The optical spectrum is limited

As a wave process, light is characterized by its wavelength X or equivalently by its frequency v. These are related by the rule Xv = c, where c is a universal constant known as the speed of light. That part of the light spectrum that we can detect with our eyes is in the frequency regime that runs from red to blue colours. This regime is a relatively miniscule part of the entire frequency spectrum of light: in principle, electromagnetic radiation (for that is what light is) can contain frequency

Images of Time. First Edition. George Jaroszkiewicz.

© George Jaroszkiewicz 2016. Published in 2016 by Oxford University Press.

components ranging from near zero to near infinity. When scientists analyse information from other frequency regimes such as x-rays or infra-red light, the universe looks very different.

Animals such as bats and dogs build complex and successful mental images of their environment based on non-visual information: bats use sound waves and dogs have a powerful sense of smell. Likewise, in the absence of visible light or a breakdown of vision, humans have developed alternative mental images of their environment. In medicine, for instance, humans exploit non-visual techniques such as x-rays, thermal and magnetic imaging, and ultrasound to give radically different images of the human body compared to visual images. Generally, these technologies are translated into visual images that are then seen by the human eye as if they were optical images.

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