The Fence

Everybody decided to divide the planet into two halves.
We’d stay on the north half of the planet while they’d stay on the south half of the planet.
A gigantic fence was to be built around the equator, with the occasional gate here and there to allow folks to walk through and visit now and then.
Lots of people liked the idea, but even more thought it was completely nuts.
“What if people cut through the fence or dig under it?” they said, worried.
So, the plan was changed to a gigantic wall with razor wire.
That satisfied the doubters.