你生日在圆周率第几位？

今天没有瓜。来看点有意思的，查一查你的生日日期在圆周率那么多数字里排在第几位？

查询方法：直接在微信公众号后台发送你的生日日期8位数字就可以查询。注意，是微信公众号，不是视频号。

借（cèng）此（gè）机（rè）会（diǎn），我们来看看《科学美国人》（Scientific American）对圆周率历史的介绍。

无注释原文：

What Is Pi, and How Did It Originate?

Scientific American

Steven Bogart, a mathematics instructor at Georgia Perimeter College, answers

Succinctly, pi—which is written as the Greek letter for p, or π—is the ratio of the circumference of any circle to the diameter of that circle. Regardless of the circle's size, this ratio will always equal pi. In decimal form, the value of pi is approximately 3.14. But pi is an irrational number, meaning that its decimal form neither ends (like 1/4 = 0.25) nor becomes repetitive (like 1/6 = 0.166666...). (To only 18 decimal places, pi is 3.141592653589793238.)

Hence, it is useful to have shorthand for this ratio of circumference to diameter. According to Petr Beckmann's A History of Pi, the Greek letter π was first used for this purpose by William Jones in 1706, probably as an abbreviation of periphery, and became standard mathematical notation roughly 30 years later.

Try a brief experiment: Using a compass, draw a circle. Take one piece of string and place it on top of the circle, exactly once around. Now straighten out the string; its length is called the circumference of the circle. Measure the circumference with a ruler. Next, measure the diameter of the circle, which is the length from any point on the circle straight through its center to another point on the opposite side. (The diameter is twice the radius, the length from any point on the circle to its center.) If you divide the circumference of the circle by the diameter, you will get approximately 3.14—no matter what size circle you drew! A larger circle will have a larger circumference and a larger radius, but the ratio will always be the same. If you could measure and divide perfectly, you would get 3.141592653589793238..., or pi.

In other words, if you cut several pieces of string equal in length to the diameter, you will need a little more than three of them to cover the circumference of the circle.

Pi is most commonly used in certain computations regarding circles. Pi not only relates circumference and diameter. Amazingly, it also connects the diameter or radius of a circle with the area of that circle by the formula: the area is equal to pi times the radius squared. Additionally, pi shows up often unexpectedly in many mathematical situations. For example, the sum of the infinite series

1 + 1/4 + 1/9 + 1/16 + 1/25 + ... + 1/n^2 + ... is π^2/6

The importance of pi has been recognized for at least 4,000 years. A History of Pi notes that by 2000 B.C., "the Babylonians and the Egyptians (at least) were aware of the existence and significance of the constant π," recognizing that every circle has the same ratio of circumference to diameter. Both the Babylonians and Egyptians had rough numerical approximations to the value of pi, and later mathematicians in ancient Greece, particularly Archimedes, improved on those approximations. By the start of the 20th century, about 500 digits of pi were known. With computation advances, thanks to computers, we now know more than the first six billion digits of pi.

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注：中文文本为机器翻译仅供参考，并非一一对应

含注释全文：

What Is Pi, and How Did It Originate?

Scientific American

Steven Bogart, a mathematics instructor at Georgia Perimeter College, answers

Succinctly, pi—which is written as the Greek letter for p, or π—is the ratio of the circumference of any circle to the diameter of that circle. Regardless of the circle's size, this ratio will always equal pi. In decimal form, the value of pi is approximately 3.14. But pi is an irrational number, meaning that its decimal form neither ends (like 1/4 = 0.25) nor becomes repetitive (like 1/6 = 0.166666...). (To only 18 decimal places, pi is 3.141592653589793238.)

简而言之，pi--写成希腊字母p，或π--是任何圆的周长与该圆直径的比值。无论圆的大小，这个比值总是等于pi。在十进制形式中，pi的值大约是3.14。但pi是一个无理数，也就是说它的十进制形式既不会结束（如1/4=0.25），也不会无限重复（如1/6=0.166666...）。（pi的小数点后18位是3.141592653589793238。）

succinct /səkˈsɪŋkt/ 表示“简明的；言简意赅的”，英文解释为“expressed clearly and in a few words”举个🌰：

Keep your answers as succinct as possible.

你们的答案要尽可能简洁明了。

表示“比率；比例”，英文解释为“the relationship between two groups of people or things that is represented by two numbers showing how much larger one group is than the other”举个🌰：

The school has a very high teacher-student ratio.

这所学校的师生比例很高。 

circumference /səˈkʌmfərəns/ | 表示“圆周；圆周长”，英文解释为“a line that goes around a circle or any other curved shape; the length of this line”举个🌰：

The earth is almost 25 000 miles in circumference.

