Degree (angle)

Imagine you are spinning in a circle. We can measure how much you turn using a unit called a degree. A full, complete rotation is always assigned the value of 360 degrees.

You might see a small circle symbol, like this °, used to show degrees. While scientists often use a unit called a radian, degrees are still very common. In fact, the SI brochure says degrees are an accepted unit. One full turn of 360 degrees is equal to exactly 2 radians.

This helps us understand how different ways of measuring angles relate to each other.

Why did people choose the number 360? We do not know the exact reason. One theory is that it relates to the sun. Ancient astronomers saw the sun move about one degree each day along its path. Because of this, some old calendars used 360 days for a year. The Persian and Babylonian calendars are examples of this. Another idea is that 360 is very easy to divide into parts. It has 24 different divisors. It can be divided by every number from 1 to 10, except for the number 7. This makes it very useful for splitting things up.

History shows us that many smart people used these measurements. The Babylonians used a system based on the number 60. They might have used the angle of an equilateral triangle as a base.

They used chords of a circle to do early math. Greek scientists like Hipparchus and Aristarchus used Babylonian knowledge too. Other Greeks like Archimedes and Timocharis also worked with these divisions. They helped divide the circle into 360 degrees. Eratosthenes used a simpler system with 60 parts. These early thinkers helped build the math we use today.

Sometimes a single degree is not precise enough for a job. This happens in places like astronomy or when looking at maps. We can make a degree even smaller by splitting it up. One degree can be divided into 60 parts called minutes. Each minute can be divided into 60 parts called seconds. These are also known as arcminutes and arcseconds. You might see them written with tiny marks like ′ or ″. Sailors use these small measurements on maritime charts to stay on course. They use decimal minutes to help them find their way.

There have been other attempts to change how we measure turns. In France, people tried to use a system called the gon. In this system, a full circle is 400 gon instead of 360 degrees. This was part of a plan to use a metric system. This idea was eventually abandoned by Napoleon, but grades are still used in some tools. Some military tools use a different unit called a mil. In the Russian army, they used a system with 600 units. Even with these different ways, the degree remains a very important tool for our world.