Throughout the history of mankind, we’ve been building walls. Short ones, like the walls that make up your home and long ones; Really, really long ones. Suppose, for some reason, we’d want to build a wall that stretches around the world. Would that even be possible?
The Great Wall of China is the current record holder for longest wall in the world. It was built over a period of many centuries and basically served to protect the Chinese Empire against outside forces. It’s actual length depends on what you’re measuring. Its world record entry mentions a length 3.460 KM. That’s just the main branch though. It also mentions 3.530 KM worth of branches. That’s a total length of 6.990 KM. That’s a long wall, but that’s not all of the Great Wall of China. Part of the defensive structure were trenches and in some locations the natural landscape served as a wall. Adding all this to the actual brick structures and you come with a defensive structure well over 20.000 KM in length.
If we wanted to build a wall that goes around the world (and by that I mean a wall that goes around the earth at it’s widest point, the Equator), 6.990 KM of wall won’t cut it. We need 40.075 KM of wall. That’s 5.7 times as much wall. And most of that wall would be built over water. Let’s say our wall is 5 meters wide and 5 meters high. Our wall would be 1.001.875.000 M3. Let’s say we’re using bricks that are 194 x 92 x 57 mm (a common size in the U.S. and very similar to sizes used around the world), we’d need 9.84802x1011 bricks. Let’s say a single brick costs 0.25 cents, we’d need at least 3.73 Bill Gates to pay for the bricks. And we’re not even taking into account the many kilo’s of sand needed to to fill up the parts of the oceans and seas the wall would cross.
Maybe, if we can’t convince Bill Gates and several of his very wealthy friends to pay for a brick wall, we could go with a fence. Like Australia’s Dingo Fence. That fence is about 5.614 KM long, so we’d need only about seven times as much fence. Let’s say, using 1m high coated (we need to cross the ocean, remember) chicken wire at €40,- per 25 M, we’d need about €64.120.000,- to pay for the chicken wire. We also wouldn’t need to fill up part of the ocean because we could easily fit our fence with floaters. Bill Gates could easily afford that.