It has been assumed that the human eye has evolved to absorb the most energetic wavelengths of the visible spectrum available on Earth. That in turn, depends on the temperature of our star, the Sun, and on the composition of the atmosphere. But, the new research concludes that the evolution of human vision has not only been determined by the intensity of the radiation received from the Sun (the amount of energy it carries) but also for the amount of information it provides, its entropy. When we see something, the brain also interprets the environment. As the human brain has evolved, there has been an iterative process between our brain and our eyes that has optimized the eyes in order to get the most information of the environment. The evolution has favored the reception of the wavelengths in which there is an optimal relation between the information and the intensity, that is entropy and energy.
– In this paper we present that in order to get the most appropriate information from an environment illuminated at the wavelengths that the Sun emits, our human eye has evolved not only to be able to capture the maximum intensity of the radiation emitted by the Sun, as it was commonly accepted, but also to receive the maximum information content of the radiation, says Javier Martín-Torres.
Calculated proportionality ratio
For reaching their conclusion, Javier Martín-Torres and Alfonso Delgado-Bonal, Instituto Andaluz de Ciencias de la Tierra, have calculated a proportionality ratio to establish the wavelengths at which the content of information and energy per wavelength is optimal. They present the calculations for two different lighting conditions, which correspond to the two types of vision in the eye: the photonic one, mediated by the photoreceptor cells known as “cones” that works under full light during the central hours of the day, and the scotopic vision, under low light conditions, which is mediated by the “rod” cells. The optimal wavelengths found for these two different situations were, respectively, 555 nm and 508 nm, which match almost exactly with the experimentally observed peaks of absorption in the human eye at 555nm and 507 nm.
– One important aspect of the article is that we have derived a law for the spectral entropy similar to the extensively known Wien´s Law that applies to the intensity of the blackbody radiation, and that we have found a practical application to this law, says Javier Martín-Torres.
Will affect future technology
The research is expected to have an impact on a wide variety of scientific and technological areas, such as instrument design and telecommunication.
–As for the eye, our result should be applied to any other system dealing with electromagnetic radiation and information content, so the implications for instrument design and telecommunication system is clear. The maximization of information occurs in the process of maximizing the entropy, and the systems that we develop should accomplish that.