My remarks today will deal with the relationship of contemporary scientific cosmology with Humanism. I approach cosmology as a professional practitioner, but must apologize in advance for the fact that my discussion can only be superficial in the time I have. I approach Humanism as a nonprofessional practitioner and must plead relative ignorance of the history, literature and philosophy of Humanism as compared to many of you in the audience. But, the better part of a lifetime spent in research and contemplation on scientific cosmology has led me to the conclusion that there no evidence for the universe being other than completely neutral to our existence. This leads inevitably to my identifying philosophically as an agnostic and a humanist, and explains my temerity in sharing my views with you.
Some Definitions and Assumptions
Cosmology is that branch of science which deals with the origin, structure and evolution of the universe. The universe is defined to be the observable ensemble of atoms, molecules, radiation, gas, dust, stars, galaxies of stars and clusters of galaxies. To make any progress at all toward a scientific understanding of the universe certain assumptions are required. You may find the assumptions to be patently oversimplified, but it is good scientific practice in developing a theory to keep one’s assumptions as simple as is consistent with developing a successful model. Thus we assume that what we now observe in the astronomical universe is a major fraction of what we shall ever be physically able to observe. Relativity theory postulates the constancy and finitude of the velocity of light (186,000 miles per second). Information travels at best at the velocity of light, so that if the universe is now 18 billion years old, then clearly we can observe at most only to a distance of 18 billion light years. This horizon to which we can in principle observe grows with the aging universe at the velocity of light. When the universe is a billion years older than it is now, we should be able to see to a distance of 19 billion light years, at most. But notice that if we observe a celestial object a distance of, say, 10 billion light years, we see that object by light emitted 10 billion years ago, when it was a younger and much less evolved entity. And so relativity provides us with a kind of “time travel. “
A second point to be made is again a consequence of the theory of relativity. The generally accepted view is that the universe is infinite in extent. A simple way to think about this is to realize that if it were finite, then one would have to deal with the idea that there is something beyond. But the word universe, and the concepts we are pursuing, ascribe as the meaning of the word universe “all there is.” All observers are assumed equivalent, wherever and whenever they may be; there are no privileged observers. It follows that we have assumed the universe to be the same everywhere, homogeneous on the large scale (i.e., when viewed on the scale of clusters of galaxies), and the same in whatever direction viewed, which is to say that it is isotropic, with no preferred direction. If I say the universe is 18 billion years old, then any observer elsewhere in the universe would say the same, given the same evidence at this time. Moreover, an observer on an object which we now see at a distance of 10 billion light years has the same 18 billion light year horizon that we have. If that distant observer could see the Milky Way galaxy in which we reside, he would see it as it existed 10 billion years ago.