A well-spun egg also jumps

Physicists have demonstrated that spinning a hard-boiled egg horizontally makes it jump into the air.

Scientists already knew that a fast-spinning egg spontaneously stands on its end. Random jitters during that process could amplify into leaps, researchers had theorized.

In some high-speed video images, hand-twirled eggs seemed to jump. But, no one knew whether those jumps were real or resulted from inadvertent upward propulsion from a spinner’s hand, notes Yutaka Shimomura of Keio University in Yokohama, Japan.

In new tests, he and his colleagues spun egg-shaped pieces of aluminum at initial rates of up to 2,500 revolutions per minute in a machine custom-built to impart strictly horizontal spins. By means of optical, acoustic, and electronic measurements, the team detected that the mock eggs leaped a fraction of a millimeter off the surface for up to a few hundredths of a second. During spins of actual hard-boiled eggs at 1,800 rpm, the researchers saw gaps momentarily appear beneath the eggs.

The team’s findings, reported in an upcoming Proceedings of the Royal Society: A, illuminate how tiny fluctuations in physical systems can lead to unexpected effects, Shimomura says.

Use up and down arrow keys to explore.Use right arrow key to move into the list.Use left arrow key to move back to the parent list.Use tab key to enter the current list item.Use escape to exit the menu.Use the Shift key with the Tab key to tab back to the search input.