Yesterday I spent some time wondering how to explain the modern economy to an ancient Roman brought forward from the first millennium BCE. For now I’ll assume language isn’t a barrier, but not much more. Here’s my rough take:

“There have been five really important things that were discovered since when you left and now.

First, every living thing has a tiny blueprint inside it. We learned how to rewrite those, and now we can make crops that resist pests, grow healthy, and take minimal effort to cultivate. The same tool also let us make creatures that manufacture medicine, as well as animals different from anything that existed before. Food became cheap because of this.

Second, we learned that hot air and steam expand. This means you can burn oil or coal and use that to push air around, which in turn can push against solid objects. With this we’ve made vehicles that can go the span of the Empire from Rome to Londinium and back in hours rather than weeks. Similar mechanisms can be used to work farms, forge metal, and so on. Manufactured goods became cheap as a result.

Third, we discovered an invisible fluid that lives in metals. It flows unimaginably quickly and with minimal force through even very narrow channels, so by pushing on it in one city it may be made to move almost instantly in another. That lets you work with energy as a kind of commodity, rather than something that hooks up and is generated specifically for each device.

Fourth, we found that this fluid can be pushed around by light, including a kind human eyes can’t see. This lets a device make light in one place and push on the fluid in a different device with no metal in between. Communication became fast, cheap, and easy.

Finally, and this one takes some explaining, our machines can make decisions. Imagine you had a channel for water with a fork. You can insert a blade to control which route the water takes. If you attach that blade to a lever you can change the direction of the flow. If you dip that lever in another channel of water, then what flows in one channel can set which way another channel goes. It turns out that that’s all you need to make simple decisions like “If water is in this channel, flow down that other one.”, which can then be turned into useful statements like “Put water in this channel if you’re attacked. It’ll redirect the other channel and release boiling oil.” With enough of these water switches you can do really complicated things like tracking money, searching for patterns, predicting the weather, and so on. While water is hard to work with, you can make these channels and switches almost perfect for the invisible fluid, and you can make them tiny, vastly smaller than the width of a hair. A device that fits in your hand might have more switches than there are grains in a cubic meter of sand. The number of switches we’ve made so far outnumbers all the grains of sand on Earth, and we’re just getting started.”