According to:
hypertextbook.com...
the high end of normal human visible range is 780 nm
the low end of normal human visible range is 380 nm
According to:
www.encyclopedia.com...
the high end of wavelength x-ray range is 100 nm
from the low point of normal human visible range, there is a difference of 400 nm to the highest wavelength of visible range, but only 280 nm to the
high end of x-ray wavelength range.
If I only knew that humans can see 380 nm, I would be more inclined to believe they can also see 100 nm than that they can see 780 nm. Being able to
see x-rays would not be any more unnatural than snake seeing infrared radiation, it's just a question of what our eyes have evolved to capture.
X-ray vision is not impossible in the "breaking the speed of light" class, but more like in "chickens can fly" class. If someone would be able to
see x-rays there would be no magic, aliens or psionics involved but rather a mutation in the cells of the eyes that determine what wavelengths of
electromagnetic radiation are appropriate. And if brains would still believe they would be receiving visible light, xrays could be quite a colorful
display for such a person.


