ABSTRACT
Humans are primarily visual creatures. As discussed in Chapter 2, not all animals depend on their eyes, as we do, for most of the information received about their surroundings. This bias in everyday life extends to how we pursue more technical goals as well. Scientific instruments commonly produce images to communicate their results to the operator, rather than generating audible tones or emitting a smell. Space missions to other planets and equally arduous explorations of the ocean depths always include cameras as major components, and we judge the success of those missions by the quality of the images returned. This suggests a few of the ways in which we have extended the range of our natural vision. Simple optical devices such as microscopes and telescopes allow us to see things that are vastly smaller or larger than we could otherwise. Beyond the visible portion of the electromagnetic spectrum (a narrow range of wavelengths between about 400 and 700 nm), we now have sensors capable of detecting infrared and ultraviolet light, X-rays, and radio waves, and perhaps soon even gravity waves. Figure 1.1 shows an example, an image presenting radio-telescope data in the form of an image in which color represents the Doppler shift in the radio signal. Such devices and presentations are used to further extend our imaging capability.
