Unprecedented growth was once again the bottom line describing the advance of astrophysical knowledge in the 1970's. From Earth and planets to stars and galaxies, space scientists have accelerated their exploration of previously uncharted voids of space and time. Over the course of the past two decades, we have learned more about the cosmos, and our place in it, than in the entire previous 10,000 years of civilization.
Basically, we still ask the same questions as did the ancients. We wonder about ourselves and our environment. We inquire who we are, and from where we came. We long for an understanding of the starry points of light in the nighttime sky. We seek the origin and destiny of things. but now attempts to provide answers are aided by the experimental tools of modern technology: astronomical telescopes to improve perception of the macroscopic universe; high-energy accelerators to aid understanding of the microscopic world; automated spaceprobes to gather data unavailable on Earth; sophisticated computers to help keep pace with the increased flow of this wealth of new information.
We live in an age of technology. And, even though that technology threatens to doom us, that same technology threatens to doom us, that same technology is now providing us with an exceptionally rich view of ourselves and our universe.
Supported by a society that wants answers to the time-honored philosophical questions, astrophysicists have enormously widened human understanding of the ways that matter and energy interact throughout our Milky Way and beyond. The technological boom of the 1960s and 70s has created nothing less than a second Renaissance--whole new ways of perceiving the universe. Conputerized equipment now operates, from the ground or from orbit, in each of the invisible domains of the electromagnetic spectrum.
Radio antennas as large as engineers can now build them scan the cosmos for signals from dense, dark and dusty pieces of galactic real estate that cannot be observed visually. State-of-the-art infrared detectors routinely fly aboard high-altitude balloons and reconnaissance aircraft, seeking evidence for heretofore unrecognized warm regions of space. Ultraviolet and x-ray spacecraft, perched in orbit far above Earth's opaque atmosphere, map distant sources of potent radiation emitted by previously unknown exotic astronomical objects; these are not merely passive probes like pioneering satellites that marked the dawn of the Space Age, but whole observatories remotely operated by teams of scientists, much like major ground-based telescopes. And robot spaceprobes navigate through the system of known planets, telemetring to Earth visible and invisible impressions of these totally new worlds.
All in all, the 1970s saw the astrophysical community do for invisible radiation what Galileo had done nearly four centuries earlier for visible light. For the first time. humans now probe the universe in its full grandeur, the bulk of which, it seems, is unaccessible to the eyes that serve us so well on planet Earth.
Here's sampler of the advances made largely by means of the invisible ultraviolet and x-ray radiation they emit. Researchers have especially concentrated on the active, flaring regions of bright stars, for it now seems that their atmospheres are energized far more powerfully than our Sun. A number of unanticipated discoveries concerning rotation, magnetism, size and dynamics suggest that a completely new outlook on the physics of stars may be required to fully understand them.
Dense, dark and dusty hodgepodges of galactic gas and dust where, quite literally, there is nothing to see were examined by means of the invisible radiation they emit. Radio and infrared techniques now enable us to "listen" to huge interstellar clouds slowly contracting to form stars. Thus, we are now learning a great deal about the embryonic stages of stars, a subject about which the oldest science--astronomy--had been experimentally ignorant until the dawn of the 1970s.
Use of the same radio techniques produced repeatedly surprising discoveries of rather complex molecules in the murky recesses of interstellar space. Now totaling more than 50 in number, many of these modecules are complex enough to be of some interest to biochemists. Theorists remain mystified about the severely non-terrestrial conditions that give rise to such a pharmaceutical array of chemicals, yet it does not seem inconceivable that they could be mere fragments of even larger molecules thus far undiscovered. If so, then the most startling revelation of all may be that what was once though to be a galactic wasteland is really the biochemical seedbed of life.
A combination of radio and x-ray observations has unexpectedly established the existence of neutron stars. Spinning rapidly and emitting pulses of radiation, neutron stars are not really stars at all; they are ultradense balls of nucleons compressed by the catastrophic death of a massive star into an object not much larger than a typical city. Gravity is so intense that a teaspoon of neutron-star stuff would weigh about a million tons, a human would be crushed to the thickness of a postage stamp, and the entire population of planet Earth, if shipped to a neutron star, would be compressed into a volume about the size of an aspirin tablet. Strange objects, these neutron stars they represent demonstrably non-terrestrial states of matter. Their abnormal properties are surpassed by only one other type of phenomenon--the black hole.
Within the past decade, observations of x-rays from a handful of small regions within our Milky Way suggest that matter is being pulled into warped regions of space where gravity is almost unimaginably powerful. Such a regions not really an object, as much as a hole--a spatial domain from which neither visible nor invisible radiation can escape. It seems that the guts of black holes are unexplorable. But matter falling into such weird regions can, and apparently does, emit radiation just before being swallowed, perhaps forever.
Once thought to be convenient cop-outs for unexplained phenomena, or even figments of theorists' imaginations, black holes apparently do exist. Radio and infrared data gathered within just the past few years imply that the centers of all galaxies are dominated by supermassive objects. For example, current exploration of the heart of our own Milky Way galaxy has recently revealed a gargantuan whirlpool of matter whose integrity can be maintained only by the existence of a heretofore unrecognized "something" having several million times the mass of our Sun. Gulping perhaps whole stars, and presumably growing, this bizarre region is probably a black hole. The qualifier is needed because we are still learning how to grope in the dark, to sift through the clues contained in invisible radiation. Like the archeologist who digs through ancient rubble in search of hints about the origin and evolution of culture, the astrophysicist interprets radiation, seeking clues about the origin and evolution of galaxies, all of which may have black holes in their hearts.
Astronomy no longer evokes visions of plodding intellectuals peering through long telescope tubes. Nor does the cosmos any longer refer to that seemingly inactive, immutable regime captured while occasionally gazing at the nighttime sky.
Modern astrophysics now deciphers a more vibrant, evolving universe--one in which life seems to be nothing more than a natural consequence of the evolution of matter. Soberingly though, our planetary system apparently palys no special role in this vast array of material coagulations. Magnificent mediocrity, so it seems, is the catchword describing our condition on the rock called Earth.
As is so often the case during periods of startling revelations, discoveries not only advance knowledge, but they also raise many new questions. Indeed, there are several basic physical problems that astrophysicists must strive to unravel in the 1980s. But the creation of additional queries should not cause dismay or frustration, for this is precisely how science operates. Each discovery that adds to the storehouse of information generates a host of new questions that eventually lead to more discoveries and so on, thus causing a rich acceleration of basic knowledge. It was the great rate of discovery that seems to have made the 1970s special.