In the days when countries could afford to send their heroic and patriotic citizens into space, life in the space-capsule was not too different from the life of a goldfish confined in a small fishbowl. Compressed into a circular, constricted area the size of an under-stair cupboard, with no method of obtaining food, or indeed anything, from the hostile outside, with just the emptiness of space to stare at from one end of the dawn-less day to the other, it couldn’t have been much fun. If not for the fact that the President himself would speak to you, if and when you returned, few would have volunteered.
The worst part was the total dependence on other agencies for your every need. If you wanted dinner, you had to hope that the ground crew had remembered to pack your “high calorific super energizer” pill, mushroom flavored. If you needed to blow your nose, you would have needed special lessons on how to perform that feat where no gravity exists. Oxygen, water, food, radio contact, fuel, tools, and, above all, the ability to get out of this unusual, cramped abode, all had to be supplied by outside forces, on whose efficiency and capability your life depended. Any number of things could go wrong – you could lose radio contact, the oxygen supply might be insufficient, a passing meteorite might like the look of your little craft and collide, or – horror of horrors – a power failure could knock out the computer systems controlling the spaceship down on earth. Help!
Well, this is pretty much what it’s like being a little chick growing inside an egg. The brave astronaut in his space capsule, the small goldfish in its bowl, and the tiny chicken in its shell all share a common denominator: the absolute reliance on forces outside of themselves, and far beyond their control, for their survival. In the case of the spaceman, we understand the complex but well-orchestrated coordination on which his survival depends. But how is this true of an egg?
Have you ever wondered how a chicken manages to sit on her eggs during the incubating period without producing scrambled eggs? Eggs are such delicate things – why doesn’t it crack under the mother’s weight?
To understand the answer, we must understand how an electric light bulb works. The glass of a light bulb is not much thicker than the paper on this page, yet it withstands a strong grip when you push it into a light fitting. The reason is the shape of the bulb, which is modeled after the shape of the egg. The egg-shape provides structural strength to withstand all-round pressure, even with a thin shell. (If the shell were too thick, the chick inside would not be able to peck its way out; but more about that later.) Light bulbs and eggs have a rounded profile over the whole surface. When you grip an egg, or a light bulb, the force that you apply is transmitted in all directions away from the point of contact by its curved shape. This results in the force being distributed over a wide area, with no excessive force being applied to any one point. Hence, the egg and light bulb can survive.
If imitation is the greatest form of flattery, then the millions of light bulbs are the most eloquent testimony to the incredibly efficient design of the egg. The phenomenal strength of an egg is attested to by the fact that a chicken’s egg can survive a 600foot drop from a helicopter, and an ostrich egg will withstand the weight of a 250-pound man. It is said that you can balance a table on four eggs, without them breaking.
Enormous research was invested into finding the appropriate material for the exterior of the space-module. It has to withstand the intense heat of reentry into the earth’s atmosphere, and repel the adverse radiation of space. An egg-shell is no less equipped for its duties. Constructed from chalky calcium carbonate, it protects the egg and is sufficiently impervious to prevent water evaporating from it.
If the outside of an egg is impressive, then the inside is a veritable wonderland. The blood spot, although unwelcome in the kitchen, is in fact the beginning of an embryo, the beginning of life, which eventually develops into a chick. The tiny embryo rests on top of a bag of yellow yolk, which serves as the chick’s food supply, nourishing it whilst it develops. And develop it does, at remarkable speed. After just three days, the chick’s heart already beats, and it has blood vessels. After 15 days, the chick is already recognizable as a bird, and five short days later, 20 days after the egg was first laid, it is fully developed and ready to hatch the next day!
The embryo and yolk sac are surrounded by a watery fluid (the white of the egg) that contains a protein called albumen. The fluid’s main job is to supply the embryo with water during its development. But the embryo also needs oxygen. If you take a close, careful look at an egg, you’ll notice that one end of the egg is blunter than the other, and at the blunt end, just under the shell, there is airspace. The shell has tiny holes running through it, which allow oxygen to diffuse into the air space from the outside. The oxygen is then carried via blood vessels to the embryo, and carbon dioxide passes out in the reverse direction. In essence, this is how the embryo breathes. Imagine – a breathing egg!
The yolk sac must be kept in place so that the developing chick can obtain the nourishment it requires to survive. What keeps it in place and prevents it from slopping from side to side? The albumen twists and densifies like a rope from the two extremes of the egg, holding the yolk firmly and securely in place. And just three days after it is laid, the egg develops an excretory sac, in which the developing embryo is able to deposit its nitrogenous waste. Nothing that the little chick needs is missing, and everything is in its place.
Every mother bird knows, without ever having been taught, that her eggs require a stable and warm temperature in order to develop. Most birds satisfy this requirement simply by sitting on the eggs, but somehow the mother birds know when the eggs require extra heat. When the air temperature is very low; birds incubate very closely, and shiver to keep both themselves and the eggs warm. In climates where the air temperature rises above that which is beneficial for the eggs, the birds will again incubate very closely to prevent the egg temperature from rising above the mother’s body temperature. The egg has no way of regulating its temperature, and relies entirely on its mother, who knows exactly what to do. Similarly, the eggs must be turned regularly by the parents to help the chick develop properly. With instinct and devotion, the parents do their job, without ever having been taught.
Soon enough, it is time for the little one to come out into the world. It is interesting that there are no known cases in which the parent helps the chick by pecking or otherwise breaking the shell open. It has to do it itself. What precisely stimulates hatching is not known to man. All we know is that the little chick is superbly equipped to achieve a successful landfall. Baby birds have an “egg tooth” to help them break out of the shell. This is a tiny knob at the tip of their beak, precisely designed to allow junior to make a speedy exit. In the case of the chick, it takes approximately one hour from the first crack until the shell cap is broken, always in a counterclockwise direction from the first crack, and the chick, wet and bedraggled, but very much alive and healthy, clambers from its shell. Some chicks make peeping calls from inside the egg several days before hatching, and the hen replies, so when the chick hatches, it already knows its mother’s voice!
When you see a fully grown chick emerge from its shell, you wonder how this rather large baby managed to squeeze inside a little egg. You begin to wonder a little more and realize that if the shell had been a fraction thinner, the chick would never have survived being laid, if it would have been any thicker, the chick would not have been able to break through. You also wonder what would have happened if the chick did not have its beak, or its complete supply of food, or bag for waste, or if the egg would not have been its perfect shape… And you begin to discern Divine design, wisdom and planning.
If you think the men at NASA are wise, what would you say about the Designer of the living miracles called eggs?
Tuvia Cohen, is a humorist, scientist, and an accomplished author. This article was adapted from his book, ‘Designer World’.