POPULAR ASTRONOMY: 1870-1879
Or, The Effects of Sunspots Upon the Price of Corn
Being a look at what our ancestors knew, or thought they knew, about the sun, the planets, and the stars, as seen through the pages of one of the illustrious journals of the day.
It was the decade after Jules Verne journeyed From Earth to the Moon, and nearly three decades before The War of the Worlds. Pioneer 10 lay a century away. There were eight known planets, and people took for granted the existence of life on some of them. The telescope had reached a high state of development, spectroscopes (devices used to study light and radiation emitted by stars or other objects) were in common use, and scientists were making efforts at astrophotography. Astronomy, particularly astronomy from the layman's viewpoint, bloomed in the 1870s.
Americans of the time looked upon their world with insatiable, all-inclusive curiosity, as the popular journals of the day attest. The Galaxy provides a good example. Billed as "a magazine of entertaining reading", it gave its subscribers condensations of current novels, essays on history, politics and the arts, a few poems, an occasional short story … and a fascinating column called 'Scientific Miscellany".
Here, among cases of suicide in dogs, notes on the cultivation of green oysters and warnings about the harmful effects of excessive tea drinking, appeared bits of astronomical theory, 'fact' and just plain speculation which show Yankee ingenuity extended to the cosmos.
The sun received a lion's share of attention, being the most prominent object in the sky, and the most important to human life. It brought out the poet within the heart of the statistician.
"That great stellar fountain of light and life which sends away into space each hour heat enough to boil seven hundred thousand million cubic miles of ice-cold water ...." [02/1872/267] presented a source of mystery, fascination, and occasional trepidation. All its features were carefully observed and duly noted, and their significance vigorously debated by scientists. The Galaxy synthesized and published the results.
By 1872, most observers recognized the corona (the faintly luminous area around the sun) as actually a part of the sun, and not a trick of the earth's atmosphere, as had been believed. But sunspots proved a greater puzzle [04/1872/557], and they led theorists into strange investigations.
Professor Jevons of the British Association decided to compare the eleven year sunspot cycle with the price of corn in England between the year 1259 and 1400. And, he got results. During the first four years of the cycle, prices rose. In other years, they fell. What did it mean? Jevons had no idea; he just presented his facts for the world to do with as it chose [02/1876/275]. The correlation remains a mystery; perhaps changes in solar radiation affect Earth's climate, and thus harvests and prices.
Others tried to determine the nature of these odd dark blotches upon the sun's face. They are, of course, regions of slightly cooler surface temperatures. Against their brighter surroundings, they appear dark, although alone in space they would shine more brightly than any star. They baffled scientists of the 1870s.
Explanations often involved analogies to familiar terrestrial events. According to "Faye's Theory" [10/1873/416], the spots were cyclones on the sun. When storm-swirled vapors reached the high regions of the solar atmosphere, they condensed and fell as liquid drops. From earth, this looked like spots. How could liquids exist on the sun, at a temperature of some 5800 degrees centigrade? No one knew it was that hot. M. Cailletet of the French Academy determined that the hottest part of the sun could not be more than 2000 degrees centigrade. To a world innocent of atomic theory, Cailletet's argument seemed indisputable; he had proved it with a candle flame [02/1875/272].
There were the alarmists. Although chiefly specializing in threats of comet collision, a few foresaw dire tragedy involving the sun. In 1872, an Italian astronomer named Tachini looked through his spectroscope and decided the sun was burning such tremendous amounts of magnesium that it must soon go out.
The Galaxy editor was not impressed:
"In the case of the comet, it had come to be thought quite a matter of course that we should have to try a collision; but according to the scientific croakers our danger from the sun is that he will burn out, and that life upon the earth will cease from decline in the intensity of radiation. But the experience of the past summer certainly lends little countenance to this hypothesis ...." [11/1872/708]
Unfortunately for Tachini, he made his prediction in the midst of a severe general heat wave.
Forebodings of solar disaster or not, planetary astronomy proceeded with enthusiasm. During the 1870s, astronomers discovered the two moons of Mars [11/1877/698], found that Saturn's rings are tiny individual bodies orbiting the planet [02/1873/276] and located new asteroids with such rapidity that astronomical authorities quit calculating and publishing their orbits [07/1877/131]. The search for the ninth planet (then called Vulcan instead of Pluto) remained unsuccessful, though calculations indicated its existence [05/1877/706]. Nineteenth Century telescopes just lacked the moxie to find a chunk of rock smaller than the Earth and 3,600 million miles distant.
