Vienna (LOWW) is located at 016° 34'E, Salzburg (LOWS) at 013° 00'E. The latitude of both positions can be considered as equal. What is the difference in sunrise and sunset times, expressed in UTC, between Wien and Salzburg?
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A
In Vienna, the sunrise and sunset are about 14 minutes earlier than in Salzburg.
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B
In Vienna, the sunrise is 14 minutes earlier and the sunset is 14 minutes later than in Salzburg.
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C
In Vienna, the sunrise and sunset are about 4 minutes later than in Salzburg.
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D
In Vienna, the sunrise is 4 minutes later and the sunset is 4 minutes earlier than in Salzburg.
The longitude is expressed in degrees and is the angle difference between the Greenwich meridian and the local meridian. Vienna (LOWW), with longitude 016° 34'E, distants more than Salzburg (LOWS), with longitude 013° 00'E, from the Greenwich meridian. The change in longitude between the two airports is:
- 016° 34'E - 013° 00'E = 003° 34'
The Earth rotates anti-clockwise, i.e. towards East. Thus, Vienna (LOWW), being more eastern than Salzburg (LOWS), will experience sunrise and sunset earlier.
At the Equator arc, and therefore longitude, can be directly related to distance. Arc, and therefore longitude, can also be related to time. As the mean Sun appears to travel 360° in 24 hours, we can get the following Arc-to-Time conversions:
- 360° = 24 hours
- 15° = 1 hour
- 1° = 4 minutes
- 1' = 4 seconds
So, since 1° = 4 minutes and 1' = 4 seconds, then 003° 34' of longitude are equal to:
- 3° x 4 min = 12 min, and
- 34' x 4 sec = 136 sec, or
- In total, 14 min approximately.
Therefore, in Vienna, the sunrise and sunset are about 14 minutes earlier than in Salzburg.
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