OTHER WINDOWS ON THE UNIVERSE
There is a wealth of information about the physical universe that lies beyond the realm of visible light.
The physical universe is represented by more than what our eyes are able to see. Radiation spanning the full electromagnetic spectrum (see diagram, facing page) can tell us a great deal about celestial objects.
Signals from space—such as visible light, X-rays, and ultraviolet, gamma, and infrared rays—all reach Earth as waves, and the various "wavelengths" indicate the distances between the crests of the waves.
The features in these other regions of the spectrum are picked up by telescopes designed specifically to "see" them. The air above us absorbs and scatters particular wave-lengths; to pick these up, some telescopes are placed beyond Earth's atmosphere.