- Unit 8. Philosophy and Science
- Getting Started
  - What Are We Learning
  - Observe and Think
  - Map Your Mind
- Philosophy and Science
  - First Steps of Science
    - Some Scientific Principles
    - Numbers and Paradoxes
    - First Steps of Medicine
    - Greek Tecnological Achievements
  - Philosophy
    - Socrates
    - Plato
    - Aristotle
    - Epicureans and Stoics
    - A Wall for Reflection
- Self-Evaluation Quiz
- Complementary Activities
  - The Greek and Latin Roots of English
  - One Myth, One Song
  - Games, Comics and Stuff
- References

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# Some Scientific Principles

### Archimedes' Principle

Have you heard of Archimides' principle? It says: "Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object." Maybe it is a little difficult for you to understand. Let's try it with this funny demostration by the physicist Paul Hewitt.

Did you get it? I am pretty sure that you did and you are ready to do both activities below.

Think about it

Explain this picture in your own words.

Looking for information

Did you know that Archimedes figured out his principle thanks to a tricky question that tyrant Hieron had proposed to him? Look for information and write in your own words the whole anecdote. This picture will give you a hint.

### Erasthostenes' measurement of the earth's circumference

What an amazing guy Erathostenes was! He measured the earth's circumference just by travelling from Syene to Alexandria in Egypt. Would you like to know how? Look at this video and then complete the cloze exercise below.

Now it's your turn
While visiting the city of Syene one JXUwMDM1JXUwMDA0JXUwMDBkJXUwMDQ5JXUwMDVlJXUwMDA2JXUwMDE4JXUwMDAwJXUwMDA4JXUw MDE3JXUwMDU1JXUwMDU0 day, Erathostenes noticed that the JXUwMDJhJXUwMDE3JXUwMDAzJXUwMDBhJXUwMDA5JXUwMDA2JXUwMDE3JXUwMDFkJXUwMDA2JXUw MDAx of the sun could be seen in the JXUwMDNhJXUwMDBkJXUwMDFiJXUwMDAwJXUwMDFiJXUwMDAy of a deep well. The sun was JXUwMDM3JXUwMDE5JXUwMDEzJXUwMDE3JXUwMDFhJXUwMDBkJXUwMDA0JXUwMDA1 and the rays pointed to the JXUwMDNiJXUwMDA2JXUwMDBiJXUwMDFhJXUwMDA2JXUwMDE3 of the earth. He remembered this and in the next mid-summer's day, in Alexandria, he JXUwMDM1JXUwMDA4JXUwMDA0JXUwMDEyJXUwMDA2JXUwMDA3JXUwMDE3JXUwMDAx the shadow cast by an JXUwMDM3JXUwMDBkJXUwMDA3JXUwMDA5JXUwMDA1JXUwMDFhJXUwMDE4 . Sunbeams travel in JXUwMDI4JXUwMDExJXUwMDEzJXUwMDEzJXUwMDBkJXUwMDAwJXUwMDA5JXUwMDA5 lines so the difference in JXUwMDM5JXUwMDBmJXUwMDA5JXUwMDBiJXUwMDA5 had to result from the JXUwMDNiJXUwMDE2JXUwMDA3JXUwMDA0JXUwMDE3JXUwMDE1JXUwMDAxJXUwMDA3JXUwMDE3 of the earth.
If the angle was one-fiftieth of the JXUwMDNiJXUwMDBhJXUwMDFiJXUwMDExJXUwMDBmJXUwMDA5 , then the distance around the world must be JXUwMDNlJXUwMDBmJXUwMDBmJXUwMDEyJXUwMDBk times the distance from Alexandria to Syene. With these simple JXUwMDJjJXUwMDFiJXUwMDAwJXUwMDAzJXUwMDFm , Erathostenes made this almost exact measurement of the world more than JXUwMDJiJXUwMDE2JXUwMDEzJXUwMDEzJXUwMDBiJXUwMDFhJXUwMDExJXUwMDAwJXUwMDBi hundred years before Magellan JXUwMDJiJXUwMDEyJXUwMDA4JXUwMDA1JXUwMDA5JXUwMDAx around it.
While visiting the city of Syene one mid-summer's day, Erathostenes noticed that the reflection of the sun could be seen in the bottom of a deep well. The sun was overhead and the rays pointed to the centre of the earth. He remembered this and in the next mid-summer's day, in Alexandria, he measured the shadow cast by an obelisk . Sunbeams travel in parallel lines so the difference in angle had to result from the curvature of the earth.
If the angle was one-fiftieth of the circle, then the distance around the world must be fifty times the distance from Alexandria to Syene. With these simple tools, Erathostenes made this almost exact measurement of the world more than seventeen hundred years before Magellan sailed around it.
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