How to measure the radius of the earth with lego

More than 2000 Years ago, almost every educated person knew that the earth was round. After all, there are pretty obvious clues. If you travel south, you’ll see stars and constellations you’ve never seen before (because they’re blocked by the curvature of the Earth). When a ship comes into port, you see the top before the bottom (because the surface of the ocean is curved). Finally, when the Earth’s shadow falls on the Moon during a lunar eclipse, the shadow is a circle. I mean, come!

But this is remarkable: Around 240 BC, the Greek mathematician Eratosthenes, head of the famous library of Alexandria in Egypt, came up with a brilliant method for calculating the radius of the spherical Earth. You can do it too, and it doesn’t require fancy equipment. I will show you how to measure the size of the land using Lego pieces.

Of course, Eratosthenes did not have Lego. But he knew that at midday on the summer solstice, the sun shines directly through a vertical well in Sina, Egypt. This meant that the sun was directly overhead. So what did he do? In Alexandria, he stuck an arrow in the ground and noticed at noon that day that it cast a shadow, meaning the sun. was not There is overhead

In the image below, I’ve used a rod in Syene (obviously not to scale) instead of a well, but it’s the same idea. You can see that if the sun is in line with the Sine Pole, it will not be in line with the Alexandria Pole. It can only mean that the earth is curved. But, yes, he knew that.

Image: Rhett Allen