How You Invented Bridges (Accidentally)

If you toss a few stones into a river, you can step on them to cross.Congratulations, you just accidentally invented stepping stone.But if the water rises and submerges them, you have a problem.Being the absolute genius you are, you chop down a massive tree and lay it across the banks.Look at that, you just invented a log bridge.But as the river gets wider, a long log placed across will easily bend.

With your big brain, you decide to add a pier in the middle to support it, instantly doubling its load capacity.A log bridge can only let one person cross at a time, so if there are more people, to wait in line.Being smart, you just tie several logs together to widen the surface so multiple people can cross at the same time.Congratulations, you just invented a raft bridge.

As the river gets even wider and you cannot find logs long enough, you think of resting one end of the logs on the bank and crushing it with massive boulders to hold it down, letting the logs extend naturally over the water.If that is still not long enough, you just start stacking logs layer by layer, letting them extend further out.You build one of these structures on each side and connect them in the middle to make another bridge.

If the river is wide or still, you place wooden poles between the two extended structures to stretch the span.Congratulations, you just unlocked the skill to build a cantilever bridge.