Across ancient cosmogonies, from Orphic fragments to Vedic scripture, the cosmic egg divides into heaven and earth. Modern drawings often divide it by cutting the egg across the middle, then treating the two halves as a flat world below and a sky above. That move changes the geometry before the old story has a chance to speak.
Cosmogony joins the Greek κόσμος (kosmos), meaning order, arrangement, world, or universe, with -γονία (-gonia), meaning birth or coming into being. Κοσμογονία (kosmogonia) is the birth of the ordered world.
The egg has an inside. From there, the lower realm need not mean a flat floor. It can mean the enclosing inner shell, Earth. The upper realm can mean the yolk or central firmament: the point toward which the inhabited surface faces. Heaven and Earth are not two hemispheres cut apart. They are parts of one enclosed arrangement.
It's important to remember that the surviving record is not a set of complete, pristine manuscripts. The Orphic material, especially, often reaches us through doxographies: later philosophers summarizing older traditions, sometimes with their own purposes. Once a fragment is lifted from its setting and carried into another language, the geometry can disappear with it.
Transliteration only moves a word from one alphabet to another. Translation does the heavier work. A word for "below" can become "underneath a surface" when it may have meant inward, toward the center. After enough retellings, heaven and earth arrive as a modern diagram: a ground plane below, a sky somewhere above it.
From inside the cosmic egg, the terms change shape. The inner shell is the lower realm because it encloses the observer. Water rises around the inhabited surface. The central sphere is upper because every point on that surface faces toward it. The sky is the ball in the middle, not the Earth.
The old egg is not a flat-earth picture waiting to be corrected. It is an enclosed world whose language was flattened by the way it was drawn. Once the shell is cut at the equator, the cosmos becomes two opposing halves. Put the observer back inside it and the old division of heaven and earth becomes legible again.