I’ve been hearing about Mark Kasevich’s super fountain tower for a while (including someone who was involved in funding it who was trying dazzle me a little. It worked.) A 10m tall device is imposing; one might ask what you can do with such a device that you can’t do with something that fits in one room. The answer is some really neat interferometry:

Viewpoint: A New Starting Point for Atom Interferometry

Point Sources and Towers: “Multiaxis Inertial Sensing with Long-Time Point Source Atom Interferometry”