A 4 mm eyepiece does not alter the physical distance light travels from celestial objects, which remain billions of kilometers away; instead, it provides high angular magnification by compressing the apparent field of view into a detailed, immersive image. Visibility depends on the telescope's focal length divided by the eyepiece's 4 mm focal length, yielding magnifications typically from 100x (e.g., 400 mm telescope) to 250x or more (e.g., 1000 mm telescope), resolving fine details like planetary rings or lunar rilles under stable atmospheric conditions.