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Variations between Sunrise & Sunset timings

  1. Jun 20, 2015 #1
    I have recently noticed that there is a huge variation between sunrise and sunset timings when it comes to different latitudes. Take an Example of London, UK and Valencia, Spain. As on today (20 Jun 2015), the sunrise in London is at 4:43 am and is 6:34 am in Valencia (1h 51m difference)... But when it comes to the sunset, London's Sunset is at 21:21 pm while Valencia is at 21:32 pm ( mere 11m difference). Considering that both of them are at the same longitude (but at different latitudes), why is London getting sunlight 2 hours ahead of Valencia but the sun is setting with a mere 11 minutes difference? Shouldn't these two be almost proportional? As I understand, the longitude which carries London & Valencia should face the sun and face away from the sun at same time and the difference in sunset and sunrise timings should be equal. I have noticed the same trend in all other places. the difference between sunrise timings keeps increasing with distance along longitudes, while the sunset timings seem to be almost identical regardless of distance along longitudes ... why is that?
     
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  3. Jun 20, 2015 #2

    Vanadium 50

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    If you correct for time zones, things will look a lot more symmetric.
     
  4. Jun 20, 2015 #3
    Vanadium, accounting for the time zone will still not answer my question. The above timings are based on local time zones. The question is as to why is there a 2 hour difference in sunrise timings (based on local times) but only an 11 minute difference in sunset timings (again, based on local times). If sunrise in London is 2 hours earlier (based on local time), then should not the sunset also be 2 hours earlier (based on local time)?
     
  5. Jun 20, 2015 #4

    Vanadium 50

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    Valencia and London are not in the same time zone. If you correct for that, things look a lot more symmetric.
     
  6. Jun 20, 2015 #5

    SteamKing

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    Also, in the northern hemisphere in the summer months, the length of time between sunrise and sunset increases as one moves north from the equator.

    In fact, above the Arctic Circle, there are a few days where the sun doesn't set at all.

    https://en.wikipedia.org/wiki/Midnight_sun

    Also Vanadium50 is correct: although Valencia and London lie approximately on the same line of longitude, currently Valencia is in the GMT+2 zone while London is GMT+1, which is a quirk of how Summer Time is set up in the UK and in Central Europe.
     
  7. Jun 20, 2015 #6

    D H

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    London is in the Western European Time Zone (also with summertime). Valencia is in the Central European Time Zone (with summertime). If science ruled the day, both would be in the Western European Time Zone, and that summertime nonsense would be gone. In other words, both would use UTC (formerly known as GMT) to represent time.

    You can see this by looking at when local solar noon happens in the two cities. Today (20 June 2015), local solar noon occurred at 13:02 British Summer Time in London, and at 14:03 Central European Summer Time in Valencia. That's not an hour apart. It's almost simultaneous, as would be expected by the tiny difference in longitude.

    Today, in London, sunrise occurred at 04:43 BST (03:43 UTC), or 8 hours and 19 minutes before local noon. Sunrise in Valencia didn't happen until 06:34 WEST (05:34 UTC), or 7 hours and 29 minutes before local noon. The Sun set on Valencia at 21:32 WEST (19:32 UTC), or 7 hours and 29 minutes after local noon. Sunset in London didn't happen in London until 21:21 BST (or 20:21 UTC), 8 hours and 19 minutes after local noon.

    Note how nice and symmetric sunrise and sunset are about local noon (or about UTC). Sunrise occurs earlier in and sunset occurs later in London solely because of London's latitude.
     
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