The man who
MEASURED THE earth
Eratosthenes was born in 276 BC in the city of
Cyrene which is now commonly known as Libya.
Eratosthenes was a very intelligent person; he
always wanted to know the answers to things. He studied in Athens then later
went to Alexandria Egypt.
While working on a geometry problem one day he
was sent for from the king Ptolemy the 3rd
And was asked to tutor his son in literature,
history, math and science. He was ecstatic to be able to tutor the king’s son.
It was during Eratosthenes time when the first encyclopedia and dictionary was
printed. After this time Eratosthenes had been asked to run the library in
Alexandria it was then that Aristophanes invented punctuation .during this time
as a librarian he read more about geography and the world, Eratosthenes had a
lot of questions about the earth like: How far does the earth tilt on its axis?
Does the ocean go across the whole earth? The sometimes felt discouraged about
how to measure the whole earth, did that stop him? Apparently not! Eratosthenes
began doing his intense research looking at scroll after scroll, Even though he was at the wealthiest library in
the world at the time ,all the scrolls had different answers , Eratosthenes
said to himself that he is going to make the first COMPLETE book on geography.
It took him many years to even get started on measuring the earth’s circumference;
He knew the book he was writing wouldn’t be complete without it.
Eratosthenes imagined the earth as a
grapefruit. (Show)
If it is sliced in half you can see the
sections, in order to measure the distance all the way around the edge of the
grape fruit,(The circumference) all you need to know is the distance along the
edge of one section, and how much it would take to make up the whole grapefruit.
The question is how any sections are needed? He
knew that every circle whether it is a small as a grapefruit or as big as the
earth, it is made up of 360 degrees. so if he could measure the inside angle of
one of his imaginary grapefruit in degrees , he could divide 360 by the answer
and know how many sections of that size would make a whole .
Eratosthenes pictured a section of the earth
form the outer edges of Alexandria to syene (SI-EE-NEE) (A city in S
Egypt) degrees. “I Eratosthenes could
figure out the distance between Alexandria to Syene”. And then measure the
grapefruit section he created. He would then be able to calculate the earth’s
circumference. But the question is how
he would be able to measure that angle, if it lies below the ground, at the
center of the earth. Then Eratosthenes realized that the sun could help him
with his angle problem. Eratosthenes heard from a caravan passing through
Alexandria that on the 21st day on June at precisely mid-day the sun
would shine directly down on a certain well in Syene, lighting up the well, but
not showing any shadows over the walls . But yet at the same time in Alexandria
it would show shadows. Eratosthenes knew exactly why because if the earth were
flat then the sun would strike the whole earth at the same time. Eratosthenes also
knew he could measure the angle of the sun from the shadow. So on June 21st
there would be an exact angle that lay at the 12pm center of the earth making
the inside of Alexandria – Syene a “Grapefruit” section. So Eratosthenes stood
waiting outside of the library at noon of June 21st and just as the
sun falling strait down
Also in Syene as well. He measured the angle to
be about 7.2 degrees then he divided 360 into 7.2 witch equaled 50. Now he knew
how to take 60 sections from Alexandria to Syene to get the circumference of
the earth.
Now Eratosthenes had all the numbers he needed
for the formula. He calculated the
circumference of the earth to be 255,000 shares or 24,662 miles.
2000 years later with modern technology they
figured out that Eratosthenes was only 16% off,
This is pretty good if you think about it he
was the first one to measure the earth. Eratosthenes never stopped asking
questions and lived till he was 82.
