CHAPTER II

ACHIEVEMENTS IN SCIENCE

Geographical exploration for the most part is commercial in motive, though the exploration of regions that cannot be used by civilization is due to the scientific spirit of modern times. That same scientific spirit is the moving cause of archæological investigations. To round out the sum of human knowledge man must be acquainted with every detail of his geographical environment; must trace human history back almost to the dawn of consciousness. Improvement, as moderns see it, is dependent upon science. Man can make his life easier and happier only as he increases his knowledge of the facts of life and of nature.

But geography and archæology are, in a sense, superficial sciences. One extends the map of nature; the other extends the map of history. Astronomy, physics, chemistry-all the pure sciences-are, so to speak, sciences of depth rather than of area. They seek to determine natural forces and the laws that govern those forces. They aim to fix the place of the earth in the universe; to define matter; to discover the point at which matter and mind merge the one into the other, or the extreme edge of the gulf that may yawn between them; to dig the heart out of the atom; to approach as closely as they may from the objective side the meaning of life. The work of science is patient, laborious, unending.

The Work of the Astronomers

Astronomers in 1901 were especially interested in three astronomical problems-the asteroid Eros and its relation to the sun's distance from earth; the new star which suddenly flamed up in the Constellation Perseus; and various problems in connection with the Planet Mars-the prominence of which was, however, perhaps more popular than scientific.

DETERMINING THE SUN'S DISTANCE

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I

The distance of the Earth from the Sun is the base line of celestial measurements, and the exact determination of that distance is, accordingly, a problem of the utmost importance. Up to recent years the most accurate means of determining the distance was by observation of that somewhat rare phenomenon, the transit of Venus across the face of the Sun. The transit of 1769 led astronomers to give the distance between the Earth and the Sun as ninety-five million miles. The transits of 1874 and 1882 reduced the computation to ninety-three million miles. And now, by a new measurement, the estimate has been lowered still further to 92,850,000, with a promise of greater exactitude in years to come. These reduced figures for the distance between the Earth and the Sun involve a reduction in all previous estimates of celestial distance and magnitudes, excepting those of the Moon, which is not measured by the Sun-Earth base line.

The new measurement is due to the discovery by Witt, of Berlin, in 1898, of the asteroid, or minor planet, Eros, which is almost twice as near the Earth as Venus. The nearer a planet to the Earth, the greater its parallax will be; and the exact ascertainment of a planetary parallax is essential to a determination of the Sun's distance by Kepler's third law, which says: "The squares of the periodic times of the planet's revolution around the Sun are proportional to the cubes of their mean distances from him."

Eros, at rare intervals, approaches to within thirty-five million miles of the Earth. It will do so in 1930 for the first time since its discovery. But in December, 1900, it was in an opposition sufficiently favorable to make possible a careful approximate determination of its parallax. The distance of this tiny planet-its diameter is thought to be about eighteen. miles from the center of the Earth was then obtained with an approach to accuracy by determining certain angles, and from this distance astronomers were able to revise their estimates of the Sun's distance from the Earth. When Eros comes still nearer to the Earth, closer figures will be secured.

About 465 asteroids were already known when Eros was discovered. But Eros promptly became of first importance to astronomers not only because of its relation to the problem of the Sun's distance, but also because of a singular variability in its reflection of light. That a dark

planet which shines only by favor of the Sun should be more brilliant at one time than at another is curiously difficult to explain. Yet there is no question that the light of Eros varies greatly, for photographic plates tell the story. Of the theories offered in explanation of the phenomenon, the most plausible suggests that the light of Eros is periodically cut off by some heavenly object.

II

On February 21, 1901, the Rev. Doctor T. D. Anderson, of Edinburgh, Scotland, while scanning the northern heavens, noted in the constellation Perseus a point of light that did not appear in existing astronomical maps. The discovery of this "new" star-it was promptly named Nova Persei-became at once a subject of profound interest. A photograph of the same stellar region, taken only twenty-eight hours before Doctor Anderson's discovery, showed no trace of Nova Persei, thus proving that if it had then existed it would have been as faint as of 12.5 magnitude. This means that in a little more than a day its brightness had increased at least one hundred thousand times. It was of 2.7 magnitude when Doctor Anderson first saw it, and it continued to grow brighter until noon of February 24, when the maximum was reached. The magnitude thereafter decreased and increased alternately for some time, the result being a gradual general diminution in brilliancy.

