The Exploration of Outer Space
Sir Bernard Lovell is director of the Jodrell Bank Experiment Station and professor of radioastronomy at the University of Manchester. The subject he teaches and of which he is a foremost student illustrates perfectly the astonishing pace of physical science in the twentieth century. Thirty years ago radioastronomy did not exist. Astronomers gathered their information, as they had for three centuries, through optical telescopes. Methods had of course become much more refined and the instruments had grown enormously since Galileo first poked a small brass tube filled with two glass lenses in the direction of Jupiter and the moon to see what he could see; but telescopes remained effective only in penetrating the optical window of the earth’s atmosphere—that part of the spectrum in the visible region between the ultra violet and the infra red to which our eyes are sensitive.
The advent of radio opened new possibilities. Research on radio waves in the 1920’s made it clear that there was yet another window through the earth’s atmosphere, a window opaque to the very short waves of visible light but transparent to a segment of the electromagnetic span comprising wave lengths from a fraction of a centimeter to many meters. In 1931 an electrical engineer names Karl Jansky, who was working at the Bell Telephone Laboratories in New Jersey, built himself a complicated aerial made of an array of rods, which could be rotated on a brick foundation. The purpose of this rig was to investigate the static interference that plagued radio communications around the world. His observations served their purpose, but led also to a profoundly important discovery which was to free man from exclusive dependence on his eyes in studying the solar system and the stars.
Jansky found that his receiver was picking up radiations or signals apparently unrelated to atmospheric disturbances and showing variations in strength throughout the day. This residual noise, he concluded, must come from radio waves generated somewhere in regions of space outside the solar system. He offered convincing proof of the validity of this explanation but astronomers were not much impressed, and in the years before the Second World War only one other significant advance in the field was made, when an amateur, Grote Reber, built the prototype for the modern radiotelescope—a parabolic bowl thirty feet in diameter, mounted so that it could be directed to any part of the sky—in the garden of his home in Illinois.
Immediately after the War, however, radioastronomy burst into flower. Techniques and ideas in radio and radar, which were developed for military purposes, were the foundations of the resurgence. And because science had suddenly become fashionable even among politicians (hypochondria and the cold war made many a congressman a champion of the new learning), large sums of money were available for the building of expensive instruments in this as in other branches of physical research. A lavish purse was essential for developing radioastronomy, for it was soon realized that just as large optical telescopes with huge mirrors are needed to collect and resolve the light from far reaches of space, so large radiotelescopes with huge bowls are needed to collect the radio waves over a big area to improve the signal strength of the faint emissions which are generated at great distances in the cosmos.
Today radioastronomy is being vigorously pursued in the U.S., Britain, Australia, the U.S.S.R., and other countries. The strange music of incredibly remote spheres keeps pouring into steerable dishes and saucers of all kinds and sizes, and is then transformed by electronic apparatus and recorded on tapes. Among the sources of the signals are both ionized and neutral interstellar hydrogen gas, the sun, free electrons moving in the galactic magnetic field, the ruins of exploded giant stars (e.g., the famous Crab nebula), extragalactic nebula. (Paradoxically , the stars themselves do not appear to be radio emitters—at least not of waves which can be detected by present instruments—but play their part in energizing hydrogen atoms in their vicinity.) Computers are used to interpret the record and also to control the telescopes driving and steering mechanism so that the instrument is properly directed and will automatically follow a given star from rising to setting, or a planet, or the sun, depending on the program. Closely associated with the radiotelescope are the satellites and space probes. They can be tracked and the faint signals reporting their experiences and encounters picked up by the more powerful bowls. The 250-foot diameter Jodrell Bank telescope, for example, tracked the American space probe Pioneer V for four months after launching to a distance of nearly 23 million miles (when its power supply failed).
Lovell gives a lucid account in this little book of the techniques of radioastronomical investigation, of what has been learned about the solar system with the help of all kinds of telescopes, satellites and probes. The larger radiotelescopes have increased knowledge about our near neighbor the moon—a number of accepted ideas have simply been turned upside down—and have had a major impact on methods of study and understanding of the regions of the universe which lie beyond the solar system. A triumph of radioastronomy is its solution of a long unanswered question. Optical telescopes showed quite clearly the spiral arrangement of stars in the external galaxies millions of light years away; yet because of the obscuring effects of interstellar dust it was not known whether the stars in our own Milky Way were arranged in similar spiral formations. But the dust forms no barrier to radio waves and it has now been established that the arms of our system are in fact spirals. Moreover, as the galaxy rotates like a “giant cartwheel” and the solar system moves with it (rotating once in 250 million years), the arms trail as though the galaxy were fluid, and not rigid, “so that the speed at the edge of the arms is about twice as great as the speed of rotation of the material near the nucleus of the galaxy.”
Among other effects of the development of radioastronomy are dramatic turns in cosmological theory. A mysterious object has been detected at the very great distance of 700 million light years, which many astronomers believe to be an instance of two galaxies in collision. This phenomenon barely lay within the reach of optical telescopes, but was a very strong source of radio emissions. Even if it had been ten times as far away, and completely out of range of the world’s largest optical telescopes, radio telescopes would have been able to record its signals. Thus the scope of investigations of outer space has been enormously widened, and we may expect future observations to furnish essential evidence as to the validity of our ideas about the evolution and origin of the cosmos, as to whether this or that model—steady state or evolutionary—has anything more to support it than the ingenious imaginings of various men.
