PureInsight | May 21, 2001
We can see an object with our eyes because the retina in our eyes can sense light, precisely speaking, visible light. The wavelengths of visible light range from 400nm to 760nm. Light of different colors can be distinguished because the wavelengths of different colors are different. The retina of a patient with achromatopsia cannot sense a full spectrum of light. So light in a particular range of wavelengths would be invisible to him, though it is visible to healthy people.
Visible light is a form of electromagnetic waves. Electromagnetic waves with wavelengths longer than 760nm and shorter than 400nm are invisible to human eyes. We call them invisible light. Invisible light, which we can detect using certain technology, includes X rays, ultraviolet rays and so on. But our human eyes cannot sense them. Among the wide spectrum of electromagnetic waves, visible light occupies only a narrow field. From this perspective, we humans are all “color blind”.
By using certain technology, we can extend our “vision” to invisible light. As mentioned above, our modern instruments can enable us to “see” objects invisible to our eyes; One example is that some stars in the remote space can be detected only within the ultraviolet range through specifically designed telescopes. But we still cannot detect magnetic waves with even longer or shorter wavelengths, even with our modern technology. It is conceivable that there are still many objects in our universe invisible to us.
(To be continued)
