Before the Bell…
• Open to a blank page in your notes…
• Get out a pencil…not a pen
On a piece of paper in your notes…
Copy down this diagram and TRY TO find the circumference
of the circle, using the given information.
A
9 degrees
B
The distance
from A to B is
10 meters.
Eratosthenes Method to Finding
Circumference of Earth
• Answer these questions to get you started understanding…
– State the alternate interior angle hypothesis in your own words…
– Why is it strange its considered a hypothesis?
– Where does the sun shine its rays at 90 degrees on the summer
solstice?
– If you were standing somewhere at noon in that area (question
above) on the summer solstice…what would your shadow look
like? Why?
– If someone was standing on a different location on Earth during
the summer solstice, what would their shadow look like compared
to someone of tropic of Cancer?
– Where does the sun shine its rays at 90 degrees on the autumnal
equinox?
How does the sun cast different
shadows in different locations?
Eratosthenes YouTube Video
This is my Homeboy Carl Sagan-Eratosthenes YouTube Video 2
Whale song- https://www.youtube.com/watch?v=elw-459P8kE
Let’s see if you understand…
• What was unique about the town of Syene’s
location…and what happened there that was
“special”.
• What does getting the shadow angle help us
find about our specific location?
• Why does this help us find the circumference
of earth?
So How Do I Calculate the Circumference?
Θ= Shadow Angle
c = distance between
shadow area and no
shadow area
C = Circumference of Earth
c
θ
c
=
360
C=
C
C * 360
θ
***how did we get to C=?***
Let’s Look at a Ruler Example