At the dawn of man's existence, all information about astronomy was gained from looking up at the sky. That remained man's only way of gathering astronomical information until the year 1609, when Galileo first used a reflecting telescope to observe the sky. Modeled after other telescopes already invented, Galileo's had a much higher magnification. Afterward, the race was on, and telescopes have been undergoing improvements and modifications ever since--and will continue to into the future.
Sir Isaac Newton invented the first useful reflecting telescope, which used mirrors, instead of glass, to gather and focus light. Early telescopes, such as Newton's, gathered visible light, but later telescopes gathered ultraviolet and infrared light. Later examples observed radio waves, gamma waves, low and high energy X-rays, gamma rays, and even gravitational waves.
Telescope technology continues to evolve. Most people are familiar with the spectacular images from the Hubble telescope, but many people have never even heard of the Compton, Chandra, and Spitzer space telescopes, which together constitute the four instruments in the Great Observatory program. The James Webb Space Telescope (scheduled to be completed in 2018), as tall as a 4 story building and as big as a tennis court, has the capability to image distances so great that it will allow us to observe the very first stars and galaxies formed in our universe.
Whole areas of astronomy have been opened up as telescope technology has evolved. They have already told us much about very distant objects, but they will also continue to allow us to understand much closer objects. Comet and asteroid seeking telescopes, in particular, may someday help avert disaster here on earth.
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