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Stump Edvard about Eratosthenes

Eratosthenes was one of the most influential mathematicians in history. He is best known for measuring Earth’s circumference by measuring the Sun’s angle from vertical simultaneously at two different places – Syene and Alexandria – that are a known distance apart.

Our very own “Dynamite Eating” Edvard van de Kamp, when he is not hosting Adventures of the Schmilblick Patrol or curating the avian wing of the Utrecht Museum of Natural History, takes questions about various topics. This week, Eratosthenes was the topic of interest, which drew a total of nine questions. We always publish eight questions, so that leaves one out. Sorry, Panagiota Daskalopoulos of New York City, NY, USA.

In the meantime, here are the other eight questions and Edvard’s responses.

Dear Edvard: Where and when did Eratosthenes live?

– Lise Lelongway
Hardhome Springs, FL, USA

Dear Lise: Eratosthenes was born in 276 BC in Cyrene, located in what is now Libya. He later moved to Athens, and then to Alexandria. He died there in 194 BC.

Dear Edvard: How accurate was Eratosthenes’s measurement of the circumference of the Earth?

– Joan Cuddlemonster
Berekua, Dominica

Dear Joan: We don’t know for sure. His result was 250,000 stadia, but historians disagree on just how long a stadion was. If it was 166.7 m, he was off by about four percent. If it was 157.2 m, he was off by less than two percent.

Dear Edvard: Is Eratosthenes known for anything else besides measuring the circumference of the Earth?

– Paula Rockerby
Athens, OH, USA

Dear Paula: Yes. Eratosthenes also calculated Earth’s axial tilt, created the first map of Earth, and was the chief librarian at the Library of Alexandria.

Dear Edvard: I read that Eratosthenes is called the father of geography. What did he do that’s so geographically fatherly?

– CB Bianca
Atlantic City, NJ, USA

Dear CB: Eratosthenes wrote the book on geography. Literally: his three volume work, Geography, contains the foundations of modern geography, including a map of the known world showing the locations of hundreds of cities, the first use of parallels and meridians to mark longitude and latitude, and a description of his method for measuring Earth’s circumference.

Dear Edvard: Did other mathematicians really call Eratosthenes “Beta”?

– Blaine Jones
Ottawa, ON, Canada

Dear Blaine: Yes. Apparently, Eratosthenes had a reputation for being second best in all categories. They also called him “Pentathlos”, for someone who is very good at five sports but not the best in any single one of them.

Dear Edvard: What did Eratosthenes wear on Sundays?

– Irene Ngo
Sydney, NSW, Australia

Dear Irene: Togas?

Dear Edvard: I wanted to figure out whether 717 is prime, so I used the Sieve of Eratosthenes. I wrote down all the numbers from 1 to 1,000. Then I crossed out all the even numbers, all the multiples of 3, all the multiples of 5, and so on. Then I got confused around 319, and I had to start again. Then I lost the paper I was using. Anyway, is 717 prime?

– Joey McCallister
Telluride, CO, USA

Dear Joey: 717 is not prime. It is equal to 3 × 239. Pro tip: If a number’s digits add up to a multiple of three, the number is itself a multiple of three. If they add up to a multiple of nine, the number is a multiple of nine.

Dear Edvard: Please do not perpetuate the myth that Eratosthenes measured the circumference of the Earth. It is a vast scientific conspiracy with assistance from National Public Radio, the Centers for Disease Control, the sextant manufacturers’ cartel, and the Clinton Foundation. My own measurements prove conclusively that the Earth is flat and that the Sun is an egg hatched every morning by a giant naga with the lower body of a king cobra and the upper body of Serena Williams before it travels across the sky in a chariot pulled by Dwayne “The Rock” Johnson and RuPaul, until it sets in the vicinity of Flagstaff, Arizona, every night. You can read all the conclusive, indisputable evidence at Thank you.

– Eric Arcapone
Anstair, MT, USA

Dear Eric: Thank you for clearing that up. We are now prepared to admit that we here at GoobNet receive an annual stipend from the sextant manufacturers’ cartel, in exchange for which we perpetuate the myth that reality is real. You have taught us the error of our ways. I have decided to quit my job at the natural history museum, and from now on we will help you prove your hypothesis by launching homemade submarine expeditions to Atlantis, where we will attempt to obtain the first ever photographs of Serena Cobra Kai in her lair. Also, we will launch an expedition to the face on Mars, and we will teach Amber Lynn to become a real life Dr Doolittle and yak with animals. We will begin doing all this just as soon as our King Fan Club card arrives in the mail.