Astronomers could see the Moon clearly, and chart its major features without debate, so interest in it took a different turn. Luna was close enough to affect Earth's tides, and it got the blame for a wide array of other phenomena. M. Charbonnier thought a full moon, and especially the lunar equinox, made the water in his aquarium turn green [03/1875/420].
Other theories tried to clothe ancient superstition in the garb of modern science. "Moon madness" was believed caused by the full moon dissipating clouds, thus permitting rapid radiation of heat from the earth. The resulting chill damaged the nervous system of anyone exposed to it, and brought on madness [03/1877/424].
Though the Moon looked indubitably dead, people took the presence of life on Mars and Venus as a given. But how to contact it? In 1874, Charles Cros suggested signaling Venus during a coming transit, when that planet would be much closer than usual to Earth. Venerian astronomers would no doubt be watching for such communication, and would signal back - like ships passing one another at sea, waving their flags and sounding their horns, we may imagine.
Stanislas Meunier of the French Academy scoffed at such American idiocy. "There is every ground for believing," he wrote, "that the inhabitants of Mars are more advanced than we in every way, and immensely superior to those of Venus, which is a newer planet." [01/1874/126-127] We ought to be signaling Mars, apparently.
According to the cosmology of the time, all planets began as hot, gaseous bodies like the sun, and gradually got colder and drier until they became like the Moon. That Mars had gone farther along this road than the Earth could be seen by the condition of the Martian oceans, which scientists thought to be actual bodies of water. The seas of Mars, as observed by Meunier [01/1874/126], appeared bottle-necked, with long, winding inlets, just as the seas of Earth would look, when more of the water had evaporated.
Dr. Nageli challenged this traditional view of planetary evolution in 1878 [01/1878/126-127]. Nageli pictured a series of cold and warm currents running throughout the universe, like air or ocean currents on Earth. "Our starry heaven" was now in a cold area, but presently it would hit a warm stream, and all would return to gas. The sun's magnesium burning seems innocent in comparison.
While Galaxy articles of the 1870s contain much on the sun and the planets, they hardly mention the stars. Little was known. Sir William Herschel and his son had devoted years to mapping the heavens, but their work served only as a beginning. Astronomers, armed with their telescopes and not much else, were in a poor position to carry on this effort.
Still, they made progress. By 1872, some scientists were suggesting that rather than being evenly distributed throughout the universe, stars were grouped in certain "rich regions", while other areas were either empty or very sparsely strewn [08/1872/271]. In 1874, Professor Gould, just returned from Argentina, reported that the number of stars seemed to increase toward the "Galaxy" [11/1874/705]. It is unclear what he meant by "Galaxy"; perhaps the Milky Way. In any case, Gould deemed it astronomy's most important task to determine the sun's position in relation to "its own cluster."
Not only was the arrangement of the heavens somewhat difficult to determine, but confusion abounded as to its nature and composition. Having no concept of fusion reactions, scientists quite reasonably estimated stellar temperatures as being all about the same, and not over 2000 degrees centigrade, probably lower. Red giants and white dwarfs lay totally beyond their ken. But stars come in a variety of colors, and that had to be explained. Dr. Higgens attempted such an explanation in 1874 [09/1874/419]. All stars, he said, radiate white light, but every star is surrounded by a cloud of colored vapors through which the light rays must pass, thus making the star appear colored. Substances contained in the vapors determine the color. He does not mention temperature, the real reason for the varied hues of stars.
So spoke the decade's best known scientists, most of whom were European. Americans read about these theories, and no doubt discussed them, along with the home life of the red ant and new fossil discoveries in Peru. Astronomy held no great place in most people's thoughts in the 1870s, but they were interested.
As for the astronomers, they cherished a lot of wrong-headed, sometimes comical ideas. But they did the best they could with what they had. They made mistakes, and they made progress as well. They realized they could not solve every problem, answer every question. A constant refrain rings through their writings: "the science is in its infancy", "the wonders of the heavens are not yet exhausted", "there is so much work still to be done". They could not do it all, just as we cannot, but they could contribute, and they did.