First Light: The Search for the Edge of the Universe by Richard Preston Read Free Book Online Page A

radio hiss of the Big Bang. The astronomers had arrived at a dark time. Beyond the realm of the quasars stretched the visible darkness of the early universe, out of which came no detectable light. Astronomers called this the redshift cutoff. It was the horizon of the quasars. The early universe, before the age of quasars, seemed to be a dim shell surrounding the quasars, beyond the redshift cutoff. The cutoff corresponded to the time at which quasars had first appeared. How and when the quasars had popped on remained a mystery. Quasars seemed to have appeared without precursors or any kind of warning signal. “I suspect that the rise of quasars may have signaled the birth of galaxies,” Maarten said. The earliest quasars seemed to be associated with cataclysmic events that had occurred as clouds of hydrogen that had filled the early universe had condensed into galaxies full of stars—a time when the universe had been compact, turbulent, undergoing strong, rapid evolution. Maarten Schmidt felt that if his team could map the rise of quasars over time, they might get a glimpse of the architecture of the creation.
    The theorists babbled on at conferences about the nature of the early universe. Maarten Schmidt found something amusing in all this talk. “The theoreticians”—he smiled—“the theoreticians are so clever. Once we have found something, they can find four ways to explain it.” In the case of quasars, the theoreticians had already found at least four ways to explain the redshift cutoff
before
it had been mapped. “In all these discussions,” Maarten said, “you find that you need hard numbers. How many quasars of this redshift? How many of that redshift? How many quasars of a particular luminosity? It seemed that the bullet had to be bitten.”
    Exploring the edge of the universe was a dirty job, but somebody had to do it. Somebody had to look. Somebody had to commitquite a few years of a scientific career toward the goal of mapping the realm of the earliest quasars—a gamble that so far had not shown signs of a big payoff. Schmidt and his people had already fed plenty of nickels into the slot machine. Schmidt guessed that years of work lay ahead of him before he might see the structure of the redshift cutoff—if ever. Astronomers learned not to count on results. “This exercise,” he said, “is to gather in the facts. You cannot, of course, solve all the questions in the field. Sometimes you get answers to questions you didn’t ask.”
    Edwin Hubble had showed that the redshift of a galaxy depended on its distance from earth: the more redshifted the galaxy, the farther away it was. Much to their regret, astronomers had not yet been able to link this redshift scale to an absolute measure of distance. Thus they could not tell precisely how far away from earth any galaxy or quasar was, except within a relative range. But even if he could not know exactly how far away the quasars were, Maarten Schmidt felt that if he could collect a sample of quasars of the highest redshifts and plot their redshifts on a graph, then he could learn things about the birth of quasars. He wanted to see the distribution of quasars through time in the vicinity of the redshift cutoff.
    He had urged Gunn to try to jury-rig 4-shooter, so that the camera would scan long ribbons of sky. To gather a tapestry of stars and then to search the tapestry for quasars might be a good way to find a lot of quasars. The strips of sky would be recorded on magnetic tape. When enough tapes had piled up, from a variety of scans, then Don Schneider, the team’s image-processing expert, would analyze the tapes, searching for stabs of quasar light. They could sweep the Hale Telescope across the sky, of course, but it seemed easier to stop the motion of the telescope and let the turning of the earth move the sky past the mouth of the telescope. This was a technique known as a transit. To put a telescope in transit, you shut down the telescope’s drive