Okay, this is really cool, and I’ve seen it before but this is the first time I’ve had it explained and gotten it. This is big sphere swinging back and forth is proof the Earth rotates. If I remember correctly it takes this one about 42 hours to do a full rotation. You can learn a touch more here and a lot more about Foucault pendulums here. It’s cool.
This was also where I got to hear an 85-year-old grandmother ask her granddaughter, Erin, “Is he always such a sadist?” It was a good day.