Reading Eratosthenes Content Mathematics Q: Where were you born? A: I was born in Cyrene, Greece (which is present-day Libya), in 276 BC Both of my parents were Greek Q: Did you have any nicknames growing up? A: I did have one; my friends called me Beta, which is the second letter of the Greek alphabet They teased me, saying I fell just short of first place (which was occupied by Archimedes) Later in my life, I received the nickname Pentathlos It’s funny, because literally this word refers to an athlete who participated in five sporting events, but eventually was used to describe someone who was well rounded, or good at several different things Q: What was your childhood like? A: My parents told me that I had always been a curious baby, sticking my hands into new and foreign objects, typical baby behavior But as I grew older, I asked thousands of questions that nobody could answer I was fascinated by the sky, because it was something that I could not reach and touch I wondered how far away the sun was, what it was made of, where the winds came from, and how the stars moved When I was about six years old, I began to go to the gymnasium, which is a school I learned reading, writing, arithmetic, music, and poetry I was very strong in math, but geography was by far my favorite subject Reading Strategy Ask Questions What other information you want to know about Eratosthenes’ nicknames? Ask him a question about them How you think Eratosthenes would answer? The world as known to Eratosthenes, 200 BC nicknames informal names that are different from people’s actual names Archimedes an ancient Greek mathematician and scholar foreign unknown 218 Unit • Chapter Q: What were the turning points of your life? A: Well, I sailed to Athens to study there Somehow I made myself so known in several fields that Ptolemy III of Egypt invited me to Alexandria There I tutored his son Philopater and became the librarian for the great Alexandrian University That completely changed my life It was the most exciting place to be, because it was considered the center of all learning The library and museum were the best in the world In the library at Alexandria, there were 700,000 papyrus scrolls and 40 librarians Reading Strategy Ask Questions Think of another question to ask Eratosthenes about his work as a librarian Do research to see if you can find the answer to your question Library of Alexandria, 300 BC Q: What were your major accomplishments? 10 A: I was able to accurately measure the circumference of the earth And I, being the list maker that I am, worked on figuring out the dates of literary and political events, a list called a chronology I wrote some books as well—one on comedy, one on history, and one on the constellations ✓ Reading Check Recall details Where did Eratosthenes grow up? What is the name of that country today? Make inferences Ptolemy III an ancient Egyptian ruler papyrus type of paper invented in ancient Egypt scrolls pieces of paper rolled into a circular shape circumference distance around something circular chronology list of events in the order they happen constellations groupings of stars that look like objects Why was Eratosthenes given the nickname Pentathlos? Draw conclusions Did Eratosthenes enjoy being a librarian? Explain Unit • Chapter 219 11 Q: How did you measure the circumference of the earth? 12 A: Well in order to find a circumference, I made two assumptions: that the earth was round and that the sun’s rays were essentially parallel because the sun was so far away I imagined that a section of the earth ran from Alexandria to Syene, and if I could figure out the distance, and measure the inside of the section they created, I would be able to calculate the earth’s circumference I picked Syene because I heard from a caravan passing through Alexandria that on the twenty-first day of June at precisely midday, the sun would shine directly down a certain well in Syene, lighting up the well but casting no shadows on its walls I supposed the earth was like a giant grapefruit; if I could find the distance of one section of the arc, I could find out how many of these same-size sections it would take to make up the whole grapefruit Since a circle is made up of 360 degrees, with the inside angle I could figure out how many inside angles make up 360, and then the whole circumference 13 The circumference of the earth calculated by Eratosthenes was only 200 miles off from the modern-day figure, and considering the magnitude of the numbers, it can be considered the first accurate measurement After his discovery, he provided the first mathematically based map of the world His Geographica, geography book of the world, was finally complete Reading Strategy Ask Questions Eratosthenes tells how he calculated the circumference of the earth Ask three questions about the method he used Eratosthenes made his calculations based on the distance between Alexandria and Syene assumptions beliefs that something is true essentially just about calculate figure out using math caravan group of people making a trip together precisely exactly casting throwing magnitude great size 220 Unit • Chapter Alexandria Heliopolis Cairo Memphis Nile River Antinoopolis Ptolemais Syene