Because that's the stable position. A shelf slightly out of level, a statue heavier on one side, it'll rotate until its heavier side is on the down side of the shelf. Or more technically, until its gravitational potential energy is at a minimum.
The mystery of the rotating Ancient Egyptian statue at Manchester University has been solved and, unfortunately, it isn't paranormal.
Following an investigation, experts have concluded that the figure rotated as a result of vibrations from passing footfall and traffic.
ITV's Mystery Map, which investigates myths and mysterious stories, an episode of which is on ITV1 at 8pm tonight, enlisted specialists to place sensors under the cabinet to detect vibrations, which dispelled some of the more outlandish claims.
Mystery of 'rotating statue' solved: 4,000-year-old artefact turned on the spot from the vibrations of visitors' walking past
Neb-Senu statuette began to mysteriously rotate overnight Was housed in a secure glass case in Manchester Museum Explanations for its movement ranged from ancient myths to curses Figure rotated as a result of vibrations from passing footfall and traffic
The 4,000-year-old Egyptian statue had curators at Manchester Museum puzzled after it began to mysteriously rotate overnight, despite being housed in a secure glass case.
Neb-Senu is a 10in (25cm) statuette made in about 1800 BC as a medium for the soul of an ancient Egyptian man.
The mystery of the 'rotating' statue has been solved following a scientific investigation which showed it moved as a result of vibrations from passing footfall and traffic
Neb-Senu is a 10in statuette made in about 1800 BC as a medium for the soul of an ancient Egyptian man
Explanations for its movement ranged from mystical and magical ancient myths, curses and spirits to the object being possessed.
But, following an investigation, a far more 21st century reason has been unearthed - that the figure rotated as a result of vibrations from passing footfall and traffic.
ITV's Mystery Map, which investigates myths and mysterious stories, enlisted specialists to place sensors under the cabinet to detect vibrations, which dispelled some of the more outlandish claims.
Vibration expert Steve Gosling undertook a 24-hour test by placing a specialist three-axis sensor under the wall-mounted cabinet containing the relic, to record any vibrations present.
Vibration expert Steve Gosling undertook a 24-hour test by placing a specialist three-axis sensor under the wall-mounted cabinet containing the relic
Figuring it out: Steve Gosling said the vibration comes from a combination of multiple sources
Beginning the test at 6pm, he found there was a peak in vibration level which correlated with movement at this time.
Overnight the vibrations stopped and the statue stopped rotating. Movement began again at 7am the following day - at the same time the vibrations also started again.
Mr Gosling 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.'
When asked why other displays were not rotating, he added: '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. This is conclusive.'
Anna Garnett, an Egyptology curator, previously attributed the mysterious movement to 'a force beyond the physical' whilst Yulan Li, a student, ascribed the motion to magic.
Professor Brian Cox previously said he thought the movement was a result of friction between the carved serpentine figure and the glass shelf.
:: Mystery Map is presented by Ben Shephard and Julia Bradbury and is on ITV at 8pm today