Why a person can't distinguish colors in the dark.

 The phenomenon of sight is a remarkable gift, and the ability to differentiate colors is a true miracle that is often overlooked by many. Nevertheless, the intricate mechanism that governs color perception is still not fully comprehended, and many enigmas about vision continue to mystify even the most astute minds of the human race. One of the most puzzling questions is why a person cannot distinguish colors in the dark.

Isaac Newton laid the groundwork for the exploration of this complex question, demonstrating that white color is actually a combination of different shades, and he articulated his findings in his works, "Lectures on Optics" and "New Theory of Light and Colors." During his experiments, Newton passed the color through a glass prism and observed that the color is composed of a spectrum of shades ranging from red to purple, with one color transitioning smoothly into the next (this phenomenon is known as the light spectrum).

Each color refracts differently, with red refracting the least and violet refracting the most. Without this refraction (scientifically referred to as dispersion), the eye only perceives white.

The wavelength of light is responsible for the way we distinguish shades (which we likely remember well from our physics lessons). Purple has the shortest visible light waves, while red has the longest. As Arkady Likum notes in his all-encompassing encyclopedia, "Everything About Everything," most of the colors that we see encompass several light waves of varying lengths. When sunlight strikes an object, some of the waves reflect, while others are absorbed by the material from which it was made. From this, we can deduce that colors are not unique to a specific object and that color is a distinct quality apart from the quality of light itself.

Gregory Richard Langton, a well-known researcher of the visual system and a contemporary of Newton, elucidated the way we perceive colors in his book "The Eye and the Brain: The Psychology of Visual Perception." In humans, three different proteins are responsible for color perception and can respond to different wavelengths (most mammals have two such genes, resulting in bicolor vision). The human eye contains over 135 million photosensitive cells (photoreceptors), which are divided into highly sensitive rods and less sensitive cones. The cones allow us to differentiate shades in daylight - they are the cells that provide color vision. The rods, which are in the vast majority, are responsible for how we see at dusk, and in the dark, we are only capable of differentiating white, black, and gray colors.

When the eye perceives an object, nerve cells transmit a signal to the brain via the optic nerve, which then interprets these impulses and forms a complete image of the object being observed. In darkness, there is no emission of light rays from objects, and the nerve cells in the retina do not convey any information to the brain through the visual channels. Therefore, we cannot distinguish objects as well as during the day. Curiously, individuals who are colorblind often exhibit superior vision in dimly lit conditions.

Additionally, it is intriguing to note that the sun, one of the primary sources of light, appears white when it shines. The rays that penetrate the Earth's atmosphere scatter, and in the daytime, the sun appears yellow, and at sunrise and sunset, it appears orange or even red. However, when viewed from space, it is white, meaning it comprises all the different frequencies of visible light. This is a testament to the remarkable work of our incredibly intricate and complex visual system.