Humans cannot see all the light because the human visual system is sensitive to only a limited range of wavelengths within the electromagnetic spectrum. This range is known as the "visible spectrum" and encompasses wavelengths roughly between 400 to 700 nanometers.
The human eye contains specialized cells called cones that are responsible for detecting light and color. Cones are sensitive to three primary colors: red, green, and blue. By combining the signals from these cones, our brain interprets the different wavelengths of light as different colors. The sensitivity of the cones is highest within the visible spectrum, allowing us to perceive the wide range of colors within that range.
However, beyond the visible spectrum, there are other regions of the electromagnetic spectrum with wavelengths shorter or longer than what our eyes can detect. For example:
Ultraviolet (UV) Light: Wavelengths shorter than 400 nm, known as ultraviolet light, are invisible to humans. Some animals, like bees and certain birds, can see into the ultraviolet range, which enables them to perceive patterns and colors that are invisible to us.
Infrared (IR) Light: Wavelengths longer than 700 nm, known as infrared light, are also invisible to the human eye. Infrared radiation is commonly used in applications such as night vision technology and thermal imaging, but we cannot see it directly without the aid of specialized devices.
X-rays, Gamma rays, and Radio waves: Beyond the visible spectrum, there are other forms of electromagnetic radiation, such as X-rays, gamma rays, and radio waves. These types of radiation have much shorter or longer wavelengths than visible light and are also invisible to the human eye.
The limitations in our ability to see all the light are due to the evolutionary development of our visual system, which is optimized for the wavelengths most relevant for our survival and interaction with the environment. While we have developed technologies that allow us to detect and visualize other parts of the electromagnetic spectrum, our natural visual perception is confined to the visible spectrum.