Q&A: Why did Hero's engine not become practical steam power?

Could Hero's ancient steam engine have changed history if it had been scaled up?

Possibly, but the demonstration still needed major advances in materials and engineering before it could become a useful engine.

Hero's aeolipile demonstrated steam-driven motion, but making it practical required substantial development. Metallurgy, the understanding of power, and the application of force all developed over successive generations. Ideas and experiments often preceded useful machinery by a long time. A different ancient development path remains conceivable, but scaling up the demonstration would have required much more work.