The human eye can only see objects in daytime and not when it is dark by night. This is unlike, e.g. snakes, where they can see objects in dark space as well. The visibility of human eyes is made possible through the natural daylight coming from the sun which among its components some type of electro-magnetic radiation called “the visible light”. The visible light can also come from artificial light sources (http://www.continental-lighting.com/lighting-basics/artificial-light-sources.php) e.g. light bulb (heated wires), LED-lamps, flourescent, ….). Snakes for their visibility, for example, use other type of radiation called “the infra-red” which is also emitted from hot bodies including the human body. The global distribution of snakes bites leading to envenoming can be viewed at (http://www.scielo.br/scielo.php?pid=S1678-91992013000100205&script=sci_arttext&tlng=pt).

Researchers have now created possibilities for extending the visibility of human eyes to include in addition to visible light the infra-red radiation. Read the story below:

http://www.slipperybrick.com/2014/04/night-vision-contacts/