I guess some of the people might be too old or young to hold hands but even at 6 billion it could be done! Is it just me or is it a nice thought? Impractical or highly difficult, but not impossible if you allow for no people where there is water.

Thanks again for taking the challenge.

Length of 7 Billion people holding hands = 8,400,000,000 meters

Humanity at 7 billion could hold hands around the planet circling it 209 times.

]]>The problem breaks down like this:

A city of 1,000,000 with density 5,000 per km^2 will need 200 km^2;

for a circle with area 200 km^2, radius r = sqrt(200/pi) = 7.98 km.

If one hectare feeds four, then 250,000 arable hectares will be needed to feed 1,000,000;

if land is 30% arable, then a total of 833,333.33 (250,000/.3) km^2 will be needed.

Add to this the non-arable land (200 km^2) at the center occupied by the city itself, and the total land area occupied will be 833,533.33 km^2 – an area whose radius r = sqrt(833,533.33/pi) = 515.1 km, or, subtracting the area of the city, a torus around the city with a width 507.11 km.

If the land was 100% arable (nice!), then the total amount of land needed would be 250,000 km^2 + 200km^2 for the city = 450,000 km^2, radius r = sqrt(450,000/pi) = 378.47 km, or a torus around the city 370.49 km wide, a reduction in radius (or torus width) of 136.62 km from the 30% arable condition.

Either way, it is a staggeringly large amount of land to feed the city!

DBR

]]>JĂ€ttebra fĂ¶r att kommmunicera sĂ„rbarhet. Per G Berg i Living Dreams fĂ¶r ett liknande resonemang.

HĂ€ls

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