Penny bridges

I first saw coin structures like the ones a couple of years ago, but it’s still a fascination for me. Like an arch, these only things holding the structure together is gravity and friction. But unlike that most ancient architectural element, there is no strategically placed keystone. These coin structures are also much more easy to build because the structure is relatively stable during construction.

I like the way this guy kept stacking more columns of coins on a bridge spanning three coin diameters. It’s amazing when you think about how the load is carried to the ground. Notice that in the picture before collapse, the bottom-most penny at midspan doesn’t appear to be carrying any of the load above it.