Question

Suppose an observer sets his accurate watch to 12:00 noon in Greenwich, England and then travels a great distance in one particular direction. The observer then notices that the sun is highest in the sky at 5:00 according to his watch. Then which longitude is he currently on?

• A. 75° E longitude
• B. 50° E longitude
• C. 50° W longitude
• D. 75° W longitude

Answer 1

The correct option is D 75° W longitude

One hour of time difference corresponds to 15° of longitude (360°/24 hours = 15°/hour). So if an observer sets his accurate watch to 12:00 noon in Greenwich, England and then travels a great distance in one particular direction and then notices that the sun is highest in the sky at 5:00 according to his watch, the observer is at longitude 75° W. This is because 5 hours is equivalent to 75° shift in longitude. He must have travelled west as it is still 12 noon at the place he is currently in.