The ancient 'jet' engine that was used to cook meat

The turbines that propel jets through the air can be traced back to an idea originated by Hero of Alexandria in the first century AD. Find out what you do with an engine that pre-dates steam power and manned air flight by roughly two thousand years.

One of the perpetual problems of physics and engineering is how to successfully convert energy from one form to another, more useful form. Today we convert jet fuel to spinning turbines that push airplanes through the sky. Before that, we converted coal to steam which sped trains along their tracks. And before all of that, Hero (also known as Heron) of Alexandria came up with the basic idea on which all turbines are based.

Hero's engine often looks like a little covered cooking pot on three legged stool. Coming out of the 'lid' of the pot are two tubes that lead to a central ball. That ball has two little tubes coming out of it; each bent ninety degrees so between the two of them they look like a collision of bendy straws. The pot is filled with water and heated from below. As the water boils it turns to steam. The steam expands, and has nowhere to go except up through the tubes to the central ball, and then out through two bendy straws. The bend in the straws forces the steam to move at a ninety degree angle to the ball. The momentum of the steam going out one way forces the straws to move the other way, and the whole ball turns. This one principle - one way of converting carbon to motion - that has been used endlessly since, in a thousand different applications. The turbine has driven society across the land during the Industrial Revolution and into the air when commercial flight became an option.

Sadly, the Alexandrians had a long way to go before the infrastructure and accompanying technology were anywhere close to matching this little idea's power. By the third century AD, there was only one major documented use for Hero's turbine - turning meat on a grill. Up until that point, servants had turned the spit, and no one could be sure, 'that the haunch has not been pawed by the turn-spit (in the absence of the housewife's eye), for the pleasure of licking his unclean fingers.' Later, moving engines, powered by steam, animated giant metal statues that would act out simple motions like waving a sword or turning in place, creating a tableau for crowds. The idea that powered much of the modern world was just a novelty then.

Well, it's not commercial flight, but it's a start. Who doesn't want unlicked meat?

Image: Smith

Via U of H and The Physics Book.