How did we figure out that the earth is round?

Day 66 / 365

If I ask you today to prove to me that the earth is round, how would you do it? You can’t use satellite images or videos, just observe the world around you and try to conclude that the earth is a sphere. Sounds hard, doesn’t it? But that is exactly what the Greeks did, 2600 years ago!

To give you an idea how long ago that was, Aryabhatta, the man who invented zero, was born about 1500 years ago. So more than 1000 years before we had invented the concept of zero, we had figured out that the earth must be round!

So how did they do it?

The trick lies in observing the lunar eclipse. It was already known that the cause of lunar eclipses is the shadow of the earth on the moon.

People observed that this shadow was always circular. Now this means that the earth is either a disc or a sphere.

If it was a disc though, then the shape wouldn’t always be circular. depending on the angle, it could be an oval as well. Thus the only possible shape of the earth that explained the lunar eclipse was a sphere!

And so the Greeks concluded that the earth was round. But they went one step further. They even estimated the radius of the earth with accuracy in single digits! all using just simple tools and their mind.

This story is part of my 365 Day Project for 2019. Read about it here

Yesterday’s blog —When the harder you try, the less you succeed