The human eye can see up to about 5 kilometers (around 3 miles) to the horizon on a clear day due to the Earth's curvature. However, if the object is large and bright enough, such as a mountain or tall building, it can be seen from much farther away, sometimes up to 50 kilometers or more depending on size and visibility. At night, bright objects like stars and galaxies can be seen at vast distances, even millions of light-years away, because the eye detects light, not detail at those distances. The actual distance the eye can see depends on factors like eye health, brightness, object size, and obstructions in the line of sight.
