#### blackpearl

##### The Devil

I saw this on Discovery channel and want to share it with you.

Suppose we take a long ribbon and wrap it around earth, around the equator, so tight that not even a piece of paper can go between the ribbon and the earth. Now we increase the length of the ribbon by just 1 metre so that it becomes slack. Now its possible to raise the ribbon from the surface of the earth. You have to tell me by how much the ribbon can be raised from the earth. Remember, the ribbon is raised not at one point on the earth but all around the earth, equally. I have made a small diagram to make it clear.

*i18.tinypic.com/681gpki.gif

Do not take out your calculator or head to google. Just make a guess. By how many millimeter/cm/meter the ribbon can be raised.

Scroll for the answer

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Here is the math:

Radius of earth = r (meters)

Circumference of earth = 2πr

Initial Length of ribbon = 2πr

New length of ribbon = 2πr + 1

Height by which the ribbon can be raised = (Radius of the circle of ribbon) - (Radius of earth)

H = (2πr + 1)/2π - r

= r + 1/2π - r

= 1/2π

= 16 cm

Notice that H doesn't depend on the radius of the earth, which means that whether you wrap the ribbon around a football, or around earth, or around the sun, if you increase the lenght by 1m it can always be raised by 16 cm!!

Amazing, isn't it?

Suppose we take a long ribbon and wrap it around earth, around the equator, so tight that not even a piece of paper can go between the ribbon and the earth. Now we increase the length of the ribbon by just 1 metre so that it becomes slack. Now its possible to raise the ribbon from the surface of the earth. You have to tell me by how much the ribbon can be raised from the earth. Remember, the ribbon is raised not at one point on the earth but all around the earth, equally. I have made a small diagram to make it clear.

*i18.tinypic.com/681gpki.gif

Do not take out your calculator or head to google. Just make a guess. By how many millimeter/cm/meter the ribbon can be raised.

Scroll for the answer

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**The answer is 16 cm.**Sounds unbelievable, isn't it? The circumference of the earth is approximately 40,07516 metre, and so is the length of the ribbon. How can by increasing the ribbon length by just a tiny 1m enable it to be raised by 16cm all around the earth?Here is the math:

Radius of earth = r (meters)

Circumference of earth = 2πr

Initial Length of ribbon = 2πr

New length of ribbon = 2πr + 1

Height by which the ribbon can be raised = (Radius of the circle of ribbon) - (Radius of earth)

H = (2πr + 1)/2π - r

= r + 1/2π - r

= 1/2π

= 16 cm

Notice that H doesn't depend on the radius of the earth, which means that whether you wrap the ribbon around a football, or around earth, or around the sun, if you increase the lenght by 1m it can always be raised by 16 cm!!

Amazing, isn't it?

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