地球的周长大约为25000英里。

表示“直径；对径”，英文解释为“a straight line going from one side of a circle or any other round object to the other side, passing through the centre”举个🌰：

The dome is 42.3 metres in diameter.

这个穹顶直径为42.3米。

补充：

📍radius：a straight line between the centre of a circle and any point on its outer edge; the length of this line 半径（长度）

1）作形容词，表示“十进制的”，英文解释为“A decimal system involves counting in units of ten.”举个🌰：

The mathematics of ancient Egypt were based on a decimal system.

古埃及数学以十进制为基础。

2）作名词，表示“小数”，英文解释为“A decimal is a fraction that is written in the form of a dot followed by one or more numbers which represent tenths, hundredths, and so on”如：simple maths concepts, such as decimals and fractions 简单的数学概念，如小数和分数。

表示“无理数”，英文解释为“a number, for example π or the square root of 2, that cannot be expressed as the ratio of two whole numbers”。

Hence, it is useful to have shorthand for this ratio of circumference to diameter. According to Petr Beckmann's A History of Pi, the Greek letter π was first used for this purpose by William Jones in 1706, probably as an abbreviation of periphery, and became standard mathematical notation roughly 30 years later.

因此，对这个圆周率和直径的比值有一个简写是很有用的。根据彼得·贝克曼（Petr Beckmann）的《圆周率史》（A History of Pi），希腊字母π在1706年由威廉·琼斯（William Jones）首次用于此目的，可能是作为周长的缩写，并在大约30年后成为标准数学符号。

1）表示“简约表达法”，英文解释为“You can use shorthand to mean a quick or simple way of referring to something.”举个🌰：

He uses the shorthand of "second age" for the group of younger people who are creating families.

他用“第二代”来简单指称那些更年轻、正在组建家庭的人。

2）表示“速记法”，英文解释为“Shorthand is a quick way of writing and uses signs to represent words or syllables. Shorthand is sometimes used by secretaries and journalists to write down what someone is saying.”举个🌰：

He took notes in shorthand.

他用速记法记笔记。

abbreviation /əˌbriːviˈeɪʃn/ 表示“略语；缩写词；缩写形式”，英文解释为“short form of a word, etc.”举个🌰：

What's the abbreviation for ‘LearnAndRecord’?

LearnAndRecord的缩写形式是什么？

periphery /pəˈrɪfərɪ/ 表示“边缘；周围；外围”，英文解释为“If something is on the periphery of an area, place, or thing, it is on the edge of it.”举个🌰：

Taste buds are concentrated at the tip and rear of the tongue and around its periphery.

味蕾集中在舌尖、舌根及舌边。

表示“符号”，英文解释为“A system of notation is a set of written symbols that are used to represent something such as music or mathematics.”举个🌰：

Musical notation was conceived for the C major scale and each line and space represents a note in this scale. 

乐谱为C大音阶而构思，在这个音阶中的每一个线和间都代表一个音符。

Try a brief experiment: Using a compass, draw a circle. Take one piece of string and place it on top of the circle, exactly once around. Now straighten out the string; its length is called the circumference of the circle. Measure the circumference with a ruler. Next, measure the diameter of the circle, which is the length from any point on the circle straight through its center to another point on the opposite side. (The diameter is twice the radius, the length from any point on the circle to its center.)

试做一个简单的实验。用圆规画一个圆。拿一根绳子，把它放在圆的上面，正好绕一圈。现在把绳子拉直，它的长度叫做圆的周长。用尺子量出圆周长。接着，测量圆的直径，也就是圆上任何一点经过圆心到另一点的长度。直径是半径的两倍，半径也就是从圆上任何一点到圆心的长度。

通常“指南针，罗盘”，此处熟词僻义，还有“圆规；两脚规”的意思，英文解释为“an instrument with two long thin parts joined together at the top, used for drawing circles and measuring distances on a map”，通常用复数形式compasses.

表示“细绳；线；带子”，英文解释为“material made of several threads twisted together, used for tying things together; a piece of string used to fasten or pull sth or keep sth in place”如：a piece/length of string 一根/一段细绳。

If you divide the circumference of the circle by the diameter, you will get approximately 3.14—no matter what size circle you drew! A larger circle will have a larger circumference and a larger radius, but the ratio will always be the same. If you could measure and divide perfectly, you would get 3.141592653589793238..., or pi.

如果你用周长除以圆的直径，你将得到大约3.14--不管你画的是什么大小的圆！一个较大的圆，其周长会更大。较大的圆会有更大的周长和更大的半径，但比例总是相同的。如果你能完美地测量和划分，你会得到3.141592653589793238......，也就是π。

熟词僻义，表示“除；除尽”，英文解释为“If you divide a larger number by a smaller number or divide a smaller number into a larger number, you calculate how many times the smaller number can fit exactly into the larger number.”举个🌰：

Measure the floor area of the greenhouse and divide it by five.

