A new approach to egg-tops physics

When spun horizontally on a table, a hard-boiled egg rises and eventually rotates vertically about its long axis. We argue that this behavior arises because the egg begins to roll as soon as rolling becomes possible, a claim we support with experimental videos. For an ellipsoidal egg, we show that minimizing energy loss due to friction favors rolling about the axis connecting the point of contact with the table to the center of gravity. We solve Euler’s equations of motion in two models—one including initial rotational friction and one neglecting it—and obtain a convincing description of the phenomenon. In particular, the model with initial rotational friction allows us to calculate the ascent time with high accuracy. Theoretical curves to be compared with experiment are presented. This article underwent a validation process lasting more than a year at a major physics journal, at the end of which three referees recommended its publication. The editor then reversed course after soliciting two additional reviewers at the last moment. We publish it here before submitting it to another journal.