Standing an egg on its head – only on the spring equinox?
This is the kind of logic question, which needs to be asked carefully: can you stand an egg on its head on the vernal equinox? Yes, given the proper practice. Can you stand the egg on its head on any other day of the year? Yes, given the proper practice.
There are some urban myths and stories that can stand a little digging, but this is not one of them in my not very humble opinion. The equinox and by extension the seasons all depend on the tilt of the earth, relative to the sun, twice a year, (spring and autumn equinoxes) the tilt of the Earth on its axis is perpendicular to the sun and so equal distribution of day and night.
Of course historically the vernal equinox has had a great cultural significance for many people’s, being of equal length day and night , the days following would be longer, it is a time of rebirth, of new light , of new beginnings. It is likely that eggs have played an important part in these celebrations over different cultures and generations. We only have to look at the Easter Egg traditions which now accompany the Easter festival. It is thought that the traditions regarding eggs predate the Christian festival, there are of course Christian traditions which have grown up associated with eggs, such as the analogue between Christ’s birth out of the Sacred Womb and the painting of the eggs symbolises using a food to celebrate to celebrate which was banned during the Lenten period.
It is not beyond logic that the standing at the spring equinox story would gain momentum, after all it is the time of year most associated with eggs. There is a suggestion that the Chinese first started the association of egg standing and Spring equinox (note; there is some discussion around this as the Chinese festival upon which the observation occurs is actually a few weeks away from the vernal equinox, Also by-and-large, Chinese festivals follow the lunar calendar). This period is seen as a time of balance, equal day and night dark and light. The egg with its life giving associations was in balance when stood, this is a good omen for the year ahead.
What are the factors which could influence the standing of an egg?
Gravity, we know that the lower the centre of gravity, the more stable an item is (usually), so using the flatter end can help this. There is nothing in the spring equinox to alter the gravitational pull on the egg. The egg is one of two bodies and as Newton wrote (translated): Every point mass attracts every single other point mass by a force pointing along the line intersecting both points. The force is proportional to the product of the two masses and inversely proportional to the square of the distance between them. so all you need to do is have the intersection line at the right angle relative to the egg and planet. The actual angle of the planet is not of any consequence because the centre of gravity in the same (give or take, but not enough to influence the egg). Slight aside: again using logic, if the Earth’s angle had an influence, then surely the geo-location used to attempt the egg standing would be crucial. If the Earths angle is so important, then surely the only place to do it would be at the appropriate north pole (true north as against the other 5 or so north poles), after all if done anywhere else is that angle off set? If there is an offsetting, can that be built in to the equation (so to speak) for when the earth is not located at the vernal equinox.
This of course brings me to the one of the basic objections to the theory: why is it only on the vernal equinox, there is nothing gravitationally different between the two. Not only that but are we saying that the premise does not hold in the opposite hemisphere? Again I can see no difference between either hemisphere. Given that the Earth is more-or-less a sphere – we will ignore the slight flattening effect between the poles – should there be a influence on where we are East or West, left or right. We need to remember markers such as the Greenwich meridian are human constructs, the meridian could very easily have been Paris, save for political influence.
The difficulty of standing an egg is, as we know, balance. Let’s have a look at that. The oval egg is made up of the thick white of the egg, in which sits the dense yoke. This raises the centre of gravity. Also the yoke is often non-symmetrical in its location or resting in the egg. The steady hand is needed to “feel-for” where the actual centre of gravity is for a specific egg. One of the areas that have been looked at, is the nature of the shell. An egg with a rougher texture to its shell will grip a surface better than a smooth egg and so will be more likely to remain in position. Which end you try to stand also influences. As mentioned above, balancing on the narrow end (pole) of the egg is what takes the greatest skill given the limit surface area with which to work.
Given the relatively small surface areas involved (the end tip) and the corresponding points on the object the egg is standing on, it is easy to see how an outside influence like a vibration, air current or other factor could prevent standing, but a stable environment with no drafts will quickly overcome this.
Oh and by-the-way, for any of you wise-asses, we are talking about a raw egg. To show the complexity of egg balancing, take two eggs one hard boiled, the other raw. Spin both and then hold to stop, take your hand away and the boiled on will fall over while the raw egg will likely restart spinning (if you did it right) because the inside of the egg did not stop and the inertia of its spin starts the process again for the whole egg. Even better, take the hard-boiled egg, lay it on its side and start it spinning as quickly as you can, once the egg is rotating quickly enough it will rise up and rotate like a spinning top. This seems counter intuitive but Keith Muffatt and Yutake Shimomura have studied this area and explain that it’s because of friction. Friction destabalises the spinning of the egg and causes a shift in position. Essentially an amount of the kinetic energy generated by the spin is converted to potential energy, this is the energy that is stored in an object that has a distance to fall. For a few seconds the egg when standing on end has more potential energy and less kinetic energy, at least for a few seconds.
So after all of that, the big question is, which came first, the chicken or the egg? Stay tuned to fine the definitive answer…
 · – Proposition 75, Theorem 35: p.956 – I.Bernard Cohen and Anne Whitman, translators: Isaac Newton, The Principia: Mathematical Principles of Natural Philosophy. Preceded by A Guide to Newton’s Principia, by I.Bernard Cohen. University of California Press 1999 ISBN 0-520-08816-6 ISBN 0-520-08817-4