We are all familiar with the decimal number system including the decimal point as in 1.5 or 2.31. The decimal point is fundamental to how we perform mathematics today to the level we take it for granted as it seems like it should have existed forever.
But how old is the invention of the decimal point?
Until recently, mathematicians and historians had credited the German mathematician Christopher Clavius with the introduction of the decimal point in 1590. Where he only used it once in one of his works and then never again.
However, the decimal point was invented around 150 years earlier than previously thought according to a recent paper published in the journal Historia Mathematica by Glen Van Brummelen, a mathematics historian at Trinity Western University in Canada. He traced the invention of the decimal point back to the 15th century in the work of the Italian merchant and mathematician Giovanni Bianchini. But why was Bianchini’s invention not discovered before?
Until the 1400s, an entirely different numerical system was being used to what we currently use. Our number system today is a “base 10” system (refer to the use of 10 fingers for counting). Every number is made of a combination of the single digits 0-9, and every new “place” in a number represents 10 of the “place” before it. For example, a hundred is 10 tens, and 10 is ten ones. This makes operations such as arithmetic straightforward.
However, in the 1400s, astronomers and mathematicians used a “base 60” number system known as a sexagesimal system, to perform astronomical calculations. You can think of it as using arithmetic on the clock system where 1 hour is 60 minutes and 1 minute is 60 seconds.
In the sexagesimal system, the operations are complicated, especially the division. The introduction of decimal point in sexagesimal does not behave in the same way as in our decimal system, for example, 7.5 in sexagesimal system will mean 7 hours and 30 minutes!
The decimal point may still not have caught on for some time, but it has now become fundamental in the world of mathematics. It allows easier manipulation of non-whole numbers, or fractions, alongside whole numbers. Without it, our current monetary system wouldn’t work as it does, and we couldn’t make calculations to the degree of accuracy we do in our daily activities.
Abdulla Eid
Assistant Professor of Mathematics
Department of Mathematics
University of Bahrain
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