Eratosthene experiment in Scuola Secondaria di 1' grado G.G.Belli Rome Italy

1. Measuring the radius of the Earth THE ERASTOSTHENES’ METHOD Scuola Media Statale “G.G. Belli” - Rome Class 2H Teacher: Leonarda Fucili 22 September 2009

4. The location : ROME the astronomical terrace of our school 41° 54’ 57’’N 12° 27’ 52’’E

6. Eratosthenes’ Method

7. The experimenters

8. The method h Sun’s ray Shadow length on the horizontal plane IT IS THE SAME TRIANGLE !!!

9. ON THE EQUINOX at MIDDAY Altitude of the sun Latitude

10. Measuring the altitude of the sun : the instruments

11. Waiting for the local noon

12. About 1 hour before the local noon

13. Local NOON Altitude of the Sun about 48 degrees

14. Altitude of the sun = 48 degrees Latitude = 42 degs

15. 1. Distance Rome – Equator (Libreville, Gabon) SCALE 1: 30.000.000 1 cm = 300 Km 16,3 cm = about 4800 Km

16. 2. Distance Rome – Equator = about 5000Km

17. 3. Distance Rome – Equator GOOGLE EARTH 4.628,94 KM

19. THE RATIO Sun’s parallel rays Equator Rome Rome/equator distance = about 4800 Km 42 ° 42 ° 42 ° 360 ° meridian

20. THE CALCULATION (approximation in latitude: 1 degree) 360 degs 42 degs = About 4800 Km x X = circumference of the Earth = about 41.142 Km

21. Reducing uncertainties for our Earth radius value Local Latitude : 41° 54’ 57’’N Distance Rome/ Equator: 4.628,94 KM 360 ° : 41° 54’ 57’’N = 1.296.000” : 150.897” = 8,588 4.628,94 KM x 8,588 = 39.756 Km