All the Fancy Measuring Devices Used in Science Rely on Two Stone-Age Techniques
All the Fancy Measuring Devices Used in Science Rely on Two Stone-Age Techniques
科学中使用的所有精密测量设备，都依赖于两种石器时代的技术
Humans are animals that measure things. Call us Homo mensura. We have a compulsion to quantify, and for millennia we’ve been inventing new ways to go about it. For anything you can think of, there’s a device to measure it—from sphygmomanometers to spectrophotofluorometers. And of course nowhere is this more true than in science. Well, science and baseball. 人类是会测量事物的动物。称我们为“测量人”（Homo mensura）吧。我们有一种量化的冲动，几千年来，我们一直在发明各种方法来实现这一目标。对于你能想到的任何事物，都有相应的测量设备——从血压计到分光荧光计。当然，这一点在科学领域体现得最为明显。好吧，科学和棒球都是如此。
Physicists build models to explain how the world works. It might be an equation, like the ideal gas law: PV = nRT. This tells us, for example, that if you double the temperature (T) of a gas, all else equal, its gas pressure (P) will double. But to see if the model is legit, or at least useful, we need to get some real-world values and check whether the equation holds. Modeling and measuring, measuring and modeling—that’s science in a nutshell. 物理学家建立模型来解释世界是如何运作的。它可能是一个方程，比如理想气体定律：PV = nRT。例如，这告诉我们，如果气体的温度（T）加倍，在其他条件不变的情况下，其气体压力（P）也会加倍。但要验证该模型是否合理，或者至少是否有用，我们需要获取一些现实世界的数据，并检查方程是否成立。建模与测量，测量与建模——这就是科学的精髓。
Of course, today we have some pretty fancy instruments for this. But I’m going to let you in on a little secret: With all of our cool tools, measurement still comes down to either comparison or counting. In that sense, it hasn’t changed much since Noah built his ark from a spec sheet in cubits—the length of a human forearm from elbow to fingertip. Let me show you what I mean. 当然，今天我们拥有一些非常先进的仪器来完成这些工作。但我得告诉你一个小秘密：尽管我们拥有各种酷炫的工具，但测量归根结底还是离不开“比较”或“计数”。从这个意义上说，它与诺亚根据“肘尺”（从肘部到指尖的人类前臂长度）规格建造方舟时相比，并没有太大的变化。让我来告诉你我的意思。
Measuring Length
测量长度
I’m going to start with a measurement that everyone has used at some point: length or distance. It seems simple, right? If you want to know the length of a pencil, you lay it down next to a ruler. There, it’s 18.7 centimeters. (Yeah, in science we’re on that side of the ruler.) 我将从每个人都曾使用过的测量方式开始：长度或距离。这看起来很简单，对吧？如果你想知道一支铅笔的长度，你把它放在尺子旁边。好了，它是 18.7 厘米。（是的，在科学领域，我们使用尺子的这一面。）
What you’re doing here is comparing the length of a pencil and the length of a ruler side by side. (Of course this brings up another issue: How do you know if that ruler you bought online is accurate? That’s a whole other discussion about standards. We can save that for another day.) 你在这里所做的，是将铅笔的长度与尺子的长度并排进行比较。（当然，这引出了另一个问题：你怎么知道你在网上买的那把尺子是准确的？那是关于标准的另一个话题了。我们可以改天再讨论。）
The nuttiest comparison measurement ever took place in 1958 when a group of MIT undergrads set out to find the length of a bridge over the Charles River. They had the shortest member of their group, Oliver Smoot (5′ 7″, or 170 centimeters), lie down repeatedly, marking the sidewalk with chalk, all the way across, and found the bridge to be 364.4 smoots, “give or take an ear.” 有史以来最疯狂的比较测量发生在 1958 年，当时一群麻省理工学院的本科生决定测量查尔斯河上一座桥的长度。他们让组里最矮的成员奥利弗·斯穆特（Oliver Smoot，身高 5 英尺 7 英寸，即 170 厘米）反复躺下，用粉笔在人行道上做标记，一直横跨整座桥，最终测得桥长为 364.4 个“斯穆特”，“误差大约是一个耳朵的长度”。
(You can’t make this stuff up: Smoot went on to become head of the American National Standards Institute and later the International Organization for Standardization. The definition of a smoot was revised in 2015, when photographic evidence revealed that at age 75, his stature had diminished by 3 centimeters.) （你无法编造这些事：斯穆特后来成为了美国国家标准学会的负责人，后来又担任了国际标准化组织的主席。2015 年，“斯穆特”的定义进行了修订，因为照片证据显示，在他 75 岁时，他的身高缩短了 3 厘米。）
Anyway, it turns out that measuring length or distance by comparison is the most common method used in analog devices. 总之，事实证明，通过比较来测量长度或距离是模拟设备中最常用的方法。
Other Distance Measurements
其他距离测量
