The human eye is able to see objects at any distance

The human eye can perceive objects at all distances. If in a very clear night to look at the sky, you can see the galaxy of the Triangle, located in the 3 of us, 14 million light-years. Also, sometimes you can see and the Andromeda galaxy, which is in 2, 5 million light years away. In fact, no matter how far away objects are from us; because we perceive them to reflected light rays that affect our organs of vision. Thus, we see not the objects themselves, and rays of light.

Light affects our optic nerve which sends a signal to the brain. The brain receives the signal and interprets it as an image. The brighter the object, the farther it is noticeable. The star Rigel, for example, is much brighter than the star Alpha Centauri. But while Alpha Centauri is much closer to us. According to Dr. Brent Archinal, the human eye can distinguish about 2500 stars in the clear night sky. But because of the weather conditions, air pollution, urban reflections and other factors, this number is reduced to 1500-2000. Under ideal conditions, visible from Earth five planets: Mercury, Venus, Mars, Jupiter and Saturn.

Source: Stephen Juan, «The odd body - 2»

via factroom.ru