be a good idea to perform astronomical observations from high altitudes-from, for example, a free balloon. He suggested that there would be at least two advantages: better seeing and ultraviolet spectroscopy. Goddard later made similar proposals for rocket-launched observatories (Chapter 18).
Hermann Vogel had previously found, by eyeball spectroscopy, an absorption band at 6183 A in the body of Saturn. Subsequently the International Color Photo Company of Chicago made photographic plates, which were so good that wavelengths as long as H Alpha in the red could be detected for a fifth-magnitude star. This new emulsion was used at Yerkes, and Hale reported that there was no sign of the 6183 A band for the rings of Saturn. The band is now known to be at 6190 A and is 6
Another reaction to Percival Lowell’s writings can be gleaned from the address of James Keeler at the dedication of the Yerkes Observatory:
It is to be regretted that the habitability of the planets, a subject of which astronomers profess to know little, has been chosen as a theme for exploitation by the romancer, to whom the step from habitability to inhabitants is a very short one. The result of his ingenuity is that fact and fancy become inextricably tangled in the mind of the layman, who learns to regard communication with the inhabitants of Mars as a project deserving serious consideration (for which he may even wish to give money to scientific societies), and who does not know that it is condemned as a vagary by the very men whose labors have excited the imagination of the novelist. When he is made to understand the true state of our knowledge of these subjects, he is much disappointed and feels a certain resentment towards science, as if it had imposed upon him. Science is not responsible for these erroneous ideas, which, having no solid basis, gradually die out and are forgotten.
The address of Simon Newcomb on this occasion contains some remarks which apply generally, if a little idealistically, to the scientific endeavor:
Is the man thus moved into the exploration of nature by an unconquerable passion more to be envied or pitied? In no other pursuit does such certainty come to him who deserves it No life is so enjoyable as that whose energies are devoted to following out the inborn impulses of one’s nature. The investigator of truth is little subject to the disappointments which await the ambitious man in other fields of activity. It is pleasant to be one of a brotherhood extending over the world in which no rivalry exists except that which comes out of trying to do better work than anyone else, while mutual admiration stifles jealousy… As the great captain of industry is amoved by the love of wealth and the politician by the love of power, so the astronomer is moved by the love of knowledge for its own sake and not for the sake of its application. Yet he is proud to know that his science has been worth more to mankind than it has cost… He feels that man does not live by bread alone. If it is not more than bread to know the place we occupy in the universe, it is certainly something that we should place not far behind the means of subsistence.
AFTER READING through the publications of astronomers three-quarters of a century ago, I felt an irresistible temptation to imagine the 150th Anniversary Meeting of the American Astronomical Society-or whatever name it will have metamorphosed into by then-and guess how our present endeavors will be viewed.
In examining the late-nineteenth-century literature, we are amused at some of the debates on sunspots, and impressed that the Zeeman effect was not considered a laboratory curiosity but something to which astronomers should devote considerable attention. These two threads intertwined, as if prefigured, a few years later in G. E. Hale’s discovery of large magnetic field strengths in sunspots.
Likewise we find innumerable papers in which the existence of a stellar evolution is assumed but its nature remains hidden; in which the Kelvin-Helmholtz gravitational contraction was considered the only possible stellar energy source, and nuclear energy remained entirely unanticipated. But at the same time, and sometimes in the same volume of the
There are many related examples-for instance, in the interpretation of series spectra of nonhydrogenic elements obtained at the telescope and pursued in the laboratory. New physics and new astronomy were the complementary sides of the emerging science of astrophysics.
Accordingly, it is difficult not to wonder how many of the deepest present debates-for example, on the nature of quasars, or the properties of black holes, or the emission geometry of pulsars-must await an intertwining with new developments in physics. If the experience of seventy-five years ago is any guide, there will already be people today who dimly guess which physics will join with which astronomy. And a few years later, the connection will be considered obvious.
We also see in the nineteenth-century material a number of cases where the observational methods or their interpretations are clearly in default by present standards. Planetary periods deduced to ten significant figures by the comparison of two drawings made by different people of features we now know to be unreal to begin with is one of the worst examples. But there are many others, including a plethora of “double-star measurements” of widely separated objects, which are mainly physically unconnected stars; a fascination with pressure and other effects on the frequencies of spectral lines when no one is paying any attention to curve of growth analysis; and acrimonious debates on the presence or absence of some substance based solely upon naked-eye spectroscopy.
Also curious is the sparseness of the physics in late-Victorian astrophysics. Reasonably sophisticated physics is almost exclusively the province of geometrical and physical optics, the photographic process, and celestial mechanics. To make theories of stellar evolution based on stellar spectra without wondering much about the dependence of excitation and ionization on temperature, or attempting to calculate the subsurface temperature of the Moon without ever solving Fourier’s equation of heat conduction seems to me to be less than quaint. In seeing elaborate empirical representations of laboratory spectra, the modern reader becomes impatient for Bohr and Schrodinger and their successors to come along and develop quantum mechanics.
I wonder how many of our present debates and most celebrated theories will appear, from the vantage point of the year 2049, marked by shoddy observations, indifferent intellectual powers or inadequate physical insight. I have the sense that we are today more self-critical than scientists were in 1899; that because of the larger population of astronomers, we check each other’s results more often; and that, in part because of the existence of organizations like the American Astronomical Society, the standards of exchange and discussion of results have risen significantly. I hope our colleagues of 2049 will agree.
The major advance between 1899 and 1974 must be considered technological. But in 1899 the world’s largest refractor had been built. It is still the world’s largest refractor. A reflector of 100-inch aperture was beginning to be considered. We have improved on that aperture only by a factor of two in the intervening years. But what would our colleagues of 1899-living after Hertz but before Marconi-have made of the Arecibo Observatory, or the Very Large Array, or Very Long Baseline Interferometry (VLBI)? Or checking out the debate on the period of rotation of Mercury by radar Doppler spectroscopy? Or testing the nature of the lunar surface by returning some of it to Earth? Or pursuing the problem of the nature and habitability of Mars by orbiting it for a year and returning 7,200 photographs of it, each of higher quality than the best 1899 photographs of the Moon? Or landing on the planet with imaging systems, microbiology experimentation, seismometers and gas chromatograph/mass spectrometers, which did not even vaguely exist in 1899? Or testing cosmological models by orbital ultraviolet spectroscopy of interstellar deuterium-when neither the models to be tested nor the existence of the atom that tests it were known in 1899, much less the technique of observation?
It is clear that in the past seventy-five years American and world astronomy has moved enormously beyond even the most romantic speculations of the late-Victorian astronomers. And in the next seventy-five years? It is possible to make pedestrian predictions. We will have completely examined the electromagnetic spectrum from rather short gamma rays to rather long radio waves. We will have sent unmanned spacecraft to all of the planets and most of the satellites in the solar system. We will have launched spacecraft into the Sun to do experimental stellar structure, beginning perhaps-because of the low temperatures-with the sunspots. Hale would have appreciated that. I think it possible that seventy-five years from now, we will have launched subrelativistic spacecraft-traveling at about 0.1 the speed of light-to the nearby stars. Among other benefits, such missions would permit direct examination of the interstellar medium and give us a longer baseline for VLBI than many are thinking of today. We will have to invent some new superlative to succeed “very”-perhaps “ultra.” The nature of pulsars,
