If you want to determine whether an object is on the surface of a sphere without physically touching it, you can use visual or observational methods. Here are a few approaches:
Line of sight: Stand at a distance and observe the object from different angles. If the object appears to be tangent to the curvature of the sphere from all angles, it is likely on the surface.
Shadows: If the object casts a shadow on the sphere's surface that aligns with the curvature, it suggests that the object is on the surface. This can be observed by analyzing the direction and shape of the shadow relative to the sphere.
Reflections: If the object reflects the shape of the sphere, it indicates that the object is likely on the surface. By observing the reflections on the object's surface and comparing them to the known shape of the sphere, you can make an inference.
Parallax effect: Move around the sphere while observing the object. If the object appears to move in relation to the background or other objects on the sphere, it suggests that the object is not on the surface but is positioned at a different distance.
These methods rely on visual observations and interpretations of the object's relationship with the sphere's surface. While they can provide reasonable indications, they are not as precise as physically touching the object or using more advanced techniques like 3D scanning or imaging technologies.