Eggs roll in a funny and wobbly way. Measuring things helps us find out exactly how big or tall something is. Eggs may look like they are the same size, but they aren't. We can measure the vertical and horizontal lines of eggs to see just how big they are. Eggshells are porous so that air get in and out of the egg.
Many objects roll.
Eggs have inside them everything that a baby bird needs to grow to the point of being ready to be hatched and finish growing in the world. Because eggs are a funny and oblong shape, they roll and wobble around in a certain way. If eggs were round, they would probably roll out of nests or too far away from the mother hen. Eggshells have to have little holes in them so that air can move through and into the egg for the growing baby bird. We can see evidence that there are little holes in an eggshell by putting it in water and seeing air bubbles.