World’s Oldest Known Decimal Point Discovered in Italy

Newly discovered notes from 15th-century Italy show that the decimal point is actually 150 years older than what historians previously believed.

Decimal points may seem basic, but they’re incredibly helpful in math. They divide whole numbers into tenths, hundredths, and thousandths, which makes calculations a lot easier compared to using fractions.

Some forms of decimals have been around since the 900s in Damascus and the 1200s in China, as reported by Live Science.

A solid system of decimals didn’t become fully established until 1593. This happened when the German mathematician Christopher Clavius included decimals in astronomical work.

However, recent studies propose that Clavius was actually following an older practice. He likely adopted the use of decimals from Giovanni Bianchini, a Venetian merchant from the 15th century.

Decimal point is a century and a half older than Clavius’ use

The authors of the latest research say that Bianchini’s work, dating back to between 1441 and 1450, precedes Clavius’ use of the decimal point by a century and a half.

Glen Van Brummelen, a mathematics historian at Trinity Western University in Canada, stumbled upon Bianchini’s use of decimals while teaching a math camp for middle school students.

Van Brummelen recalls his excitement, rushing through the dormitory halls with his computer, eager to share his discovery. He shouted, “Look at this, this guy is doing decimal points in the 1440s!”

The concept of dividing whole numbers into smaller parts has ancient roots, but before the Middle Ages, most mathematicians leaned towards using fractions. Although astronomers did use decimals, their method differed from the familiar base-10 system taught in elementary school.

Instead, they utilized base-60 decimals. This involved dividing circles, such as the 360-degree circle, into sixty minutes, which could further be broken down into sixty seconds, as reported by Live Science.

In a paper published online for the journal Historia Mathematica, Van Brummelen noted that, occasionally, mathematicians did experiment with notations resembling today’s decimal system. However, these concepts often failed to gain traction and weren’t consistently adopted by subsequent mathematicians.

Decimal point first seen in Bianchini’s “Tabulae primi mobilis B”

Van Brummelen highlighted that while pinpointing the exact origins of decimal notation can be challenging, the history of the decimal point is comparatively clearer. This enduring symbol first emerges in Bianchini’s “Tabulae primi mobilis B,” a work focused on computing stellar coordinates.

Bianchini, originally a merchant, later served as an administrator to Venice’s ruling d’Este family. In this role, he was tasked with calculating horoscopes and engaging in astrology.

Within his text, Bianchini used the decimal point in a manner similar to modern mathematicians, marking a significant early usage of this decimal point.