In the rich, velvety darkness of prehistoric night, humans no doubt gazed up at the starry sky in awe at its sublime beauty and mystery. Simple human nature led them to wonder why such gorgeous lights appeared above, and moved as they did. As cultures developed, complex mythological systems were created in an imaginative effort to explain the existence and movements of those heavenly bodies. Burgeoning civilizations created the need for accurate time keeping. Ancient people turned to the sky to fill that need. Gradually, science began to come into the picture. Imagination and fables gave way to investigation and facts, bringing ever more marvelous wonders, and new mystery.
When Galileo Galilei first turned a primitive telescope to the sky in 1609 he saw things no human had ever seen before, like the four largest moons of Jupiter. Modern astronomers have developed new types of telescopes that detect all sorts of electromagnetic waves - gamma rays, X-Rays, ultraviolet, infrared, microwaves, and radio, as well as visible light. They've even developed instruments that allow them to watch as other types of particles - such as cosmic rays and neutrinos - stream toward us from the most distant reaches of the cosmos.
{What we've seen/discovered with astronomy. How far, how old, how many...}
{Limitations of optical and particle astronomy. (Hidden behind clouds, in distant time. Swallowed by intense gravity. Early Universe was too hot.)} The development of astronomy has led an expansion of human knowledge reaching out, ever farther from our home. Yet this growth in our understanding is limited by our tools. The limits are familiar to us. Light cannot be used to see through objects. Although certain ``colors'' can penetrate objects better than others - like X-Rays through our bodies - there is always a limit. Light can always be absorbed, which means that certain things will always be hidden to us if we only use light. In fact, for the first million years after the Big Bang, all of the matter in the Universe was so hot it glowed, and light could barely travel anywhere. If astronomers want to see the Universe much before this time, they can't use
{Possibilities of gravitational waves (see/hear black holes; lift the veil of dust and clouds; probe the earliest moments of the Universe)} We know very well that it is impossible to see through a dense fog. Parts of space have something that is very much like fog. Our telescopes are useless to see past them. It may be possible to see slightly further with different colors, but there is always a limit.
