What might have been had the Romans developed the steam engine? By the late 3rd century AD, all of the essential elements for constructing a steam engine were known to Roman engineers: steam power – Hero’s aeolipile, the crank and connecting rod mechanism in the sawmills and marble quarries, the cylinder and piston in metal force pumps, non-return valves in water pumps and gearing in water mills and clocks. Suppose that the Roman Empire emerged, as it did, from the crisis of the third century with all its administrative and military institutions changed, bureaucratic, rigid, and constantly geared for war, with its capital no longer in Rome but in Constantinople – and with steam power. (Such a development might have occurred not in Italy, but in the Eastern Empire – the stirrup was first put into wide use there, and reserves of coal and other minerals are available without deep mining in, for example, Dacia, Moesia and Thracia – present-day Romania and Bulgaria.)
The rise of an entrepreneurial middle class – not possible under an economy based on slave-power – might have avoided the fragmentation of the Western Empire because of the cost of maintaining communications, garrisons, civil government, etc., which could no longer be solved by acquiring more territory, slaves and resources. The deterioration of the Eastern Empire into a form of state socialism where monetary taxation was replaced with direct requisitioning, individuals were forced to work at and remain in their given occupations, farmers were tied to the land, as were their children, and workers and businesses were organised into guilds and collegia which were de facto organs of the state, controlling and directing their members to work and produce for the state. (Marx, Lenin and Mao would have approved.)
Imagine, then, a third Century Rome like Great Britain in the late 18th Century where the advances in technology which would drive the industrialisation and expansion of the 19th were almost at the point of general utility. Increases in productive capacity might have solved the problems of meeting the cost of Empire and generation of a real surplus might have enabled the development of a real market/trading economy. With a solid economic foundation the Empire might have endured, avoiding the fragmentation of most of Western Europe and, therefore, most of the strife and conflicts of the ages of feudal and nation states. An extended market and polity across Western Europe and, in time, extending into Eastern Europe, might easily have been developed, with the centre of gravity of industry and transport being in Central Europe where the Danube makes an easily navigable route for steam-powered vessels. With such a large, diverse and potentially prosperous market, perhaps the acquisition of cross-continental Empires might never have been necessary, replaced by trade links with China and India – already nascent in the 3rd Century, and a possible gradual expansion of Roman Africa.
In the realm of science and technology, where might we be with a century and a half head start? In a bit less than a couple of Centuries, (in the West,) we have gone from wind and muscle power to the power of elemental particles. From lives of drudgery, disease and poverty to long and mainly disease-free lives of extended leisure, and riches and personal power beyond the dreams of ancient kings. Our individual potential has expanded from concentrating on survival to limits only of our own imagination and application. How far could we have come with an extra dozen or so Centuries of wide-spread development opportunity?