s not the first time.
奇怪的是 这并不是第一次