The History of Pi, by Marie Gugle 1920

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The History of Pi, by Marie Gugle 1920
It was not until the middle of the eighteenth century that the Greek letter (PI) came into use as a symbol for the ratio of the circumference to the diameter of a circle. But from earliest times mathematicians knew that there was such a constant ratio. Different values were given it in different periods of history.

1. One of the earliest books we have is the Ahmes (Ah'mez) Papyrus, written about 1700 B.c. In this manuscript a value is given to PI equal to 256/81 or 3.1604.

2. The Jews and Babylonians considered PI equal to 3. This fact is shown in the measures given for sacred vessels in I Kings vii, 23 and II Chronicles iv, 2.

3. Archimedes of Syracuse, who lived between 287 and 212 B.c, was a great mechanical genius as well as mathematician. You will find it interesting to read the stories of his detection of the fraudulent goldsmith; his use of burning glasses to destroy the Roman ships; his apparatus for launching ships; and the Archimedean screw used to drain the flooded fields of Egypt.

Archimedes proved that the value of PI is between 3 1/7 and 3 10/71.

We can understand these values better by putting them in decimal form, but Archimedes did not have this advantage, because no one knew anything about decimal fractions until nearly 1600 A.d.

4. Ptolemy, a great astronomer of Alexandria about 150 A.d., used 3 17/120 as the value of PI. As a decimal 3 17/120 = 3.14166.
5. Between 400 and 600 A.d. the Hindus used PI = 3 or 3 1/8 and PI = which is 3.1622.

The Chinese had used PI = about 200 A.d.

6. The exact value of PI cannot be expressed in ordinary figures, although many persons have contended long and earnestly that it could be done. If this were possible, a square could be constructed exactly equal to a circle. These people are known as "circle-squarers."

About 1600 the value of PI was calculated to 35 decimal places. Since then it has been calculated to 707 decimal places, but it will never come out "even." In other words no square can be constructed that is exactly equal to a circle.

The value correct to the first 35 places is as follows:

PI = 3.14159265358979323846246338327905288 When very exact measures are needed, we use 7r = 3.14159 or 3.1416.

For less exact measures, we use PI = 3.14 or PI = 3 1/7.

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