The naked eye is one of the most commonly used sensory organs in humans, allowing us to observe and perceive the world around us. However, the naked eye has certain limitations for observing objects at a distance.

Vision of the human naked eye is achieved through light-sensitive cells on the retina. These cells are called cones and rods. Cones are mainly responsible for observing the details and colors of objects in bright environments, while rods play an important role in visual perception in dark environments.

From the perspective of cones, human vision is able to observe details of about 34.0 degrees. This means that if an object is 0 meters in size, then the human eye can observe about 0.0 millimeters of detail. However, this number is only a theoretical estimate and is influenced by a variety of factors in practical observations, such as the intensity of light, the shape of the object, and the background.

When we look at distant objects, the biggest limitation comes from the refraction of the atmosphere. Air molecules in the atmosphere scatter light, causing objects to become obscured at long distances. This phenomenon is known as atmospheric turbulence. In general, the visual distance for observing distant objects with the naked eye is about 10 km.

Human perception of distant objects does not depend solely on the naked eye. We invented optical instruments such as telescopes and microscopes that solved the limitations of visual distance by magnifying the details of objects. Telescopes can observe galaxies billions of light-years away, while microscopes can observe tiny cellular and molecular structures.