Why is a circle divided into 360 degrees?

The Babylonians 3000 years ago used the sexagesimal system of numbering, which was based upon a multiplication of 6, instead of the decimal system which we now use. They divided the circle for example into 60×6 parts – the 360 degrees. Each degree in turn was divided into 60 parts was again divided into 60.

Claudius Ptolemy took this method of division from the Babylonians and called the first division of the degree the parts minutiae, or a small part. The division of this first small part he called the ‘pars minutiae secundae’ or the second small part, Ptolemy’s names became known as minutes and seconds.

Extracted from the book by title ‘Tick Tock’ compiled by I. Step nova, Prosveshcheniye Publishers, Moscow 1981, Page 36.The Babylonians calculated the number of days in a year as 360.

 The earth moved through the Zodiac in 360days as per their estimate and hence the division of the circle into 360 degrees, that is one degree per day. Time measurement is also based upon the sexagesimal system as there are 60 seconds to a minute, sixty minutes to an hour, 24 hours to a day, 30 days to a month and 12 months to an year and also 12 Zodiacal signs in astronomy.

The frequently used angular measurements in Geometry – 30’, 60’, 90’, 180’, & 360′ are all multiples of six. The Gradian measure of dividing the quarter of a circle into 100 parts has not become popular. The angular and time measurements remain sexagesimal to this day even though the other two viz. Length and mass of the fundamental measurements have been metricated long back.