Theory question 306
Latitude, Longitude and Time(a) Draw an outline of the Earth and show the following: (i) Equator; (ii) tropic of Cancer; (iii) Antarctic Circle. (b) Describe three characteristics of lines of longitude. (c) A football match is scheduled for 5.45 pm local time on Saturday in Onitsha, Nigeria (longitude 7°E). Calculate the local time football fans in Mambola, Sierra Leone (longitude 13°W) can tune their radio sets for the commentary.
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(a) Circle for the earth with the Equator (0°) across the middle; Tropic of Cancer at 23½°N; Antarctic Circle at 66½°S, all labelled.
(b) They run north-south and meet at the poles; they are semicircles of equal length (half great circles); they are farthest apart at the Equator and converge towards the poles; measured in degrees east or west of the Prime (Greenwich) Meridian, 0° to 180°; used to calculate local time (15° = 1 hour); places on the same longitude have the same local time.
(c) Longitude difference = 7° + 13° = 20°; time difference = 20 × 4 minutes = 80 minutes = 1 hour 20 minutes; Mambola is west, so behind: 5.45 pm − 1 h 20 min = 4.25 pm on Saturday.
Add longitudes on opposite sides of Greenwich.