测量温室的地表面积，再除以5。

In other words, if you cut several pieces of string equal in length to the diameter, you will need a little more than three of them to cover the circumference of the circle.

换句话说，如果你剪下几根长度与直径相等的绳子，你需要三根以上的绳子才能覆盖圆的周长。

Pi is most commonly used in certain computations regarding circles. Pi not only relates circumference and diameter. Amazingly, it also connects the diameter or radius of a circle with the area of that circle by the formula: the area is equal to pi times the radius squared. Additionally, pi shows up often unexpectedly in many mathematical situations. For example, the sum of the infinite series 1 + 1/4 + 1/9 + 1/16 + 1/25 + ... + 1/n^2 + ... is π^2/6.

π最常用于某些关于圆的计算。π不仅关系到圆周率和直径。令人惊奇的是，它还将圆的直径或半径与该圆的面积联系起来，公式为：面积等于π乘以半径的平方。此外，π在许多数学情境中常常出人意料地出现。例如，无限数列：1 + 1/4 + 1/9 + 1/16 + 1/25 + ... + 1/n^2+... 和为 π^2/6。

表示“关于；至于”，英文解释为“concerning sb/sth; about sb/sth”举个🌰：

Call me if you have any problems regarding your work.

你如果还有什么工作方面的问题就给我打电话。

表示“面积”，英文解释为“the amount of space covered by a flat surface or piece of land, described as a measurement”如：the area of a triangle 三角形的面积。

表示“公式”，英文解释为“A formula is a group of letters, numbers, or other symbols which represents a scientific or mathematical rule.”举个🌰：

He developed a mathematical formula describing the distances of the planets from the Sun.

他提出了一个描述各行星与太阳之间距离的数学公式。

表示“乘”，英文解释为“You use times to show multiplication.”举个🌰：

Four times six is/equals 24.

4乘以6等于24。

补充：

📍multiply作动词，表示“乘”（If you multiply one number by another, you add the first number to itself as many times as is indicated by the second number. For example 2 multiplied by 3 is equal to 6.）

What do you get if you multiply four by six?

4乘以6得多少？

表示“使成平方；使成二次幂”，英文解释为“to multiply a number by itself”举个🌰：

Three squared is written 3^2.

3的平方写作3^2。

The importance of pi has been recognized for at least 4,000 years. A History of Pi notes that by 2000 B.C., "the Babylonians and the Egyptians (at least) were aware of the existence and significance of the constant π," recognizing that every circle has the same ratio of circumference to diameter. Both the Babylonians and Egyptians had rough numerical approximations to the value of pi, and later mathematicians in ancient Greece, particularly Archimedes, improved on those approximations. By the start of the 20th century, about 500 digits of pi were known. With computation advances, thanks to computers, we now know more than the first six billion digits of pi.

圆周率的重要性至少在4000年前就已经被认识到了。《圆周率史》指出，到公元前2000年，“巴比伦人（Babylonians）和埃及人（至少）已经意识到常数π的存在和意义”，认识到每一个圆的周长和直径的比例都是一样的。巴比伦人和埃及人对π的数值都有粗略的近似值，后来古希腊的数学家，特别是阿基米德（Archimedes），对这些近似值进行了改进。到20世纪初，已经知道了圆周率的约500位数。随着计算的进步，由于计算机的发展，我们现在已经知道了圆周率前60亿多位的数字。

表示“意识到…的”，英文解释为“If you are aware of something, you know about it.”举个🌰：

Smokers are well aware of the dangers to their own health.

吸烟者们都很清楚吸烟对其自身健康的那些危害。

作名词，熟词僻义，表示“常数；常量”，英文解释为“a number or quantity that does not vary”。

补充：

📍variable表示“可变情况；变量；可变因素”（a situation, number or quantity that can vary or be varied）。

1）表示“近似值”，英文解释为“An approximation is a number, calculation, or position that is close to a correct number, time, or position, but is not exact.”举个🌰：

As we know, 3.14159 is only an approximation.

如我们所知，3.14159只是一个近似值。

2）表示“近似物”，英文解释为“An approximation is a fact, object, or description which is similar to something else, but which is not exactly the same.”举个🌰：

That is a fair approximation of the way in which the next boss is being chosen.

那是一个挑选下任老板的大体近似方式。

表示“（0到9的任一）数字”，英文解释为“A digit is a written symbol for any of the ten numbers from 0 to 9.”举个🌰：

Her telephone number differs from mine by one digit.

她的电话号码跟我的差一个数字。

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