Introduction Adventure Imagination and Curiosity

The Exploration of the Radio Astronomical Unknown

Radio astronomy is one of the great adventures of the human spirit. Exploratory behavior, the primal urge that drives us into the unknown, is rooted in curiosity and expressed in a deep human hunger for venturing into new worlds, a hunger that has been dramatically expressed in thousands of years of slow, systematic, and sometimes frightening journeys of exploration and evolution. Such journeys, overland and across the seas and oceans, have carried people from their birthplaces to the most distant corners of the planet and farther. Like pollen on the wind, our species has moved from the caves of earth to the craters of the moon. Our instinct drives us on, not just to the planets, but further, into the universe beyond our senses where profound mysteries have been uncovered, mysteries that challenge our imagination and our capacity for comprehension.

Radio waves from space carry information about some of the most intriguing natural phenomena yet discovered by human beings. This is the bailiwick of radio astronomy. However, the cosmic radio whispers reaching the earth compete with the electrical din produced by TV, radio, FM, radar, satellite, and cell phone signals. Thus the faint radio signals from space that memorialize the death of stars, or tell of awesome explosions triggered by black holes in galaxies well beyond sight, are nearly lost against the background of human-made static. Yet such radio waves contain the secrets of interstellar gas clouds and carry messages from the remnants of the Big Bang that propelled our universe into existence.

In order to gather the faint cosmic signals and avoid the unwanted stuff, astronomers use powerful radio telescopes located far from cities. Those telescopes are huge metal reflectors that focus the electromagnetic messages from space, which are then amplified in sensitive receivers and fed to computers where they are converted into a visual form to be displayed, analyzed, interpreted, and hopefully understood.

The story of radio astronomy is a tale of the constant quest to express in clearer visual forms the information carried by the radio waves. For this reason radio astronomers are always inventing new techniques to allow them to "see" the radio

2 Introduction: Adventure. Imagination, and Curiosity sources more clearly. The better we "see" the sources of those radio waves, the more likely we may be to understand their inner secrets.

Ever since Galileo first turned a telescope toward the heavens in 1609 ADV centuries of technological innovation have afforded an increasingly clear view of astronomical objects in the far reaches of space. Larger and more sophisticated telescopes are always being designed and constructed. Today, modern technological marvels such as the Hubble Space Telescope, the mightiest optical telescope ever built, allow astronomers to perceive the visible universe with fabulous clarity. Not to be outdone, giant radio telescopes reveal the radio universe in comparable detail, and they have opened our imagination to a cosmos beyond our senses in a way previously undreamed of.

Seeking New Knowledge

Like any science that seeks answers beyond the borders of the unknown, radio astronomy requires a great deal of thought and effort and, especially recently, significant amounts of money. In asking governments for funds to construct a new radio telescope, the modern explorers of space are following a time-honored tradition. Voyages of discover)' have always been costly affairs, usually sponsored by monarchs, business interests, or empires. Even Columbus needed a "research grant" from 0£en Isabella to carry him across the ocean. Today, tax dollars fund scientific instruments, the new vessels of discovery, and the scientist/explorer's challenge has become far more subtle than it once was.

In ancient times the sponsor of an explorer's journey had an expectation that the ship would return with a cargo of spices, gold, or silver—something that could be used in barter. It is no longer so. The new explorer searches for knowledge-subtle, ethereal knowledge. This may be returned in the form of a radio image of a distant galaxy or of the invisible center of an interstellar gas cloud. It is impossible to attach financial worth to such images, just as it is impossible to attach value to any bits of that elusive substance called knowledge. What is clear, however, is that many of the pictures of radio sources in this book are beautiful in their own right even as they reveal the existence of previously unknown phenomena, knowledge of which broadens our perspectives about the universe into which we are born.

Radio Astronomy and Imagination

The invisible universe of radio astronomy is revealed in images that startle the imagination. Although this book contains only static pictures, each radiograph is a snapshot of an object in a state of continual upheaval. The motion, the chaos, and the violence found in the invisible universe can only be recognized when you wrap your imagination around the images. Do not hesitate, because your imagination is as valid as the next person's in trying to visualize this.

Full appreciation of the new discoveries requires the continual involvement of your imagination. Exploration of the cosmos becomes an adventure when it takes place in the mind. The explosion of a quasar is not witnessed in space somewhere, but in your imagination. All we see out there, now, is but an instantaneous snapshot of what took place millions or even billions of years ago.

The dynamical aspects of astronomy are revealed not by what is seen at the far end of the telescope, but what is experienced at this end. This is where the excitement is to be found. Thanks to the workings of the human mind, aided by physics, mathematics, and computers, astronomers can simulate cosmic phenomena that allow us to recognize how evolution, change, and catastrophic events shape distant gas clouds, dying stars, galaxies, and quasars.

The human race looks out into space and discovers marvelous beauty, a beauty that often lies beyond our normal powers of perception. Yet it is a beauty that can touch us as profoundly as any terrestrial sunset, symphony, or songbird. In radio astronomy the beauty is perceived by fully harnessing our imagination as we travel beyond the senses. In the following pages you will join in the adventure and share the excitement of exploration as we journey into the invisible universe, a universe revealed by tiny amounts of radio energy reaching us from millions or even billions of light-years away.

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