Theory question 202
The Earth and Solar System(a) State three reasons to show that the earth is spherical
(b) Describe three effects of the revolution of the earth
(c) Calculate the noon altitude of the sun at the Tropic of Capricorn on June 21
Show the model answer
(a) Any three: circumnavigation of the earth; circular shadow of the earth on the moon during a lunar eclipse; ship's hull disappears before its mast over the horizon; sunrise/sunset at different times east to west; horizon is circular and widens with height; photographs from space
(b) Seasons; changing length of day and night; changing altitude of the midday sun (overhead sun moves between the tropics); midnight sun/polar night; shifting of wind and pressure belts
(c) On 21 June the sun is overhead at 23½°N; angular distance to 23½°S = 47°; noon altitude = 90° − 47° = 43°
Noon altitude = 90° − (angle between the place and the latitude where the sun is overhead).