Until just a few decades ago astronomers believed in the uniqueness of the solar system. This belief was based on prevailing scientific concepts as to how the system was formed. The central notion was that a star had at one time approached close enough to our sun “to raise great tides and pull out from it streams of stellar material. The wandering star continued on its journey through space. The ejected material was captured by the sun and after aeons of time condensed to form the earth and the planetary system.” It was most probable that the close approach of these two stars must be a very rare occurrence; also it followed from the theory “that the earth, and the planets condensed initially in a molten state and that therefore the evolution of organic material on earth must have occurred locally after the cooling of the earth’s surface.”
But during the past twenty years astronomers have shown that this model of the origins of our world is untenable, While they differ as to precisely what did take place, the general view now widely held is that several billion years ago our sun was surrounded by a nebula of gas and dust, and that the earth and planets were formed “through the successive aggregation into larger and larger bodies from the material of the nebula.” This view has at least two important corollaries. The first is that the Milky Way, though it contains a hundred billion stars, does not fill the cosmos. The 200-inch Mount Palomar telescope can photograph clusters of galaxies at distances of a few thousand million light years so that within this optically observable part of the universe alone there must be a billion galaxies with a size, structure, and stellar content not dissimilar from that of the Milky Way. The second corollary is that there are many other stars in the Milky Way surrounded like our sun by nebulae of gas and dust, and hence vast numbers of planetary systems similar to that which we ourselves inhabit. Since systems like ours are very common it is reasonable to infer that extraterrestrial life is very common. The basic chemical bricks of life, particularly hydrogen and carbon, are plentiful throughout the universe; complex organic molecules have been discovered on fallen meteorites; there is strong evidence that these molecules have arisen through abiotic processes. Lovell says that there are probably some trillion stars possessing planets in a suitable condition for the support of organic evolution.
The chain of argument on behalf of extraterrestrial life is engrossing and impressive, but it is not without gaps. The most serious of these concerns the formation of replicating polymers, strings of molecules essential to life. A self-generating organic molecule, while something of a miracle, is not after all as much of a miracle as a mosquito or a horseshoe crab, let alone a dinosaur or a man. How the “voracious organisms,” in other words, can arise without biological intervention is not yet understood. Nevertheless it is overwhelmingly likely that we are not alone in the universe. This state of affairs has ethical consequences.
In the ferocious state of our own civilization these consequences may not seem impressive. If men are relatively indifferent to the effect on millions of persons of nuclear testing and if they are quite prepared to put an end to their own kind in order to vindicate this or that principle, it is hard to imagine they will be overmuch concerned with the possible effect on organic life on other planets of rockets and other vehicles launched from the earth. A number of scientists have taken thought to these ethical questions. They have concerned themselves not alone with the fate of our civilization but with the fate of possible other civilizations of the cosmos in the event that vehicles we now plan to launch attain their objective and land on planets where life exists.
Assuming there is life on other planets, one may suppose that it exists at various stages of development; from the very primitive to the very highly developed, including not only communities much more advanced than our own but others which have passed their zenith and fallen into decay. Various scientists have proposed the use of radiotelescopes to search for signals such as might be sent out by intelligent beings in space. A group of American radio astronomers has carried out a search along such lines and is continuing to listen for “messages.” Thus far the results have been negative but the search will undoubtedly continue. Quite recently a Dutch mathematician, Hans Freudenthal, published a book, Lincos, which presents a “design of a language for cosmic intercourse.” We have obviously reached the point where the line between fantastic speculations as to reality and the innate queerness of reality is as hard to draw as the line between the observer and what he observes. The latter circumstance led to a revolution in physics; the former may, if we are lucky, lead to an even greater revolution in ethics and metaphysics.
Forty years ago Albert Schweitzer, in his Civilization and Ethics, considered the problem “of why in the sphere of ethics we live in a town full of ruins in which one generation builds for itself here and another there, what is absolutely necessary.” “Then,” says Lovell, “the dichotomy was of minor significance, in that the consequential failings of man involved human suffering and death individually and sometimes nationally. Now we have moved to a new horizon where the entire fate of another of the civilizations of the cosmos is at stake.” And if this fact does not suffice to rouse man’s faint and failing conscience, there is today yet another peril, a byproduct of scientific and technological progress, namely the possibility that by space probes man may contaminate extraterrestrial space and the planets of the solar system. We know next to nothing about the biological situation on Mars and Venus, and if we crash on to these planets before we know a good deal more we will be disregarding, in Lovell’s view, every principle of science and ethics. It will be a scientific disaster “because the rocket could carry to the planet earthly organisms and thereby severely handicap future biological work, and a moral disaster because man will have presumed the right to inject his own contaminated material into an extraterrestrial environment where organic evolution may well be in progress.”
I myself do not find the prevailing space-race chauvinism and the threats to other planets as horrifying as the threat of global extermination. Nor do I derive consolation from the thought that if our managers turn the earth into a lifeless stone other forms of life will continue elsewhere in the universe. But I am impressed with Lovell’s deep sense of responsibility about life everywhere, and I wish there were many more scientists like him.