The maximum distance the eye can see is about 5 km due to the curvature of the earth, and it is impossible to see any object beyond the horizon line.
However, if the earth were not round, the eye could reach a far greater distance, which can be achieved if the person is in a high building or a high mountain.
What is the maximum distance the vision reaches
The maximum distance the eye can see depends very much on the size of what is observed, as well as the light it may be emitting. If it is a small object, the vision can not exceed a few meters, however, if it emits light on a dark background, such as a lamp or a lit candle, the eye can already reach almost 50 km .
Besides the light factor, it is also important the size of this object, which justifies that it is possible to observe an airplane in the sky, that can be more than 30 kilometers of the ground, or even the moon, the sun and the stars, millions of miles away from land.
In addition to the size and luminosity of the observed objects, there are other factors that can alter the capacity of vision, such as visual obstacles or eye health, for example. See the 7 most common vision problems and how to treat them.
