Calculate Circumference facts
While investigating facts about Calculate Circumference Of A Circle and Calculate Circumference From Diameter, I found out little known, but curios details like:
NASA calculated that you only need 40 digits of Pi to calculate the circumference of the observable universe, to the accuracy of 1 hydrogen atom
how calculate circumference of a circle?
You only need 40 digits of pi to calculate the circumference of the observable universe to a margin of error of 1 hydrogen atom
What is the formula to calculate circumference?
In my opinion, it is useful to put together a list of the most interesting details from trusted sources that I've come across answering what formula is used to calculate the circumference of a circle. Here are 25 of the best facts about Calculate Circumference From Radius and Calculate Circumference Of Circle From Diameter I managed to collect.
what is the formula to calculate the circumference of a circle?

The ancient Greeks had known the world is round since Pythagoras, and successfully calculated the circumference of the globe when Eratosthenes measued the angles of the midday sun between two towns of a known distance. His calculation had only about a 10% margin of error.

With only 40 digits of PI, you could calculate the circumference of the entire universe to within a single hydrogen atom.

62 decimal digits of pi is all that is needed to calculate the circumference of the known universe to Planck length precision

Before 194 BC, using sticks and shadows, Eratosthenes of Cyrene calculated the Earth's circumference with an error between 2 and 15%, and calculated the tilt of the Earth and the distance of the Sun to the Earth with near perfect accuracy.

The ancient Greek astronomer Eratosthenes of Cyrene, proved that the earth was round in 240 B.C. and also came up with latitude/longitude and was able to calculate the earth's circumference within 2%.

By the time you get to the 39th digit of Pi, you can calculate the circumference of the known universe to within the width of an atom.

It only takes the first 39 digits of pi to calculate the circumference of the observable universe

Ancient Greek scientist Eratosthenes calculated the circumference of the Earth with remarkable accuracy, invented the leap day and geography, created the first map of the world incorporating parallels and meridians

Eratosthenes (276194 BCE) and his many accomplishments: first to accurately calculate and record the Earth's circumference, discover a method for finding prime numbers, explain the annual flooding of the Nile, coin the term "geography", and use longitude and latitude on a map.
What is true about calculate circumference?
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Eratosthenes ( ~200 be), who calculated the Earth's circumference with remarkable accuracy at 25 000 miles, using a rod and a hole/well. Modern day measurement of the earth’s circumference is 24,859.734 mi at the Poles and 24,901.461 mi at the Equator.
The Book of Roger, a world atlas by Arab geographer Muhammad alIdrisi in 1154 for the Norman King Roger II of Sicily. It took him 15 years to make, and was the most accurate world map for the next 300 years: the circumference calculated in the book was off by less than 10%.  source
Christopher Columbus did not think the world was flat. He was concerned the East Indies were further than expected. Columbus underestimated the Earth's circumference because of two calculation errors. His crew would have starved to death if they had not found North America.  source
How to calculate radius when circumference is given?
Greek mathematician Eratosthenes accurately calculated the circumference of the Earth in the 2nd century B.C.
How calculate circumference from diameter?
NASA uses 15 digits of Pi to calculate interplanetary spacecraft trajectories. A calculation using 40 digits of Pi could calculate a circle of circumference of the visible universe with a margin of error less than the width of a hydrogen atom.
Eratosthenes, the Greek scholar best known for calculating the circumference of the Earth, was derisively nicknamed 'Beta' by his peers because he was seen as second best in most of his endeavors
The Chinese never calculated the circumference of the Earth. Where Eratosthenes assumed the Earth was spherical and the Sun was infinitely far away, the Chinese assumed that the Earth was flat and the Sun was just close above; the maths works either way
The circumference of Earth was calculated by Eratosthenes, without ever leaving Egypt.
A man, Eratosthenes, roughly 200 years before Christ, calculated almost precisely the tilt of the Earth and its circumference by using two sticks and a lot of step counting.