This is at the MIT museum. I first saw it as a child decades ago and many times sense. The motor has been visibly replaced/refurbed and I'm sure they turn it of

This is at the MIT museum. I first saw it as a child decades ago and many times sense. The motor has been visibly replaced/refurbed and I'm sure they turn it off at night. All that said, when you see the first gear or two zipping around and stand there and stare at the Nth gear trying to see any movement at all it really drives home how these things scale. As a kid I once watched it for over an hour to see if could see ANY movement in the first gear that looked still.