Theory question 202
The Earth and Solar System(a) Draw a diagram to show the four major positions of the earth during its revolution around the sun
(b) describe the effects of the revolution of the earth
Show the model answer
(a) Diagram: sun at centre, earth at four positions with axis tilted the same way: 21 March (vernal/spring equinox), 21 June (summer solstice, sun overhead at Tropic of Cancer), 23 September (autumnal equinox), 22 December (winter solstice, sun overhead at Tropic of Capricorn); show lit and dark halves
(b) Causes the four seasons; varies the length of day and night through the year (equal at equinoxes); changes the altitude of the midday sun (apparent movement of the overhead sun between the tropics); midnight sun and polar night within the polar circles; shifting of pressure and wind belts; the calendar year (365¼ days, leap year)
Keep the axis tilted in the same direction at every position.