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Around the world in 6 inches

  • 17-06-2013 11:54pm
    #1
    Uncle Dad
    Closed Accounts Posts: 9 ✭


    Lay a rope around the equator. Now lengthen it by 6 inches.

    This gives you enough slack to raise the rope by 1 inch from the ground AROUND THE WHOLE PLANET. :eek:


Comments

  • #2
    locum-motion
    Registered Users, Registered Users 2 Posts: 5,143 ✭✭✭locum-motion


    Approximating the circumference as 25,000 miles(*1), the radius of the earth is 252,101,429 inches.
    If your lengthened rope is 25,000miles & 6" long(*2), then the radius of its circle is 252,101,430 inches.

    Wow, you're right! I didn't expect you to be!


    (*1) 1,584,000,000 inches
    (*2) 1,584,000,006 inches


    (Calculated using whatever the value of Pi that's stored in the iPhone's Calculator app is.)


  • #3
    Uncle Dad
    Closed Accounts Posts: 9 ✭Uncle Dad


    Surprising, eh? The same thing works for a circle of any size because the formula for the circumference is linear. It would work for a circle the size of our galaxy or the whole universe.

    If you add 2pi (ok, it's not 6 exactly but 6.283..) to 2pi*r you get,

    2pi*r + 2pi.

    Which is of course the same as,

    2pi*(r+1).

    That's an extra inch in radius, regardless of what you started with!


  • #4
    Capt'n Midnight
    Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 93,581 Mod ✭✭✭✭Capt'n Midnight


    Since this is science rather than maths

    work out what temperature you would need to heat the rope by to give you that extra inch/mile and then translate it into the temperature profile of our atmosphere

    http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html


  • #5
    Lbeard
    Banned (with Prison Access) Posts: 311 ✭✭Lbeard


    Capt'n Midnight wrote: »

    work out what temperature you would need to heat the rope by to give you that extra inch/mile and then translate it into the temperature profile of our atmosphere

    But the temperature would change at different locations depending on time of day, year, weather on the day.

    Average atmospheric temperature is not like the average temperature in a cup of tea.


  • #6
    OCorcrainn
    Closed Accounts Posts: 428 ✭✭OCorcrainn


    At first when I saw the thread title I thought it read "Around the world with 6 inches".


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