The history of the barometer (and how it works) - Asaf Bar-Yosef

氣壓計的歷史 (及原理) — 阿薩夫·巴約瑟 (Asaf Bar-Yosef)

譯者: Regina Chu 審譯者: Geoff Chen

Aristotle famously said, "Nature fears of empty space"

亞里斯多德有句名言： 「大自然害怕空白」

when he claimed that a true vacuum, a space devoid of matter, could not exist

他宣稱真正的真空，即無物質的空間 是不可能存在的

because the surrounding matter would immediately fill it.

因為四周的物質會立刻充滿它

Fortunately, he turned out to be wrong.

所幸，他是錯的

A vacuum is a key component of the barometer,

真空是氣壓計的主要部分

an instrument for measuring air pressure.

氣壓計是測量大氣壓力的儀器

And because air pressure correlates to temperature

因為大氣壓力與溫度相關

and rapid shifts in it can contribute to

而大氣中溫度的急遽變化會造成

hurricanes, tornadoes and other extreme weather events,

颶風、龍捲風及其它 極端惡劣的天氣情況

a barometer is one of the most essential tools

所以氣壓計是最基本的工具

for weather forecasters and scientists alike.

為天氣預報專家及科學家所用

How does a barometer work, and how was it invented?

但氣壓計原理是什麼？ 又是如何發明出來的？

Well, it took awhile.

嗯，這花了點時間

Because the theory of Aristotle and other ancient philosophers

因為亞里斯多德及別的古代哲學家

regarding the impossibility of a vacuum seemed to hold true in everyday life,

視真空為不可能的理論 在每日生活中似乎說得通

few seriously thought to question it for nearly 2,000 years --

將近二千年來 很少人認真思考過這個問題

until necessity raised the issue.

直到有實際應用的問題出現

In the early 17th century, Italian miners faced a serious problem

在十七世紀初，義大利礦工 面臨的一個很嚴重的問題

when they found that their pumps could not raise water

他們發現他們的泵無法汲水

more than 10.3 meters high.

超過 10.3 公尺高

Some scientists at the time, including one Galileo Galilei,

當時一些科學家 包括這位伽利略·伽利萊

proposed that sucking air out of the pipe was what made water rise to replace the void.

都提出從水管吸出空氣 是使水升高填滿空間的原理

But that its force was limited and could lift no more than 10.3 meters of water.

但是吸力是有限度的 只能吸到 10.3 公尺高的水

However, the idea of a vacuum existing at all

然而，真空終究存在的想法

was still considered controversial.

大家仍認為具爭議性

And the excitement over Galileo's unorthodox theory,

而對伽利略非正統理論的興奮情緒

led Gasparo Berti to conduct a simple but brilliant experiment

刺激了義大利人伯提 做出一個簡單卻高明的實驗

to demonstrate that it was possible.

以證明真空是可能的

A long tube was filled with water

一根充滿了水的長管

and placed standing in a shallow pool with both ends plugged.

立在一個淺池內，兩端都塞住

The bottom end of the tube was then opened

然後將管子的底端打開

and water poured out into the basin

水立刻從管中注入盆內

until the level of the water remaining in the tube was 10.3 meters.

直到剩下的水面高度 降到 10.3 公尺為止

With a gap remaining at the top, and no air having entered the tube,

因為在頂端留出空間 也沒有空氣進入管內

Berti had succeeded in directly creating a stable vacuum.

伯提成功直接製造出穩定的真空

But even though the possibility of a vacuum had been demonstrated,

但即便真空的可能性已被證明出來

not everyone was satisfied with Galileo's idea

不是所有人都滿意伽利略的想法

that this empty void was exerting some mysterious

認為這個真空空間施加了一些神秘

yet finite force on the water.

卻有限的力量在水中

Evangelista Torricelli, Galileo's young pupil and friend,

埃萬傑利斯塔·托里切利 是伽利略年輕的學生及朋友

decided to look at the problem from a different angle.

決定要從不同的角度看這個問題

Instead of focusing on the empty space inside the tube,

不去專注於管內的空間

he asked himself, "What else could be influencing the water?"

他問自己： 「還有什麼可能會對水作用？」

Because the only thing in contact with the water was the air surrounding the pool,

因為唯一接觸水的東西 就是水池四圍的空氣

he believed the pressure from this air could be the only thing preventing

他相信這些空氣的壓力是唯一

the water level in the tube from dropping further.

使管子的水面不再下降的東西

He realized that the experiment was not only a tool to create a vacuum,

他了解到這個實驗不僅是 唯一能製造真空的工具

but operated as a balance

其操作還能視為

between the atmospheric pressure on the water outside the tube

管外水面的大氣壓力

and the pressure from the water column inside the tube.

及管內水柱的壓力之間達到平衡

The water level in the tube decreases until the two pressures are equal,

管內的水會持續下降 直到兩邊的壓力相同為止

which just happens to be when the water is at 10.3 meters.

剛好就是水面高度為 10.3 公尺時

This idea was not easily accepted,

大家不太接受這個想法

as Galileo and others had traditionally thought

因為伽利略及其他人習慣上認為

that atmospheric air has no weight and exerts no pressure.

大氣沒有重量也不施加任何壓力

Torricelli decided to repeat Berti's experiment

托里切利決定重做柏提的實驗

with mercury instead of water.

但以水銀代替水

Because mercury was denser, it fell farther than the water

因為水銀密度更高 它下降的幅度會比水更大

and the mercury column stood only about 76 centimeters tall.

而且水銀柱只有 76 公分高

Not only did this allow Torricelli to make the instrument much more compact,

這不但使托里切利 能做出更小巧的儀器

it supported his idea that weight was the deciding factor.

還能以此佐證他的想法 即重量的確是決定性的因素

A variation on the experiment used two tubes with one having a large bubble at the top.

此項實驗的變化是他用兩根管子 其中一根上面有個大泡泡

If Galileo's interpretation had been correct, the bigger vacuum in the second tube

如果伽利略的詮釋是正確的 那第二根管上更大的真空空間

should have exerted more suction and lifted the mercury higher.

應施加更多的真空吸力 且使水銀升得更高

But the level in both tubes was the same.

但是兩根管子的高度都一樣

The ultimate support for Torricelli's theory came via Blaise Pascal

托里切利理論的終極佐證 來自布萊茲‧巴斯卡

who had such a mercury tube taken up a mountain

他把這樣的水銀管搬到山上

and showed that the mercury level dropped

且顯示水銀的高度降低

as the atmospheric pressure decreased with altitude.

因為大氣壓力 會隨著海拔增高而減少

Mercury barometers based on Torricelli's original model

基於托里切利的原始模型 所造出的水銀氣壓計

remained one of the most common ways to measure atmospheric pressure until 2007

仍然是測量大氣壓力最普遍的 方法，直到 2007 年

when restrictions on the use of mercury due to its toxicity

當時限制了水銀的使用 因為它有毒

led to them no longer being produced in Europe.

導致歐洲不再製造水銀氣壓計

Nevertheless, Torricelli's invention,

儘管如此，托里切利的發明

born of the willingness to question long accepted dogmas

源自其願意探究已行之有年

about vacuums and the weight of air, is an outstanding example

有關真空及空氣重量的學說 是傑出的榜樣

of how thinking outside of the box -- or the tube --

示範了跳出傳統思維 ──或說真理──

can have a heavy impact.

如何能產生強烈的衝擊