Aristotle famously said, 'Nature fears of empty space' when he claimed that a true vacuum,
亚里士多德说过一句话：'自然惧怕虚无'。当他发现真空，
a space devoid of matter, could not exist because the surrounding matter would immediately fill it.
即没有物质的空间，是不存在的的时候，因为其附近的物质会立即填补这个空间。
Fortunately, he turned out to be wrong.
幸运的是，亚里士多德被证明是错的。
A vacuum is a key component of the barometer, an instrument for measuring air pressure.
真空是气压计，一种测量空气压力的仪器的重要组成部分。
And because air pressure correlates to temperature
由于气压是受温度影响的，
and rapid shifts in it can contribute to hurricanes, tornadoes and other extreme weather events,
气压的突然改变可以引起飓风、龙卷风和其它极端天气现象，
a barometer is one of the most essential tools for weather forecasters and scientists alike.
气压计是天气预报者和从事类似工作的科学家不可或缺的的工具之一。
How does a barometer work, and how was it invented? Well, it took awhile.
气压计是如何工作的，它又是怎么被发明的呢？这个过程可得花一些时间了。
Because the theory of Aristotle and other ancient philosophers
因为亚里士多德和其他古哲学家的学说
regarding the impossibility of a vacuum seemed to hold true in everyday life,
认为真空在现实生活中是不可能存在的，
few seriously thought to question it for nearly 2,000 years -- until necessity raised the issue.
所以2000年来几乎没人想过去质疑这个理论，直到对气压计的迫切需求把这个问题再次摆在人们眼前。
In the early 17th century, Italian miners faced a serious problem
在17世纪，意大利采矿者面临着严重的问题，
when they found that their pumps could not raise water more than 10.3 meters high.
因为他们发现他们的水泵无法将水提升超过10.3米。
Some scientists at the time, including one Galileo Galilei,
当时的的科学家们，包括伽利略，
proposed that sucking air out of the pipe was what made water rise to replace the void.
都认为水被提上来是因为管中空气被抽掉了，需要水去填补空间。
But that its force was limited and could lift no more than 10.3 meters of water.
但是这个力是有限的，只能将水提高最多10.3米。
However, the idea of a vacuum existing at all was still considered controversial.
无论如何，真空是否存在的问题依然被认为是有争议的。
And the excitement over Galileo's unorthodox theory,
对于伽利略这种非传统的理论的兴奋，
led Gasparo Berti to conduct a simple but brilliant experiment to demonstrate that it was possible.
驱使盖斯帕罗·伯提做了一个简单但是天才的实验来证明真空是可能的。
A long tube was filled with water and placed standing in a shallow pool with both ends plugged.
他把一根长管子装满水，两边封住立起来置于浅水池上。
The bottom end of the tube was then opened and water poured out into the basin
然后打开管子底部，水则会流出来到盆子里去，
until the level of the water remaining in the tube was 10.3 meters.
直到在管中的水只剩下10.3米。
With a gap remaining at the top, and no air having entered the tube,
这样在管子顶端就留下了一段没有空气进入的空间，
Berti had succeeded in directly creating a stable vacuum.
伯堤成功地直接制造了一个稳定的真空状态。
But even though the possibility of a vacuum had been demonstrated,
但即便真空的存在已经得到了展示，
not everyone was satisfied with Galileo's idea that this empty void was exerting some mysterious yet finite force on the water.
也并不是所有人都赞同伽利略的观点，因为这种真空是神秘的，并且只以有限的力量作用于水。
Evangelista Torricelli, Galileo's young pupil and friend, decided to look at the problem from a different angle.
埃万杰利斯塔·托里拆利，伽利略年轻的学生和朋友，决定通过不同的角度来看待这个问题。
Instead of focusing on the empty space inside the tube,
他没有专注于管子顶端的空间，
he asked himself, 'What else could be influencing the water?'
而是问自己：“还有什么可以影响水下降的高度呢？”

Because the only thing in contact with the water was the air surrounding the pool,
因为唯一和池子里的水有所关联的就是池子附近的空气，
he believed the pressure from this air could be the only thing preventing the water level in the tube from dropping further.
所以他认为空气的压力是唯一阻止管子里的水继续下降的东西。
He realized that the experiment was not only a tool to create a vacuum,
他意识到这个实验不仅仅是创造真空的工具，
but operated as a balance between the atmospheric pressure on the water outside the tube and the pressure from the water column inside the tube.
还可以用作一个天平，用来平衡管子外部的大气压力与管子内部水柱的压力。
The water level in the tube decreases until the two pressures are equal,
管子中的水位会持续下降直到两边压力相等，
which just happens to be when the water is at 10.3 meters.
这个平衡的高度刚好是10.3米。
This idea was not easily accepted,
这个主意并不容易被接受，
as Galileo and others had traditionally thought that atmospheric air has no weight and exerts no pressure.
因为伽利略和其他人一直以来都认为大气是没重量、没压力的。
Torricelli decided to repeat Berti's experiment with mercury instead of water.
托里拆利决定重复伯堤的实验，他用的是水银而不是水。
Because mercury was denser, it fell farther than the water and the mercury column stood only about 76 centimeters tall.
因为水银比水密度大，它比水下降得更厉害，水银柱最终只停在了76厘米高。
Not only did this allow Torricelli to make the instrument much more compact,
这不仅让托里拆利把实验仪器变小了，
it supported his idea that weight was the deciding factor.
还证明了重力是决定性因素。
A variation on the experiment used two tubes with one having a large bubble at the top.
在此基础上的另一个实验使用了两根管子，其中一根顶端有个大泡泡。
If Galileo's interpretation had been correct,
如果伽利略的想法是对的，
the bigger vacuum in the second tube should have exerted more suction and lifted the mercury higher.
第二根管子中应当存在更大的真空空间，应该提供更多吸力，把水银抬得高一点。
But the level in both tubes was the same.
但是两边的高度是一样的。
The ultimate support for Torricelli's theory came via Blaise Pascal who had such a mercury tube taken up a mountain
托里拆利实验最根本的支持来自于布莱士·帕斯卡所做的实验，帕斯卡在山上做出了汞柱实验，
and showed that the mercury level dropped as the atmospheric pressure decreased with altitude.
并且发现随着海拔降低，气压降低，汞柱的高度会降低。
Mercury barometers based on Torricelli's original model
建立在托里拆利原模型上的水银气压计，
remained one of the most common ways to measure atmospheric pressure until 2007
一直到2007年还是测量大气压强最普遍的方法，
when restrictions on the use of mercury due to its toxicity led to them no longer being produced in Europe.
07年以后由于水银的毒性，它的使用受到了限制，也不能在欧洲继续生产。
Nevertheless, Torricelli's invention, born of the willingness to question long accepted dogmas about vacuums and the weight of air,
无论如何，托里拆利的发明，产生于他对长期以来被人接受的有关真空和空气重量的老教条进行质疑的意愿，
is an outstanding example of how thinking outside of the box -- or the tube -- can have a heavy impact.
这是一个告诉人们跳出条条框框去思考问题是非常有意义的事的很好的例子。