Divide again by pi to get the earth s radius 6 370km.
Rope around the earth add 3 feet.
From there it s not hard to believe that adding 3 feet to a rope around the actual earth would raise it almost 6 inches.
A corollary is that to raise the original string 16 cm 6 3 in off the ground all the way around the equator only about 1 metre 3 ft 3 in needs to be added.
In fact this brain teaser requires neither an exact measurement of the earth s circumference which in fact varies by many kilometers depending on which circumference you measure nor even an assumption that the earth has a circular cross sect.
If you put 1 metre high sticks.
You have a piece of rope that just fits around the earth.
Now raise it just one foot from the floor where you stand.
From the diagram it s pretty clear it s one foot.
Assume he has just the right length that makes this work without any slack.
15cm that s how far off the ground we re lifting the string remember out of 6 370km is close.
Suppose you tie a rope around the earth at the equator circumference approx.
40 000 divided by 2 is 20 000.
Imagine putting the rope around the earth tightly.
Suppose you tie a rope tightly around the earth s equator.
Suppose poindexter takes a very long rope and wraps it around the equator of the earth.
Suppose allistair then comes.
All around the earth the rope is raised up uniformly as high as is possible to make it tight again.
You add an extra 3 feet to the length.
Let c be the earth s circumference r be its radius c be the added string length and r be the added radius.
The idea is to imagine the earth is a cube or just a square really and ask yourself if you added say 8 feet to the rope how far would that raise it above the square earth.
For h 1 metre additional length of rope required.
Yes i know how that works out but it does not seem logical to think that there would only be 6 feet of rope needed to go all around the so called globe world being 1 foot off of the ground evenly all around.
Let s say you pull the rope as tight as it will go and then add back 6 feet of slack before tying the knot.