You know Philips as the company that made your electric toothbrush, your hi-fi speakers, or maybe the lightbulb in your hallway lamp. What you probably don't know is that for several decades in the 20th century, Philips was the world's foremost expert on a 19th-century Scottish minister's heat engine — and very nearly cornered the global market on a technology that NASA still uses today.

The story starts in the 1930s. Philips was selling radios into rural and colonial markets where mains electricity didn't exist. Their customers needed a way to power those radios, and the obvious answer — a small generator — was a problem. Internal combustion engines of that era were loud, smoky, and finicky, exactly the wrong companion for a delicate vacuum-tube receiver. Philips' engineers went looking for something quieter and more reliable, and they landed on an obscure invention from 1816: the Stirling engine, patented by Reverend Robert Stirling as a safer alternative to the boiler explosions that were routinely killing people in early steam plants.

By the time Philips picked it up, the Stirling engine had been dormant for nearly a century. Internal combustion had eaten its lunch. As Wikipedia puts it, "virtually no serious development work had been carried out on the Stirling engine for many years." Philips asserted the role themselves — and turned a hobbyist curiosity into a serious industrial program.

What's fascinating about Stirling engines is why they're so quiet. Unlike a gasoline engine, there are no explosions inside — the working gas (often helium or hydrogen in modern designs) is sealed in a closed loop and simply heated and cooled from the outside. That makes them:

• External combustion — they can burn literally anything: wood, propane, concentrated sunlight, even body heat
• Nearly silent, with no exhaust valves slamming open
• Theoretically the most efficient heat engine possible, matching the Carnot limit

Philips built thousands of generators, then pivoted hard. By the 1950s they were exploring Stirling engines for submarines (silent running!), buses, cars, and — in reverse — as cryocoolers, because running a Stirling engine backward turns it into an incredibly effective refrigerator. That last application is the one that stuck. Philips' Stirling cryocooler designs eventually became standard equipment for cooling infrared sensors, liquefying gases, and chilling MRI superconducting magnets.

The road engine never quite worked out. The thermal mass meant Stirlings warmed up too slowly to be practical for cars, and the sealed high-pressure helium had a nasty habit of leaking past piston seals. Philips eventually licensed the technology to Ford and General Motors and walked away from automotive applications.

But here's the kicker: every NASA deep-space probe that flies too far from the sun for solar panels — think New Horizons, the Mars rovers' successors, missions to the outer planets — uses a power source derived from the engineering Philips developed selling radios to farmers. Plutonium decay provides the heat. A Stirling engine descendant turns it into electricity. A Scottish minister, a Dutch lightbulb company, and Pluto: the same machine.