You almost certainly know the Montgolfier brothers as the guys who launched a sheep, a duck, and a rooster into the sky in a hot air balloon in 1783. That demonstration at Versailles, witnessed by Louis XVI and Marie Antoinette, is one of the most iconic moments in the history of technology. But here's what the textbooks usually leave out: one of the brothers went on to invent something arguably more useful than the balloon — and you've probably heard its side effects banging around in your walls.

Joseph-Michel Montgolfier, the elder and more restless inventor of the pair, spent the years after his ballooning fame tinkering with water. In 1796, he built the first self-acting hydraulic ram — a pump that moves water uphill using absolutely no external power source. No electricity, no fuel, no manual labor. It runs entirely on the energy of flowing water itself.

The principle behind it is something called water hammer — that startling BANG you sometimes hear when you shut off a faucet quickly. When a column of moving water is suddenly stopped, its momentum creates a massive pressure spike. In your plumbing, that's an annoyance. In a hydraulic ram, it's the engine.

Here's how it works:

• Water flows downhill from a source through a pipe into the ram.
• A "waste valve" lets the water flow freely until it builds enough velocity to slam the valve shut.
• The sudden stoppage creates a pressure wave that forces a small portion of water through a check valve into a delivery pipe leading uphill.
• The pressure drops, the waste valve reopens, and the cycle repeats — automatically, indefinitely, with no moving parts beyond the two valves.

The device is beautifully inefficient in one sense — it "wastes" most of the water flowing through it. But it trades volume for height, and it does so with zero energy input. A ram fed by a gentle stream can push water tens of meters uphill, day and night, for decades. Some installations from the 19th century are still operating.

What makes this doubly interesting is how it connects to Montgolfier's earlier work. The hot air balloon was, at its core, an exploitation of a simple physical principle — hot air rises — scaled up with audacious engineering. The hydraulic ram follows the exact same intellectual pattern: take an everyday phenomenon everyone has observed, and turn it into a machine. Joseph-Michel had a genius for seeing engines hidden inside nuisances.

His brother Jacques-Étienne, meanwhile, took a different path after the balloon years, founding one of France's first vocational schools for paper-making — the family trade that had funded their experiments in the first place. The Montgolfiers were papermakers before they were aviators, and papermakers after. The balloons and the rams were almost side projects from a family whose day job was turning rags into sheets.

Today, hydraulic ram pumps are experiencing a quiet revival in off-grid and developing-world water systems, prized for the same reason they were remarkable in 1796: they run forever on nothing but gravity and momentum.