The man who curved the world

Too many of us go through life without noticing, without questioning and without searching for answers. Instead we have to rely on the few that do the things that we’re all capable of…

In the Egyptian city of Alexandria, for three hundred years beginning in the third century BC, was a great library and museum. The city was founded by Alexander the Great and became the world centre of commerce, culture and learning which all centered around the library. The community of scholars studied the entire Cosmos, a Greek word meaning order of the universe implying a deep interconnectedness of all things. In 48 BC Julius Caesar accidentally burned down the library when he set fire to his own ships to block Achillas‘ attempt at sea supremacy. Who knows the depth of what was lost? We have heard from various sources that secrets and sciences that would take hundred if not thousands of years to re-discover where contained within the books of Alexandria.

How I would have loved to visit that Library!

The subjects explored included physics, literature, medicine, astronomy, geography, philosophy, mathematics, biology and engineering. The library may have contained half a million handwritten papyrus scrolls, acquired from all over the known world by agents sent out to buy up other libraries. Every ship that docked in Alexandria was searched by the police for books which were borrowed, copied and returned to their owners.

At this time of the early years of the library there lived a man called Eratosthenes. He was a philosopher, historian, theatre critic and poet. He was also the chief librarian of the great Library of Alexandria.

One day as he was reading one of the papyrus books, he came across a curious account. He read that far to the south, in the outpost of Syene, on the longest day of the year a strange thing could be seen. As noon approached, the shadows of temple columns or vertical sticks grew shorter and the suns’s rays would slither down the sides of a deep well that would normally remain libeain darkness. By noon the columns would cast no shadow and the sun’s reflection would be visible in the water at the bottom of the well. At this time, the sun would be directly overhead.

But so what? Sticks, shadows and wells. What possible importance could such an everyday observation have? But Eratosthenes was a scientist, (a scientist is of course a person who desires ‘to know’, the root of the work is Greek). His thoughts on that simple account changed the world. We could go so far as to say they made the world a ‘world’ because the experiment he performed would prove the Earth was not a flat plane.

He began by waiting until noon on June the 21st to see if vertical sticks would cast shadows in Alexandria. He found that they do.

Bu this puzzled him. How could it be that a stick in Syene casts no shadow at the same time that a stick in Alexandria casts a considerable shadow?

Having no shadows in both places is easy to understand, providing the world is flat. So too is having a shadow at both places, again provided the world is flat. But for a shadow at one and not the other the only explanation is that the surface of the world is curved. Not only that, but the greater the distance in the lengths of the shadows, the greater the curvature of the Earth.

Eratosthenes knew that the sun is so far away that its rays must be parallel when they reach the Earth, so sticks placed at different angles to the sun’s rays will cast different length shadows.

Eratosthenes imagined the sticks extending down to meet at the centre of the Earth. He calculated that they would intersect at an angle of seven degrees which is one fiftieth of the full circumference of a circle. Eratosthenes knew that the distance from Alexandria to Syene was five hundred miles. He knew that because he hired a man to pace it out. Five hundred times fifty is twenty-five thousand miles, so that must be the circumference of the Earth.

He was right. With just a small error of a few percent, he had calculated the circumference of the spherical world. The first man to do so. That’s not bad going for two thousand, two hundred years ago.

Along with this he invented the discipline of geography (as well as the word) and the system of latitude and longitude.

Erotosthenes’ careful ponderings of the ordinary, revealed something quite extraordinary. He had seen an observation from a fairly simple experiment that seemed to go against common sense. The discrepancy between what he thought he should find and what he actually found could only be explained in one way, that the world was curved.

This is how creativity and science work together: by noticing something, asking the question ‘why?’ and then devising methods to answer that question.

Ayd Instone works with people to explore and unlock their creative ideas in ways they may never have thought possible, to inspire innovation in their lives, and their business.

Book Ayd to speak about the Power of ‘What If?’ and Inspiration for Innovation at your conference, or in your business. A great way to open your event or as an after lunch energiser.

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4 comments on “The man who curved the world

    • Same reason we think the sun is far away. We look up at it and it appears to be further away than the furthest thing we can see, say a mountain in the distance. That’s enough to give parallel light.


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