The Case of the Missing Roman Railroads

150824AeliopileThe Roman empire had a problem. It was just too big. When a crisis developed on one frontier, it could take weeks for the emperor to hear about it, then months or even years to move troops and supplies into position to deal with it. The large frontier army consumed supplies which had to be delivered at great expense from the agricultural heartlands. The roads built by the Roman army helped make all this travel faster and easier, but if the Romans had built railroads they could have made it much easier still. A Roman empire with railroads might not have fallen apart in the fifth century CE. So why didn’t the Romans build them?

The obvious answer is that they didn’t have the technology of steam power, nor the resources of coal and iron needed to build a functioning railroad. It’s a good answer, but like many such obvious answers it’s missing something.

The first clear description of a working steam engine is given by the Alexandrian mathematician and engineer Heron who worked in the middle of the first century CE. The device described by Heron, called an aeolipile, uses steam from a boiler to spin a metal ball. The term aeolipile was used about a century earlier by the Roman architect Vitruvius to describe a similar device, though in less detail. Both Vitruvius and Heron drew on the earlier work of another Alexandrian engineer, Ktesibos, who developed devices powered by compressed air.

Now, the aeolipile is only a toy, not an engine you could hook up to dive a locomotive, but combined with some other devices created by Heron and his predecessors – water pumps, self-opening doors, a wind-powered organ – it shows that the essential mechanics needed to make a steam-driven engine were already well understood. Getting from there to a working railroad would still have been a significant engineering challenge, but it was a challenge that the Roman world had all the tools to meet.

The Roman empire was already mining and processing iron on an industrial scale and exploiting most of the major coal deposits in Britain. Roman engineers figured out concrete, domes, aqueducts, and brass smelting; they were no slouches when it came to applying new ideas to their problems. They had the resources and the technical knowledge to build railroads, so why didn’t they?

Now, it’s hard enough for historians to explain why people did the things they did. Explaining why they didn’t do things is orders of magnitude harder, but we can notice a few things about the Roman world that may help explain why they didn’t make this leap.

According to a story told by Petronius and Pliny the Elder, a craftsman once created a kind of glass that couldn’t be broken. When he presented his invention to the emperor Tiberius, hoping for a great reward, the emperor instead ordered the man executed and all his work destroyed, fearing that if the material became available it would upset the market for gold and silver. There is no way of knowing whether there is any truth to this story or not, but it illustrates something important about the Roman view of the world. Romans were happy to adopt practical innovations like concrete, but they were very resistant to anything that might upset established social and economic structures. The system of roads, trade routes, and military supply lines built up in the empire was deeply interconnected with local politics and economics. A technology as disruptive to the status quo as a railroad was the last thing the Roman elite wanted, no matter how useful it might have been.

There was, in fact, very little interest in any kind of labor-saving technology in the Roman world. Slaves were cheap and the easiest way to increase productivity was just to put more human labor to work. There were some crafts that operated on an industrial scale – bronze production in southern Italy, pottery in north Africa and central Gaul – but the “factories” that turned out these wares were just buildings crammed with lots and lots of slaves or poorly-paid workers. Even water- and windmills were little used in the Roman world.

The Roman economy was not a capitalist one, as we understand the word today. Capitalism works on the premise that most people most of the time are trying to accumulate as much money as they can. The main goal in the Roman economy was to acquire not wealth but status. In a capitalist society, having mastery of your wealth, knowing exactly how much you have and where it comes from, is proof of your achievement. In the Roman world, paying too much attention to your money was just seen as vulgar and the mark of a social climber. The true sign of having arrived in high society was the ability to be completely ignorant about your own finances. Even Roman business law was structured to encourage owners to be disconnected from the day-to-day affairs of their own businesses. (The legal details are rather technical and I won’t go into them here, but if anyone’s curious that could make for a future post.)

People who wanted to get ahead in Roman society cultivated a casual attitude towards money. Investing in the development of labor-saving machinery would have seemed declassé, and so there was no market for the kinds of useful devices that could have been developed from the aeolipile and paved the way towards steam engines and railroads. Instead, the aeolipile and other such devices remained toys and novelties for a few curious minds to tinker with and the Roman empire never got its railroads.

Thoughts for writers

The reasons why the Romans didn’t have railroads are social and economic, not technological. The physics of steam power are relatively straightforward and there’s no scientific reason why the world had to wait until the 1800s for steam engines and rail.

That means there’s no reason not to imagine modern technologies in past settings. Steam locomotives pulling train cars full of Roman legionaries headed to the front? Telegraph wires running from the Great Wall to the Forbidden City to report on Monogl movements? Aztec eagle warriors hang-gliding from the mountaintops to drop rudimentary bombs on enemy villages? All within the realm of possibility aided by a little imagination. ‘Punkers of all varieties, take heart!

But also take the lesson of history. There are reasons why none of these cultures developed those technologies, and even if those reasons are social and economic rather than technical, they still matter. The incentives societies create either to innovate and explore or to stick with what you know are powerful. Figuring out how to make use of basic physical and chemical properties takes time, tinkering, and a lot of blundering into blind alleys. The aeolipile is not a useful machine; it is a step towards developing one. Unless a society provides enough encouragement for the sort of tinkering that ultimately leads to a useful final product, most of that work just never happens.

So, if you want to imagine a rail-connected Roman empire or an electrified Han Dynasty, or anything else, you need to think about more than just the technology. How would that society have to have changed to encourage people to develop, perfect, and adopt the technology? There’s more to it than just plopping down a locomotive on the Apennine Way.

Image: Illustration of Heron’s Aeolipile from Meyers Konversationslexikon via Wikimedia (1885-90, print)

History for Writers is a weekly feature which looks at how history can be a fiction writer’s most useful tool. From worldbuilding to dialogue, history helps you write. Check out the introduction to History for Writers here.