The economist William (Bill) Phillips built a machine in 1949 that represents the economic cycle and shows the flow of money using coloured water. It is known as the MONIAC (Monetary National Income Analogue Computer). You can read more about it on Wikipedia.

Philips was more like Marvel’s Ironman than a typical economist. He was always building things, fought in WW2, was a POW, and returned to London to build the MONIAC from the scrap parts of bomber planes. Tim Harford has an excellent story about his life and the “computer” on his blog.

If you would like to see the MONIAC in action, watch this cool video where Cambridge engineering Professor Allan McRobie gets the machine running and explains how it calculates when the economy is in equilibrium and what happens when fiscal policy changes. The MONIAC is not just a visual representation of how the cycle works — it is a computer that can determine national accounts values!

Planet Money has the following depiction of the Philips Machine: