The letter "形" means the shape of a concentric sphere, "理" means radial lines extending from the center of the earth to the celestial sphere.
BAIEN compared the concentric sphere to a ball and wrote the celestial sphere was the biggest. He gave that a letter "形", means "Shape" from limited character resource. He compared the radial line to a chestnut-burr, and named "理". The character has several means. One of them is a sharp line such as a crease or cut or notch. It also means that the system, discipline, and order.
I think the trajectories and shapes of fireworks emitted from the center after an explosion is a better example of both metaphors. But because the two forms were static, Baien chooses the static model.
The top letter "外" which is outer the figure means out space of the celestial sphere. The center letter "中" means the center, "内" means the inner, "外" means the outer space in the sphere. "上" and "下" means upper and lower.
BAIEN knew the existence of gravity in the second half of the middle Edo period. If we think that the center of left figure is of the earth's, we have seen the celestial sphere from the Heavenly Arctic.
In that case, the center gray aria would be the earth sphere and the atmosphere. And the outer thick black circle would be the orbit of the sun as seen from the earth, and the outermost circle is the celestial equator. If we think the center is the Sun's, the thick ring may be the orbit of the earth. We can consider both possibilities, but BAIEN did not write, which it was. He showed the structure of the space itself.
The figure below is useful for the discussion of this figure.
BAIEN might have assumed the diagram below, but perhaps that is too much my thinking.
Because he could use only paper and old Japanese traditional compass, he could only draw that as a top viewing like below.
Though the upper right figure drew without any lines has the essential meaning of our universe. Because the center point means an infinitely small point, and the circle is infinite space.
More importantly, BAIEN thought that infinite space filled with infinitely small points. And any space becomes unlimited from the view of a tiny point. Our earth and the sun just happened to get one of each.
BAIEN wrote the infinitely small point is never crushed by any heavyweight. BAIEN named the infinitely small point "無内の中", which means "a point without internal".
If Baien had known the following web site, he must very surprised.
Because that is the knowledge he had most wanted to know that had been the part of the heavenly body system, which belongs to the visible field of GENGO Theory.