For example, what about time? One of the oldest timekeeping devices is the sundial, which in its familiar form was invented by the ancient Greeks. It has a triangular blade, called a gnomon, and a flat disc with numbers around the circumference for hours. 例如，时间呢？最古老的计时设备之一是日晷，其常见的形式是由古希腊人发明的。它有一个三角形的叶片，称为“晷针”，以及一个圆周上刻有小时数字的平盘。
As the sun moves across the sky, the shadow cast by the gnomon will move. But how do you turn that shadow into time? You got it—you measure the distance of the shadow from the noon position. The sundial above is pointing to 2:10 pm. 随着太阳在天空中移动，晷针投下的影子也会移动。但你如何将影子转化为时间呢？你猜对了——你测量影子距离正午位置的距离。上面的日晷指向的是下午 2:10。
(Interesting footnote: The hour labels had to be inscribed differently from city to city because the shadow changes by latitude and longitude. If you moved from Sparta to Athens and took your sundial with you, you’d be five minutes late to class at the Lyceum.) （有趣的注脚：不同城市的小时标签必须刻得不同，因为影子会随经纬度而变化。如果你从斯巴达搬到雅典并带上你的日晷，你在吕克昂学院上课时就会迟到五分钟。）
Here’s another time-measuring device you might have seen, which shows the same time, 2:10, in a different way: 这是你可能见过的另一种计时设备，它以不同的方式显示相同的时间 2:10：
I love this old clock. It’s fun to remember that “IBM” stood for International Business Machines, which weren’t just computers. Anyhow, you read the time from the location of the hands. Yup, that’s a distance measurement—the information is conveyed by how far a hand has traveled around the dial. But wait! There’s more! Here are some other things that measure using distances: 我喜欢这个老式时钟。记住“IBM”代表“国际商业机器公司”（International Business Machines）是很有趣的，它们不仅仅生产计算机。总之，你是通过指针的位置来读取时间的。没错，这就是一种距离测量——信息是通过指针在表盘上移动的距离来传达的。等等！还有更多！以下是一些其他利用距离进行测量的东西：
That force gauge above, for instance, has a calibrated spring inside. When you hang a mass on it, the spring stretches proportionately to the force exerted, and the length of extension indicates how many newtons of pulling force were applied. The result is displayed as a distance on a dial. 例如，上面的力计内部有一个校准过的弹簧。当你挂上一个物体时，弹簧会根据所施加的力成比例地拉伸，拉伸的长度表示施加了多少牛顿的拉力。结果以距离的形式显示在表盘上。
Sometimes we just do comparisons without a distance measurement. Here is a balance scale. You put an unknown mass on one side and add known masses to the other side until they’re equal. That’s how assayers measured gold during the California Gold Rush. 有时我们只是进行比较，而不进行距离测量。这是一个天平。你在一侧放上未知质量的物体，在另一侧添加已知质量的砝码，直到它们平衡。这就是加州淘金热期间化验员测量黄金的方法。
Why didn’t they use a spring scale, which would be faster? Because spring scales, like your bathroom scale, measure the gravitational force acting on an object—that’s what “weight” really is. Mass is a different concept; it’s the amount of physical matter in an object. Because the gravitational field is not uniform all over the world, a weight measurement could differ from place to place. But a balance scale will give the same measure of mass anywhere you go, since the local gravity affects both sides equally. It’s also probably harder to cheat with a balance scale. 为什么他们不使用更快的弹簧秤呢？因为弹簧秤（就像你的体重秤）测量的是作用在物体上的重力——这才是“重量”的真正含义。质量是一个不同的概念；它是物体中物理物质的数量。由于全球的重力场并不均匀，重量测量值可能会因地而异。但天平无论你走到哪里都能给出相同的质量测量值，因为当地的重力对两侧的影响是相同的。而且，用天平作弊可能也更难。
But aside from a few similar exceptions, almost all analog devices use comparison and length measurements to get a value. 但除了少数类似的例外，几乎所有的模拟设备都使用比较和长度测量来获取数值。
Counting and Digital Instruments
计数与数字仪器
What if you wanted to model the populations of wolves and rabbits? You could show that without wolves, the number of rabbits grows exponentially until they reach the resource limit. Obviously now you’re counting, not comparing. 如果你想模拟狼和兔子的种群数量呢？你可以证明，如果没有狼，兔子的数量会呈指数级增长，直到达到资源极限。显然，现在你是在计数，而不是在比较。
Here’s an old laboratory timer that counts off tenths of seconds. See how that’s different from the clock? It’s not continuous like a sweeping second hand—it can only take certain discrete values. That’s the key property of a “digital” instrument: It’s like counting on your fingers, aka digits! 这是一个老式的实验室计时器，它以十分之一秒为单位进行计数。看出它与时钟的区别了吗？它不像扫秒指针那样是连续的——它只能取某些离散的值。这就是“数字”仪器的关键特性：它就像用手指计数一样，也就是所谓的“数字”（digits）！