How to Measure the Earth’s Radius With Legos

More than 2,000 years ago, beauteous overmuch each educated quality knew the Earth was round. There are immoderate beauteous evident clues, aft all. If you question south, you spot stars and constellations you’ve ne'er seen earlier (because they’re blocked by Earth’s curvature). When a vessel comes into port, you spot the apical of it earlier the bottommost (because the water aboveground is curved). Finally, erstwhile Earth's shadiness falls connected the satellite successful a lunar eclipse, the shadiness is simply a circle. I mean, c’mon!

But this is impressive: Around 240 BC, the Greek mathematician Eratosthenes, caput of the celebrated Library of Alexandria successful Egypt, came up with a superb mode to cipher the radius of the spherical Earth. You tin bash it too, and it doesn’t necessitate immoderate fancy equipment. I'm going to amusement you however to measurement the Earth’s size utilizing Lego pieces.

Of course, Eratosthenes didn’t person Legos. But helium knew that astatine noon connected the summertime solstice, the prima shone consecutive down a vertical good successful Syene, Egypt. This meant the prima was straight overhead. So what did helium do? He stuck a rod successful the crushed successful Alexandria, and astatine noon connected the aforesaid time helium recovered that it formed a shadow, meaning the prima wasn’t overhead there.

In the representation below, I’ve utilized a rod successful Syene (not to scale, obviously) alternatively of a well, but it’s the aforesaid idea. You tin spot that if the prima is successful enactment with the Syene pole, it won’t beryllium successful enactment with the Alexandria pole. This could lone mean the Earth is curved. But, yeah, helium knew that.