Theory question 202
Latitude, Longitude and Time(a) Distinguish between (i) Latitude and Longitude (ii) Standard Time and Greenwich Mean Time
(b) If the Greenwich Mean Time is 10:00am, 5th July when Local Time in a place X is 4:48am, 4th July, find the longitude of place X.
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(a)(i) Latitude: angular distance of a place north or south of the equator, 0°-90° N/S; lines (parallels) run east-west. Longitude: angular distance east or west of the prime (Greenwich) meridian, 0°-180° E/W; lines run north-south and are used to find local time
(ii) Standard time: the time a country (or zone) adopts, based on one central meridian, so all towns keep the same time (Nigeria uses 15°E, 1 hour ahead of GMT). GMT: local time on the Greenwich meridian (0°), the reference for world time
(b) Time difference: 10:00am 5th July - 4:48am 4th July = 29 h 12 min; one full day (24 h) does not change longitude, leaving 5 h 12 min
15° per hour: 5 h = 75°; 4 min = 1°, so 12 min = 3°; total 78°
X is behind Greenwich, so it is west: longitude 78°W
Earth turns 15° each hour (1° every 4 minutes); places behind GMT are west.