The distinction between a Big Bang with expansion forever and an Oscillating Universe clearly turns on the amount of matter there is. If the critical amount of matter is exceeded, we live in an Oscillating Universe. Otherwise we live in one that expands forever. The expansion times-measured in tens of billions of years-are so long that these cosmological issues do not affect any immediate human concerns. But they are of the most profound import for our view of the nature and fate of the universe and-only a little more remotely-of ourselves.
In a remarkable scientific paper published in the December 15, 1974 issue of the Astrophysical Journal, a wide range of observational evidence is brought to bear on the question of whether the universe will continue to expand forever (an “open” universe) or whether it will gradually slow down and recontract (a “closed” universe), perhaps as part of an infinite series of oscillations. The work is by J. Richard Gott III and James E. Gunn, then both of the California Institute of Technology, and David N. Schramm and Beatrice M. Tinsely, then of the University of Texas. In one of their arguments they review calculations of the amount of mass in and between galaxies in “nearby” well-observed regions of space and extrapolate to the rest of the universe: they find that there is not enough matter to slow the expansion down.
Ordinary hydrogen has a nucleus comprising a single proton. Heavy hydrogen, called deuterium, has a nucleus comprising one proton and one neutron. An astronomical telescope in Earth orbit called “Copernicus” has measured, for the first time, the amount of deuterium between the stars. Deuterium must have been made in the Big Bang in an amount that depends on the early density of the universe. The early density of the universe is connected with the present density of the universe. The amount of deuterium found by “Copernicus” implies a value to the early density of the universe and suggests that the present density is insufficient to prevent the universe from expanding forever. [22] And what is said to be the best value of the Hubbell constant-which specifies how much faster more distant galaxies are receding from us than nearby ones-is consistent with this whole story.
Gott and his colleagues stressed that there may be loopholes in their argument, that it may be possible to hide intergalactic matter in ways which we could not then detect. Evidence for such missing mass has now begun to emerge. The High Energy Astronomical Observatories (HEAO) are a set of satellites orbiting the Earth and scanning the universe for particles and radiation that we cannot detect down here, under our thick blanket of air. Satellites of this sort have detected intense emission of X-rays from clusters of galaxies, from intergalactic spaces where there was hitherto no hint of any matter. Extremely hot gas between the galaxies would be invisible to other experimental methods and therefore missed in the inventory of cosmic matter made by Gott and his colleagues. What is more, ground-based radio astronomical studies with the Arecibo Observatory in Puerto Rico have shown that the matter in galaxies extends far beyond the optical light from the apparent edges of galaxies. When we look at a photograph of a galaxy, we see an edge or periphery beyond which there is no apparent luminous matter. But the Arecibo radio telescope has found that the matter fades off extremely slowly and that there is substantial dark matter in the peripheries and exteriors of galaxies, which had been missed by previous surveys.
The amount of missing matter required to make the universe ultimately collapse is substantial. It is thirty times the matter in standard inventories such as Gott’s. But it may be that the dark gas and dust in the galactic outskirts, and the astonishingly hot gas glowing in X-rays between the galaxies, together constitute just enough matter to close the universe, prevent an expansion forever-but condemn us to an irrevocable end in a cosmic fireball 50 billion or 100 billion years hence. The issue is still teetering. The deuterium evidence points the other way. Our inventories of mass are still far from complete. But as new observational techniques develop we will have the capability of detecting more and more of any missing mass, and so it would seem that the pendulum is swinging toward a closed universe.
It is a good idea not to make up our minds prematurely on this issue. It is probably best not to let our personal preferences influence the decision. Rather, in the long tradition of successful science, we should permit nature to reveal the truth to us. But the pace of discovery is quickening. The nature of the universe emerging from modern experimental cosmology is very different from that of the ancient Greeks who speculated on the universe and the gods. If we have avoided anthropocentrism, if we have truly and dispassionately considered all alternatives, it may be that in the next few decades we will, for the first time, rigorously determine the nature and fate of the universe. And then we shall see if Gott knows.
CHAPTER 25
It is as natural to man to die as to be born; and to a little infant, perhaps, the one is as painful as the other.
FRANCIS BACON,
Of Death (1612)
The most beautiful thing we can experience is the mysterious. It is the source of all true art and science. He to whom this emotion is a stranger, who can no longer wonder and stand rapt in awe, is as good as dead: his eyes are closed… To know that what is impenetrable to us really exists, manifesting itself as the highest wisdom and the most radiant beauty which our dull facilities can comprehend only in the most primitive forms-this knowledge, this feeling, is at the center of true religiousness. In this sense, and in this sense only, I belong to the ranks of the devoutly religious men.
ALBERT EINSTEIN,
What I Believe (1930)
WILLIAM WOLCOTT died and went to heaven. Or so it seemed. Before being wheeled to the operating table, he had been reminded that the surgical procedure would entail a certain risk. The operation was a success, but just as the anaesthesia was wearing off his heart went into fibrillation and he died. It seemed to him that he had somehow left his body and was able to look down upon it, withered and pathetic, covered only by a sheet, lying on a hard and unforgiving surface. He was only a little sad, regarded his body one last time-from a great height, it seemed-and continued a kind of upward journey. While his surroundings had been suffused by a strange permeating darkness, he realized that things were now getting brighter-looking up, you might say. And then he was being illuminated from a distance, flooded with light. He entered a kind of radiant kingdom and there, just ahead of him, he could make out in silhouette, magnificently lit from behind, a great godlike figure whom he was now effortlessly approaching. Wolcott strained to make out His face…
And then awoke. In the hospital operating room where the defibrillation machine had been rushed to him, he had been resuscitated at the last possible moment. Actually, his heart had stopped, and by some definitions of this poorly understood process, he had died. Wolcott was certain that he had died, that he had been vouchsafed a glimpse of life after death and a confirmation of Judaeo-Christian theology.
Similar experiences, now widely documented by physicians and others, have occurred all over the world. These perithanatic, or near-death, epiphanies have been experienced not only by people of conventional Western religiosity but also by Hindus and Buddhists and skeptics. It seems plausible that many of our conventional ideas about heaven are derived from such near-death experiences, which must have been related regularly over the millennia. No news could have been more interesting or more hopeful than that of the traveler returned, the report that there is a voyage and a life after death, that there is a God who awaits us, and that upon death we feel grateful and uplifted, awed and overwhelmed.