The curve of the sun?

Discussion in 'Off-Topic Members Lounge' started by 24Volts, Mar 20, 2017 at 7:44 PM.

  1. 24Volts

    24Volts

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    Hello,

    In reference to the following link:

    http://www.physicalgeography.net/fundamentals/6i.html

    In reference to the graph on page 2 of 4 (Fig. 6i-2). What are they trying to tell me? If we look at the 50 degrees North line (The red one), It seems that approximately in mid June, the maximum hours of day length should be:

    Sin(50) = 77% of a 24 hour day!

    The maximum hours of the day should equal to = 0.77*24 = 18.4 hours

    Why is the graph pointing more towards around 16 hours??

    any help would be very appreciated!

    Bob
     
    24Volts, Mar 20, 2017 at 7:44 PM
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  2. 24Volts

    Arouse1973 Adam

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    I take it as the sin function is used for the intensity of the sun not the length of the day. I might be wrong though.
    Thanks
    Adam
     
    Arouse1973, Mar 20, 2017 at 9:55 PM
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  3. 24Volts

    Gryd3

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    You got two sections mixed up!
    The sin(50) you are using is talking about light intensity based on the angle of incidence, and the graph you are looking at it indicating the length of day over time... The 50 degree line on our globe does not equal the angle of incidence...
    I'm sure there is a proper formula for what you want to calculate... it will need to take into account the angle of our Earth's axis, the degree North or South of the equator, and our relative position from the sun. It's not quite as easy as using a trig function by itself
     
    Gryd3, Mar 21, 2017 at 3:59 AM
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  4. 24Volts

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    It's more complex than that.. If it were that simple you would have to be at exactly 90 degrees of latitude to have 24 hours of daylight . As you can see, 70 degrees is sufficient to get 24 hour long days.

    I suspect that 66.5 degrees would be sufficient to get at least one 24 hour day due to the Earth's (current) tilt of 23.5 degrees.
     
    (*steve*), Mar 23, 2017 at 12:14 AM
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