Yes, in space, gravity can actually create a curve in a light beam. Basically, gravity can manipulate it's surroundings giving it somewhat some form of visibility.
Yes, black holes are invisible to the human eye because they do not emit any light.
No, it is not scientifically possible for a person to have an eye in their forehead. Human anatomy does not support the existence of such a feature.
Yes. and I'm superman
The planets have constant effects on human lives despite the inability to see the majority by human eye. The planets alter weather, gravity, daylight, and many other aspects.
While it is possible to be struck hard enough to dislodge an eye, the force necessary to do so is not likely possible with the human hand. There are records of accident victims who have lost an eye due to extreme impact trauma, but usually this is associated with auto crashes or similar trauma, and the damage done surrounding the eye is usually sufficient to cause death.
choroid
Yes, "visible" light.
Red! Any vampire that feasts on human blood has red eyes!
A tornado
There are quite a few aids to the human eye such as contacts. Another aid to the human eye is a set of glasses.
Some body might have done such an attempt. But such attempt will not be successful in any given time in case of the human being. That is not possible. Can you explain why is that impossible? It is unethical and immoral also. Will you allow such an experiment on your son? He can get permanently blind. He may get some autoimmune disease.
The human eye can refocus on objects at different distances within milliseconds, typically ranging from 300 to 500 milliseconds. This rapid adjustment is made possible by the eye's ability to change the shape of the lens to bring objects into focus.