In theoretical physics, the visibility or invisibility of a two-dimensional surface or space depends on the context and the nature of the observer.
In terms of human perception, we typically experience and perceive the world in three spatial dimensions. We are accustomed to perceiving objects that have length, width, and height. A two-dimensional surface, such as a flat sheet of paper, would appear as a line or a plane from our perspective, and we would perceive it as a visible object.
However, if we consider a hypothetical scenario where we exist as beings restricted to a two-dimensional world, with no ability to move into the third spatial dimension, our perception of a two-dimensional space would be quite different. In that scenario, our perception and understanding of objects would be limited to their two-dimensional properties, and a two-dimensional surface would be our "normal" environment. In that sense, the concept of visibility or invisibility would be relative to the properties and limitations of our two-dimensional existence.
It's important to note that visibility or invisibility are ultimately subjective experiences tied to the sensory capabilities of the observer. In theoretical physics, the concept of visibility is often approached from a mathematical and conceptual standpoint rather than a direct sensory perception. The visibility or observability of a particular space or object is determined by the interaction between the observer and the properties of that space.
In summary, the visibility or invisibility of a two-dimensional surface or space depends on the nature of the observer and the context in which it is observed. It can vary based on the dimensional framework of the observer and the means of observation available in that framework.