You need to know where you are to start your journey.
In true concave egg shape Earth model we are living on the inner eggshell surface under the glass/ice membrane called Karman line at height 100 km above the ground.
Earth is stationary and only Celestial Sphere, Sun, Moon and planets are spinning around.
Celestial Sphere “yolk” with Octahedron inside spins at the center of Universe.
Sun, Moon and planets are spinning in-between Karman line and Celestial Sphere.
Earth measurements and inner Universe are:
Radius of the Earth 6.371 km
Diameter of the Earth 12.742 km
Distance to the Celestial Sphere 3.937 km
Diameter of the Celestial Sphere 4.867 km
Diameter of the Octahedron 3.007 km
Edge length of the Octahedron all equal 2.125 km