A Sloshing-Mercury-Powered Neon Light

According to Hackaday, a hobbyist recently recreated a three-hundred-fifty-year-old discovery: the barometric light phenomenon first observed by astronomer Jean Picard in sixteen seventy-five. When Picard transported a barometer at night, he noticed an orange glow inside the tube as the mercury sloshed—static electricity was discharging and ionizing the residual gas, producing light. A hobbyist using the username Styropyro rebuilt this effect with a vacuum pump and mercury, but the glow was faint even in darkness. The breakthrough came when he backfilled the tube with neon gas to roughly forty millitorr of pressure: when shaken, the flask produced a bright orange-red glow just above the mercury surface. Krypton produced a dimmer blue glow, and other materials like Teflon and copper showed similar effects, though less dramatically. The phenomenon is fundamentally triboelectric—a charge-and-discharge effect that shifts in color and brightness depending on the material and gas.

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