How to find longitude when time is given?
Answers
Answered by
0
Because one day is 24 hours long one can easily use time to calculate longitude. One hour of time difference corresponds to 15° of longitude (360°/24 hours = 15°/hour). Suppose an observer sets his accurate watch to 12:00 at noon in Greenwich, England and then travels a great distance. The observer then notices that the sun is highest in the sky at 4:00 according his watch. The observer then knows he is at longitude 60° W (4 hours ×15°/hour = 60°).
It should be pointed out that “noon” in general does not mean 12:00 PM. Rather, it is the time when the sun is highest in the sky. Because of the use of timezones the sun will be highest in the sky from about 11:30 AM to 12:30 PM local time for an observer. If longitude is known, the time of astronomical noon can be calculated.
For example, Lincoln, NE, is at longitude 96.7° W. 96.7°/(15°/hour)=6.4467 hours. Being Central Time, Lincoln is 6 hours away from Greenwich Mean Time, so astronomical noon is (6.4467 - 6) hours = 0.4467 hours = 26.8 minutes from 12:00. Thus “noon” in Lincoln, Nebraska is about 12:27 PM (1:27 PM during daylight savings).
It should be pointed out that “noon” in general does not mean 12:00 PM. Rather, it is the time when the sun is highest in the sky. Because of the use of timezones the sun will be highest in the sky from about 11:30 AM to 12:30 PM local time for an observer. If longitude is known, the time of astronomical noon can be calculated.
For example, Lincoln, NE, is at longitude 96.7° W. 96.7°/(15°/hour)=6.4467 hours. Being Central Time, Lincoln is 6 hours away from Greenwich Mean Time, so astronomical noon is (6.4467 - 6) hours = 0.4467 hours = 26.8 minutes from 12:00. Thus “noon” in Lincoln, Nebraska is about 12:27 PM (1:27 PM during daylight savings).
Similar questions