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Apparently in the Manchester museum, an Egyptian statue turns around while in a sealed display case. There is time-lapse footage of the statue, and in the article, Brian Cox is quoted as saying that:

Brian thinks it's differential friction, where two surfaces - the serpentine stone of the statuette and glass shelf it is on - cause a subtle vibration which is making the statuette turn.

Is that possible? Watching the video it seems that the statue doesn't have a constant rate of turning; it seems to turn only during the day, and it stops turning once it has completed a half-turn.

The only references to differential friction I could find were in the context of a moving vehicle braking when the left and right tyres were on different road surfaces, resulting in differential friction which could cause the car to swerve to one side. How can it function on a stationary object?

senshin
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Nick
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  • Is this question about the differential friction explanation? Or is it about your alternative hypothesis? –  Jun 24 '13 at 12:44
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    Its about the differential friction explanation, since that's the notable claim. – Nick Jun 24 '13 at 12:49
  • There doesn't seem to be any meaningful way we could answer this question. We can all chime in with our speculations (and it seems you, Professor Cox and I all have similar ideas), but what possible evidence could we provide to support it? – Oddthinking Jun 24 '13 at 14:20
  • Well, there could be examples of differential friction turning other things around? I could only find references to that phrase being used for cars which results in a turning force when the friction on the left and right sides are different, due to different road surfaces. But that involves a moving vehicle swerving when braking. Are there any examples of it rotating a stationary object? I've edited the question to focus on the claim. – Nick Jun 24 '13 at 14:24
  • Imagine under the heaviest part of the back of statue, there is a tiny bulge under the base. That is where the greatest pressure on the shelf will be, and the highest friction [appeal to intuition]. The rest of the statue is lighter on the shelf and move likely to slide around. Now make the shelf slightly slanted down at the back, and gentle shake it. It moves slowly/pivots at the point of the bulge (high friction) and faster at the front of the statue (low friction). The differences in friction cause it to turn as it slides towards the back of the shelf. The centre of gravity moves downhill. – Oddthinking Jun 24 '13 at 14:34
  • @Oddthinking wouldn't that just be called pivoting about a point? The quote from the article makes Differential Friction sounds like something which causes vibrations. Perhaps Brian has been badly quoted. – Nick Jun 24 '13 at 15:24
  • @Nick: Yes, I agree "pivoting" would be a more understandable description, although it may be the pivot point itself is *also* moving downhill (at a slower rate). I see your point about the word "cause". I imagine Prof Cox is being misquoted, but I am speculating here, so that's not contributing much. I wonder if we can find another source for the quote? – Oddthinking Jun 24 '13 at 16:29
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    Nope, it's definitely ghosts. – SIMEL Jun 24 '13 at 20:12
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    I don't know the name of the physical effect, but isn't it common knowledge that objects tend to rotate or move if they stand on a vibrating surface? If something causes the shelf to vibrate during day-time (people walking around, outside traffic, air conditioning equipment), wouldn't that explain the statue rotating? – Tor-Einar Jarnbjo Jun 25 '13 at 15:22

1 Answers1

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Yes it does, combined with the vibrations from the traffic on the street, and the shape of the statue's base:

Professor Brian Cox, who teaches physics at the university, gave a more worldly explanation. Mr Price said: “Brian thinks it’s differential friction, where two surfaces - the serpentine stone of the statuette and glass shelf it is on - cause a subtle vibration which is making the statuette turn."

And now ITV's Mystery Map programme claims to have solved the conundrum, backing Prof Cox's explanation. Their expert Steve Gosling put three-axis vibration sensors under the cabinet, and found a peak vibration level - coinciding with movement from passers-by and traffic from the very busy Oxford Road nearby.

He said: "The vibration is a combination of multiple sources so there's buses outside on the busy road, there's footfall activity. And it's all of those things combined.

"This statue has a convex base. There's a lump at the bottom which makes it more susceptible to vibrations than the others which have a flat base.

Taken from this article at The Independent.

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