Describe how Erastothenes measured the circumference of our planet
What will be an ideal response?
Using the fact that the noon solstice Sun was directly overhead at Syene, on the Tropic of Cancer, yet was 7 degrees south of his zenith in Alexandria, Erastothenes realized this was due to the curvature of the Earth, and that the 7 degrees was about 1/50th of the Earth's total circumference, so the Earth must be about fifty times larger in circumference than the 800 kilometer separation between Alexandria and Syene, or about 40,000 kilometers around.
You might also like to view...
Ninety percent of all stars fuse helium to form carbon and lie on the main sequence
a. True b. False Indicate whether the statement is true or false
Hydrogen Balmer lines are strongest near ____ spectral class whereas ionized Calcium (CaII) lines are strong in ___ stars
a. A0, K b. O5, M5 c. M5, G1 d. M0, B0
In 1912, after studying a star cloud called the Small Magellanic Cloud, Henrietta Leavitt concluded that:
A) stars are eternal and unchanging. B) the brightest stars have the shortest pulsation periods. C) the Sun and Earth are near the edge of our Galaxy. D) there was a relationship between pulsation periods and luminosities of stars.
Charge in an Electric Field: If a point charge of -30 µC experiences an electrostatic upward force of 27 mN at a certain location in the laboratory, what are the magnitude and direction of the electric field at that location?
Fill in the blank(s) with the appropriate word(s).