I am seeking a mathematical analysis of an egg-ovoid rolling down an inclined plane,
for pedagogical reasons.
It is well-known folk lore that the shape of an egg prevents it from rolling away from
the mother's nest, e.g., the article
"Why are eggs egg-shaped?" (link), or,
a bit more formally,
"The Mathematics of Egg Shape" (PDF download) by Yutaka Nishiyama, from which I
copied this figure (and the one below):
If anyone has seen a mathematical analysis of this phenomenon, more precise than observing
that an egg-ovoid fits inside a cone, and a cone rolls a circular arc, I would appreciate
a pointer. Thanks!
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6$\begingroup$ In the ballpark: my father asked once what would happen if you took a bowling ball but installed a steel weight off center, so it was still a sphere outside but the center of mass was off. And then rolled it down a hill. Evidently my brother and I missed the point, as neither of us guessed that it could jump off the hill if rolling fast enough. $\endgroup$– Will JagyNov 4, 2012 at 1:52
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11$\begingroup$ A spherical egg fits into the cone as well, though $\endgroup$– Pietro MajerNov 4, 2012 at 21:18
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$\begingroup$ The biological premise is charming, but does not cover those birds that lay eggs in a nest, that keep them stable (they do not try and rescue fallen eggs). However, birds that lay eggs on the ground, sometimes even relocate the nest, moving the eggs by making them roll. In this case the egg-shape can actually prevent eggs from rolling down a hill. $\endgroup$– Pietro MajerMar 19, 2018 at 19:46
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1$\begingroup$ I don't have access to the paper (not even Sci-Hub at the moment...) but maybe this will be of interest? $$ $$ Narushin, Valeriy G., Michael N. Romanov, and Darren K. Griffin. "Egg and math: introducing a universal formula for egg shape." Annals of the New York Academy of Sciences (2021). nyaspubs.onlinelibrary.wiley.com/doi/10.1111/nyas.14680 $$ $$ I think it's this paper: biorxiv.org/content/10.1101/2020.08.15.252148v1.full $\endgroup$– Benjamin DickmanAug 29, 2021 at 18:31
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1 Answer
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This paper https://jeb.biologists.org/content/221/19/jeb178988 contains an experimental investigation of egg rolling. Theoretically, it seems "the relationship of egg shape to egg movement (e.g. rolling) is an understudied topic".