Columbus Knew the Earth Was a Sphere
He Certainly Knew That. He Just Got the Distances Wrong. The Reason Why He Did is compelling.
Back in third grade, our classroom teacher, whom I will call Mrs. Hale, told us that Columbus risked his life sailing west across the Atlantic from Europe because everybody back then thought the world was flat and that he would sail right over the edge into oblivion. He was brave to just ignore that and push on anyway.
But that’s not true! Columbus knew the world was a sphere and firmly believed that he would get to China if he persisted. Or maybe Japan. Or maybe India. The end point was not exactly known but he figured he could make it over there, somewhere, anywhere, before the ship’s supply of food and water ran out. What he didn’t know was just how big that gamble was.
He made it across the Atlantic because he grossly miscalculated the number of miles his ships would have to travel. He made the educated guess that the orient was only 2,400 miles from Spain! This calculation left out the whole North American landmass and the entire expanse of the Pacific Ocean! Had he known the actual distance to Asia he no doubt would have dusted off his hands and walked away and left his boats in port.
In any case, if the place where he was headed actually had been as far away from Spain as Asia is and if it had been ocean all the way, he and his crews would have been cadavers long before they got there. As sheer luck would have it, he accidentally bumped into the Bahamas. He so strongly believed his calculations were accurate that he referred to the people there as “Indians”.
What our third grade teacher didn’t know many years ago was that by the time Columbus sailed, every well educated person on Earth knew the world was a sphere. They knew that because of an amazing Greek astronomer, mathematician and geographer named Eratosthenes. Columbus would have done well to study him. But he didn’t.
Eratosthenes was the first to use the word geography. He invented a system of longitude and latitude, was first to calculate the 23.5 degree tilt of the Earth’s axis, he devised a catalog of 675 stars and designed a system for finding prime numbers which is still in use today. But his most amazing achievement was calculating the circumference of the Earth to within a just few miles! How did he do that?
Well, here’s how. He heard about a famous well in the Egyptian city of Syene (now Aswan) in which the sun’s rays went perfectly straight down that well at noon on the Summer Solstice (June 21+-). Because Aswan is on the Tropic of Cancer at 23.5 degrees north of the Equator,the Sun on this day each year is directly overhead at Seyne. Eratosthenes was at Alexandria, about 500 miles north of there and precisely at noon on the Summer Solstice, he put a pole in the ground and saw its shadow. The shadow meant that the sun’s rays were not coming straight down at Alexandria as they were at Syene.
Eratothsenes computed the length of the shadow against the height of the pole and got an angle of 7.12 degrees. Knowing that the world’s circumference was 360 degrees and that the distance from Alexandria to Seyne was 500 miles he calculated the earth’s circumference at 25,000 miles. The actual circumference is 24,901.461!
But Columbus didn’t study Eratosthenes. He chose instead the calculations of yet another Greek mathematician in Alexandria named Claudius Ptolemy. Ptolemy’s figures came out a lot smaller than those of Eratosthenes, leading Columbus to make his miscalculation.
Ptolemy made famous the notion that Earth is the center of the Universe, that the sun and planets revolved around our world. His view was the one universally accepted for 1,400 years until Copernicus committed the unspeakable heresy of proving Earth and the planets revolved around the Sun.
Incidentally, Eratothsenes lived to be 82 years old. He starved himself to death because he feared the onset of blindness.
It’s really amazing that Columbus’s huge error correctly estimated the distance which he actually did travel and got him to dry land. Think about that … you stake your life on an educated guess that turns out to be wrong by two orders of magnitude and then wind up in a place nobody back home has ever heard of and suddenly you’re an overnight sensation.
That voyage was not like sailing around the coast of Africa, as did the Portuguese, Spain’s chief trading rival. You couldn’t send the oarboat ashore for fresh water and wild game. No, you’re way out on a dark, uncharted ocean. A couple of weeks out past the point of no return and you would be toast. Columbus’s great gamble paid off precisely because he was wrong about the facts.
Despite his fateful miscalculation, Columbus was an excellent navigator and was able to locate most islands in and around the Caribbean during his four voyages to the “new world”. He also had the good sense to head west from the Canary Islands, not from Spain, thereby benefiting from favorable trade winds and then going back home on the prevailing westerly winds.
Long before Columbus’s time, Eratosthenes had become head of the famous Library at Alexandria and it was from there that he wrote and taught and contributed so much to that center of learning. The city itself was founded and named for Alexander the Great who, after becoming King of Macedonia at the ripe old age of 20, went on to become one of the greatest military minds of human history. He died at age 32.
Alexandria today stretches 20 miles along the Mediterranean coast. It is one of the biggest cities on the continent of Africa and is Egypt’s main seaport. Alexander defeated and named many cities after himself in his quest to conquer the world. He even named one after his beloved horse. He made Alexandria, Egypt, the capitol of all of them.
A Confession
This publication is partly focused on foods and food origins and the ways various food ingredients have affected history. Usually I will feature a plan that you can follow at home to make something related to the story but …
Sadly, I have never been to Alexandria. I have enjoyed a few of its popular foods; American versions of falafel, hummus and baba ganoush. I confess I don’t know how to make those things and have never made them so I won’t mislead you by giving you a plan that I never tried. It probably would be a good thing to enjoy while reflecting back on old Eratosthenes and for being thankful that Alexander the Great was not able to subdue your town and name it after himself.
So my suggestion would be to just pick up some flat bread and hummus at the grocery store, get in your easy chair, pop a beer and watch some old Egyptian movie like “The Mummy”, featuring a creepy Boris Karloff wrapped in what appears to be about ten rolls of toilet paper.
Next time, though!