How Eratosthenes measured the size of Earth - GIF

[ToolTalkBot]

How Eratosthenes measured the size of Earth.




Previously:

"Flat Earth" photo, and why it's so hard to debunk pseudoscience
Deepest places on Earth - infographic
Distribution of Earth's water - graph
Driving a car in the coldest inhabited place on Earth - video
First image of Earth from outer space - photo
Moon transiting the earth - video
Space debris orbiting the Earth- GIF and photo
The Earth's atmosphere to scale - photo

[mklotz]

Eratosthenes was born in 276 BC. The error in his calculation of the earth's circumference was about 1 %. Today, more than two millennia later, if you gave most people the great circle distance between Alexandria and Aswan, I doubt that they would know what to calculate, much less how to perform the calculation.

[Floradawg]

Carl Sagan, the first scientist that the public could relate to in a personal way. He would appear on The Tonight Show with Johnny Carson and many other TV shows and explain scientific ideas and theories to the viewers. He had a way of making potentially dull explanations interesting. He helped to mold Neil deGrasse Tyson into the scientist that he is today.

[Ralphxyz]

How was the timing done? Both shadows had to be measured at the same time.

[Frank S]

How was the timing done? Both shadows had to be measured at the same time.

For all we know he may have done both measurements himself but a year apart