> But when we talk of the breakthrough “steam engine” in the eighteenth-century sense, we don’t mean a machine that exploits steam’s expansive, or pushing force. We actually mean a machine that does the exact opposite, exploiting the apparent sucking power that occurs when hot steam is rapidly condensed with a spray of cold water. It’s the relative weight of the atmosphere, compared to the sudden vacuum from condensing steam, that does all the work.

This article connects that sort of engine to (among others) Hero of Alexandria’s temple doors, rather than the aeolipile, though suggests that it might have been known to "at least a few aeolipile-users" as a way to fill the aeolipile with water.