Manchester Museum is getting a lot of publicity for a video of a statue that slowly rotates through the course of the day. It's on a glass shelf, and it only moves when there are people walking nearby. This raises the obvious suggestion that the rotation is simply due to the vibration. The statue is hard uneven stone, and the glass shelf is very hard and perfectly flat. When two hard substances are in contact with each other, then there's not much friction because there are limited points of contact. I suspect that the base of the statue is uneven, which allows it to tilt and pivot very slightly from the vertical vibration from people walking by. The shelf is very slightly tilted towards the front, so the statue rotates until the center of gravity is at the lowest point, and then it stops. Firstly the issue of object moving on a glass shelf visitor induced vibration from wooden floors is a known problem in the museum industry, see: http://www.english-heritage.org.uk/content/imported-docs/u-z/vibration-rio.pdf To test this theory out, I made a functional replica of the situation using a glass table, a piece of wood with some screws in for the hard uneven base, and a container of salt for the statue. (Skip to 0:35 in the following video to see the experiment) Initial tests showed that the movement and rotation of the statue varied a lot based on the geometry of the base - i.e. the relative height of the screws. Adjusting one screw a fraction of a turn could entirely change the behavior. So it's pretty random that the statue ended up moving the way it did. As I did not have lots of people to walk around my table for days I accelerated the process by angling the table probably slightly more than the shelf (it's still only 2 degrees though), and by directly vibrating the table. This is obviously not the same as what happened - the magnitudes are different, but the concept is the same. Some inevitable questions: Why has it never moved before? Firstly its obvious that that it's not been on that exact same shelf for "decades" or "80 years" as some news stories report. In fact that's the new Ancient World Gallery, which opened around Oct 2012), so it's been there for a few months at most. The curator simply said it had been on a similar shelf before. Secondly, experiments show the motion is dependent on circumstances. So something must have changed, but only very slightly - the slope of the shelf, the position of the statue on the shelf, even the position of other objects can affect the vibration. Even a very slight shift in the frame of the building could be responsible. And perhaps the previous curators had been sensible, and secured it to the shelf with a dot of wax. Why are the other statues not moving? Because they are different. They are smaller, they are shorter, they have a more centered center of gravity, they are made of different materials, they have different bases, they are in different positions. Why does it spin exactly 180 degrees? Because the shelf is sloped very slightly down towards the front of the cabinet, so it stops when the center of gravity gets to the lowest position. Why does it go round in a circle? Because it's pivoting on a point in the base. In my experiment this is represented by the center screw, which is just a tiny bit more protruding than the others. But the actual geometry will vary. Why does it rotate so slowly when yours goes so fast? Because of the magnitudes of things. The vibration is less in amplitude, the pivoting on the base is smaller, the slope is less. So it's doing to very large number of much smaller motions. What about: A) The museum employees was working in the gallery, so perhaps they caused the vibration themselves B) Vibrations could come from people in other rooms, or upstairs.