Blood pressure monitor und LIGO: was sie gemeinsam haben

Schritt 1. Blood pressure monitor — entwickelte sich aus — Manometer. A blood pressure monitor is a manometer connected to a cuff: it measures the air pressure that squeezes the artery.
Schritt 2. Manometer — funktioniert wie — Barometer. Both measure pressure with a column of liquid: a barometer measures the air around us, a manometer the pressure inside a vessel.
Schritt 3. Barometer — nutzt — Vacuum. The Torricellian vacuum above the mercury.
Schritt 4. Vacuum — wird verwendet in — LIGO. 4 km vacuum tubes.