By Tracy Barrett

Picture a day in first-century Alexandria. You’re relaxing in the summer sunshine, listening to learnèd philosophers discuss their thoughts, watching as workmen hoist blocks of marble to build yet another shining temple. As you munch on olives and sip a cup of wine, you hear the sound of a train whistle and watch a paddleboat go steaming past –

Wait a second—train whistle? Paddleboat? Steam?

It could have happened. The Greek inventor Heron (or Hero) of Alexandria was an expert on the mathematics of the Babylonians, the Egyptians, and his predecessors in the Greek world; he also invented an odometer, the vending machine, surveying instruments, and a mechanism for opening doors automatically. Heron seems to have been delighted in creating models, perhaps as novelties, perhaps as miniature depictions of larger projects. One of these was the æolipyle, or “doorway of Æolos” (god of the winds), a hollow metal ball with two spouts coming out opposite sides. When partially filled with water and then heated, it spun around at great speed.

Heron’s æolipyle was an amusing toy. But what if he had thought to attach pistons to it? Reciprocating pistons apparently weren’t invented until 1100 years later, by the Arab engineer al-Jazari, and it was another six hundred years before James Watt put the two together. Just imagine—the Industrial Revolution in the ancient Mediterranean! Smokestacks towering over Alexandria, locomotives puffing through the Attic countryside, the Roman Empire expanding as steamships set out across the Atlantic . . .

Never mind.

Tracy Barrett is the author of numerous works of fiction and nonfiction for young readers. Her young-adult novel King of Ithaka will be published by Henry Holt Books for Young Readers in 2010. Visit her website at www.tracybarrett.com.