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Dublin to Dublin

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  • 24-03-2010 8:12pm
    #1
    [Deleted User]
    Posts: 0 ✭


    If you were to fly directly east of Dublin and land back in Dublin, how many miles would it take? Google has let me down :(



    (I can't believe I found a use for this forum, saw it and thought, I'll never need to post there! Good work lads!:D)


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    #2
    Flamed Diving
    Closed Accounts Posts: 6,609 ✭✭✭Flamed Diving


    The circumference of the earth at the equator is 24,901.55 miles (40,075.16 kilometers).
    But, if you measure the earth through the poles the circumference is a bit shorter - 24,859.82 miles (40,008 km). This the earth is a tad wider than it is tall, giving it a slight bulge at the equator. This shape is known as an ellipsoid or more properly, geoid (earth-like).

    Basically, the Earth is shaped like a squished orange, bulging out a bit. Anyway, I reckon around 24,900 miles is a safe estimate.


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    #3
    youwhoglue
    Registered Users Posts: 88 ✭✭youwhoglue


    Dublin's latitude is 53 degrees North so to go directly east back and around to Dublin is significantly shorter than the equator's diameter. Basically it's the length of that line of latitude.

    Wikipedia has all the formulae to work it out or else head to the Maths Forum =>

    Edit:

    Quick calc gives 24,901.55 cos(53) gives 14,986 miles taking the earth as a perfect circle.


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    #4
    YoureATowel
    Closed Accounts Posts: 85 ✭✭YoureATowel


    Papa Smut wrote: »
    If you were to fly directly east of Dublin and land back in Dublin, how many miles would it take? Google has let me down :(



    (I can't believe I found a use for this forum, saw it and thought, I'll never need to post there! Good work lads!:D)


    The closest mathematical approximation of the shape of the Earth is an oblate spheroid, ie an ellipse rotated about its minor axis. Ideally, when carrying out a calculation of this type you would use such a figure. However, if we assume that the Earth is a perfect sphere the error will be insignificant for our purposes here (the maths is also head wrecking).

    So, what we require is the circumference of the small circle (ie line of latitude) through Dublin. Wikipedia gives the latitude (ϕ) of Dublin as + 53 20' 52", this is just a random point on O'Connell Street.

    Geo_Image3copy.jpg

    Geo_Image1copy.jpg

    Using a spherical approximation of the shape of the Earth we can assume a radius of 6371km. This figure, R, is the radius of the equatorial plane.

    To calculate the radius of the small circle through Dublin, r, use

    r = cos(ϕ) x R
    = cos(53 20' 52") x 6371
    = 3803.21km

    Geo_Image2copy.jpg

    The circumference, c, of the small circle through Dublin is then simply

    c = 2πr = 2π(3803.21) = 23896.27km


    So, if you were to fly directly east of Dublin and land back in Dublin, the distance covered on the ground would be approximately 24000km.


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