OK, so when I say statue, I’m not talking life-size, it is only a 10-inch tall statue of Neb Sanu, discovered in a mummy’s tomb about 80 years ago and has been with the Museum ever since, oh and before you ask, nope, no movement until recently.
This is something you get to see yourself, they pointed a time-lapse camera and caught it moving … here you go …
Well, here are a couple of options for you to select from…
- The spirit of an ancient Egyptian has come back to very slowly rotate a small action figure of itself by 180 degrees … so slow that you need a time lapse camera to see it happen.
- Its a ghost, but one that is afraid of the dark, and so it only moves stuff during the day.
- Vibrations … notice that it only rotates during the day and not at night, so it is vibrations generated by outside traffic and/or visitors.
- Its a stunt … it does not move at all, and is just a stop motion animation to generate lots of free publicity
- Its a weeping angel (OK yes, I tossed this one in as a nod to Dr Who)
I think we can strike the first two, as for the other two viable options (ignoring 5), if you are torn between them, well here is a little more. If you pay attention to the clock in the corner – on 2013/04/06 and 2013/04/07 the statue is not moving. The museum is clearly open, ah but its a weekend so the normal weekday traffic on the busy city street outside is missing – for that reason I’d suggest that 3 is the correct answer.
What is actually going on here is “differential friction”. Tiny differences in the friction (or shape) of the base against the glass surface, driven by small vibrations, make the statue rotate slowly in one direction.
Er … what does the term “differential friction” actually mean?
OK, its like this … the underneath of the statue is not totally smooth, so it will touch the underlying glass surface via a number of points. A vibration of the appropriate frequency range will make two or three of those points rise while the others stay in contact with the underlying surface. If the surface has a slight skew, the torque produced by the weight will tend to rotate and/or translate the object so that its centre of mass moves down slope (i.e., if the friction on the points is different enough, one will stay still, the others will slide, and this leads to a simple rotation).
Sometimes this effect might cause an object to just rattle, for example glasses in a kitchen responding to washing machine vibrations, but here there is a slight imbalance that leads to the rotation.
- BBC reports it all here – and yes, the Museum rep who explains it as something mysterious is being a complete twat