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Odd question....

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  • 06-11-2011 9:18pm
    #1
    johngalway
    Closed Accounts Posts: 10,271 ✭✭✭✭


    In terms of daylight hours versus night time, are there more of either long days or short days during the year? Is there an even spread? (I'm guessing not).


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    #2
    Villain
    Registered Users Posts: 15,944 ✭✭✭✭Villain


    johngalway wrote: »
    In terms of daylight hours versus night time, are there more of either long days or short days during the year? Is there an even spread? (I'm guessing not).

    Not but you can calculate using the numbers of days between equinoxes I think


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    #3
    johngalway
    Closed Accounts Posts: 10,271 ✭✭✭✭johngalway


    Villain wrote: »
    Not but you can calculate using the numbers of days between equinoxes I think

    :o There's a thought, thanks :)


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    #4
    Pangea
    Registered Users Posts: 5,565 ✭✭✭Pangea


    I often wondered if you were to compare the hours of daylight/ night, would it be 50/50 for the whole year. Id say It pretty much evens itself out. Long daylight in summer and Long nights in the winter etc..


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    #5
    eskimocat
    Registered Users Posts: 1,204 ✭✭✭eskimocat


    Anyone care to do the maths on this one .... for those of us that might run outta fingers and toes :P


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    #6
    Harps
    Closed Accounts Posts: 3,548 ✭✭✭Harps


    At a total guess I'd say we get more daylight than darkness, around here in mid Summer we only get 5 hours max of darkness yet in mid Winter we still get around 7 hours of daylight


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    #7
    Mmcd
    Registered Users Posts: 805 ✭✭✭Mmcd


    From a quick check the sun rises in Dublin on the 21st June at 4.57am and sets at 21.57pm which is 17 hours of proper daylight while on the 21st December the times are 8.38am and 16.08 pm which is 16.5 hours of darkness. I thought it would be equal amount of light vs. darkness personally so that surprises me.

    I also checked the longest and shortest daylight times (these aren't necessarily the equinoxes) and they are 7hr 30min 12sec and 17hr 00min 13sec which also suggest more daylight.


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    #8
    Cú Giobach
    Closed Accounts Posts: 3,772 ✭✭✭Cú Giobach


    Think about it, we're on a rotating sphere, every part of the planet gets an equal amount of dark and light. The timings mentioned below wouldn't correspond to actual measured darkness/light, twilight at sunrise and sunset are of different lengths at different seasons, depending on the angle of the Sun's path.
    Because our orbit is an elipse and the Earth orbits slower when farthest from the Sun and faster closer in, there will be a discrepancy between dark and light each year (winter/summer, depending on hemisphere, will be slightly longer/shorter each year), but because the path of Earth changes (as pictured below), over a number of years it all evens out, I'm not sure how long the cycle is though.
    I'm only surmising here and could be wrong, but it seems fairly logical. :)

    180491.png


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    #9
    Mothman
    Closed Accounts Posts: 6,498 ✭✭✭Mothman


    The earth is not a perfect sphere. It bulges at the equator. Mt Chimborazo in Ecuador is the furthest point from the centre of the earth.

    Also the higher one is at any point, the earlier and later the sunrises and sunsets.


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    #10
    Cú Giobach
    Closed Accounts Posts: 3,772 ✭✭✭Cú Giobach


    Mothman wrote: »
    The earth is not a perfect sphere. It bulges at the equator. Mt Chimborazo in Ecuador is the furthest point from the centre of the earth.

    Also the higher one is at any point, the earlier and later the sunrises and sunsets.
    And the valley alongside a mountain may get hardly any sun at all, the variables on every point on the Earth are unquantifiable, but the humps and bumps on the surface are so tiny compared to the size of the planet as to be pretty much irrelevant in a measure of dark/light amounts, scaled down to billiard ball size Mt Kilimanjaro might be felt as a slight dust grain (if you have sensitive enough fingers) and though not a perfect sphere it would actually be within the tolerances to be a billiard ball, so slight is the "bulge".


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    #11
    ch750536
    Registered Users Posts: 3,736 ✭✭✭ch750536


    https://docs.google.com/spreadsheet/pub?hl=en_GB&hl=en_GB&key=0Aj7AX8ApYS8udHk3dEkwTmE3XzAwVzJ6UTdrdTJwbFE&output=html

    According to that data, 212 hrs more day than night. Rounding errors may be present.

    Kinda makes sense. Shortest day in 2011 is 7hr 30 mins. Shortest night is 6 hr 59 mins.


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    #12
    ch750536
    Registered Users Posts: 3,736 ✭✭✭ch750536


    However, what is day & night and are we asking the right question?


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    #13
    Cú Giobach
    Closed Accounts Posts: 3,772 ✭✭✭Cú Giobach


    ch750536 wrote: »
    https://docs.google.com/spreadsheet/pub?hl=en_GB&hl=en_GB&key=0Aj7AX8ApYS8udHk3dEkwTmE3XzAwVzJ6UTdrdTJwbFE&output=html

    According to that data, 212 hrs more day than night. Rounding errors may be present.

    Kinda makes sense. Shortest day in 2011 is 7hr 30 mins. Shortest night is 6 hr 59 mins.
    Wouldn't the antipodal point from where those figures are from, have 212 more hours of night than day. :)


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    #14
    Cú Giobach
    Closed Accounts Posts: 3,772 ✭✭✭Cú Giobach


    Just thought of another variable, at sunrise and sunset we see the sun above the horizon before it is actually above it and after it has actually set below it, due to refraction. Therefore resulting in more light reaching the night time side.


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    #15
    novarock
    Registered Users Posts: 1,132 ✭✭✭novarock


    Cú Giobach wrote: »
    Just thought of another variable, at sunrise and sunset we see the sun above the horizon before it is actually above it and after it has actually set below it, due to refraction. Therefore resulting in more light reaching the night time side.

    You are omitting the wobble factor as well, The earth rotates on three dimensions. I would have always assumed the further north you get the more daylight hours you see...


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    #16
    Cú Giobach
    Closed Accounts Posts: 3,772 ✭✭✭Cú Giobach


    novarock wrote: »
    You are omitting the wobble factor as well, The earth rotates on three dimensions. I would have always assumed the further north you get the more daylight hours you see...
    More daylight in summer but more darkness in winter.

    The ratio of daylight/darkness would really depend on over how long you want to measure, from one 24hr day to the period of the "rosette" pattern scribed by the eliptical orbit (the radius of which also changes), and on to the 26,000 year precessional cycle, the longer you measure the more equal the ratio would become (maybe :)).


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    #17
    ch750536
    Registered Users Posts: 3,736 ✭✭✭ch750536


    http://www.usno.navy.mil/USNO/astronomical-applications/data-services/duration-us

    For my location I get 207 more hrs daylight than darkness using that website.


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    #18
    Cú Giobach
    Closed Accounts Posts: 3,772 ✭✭✭Cú Giobach


    ch750536 wrote: »
    http://www.usno.navy.mil/USNO/astronomical-applications/data-services/duration-us

    For my location I get 207 more hrs daylight than darkness using that website.

    Could you compare two opposite points, say Ireland and New Zealand, I did NZ but don't know a way to add up the figures except individually, and I don't really feel like doing that. :D


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