In a world where everyone has a personal gravity bubble that allows them to adhere to surfaces like spherical magnets, Jinhai and Eleni are playing a game in a room with a smooth, spherical interior. Jinhai is currently standing on what would be considered the "floor" of the spherical room, while Eleni is directly opposite on the "ceiling." Assuming that both can control their personal gravity bubbles to walk along any surface, what happens when Jinhai decides to walk along the inner surface of the sphere to reach Eleni, who remains stationary on the ceiling?

Provide a short response.
Jinhai begins to walk along the inner surface of the spherical room using his personal gravity bubble to stick to the surface. The gravity bubble changes its orientation relative to Jinhai's position so that his feet are always "down" relative to him, providing the sensation of walking on a flat surface, even though he's traversing a curved space. As he walks, the walls gradually curve upward and become the ceiling from his perspective. 

From Eleni's point of view, she sees Jinhai begin to walk up the wall and then along the curved surface of the sphere's interior, slowly turning upside down relative to her own position. Her personal gravity bubble keeps her firmly in place on her own "ceiling" spot so she does not move.

When Jinhai finally reaches Eleni's position opposite his starting point, to an observer outside their gravity bubbles, it appears as if Jinhai is standing upside down relative to Eleni. However, because of his personal gravity bubble, Jinhai feels as if he is standing right-side-up, just as he did at the start of his walk, and Eleni also feels as if she is standing right-side-up relative to her own gravity bubble. If they were to reach out and touch each other's hands, they would be doing so in what appears to be an inverted manner -- Jinhai's "down" now directly opposed to Eleni's "down."