2. William Ockham (c. 1285–1349) is remembered as an influential nominalist but his popular fame as a great logician rests chiefly on the maxim attributed to him and known as Occam's razor: Entia non sunt multiplicanda praeter necessitatem or "Entities should not be multiplied unnecessarily." The term razor refers to the act of shaving away unnecessary assumptions to get to the simplest explanation.
Hanlon’s Razor: "Never attribute to malice that which can be adequately explained by stupidity".

3. He was a librarian in Alexandria, Egypt.
Image source: Wikipedia.
Image source: WordPress blog.
Eratosthenes (b. 276 BC- d. 194 BC) calculated the radius of the Earth.
He was a librarian in Alexandria, Egypt.
He made the measurement without leaving home (but getting information from travelers)

4. Credit : Inter-University Centre for Astronomy and Astrophysics, Pune.

5. Credit : Inter-University Centre for Astronomy and Astrophysics, Pune.

6. One needs two measurements to calculate radius of the Earth: angle & distance
meter stick height
Image from Wikimedia Commons, courtesy of John O’Neill C
shadow length B
angle
distance
Image of protractor from Wikimedia Commons.

7. Credit : Inter-University Centre for Astronomy and Astrophysics, Pune.θ h x

8. Image source: Wikipedia.
A note of interest: Eratosthenes was known as “beta” because he was always second best at things.

9. Sun
Foci
Earth
Draw 4 Earths on the orbit, labeling the dates in the year they are in that position.