Earth’s circumference is the distance around Earth. Measured around the equator, it is 40,075.017 km (24,901.461 mi). Measured passing through the poles, the circumference is 40,007.863 km (24,859.734 mi).
Let’s explore the history behind the meter, how figured out the earth’s circumference measurement, and the International System of Units (SI). It’s fascinating to think about how folks in the past came up with their techniques and what insights they had.
To get a handle on engineering, you need to understand the basic units. Nowadays, we frequently use units like area, volume, and speed.
However, these are actually considered derived units, not basic ones. There are only 7 basic units: length (m), mass (kg), time (s), electric current (A), temperature (K), luminous intensity (cd), and amount of substance (mol). All other units come from these basic ones.
First Earth’s Circumference Measurement
Before the metric system was in use, the first person to measure the Earth’s circumference was Eratosthenes.
At noon on the summer solstice, he observed that the sun was directly overhead in a well in Syene. Meanwhile, 800 kilometers away in Alexandria, trees cast shadows. By assuming the Earth was a perfect sphere and that sunlight hit both locations parallel to each other, he was able to calculate the Earth’s circumference.
Back then, the calculated circumference of the Earth was 46,620 km. Given how long ago this was, they actually came up with a pretty accurate estimate.
Why the metric system was created
Looking into the background of the meter’s origin, you’ll find it comes from the Greek word metron and the Latin word metrum.
The current unit of length, the meter, has ties to the French Revolution. Before the revolution, peasants and lords used different units of length and weight that often favored the lords. This inconsistency created a need for standardized measurements for surveying tools.
During the French Revolution, figures like René Descartes and Blaise Pascal worked together to create a new unit of measurement. They sought a constant standard and decided that the Earth’s circumference could serve this purpose. By 1791, it was established that 1 meter would be defined as one ten-millionth of the distance from the North Pole to the equator along the meridian.
Afterward, expeditions were undertaken to measure it in practice. Seven years later, in 1799, the measurements were completed, and the meter standard was officially established.
SI unit
In 1960, the International Conference on Weights and Measures adopted the SI system, which stands for Système International d’Unités, or the International System of Units, as the standard for weights and measures. By 1983, the definition of the meter was updated to be the distance that light travels in a vacuum in 1/299,792,458 of a second.
Today we covered the origin of the meter, how the Earth’s circumference was measured, and the SI system. It’s clear that for a unit system to be effective, it needs to be both well-established and unified across countries to avoid issues like the NASA Mars Climate Orbiter incident in 1998. Hopefully, we’ll achieve that global unity someday.
P.S.
Of course, switching to the metric system requires converting everything from the transportation system to individual components. This means the social cost is quite high, and changing people’s perceptions takes a lot of time.