According to the laws of physics — at least in simplified form — an object in motion will stay in motion, at least if no other forces act on it. That’s all well and good in the realm of theory, but here in the complex reality of Earth, there always seems to be one force or another getting in the way. Not that this has ever completely shut down mankind’s desire to build a perpetual-motion machine., that quest dates at least as far back as seventh-century India, where “the mathematician Brahmagupta, who wanted to represent the cyclical and eternal motion of the heavens, designed an overbalanced wheel whose rotation was powered by the flow of mercury inside its hollow spokes.”
More widely known is the successor design by Brahmagupta’s twelfth-century countryman and colleague, who “altered the wheel design by giving the hollow spokes a curved shape, producing an asymmetrical course in constant imbalance.” Despite this rendition’s memorable elegance, it does not, like the earlier overbalanced wheel, actually keep on turning forever. To blame are the very same laws of physics that have dogged the subsequent 900 or so years of attempts to build perpetual-motion machines, which you can see briefly explained in .
“Ideas for perpetual-motion machines all violate one or more fundamental laws of thermodynamics, the branch of physics that describes the relationship between different forms of energy,” says the narrator. The first law holds that “energy can’t be created or destroyed; you can’t get out more energy than you put in.” That alone would put an end to hopes for a “free” energy source of this kind. But even machines that just keep moving by themselves — much less useful, of course, but still scientifically earth-shattering — would eventually “have to create some extra energy to nudge the system past its stopping point, breaking the first law of thermodynamics.”
Whenever machines seem to overcome this problem, “in reality, they invariably turn out to be drawing energy from some external source.” (Nineteenth-century America seems to have offered endless opportunities for engineering charlatanism of this kind, whose perpetrators made a habit of skipping town whenever their trickery was revealed, some obtaining patents and profits all the while). But even if the first law of thermodynamics didn’t apply, there would remain the matter of the second, which dictates that “energy tends to spread out through processes like friction,” thus “reducing the energy available to move the system itself, until the machine inevitably stopped.” Hence the abandonment of interest in perpetual motion by such scientific minds as Galileo and— who must also have understood that mankind would never fully relinquish the dream.
Based in Seoul,writes and broadcasts on cities, language, and culture. His projects include the Substack newsletter , the book The Stateless City: a Walk through 21st-Century Los Angeles and the video series . Follow him on Twitter at or on .