There is an urban myth that it is possible to balance an egg on the equinox, particularly the spring equinox. Furthermore the equinox is special in this regard, meaning that balancing an egg on its end on other days is impossible. It's a myth.
Scientific Method and Experimental Controls
People often test this myth by trying to balance an egg on the equinox. If they succeed in balancing the egg, they conclude the story is true rather than a myth and that there is something special about either the fall or spring equinox that allows an egg to balance on end.
Doing the experiment only on the equinox proves absolutely nothing!
Scientific experiments need controls. To prove the equinox is special, an experimenter must conduct the experiment on the equinox and, as a control, on another day that is not the equinox. For example, the author took the images accompanying this article on September 10, 2009, which is not the equinox. The experimenter should try equally hard to balance the egg on both days, and all other conditions should be as close as possible. Ideally, the experimenter should not know which time the experiment is being performed on the equinox.
To prove that there is something special about the equinox in terms of balancing eggs, it must be possible to balance the egg on the equinox and impossible on all other days.
Balancing Eggs on their Ends
It is actually very easy to balance an egg on a sidewalk or pavement. Try it. These surfaces are rough enough to form support points for the egg. People who try the experiment on one of these surfaces only on the equinox incorrectly conclude this urban myth is reality.
It is also possible to balance an egg on a very smooth surface, such as a countertop, by sprinkling a little salt on the surface. A few strategically placed salt grains can provide support points for the egg. Beware of frauds.
An extremely patient person with very fine motor control can balance an egg on a smooth surface after considerable effort, as was done for the image for this article. Trying just as hard on a day that is not the equinox shows that the balanced egg results from patience not the equinox.
What is the Equinox?
Earth is tilted on its rotational axis. That is what causes the seasons. As Earth orbits the Sun there are two days each year when the Sun is directly overhead from the equator at noon. On the fall equinox in September the Sun appears to move southward in the sky so that it will soon be more directly overhead in the southern hemisphere. It is the first day of fall in the northern hemisphere and the first day of spring in the southern hemisphere. On the spring, or vernal, equinox in March, the Sun appears to be moving northward in the sky. It will become more directly overhead in the northern hemisphere signaling the northern spring and southern fall.
The Sun is so distant that any difference in its gravitational or tidal forces between the equinoxes and other days is completely insignificant. There is absolutely no physical mechanism that can make it easier to balance an egg on the equinox than on any other day.
Yes it is possible, with effort, to balance an egg on the equinox. With the same care it is also possible to balance an egg on any other day. The equinox signals the first day of either fall or spring. There is otherwise nothing special about the equinox to make an egg balance on its end.
Paul A. Heckert - I have a Ph.D. in astrophysics, over 30 years experience teaching physics and astronomy, and over 60 published research articles.