What is to be assumed as the cause of this new sign in the heavens? The natural explanation is that some star, too small or perhaps too dark to be ordinarily visible, had collided with another star or with a comet or a gaseous nebula. If two stars should collide they would suddenly become white-hot liquid or gas. But Nova Persei did not flare up thus suddenly. If, however, a star should enter the nebulous envelope surrounding the nucleus of a comet its brightness would increase more gradually until it struck the nucleus, and would thereafter diminish, as Nova Persei did.

Conjecture cannot but be busy with such an appearance as Nova Persei. The human imagination draws a picture. The universe is full of dead stars-that is, stars that have at least externally cooled-that shine only by reflected light. The moon is a cinder; the earth a dying coal. Nova Persei may have been a dead star-perhaps a cinder like the moon; perhaps an inhabited world. It may have teemed with life. Suddenly came a shock, and life vanished in one consuming second,

PHYSICAL CONDITIONS ON MARS

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This is a conjecture as to what may have been; it is also the indication of what would be were the Earth to collide with a star or a comet. The Earth may some day disappear in flame, while the astronomers of a distant orb turn their telescopes earthward and wonder as we have wondered concerning Nova Persei.

The appearance of new stars is not infrequent. In thirty years some twelve have been seen. But Nova Persei was the brightest of all that have been recorded, except Tycho Brahe's star of 1572, which became so brilliant that it could be seen by the naked eye in daylight. Sometimes temporary stars after a longer or shorter period of fluctuating brilliancy become gaseous nebulae.

III

The popular imagination, which was busy for a time with Nova Persei, is always busy with the Planet Mars, of all the planets the one most likely to be habitable. Mars, with its "polar snow-caps," its 'canals," its suggestion of an "atmosphere," and its "signals," offers many stimuli to those who like to speculate about the universe.

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Astronomers differ as to whether the physical conditions on Mars are such as would support life. In 1901 Doctor Bruhns wrote in the Deutsche Revue: "Mars has decided white spots at the poles, which vary according to the season. As Vogel has proved by the spectroscope that Mars contains hydrogenous vapors, it seems likely that these white spots are snow-fields, and that Mars is surrounded by an atmosphere. The planet also shows light and dark spots, which are designated as land and sea or lake, respectively, and dark streaks and lines, which are called canals. These words are merely used as designations, without implying that there really has been proved to be land and water. These spots have been so definitely fixed that Schiaparelli was able to construct an exact chart of Mars. Since 1881, some canals have often been seen double, the phenomenon of their doubling, even, having been observed. Herz says that these so-called canals of Mars are probably not canals at all, but single mountain chains which appear double owing to a phenomenon of refraction. . . . Since it has been proved by the spectroscope that Mars contains water, it is possible that the so-called land and sea really are land and water."

Set off against this a popular article by the astronomer Edward S. Holden, in McClure's Magazine for March, 1901. Commenting on

the conclusions of Sir William Herschel, Professor Holden says: He observed that the poles of Mars were sometimes covered with polar caps of a white material that he assumed to be snow. The snow was greatest in amount when the poles were coldest, just as happens on the earth. As the amount of solar heat increased, the snow-caps' grew smaller and gradually disappeared. He supposed them to melt and to become water. The explanation was correct, so far as his knowledge then went. We now know two facts that make it impossible. In the first place, according to the best knowledge attainable, the temperature of Mars is always far below the freezing-point. Water can never melt on Mars. In the second place, there is, in fact, little or no water on Mars. The observations at the Lick Observatory have shown this conclusively, and this result is now generally accepted.

"The polar caps' exist, however. What are they? The answer is that it is not certainly known. They are X for the present, like Professor Röntgen's rays. It is very likely that they may be composed of carbon dioxide. This vaporizes (and becomes invisible) at -109 degrees of Fahrenheit's thermometer. At a lower temperature than this it is deposited as a white 'snow.' A layer an inch thick (or less) would account for all the observed phenomena. This explanation may not be correct, but it is worthy of serious examination. Whether it is correct or not, it is certain that the polar caps of Mars are not composed of snow.'

"Not only is there no water on Mars, but there is no air, or very little. Spectroscopic observations at the Lick Observatory, far more complete and thorough-going than those made at other stations, lead to the conclusion that the atmosphere on Mars is certainly less in amount than that surrounding the summits of the highest Himalayan peaks. It is probably much less than this; at any rate there is not sufficient air to sustain human life. It is by no means certain that what air there is is of the right kind for human beings to breathe."

Professor Holden concludes that there is not the slightest reason for believing that human life exists on Mars. Moreover, "so far as we know, there is no likelihood that life exists on any other planet than the earth."

From what has been quoted, it appears that, even when scientists admit the possibility that life exists on Mars, they do so very cautiously.