Svante Arrhenius

“ The fissures in the crust of the Earth or of Mars are as a rule rapidly filled and their contours largely hidden from sight by alluvium or sand carried by windstorms, so that they reveal themselves only through tremors and various emanations along their course. The fissures on Mercury on the other hand must remain as yawning chasms. It is probable that reducing gases stream out of these cracks as on Earth, and colour the environment in a darker shade than the other visible part of the planet’s surface, that is the hemisphere turned toward the Sun. ”

“ A thorough critique has demonstrated that any other planet in our solar system hardly can offer an abode for higher beings, except this very Earth, which therefore justly may be called “the best of worlds” among those that we know. And yet, it was undoubtedly a great truth that Giordano Bruno gave his life for, because it is highly probable, nay almost certain, that around the countless suns which dot the firmament spin dark bodies, although unfortunately our most powerful lenses do not reveal them. ”

“ What benefit could we derive from knowing whether a star lies a hundred or a thousand billion miles from the Sun, or from understanding how the stellar bodies have evolved in the course of billions of years? ”

“ Finally, the entire planet, perhaps after having harboured life during trillions of years, becomes an ice waste with a few cracks in its hard crust through which warm and acid vapours rise and create small melted areas characterized by a darker colour than the desert and ice-landscape in general. Organic life lacks the conditions for existence and ceases therefore to cheer the planet with its interesting variations. The planet is dead but continues in obedience to gravitation to describe its orbit in space. ”

“ In fact, the geologists have found that the different epochs in earth’s evolution are best characterized by their humidity or dryness. To arrive at a clear conception in these matters we shall briefly survey our present knowledge of the importance for the evolution of life on earth that we should attach to the humid and to the dry periods or localities.
We are all familiar with the heavy, moisture-laden warmth which meets us when we enter a hothouse. It is particularly favourable to the growth of plants and to the prosperity of the lower animals. ”

“ It proved to be of a far more blue tinge than sunlight reflected from the Moon. Our conclusion must be that the Earth shines with a blue lustre. This is perfectly natural, as the diffused light which reaches us after having been scattered by particles suspended in the air (and by gas molecules as well) is a deep blue and there exists no reason why that part of the light which is thrown outward into space should be of a different colour. The Earth, therefore, is blue in contradistinction to Mars which is red, on account of its desert surface, and Venus which is bright white. ”

“ If the temperature in the middle of the day, when the sunlight falls perpendicularly on the surface of the planet, rises only to about 5° C. (41° F.) , the mean temperature for twenty-four hours, even in the midst of the summer, must in this entirely clear, light air be far below freezing and vegetation on Mars is therefore not very well conceivable. In spite of this, Lowell saw in Slipher’s measurements a confirmation of his theory that Mars is the abode of an intelligent race that utilizes, in their wrestle with existence, a verdant vegetation pushed even into the polar regions. ”

“ The Sun, as stated, is the exception as it reigns over the entire nature, the living as well as the lifeless, by virtue of the heat and light which abundantly flow from this autocrat of our planetary system. Perhaps the Moon also plays some small active part as it seems somewhat to affect the barometric pressure, the magnetic and particularly the electric conditions of the atmosphere, which, in turn, appear to influence several life processes. On the other hand we cannot point to any influence upon nature traceable to the other stellar bodies. ”

“ In the course of the many millions of years which geology has proved necessary for the evolution of our planet, the carbon dioxide in the air was gradually converted into oxygen and carbon. As long as reducing gases, such as the poisonous169 ones mentioned, or any considerable quantities of carbohydrates and hydrogen yet remained in the atmosphere, the oxygen was consumed in their combustion. If a solid crust had not existed to prevent the oxygen from entering into the interior molten mass, it would also have found its way there and would have oxidized the reducing substances in the magma. ”

“ If so, we might expect the atmosphere on Mercury to be denser yet, while we already have seen that it is almost wholly lacking on that planet. The explanation is that Mercury has lost its spin around its own axis and therefore always presents the same side to the Sun—just as the Moon and probably all other satellites turn one side only toward their respective central bodies—hence the opposite side becomes so cold that all gases are there condensed to fluids or solids except the two most volatile ones, hydrogen and helium, which on the other hand leave the planet on its hot side. ”

“ Taking proper account of the low temperature on Mars we may easily compute, by means of a formula given by Stokes, that a particle of dust should sink 2.3 times slower on Mars than on Earth. When, nevertheless and in spite of frequent but thin mists, so few particles of dust float in the atmosphere of Mars, the conception inevitably comes to our mind that the air on that planet must be extremely rarefied so that the wind-puffs have little power to raise the dust from the ground. Lowell estimated the barometric pressure at the surface of Mars to be about 64 mm. ”

“ There remain in the whole series of planets and satellites in our solar system only two bodies besides the Earth which are endowed with an atmosphere in the original sense of the word—namely, Mars and Venus.
We reach the same conclusion when investigating the ability of the planets to reflect the sunlight falling upon them. The bodies which possess an atmosphere hold also suspended therein clouds of water or ice, and also of dust, whirled up from below. These floating particles reflect light far more efficiently than the solid or fluid surface of a planet. ”

“ As the water vapour diffuses in the air, the canal becomes liquid along its entire length independent of the altitude of its various parts.
All agree upon the desert climate of the mainland on Mars. Like most deserts on the Earth, it is, therefore, probably a table-land, where one plateau mounts above the other, each one nearly level. By the action of the wind, the upper layers have been transformed into fine sand. On the dead planet no further sediments are deposited by the sea. The only accretions to the planet are meteorites and cosmic dust which slowly rains down. ”

“ The cloud-formation is enormous and dense rainclouds travel as high up as 10 km. (6.2 miles) . The heat from the Sun does not attack the ground but the dense clouds, causing a powerful external circulation of air which carries the vapour to higher strata where it condenses into new clouds. Thus, an effective barrier is formed against horizontal air currents in the great expanses below. At the surface of Venus, therefore, there exists a complete absence of wind both vertically, as the Sun’s radiation is absorbed by the ever present clouds above, and horizontally due to friction. ”

“ We have seemingly agreed that all life originates in the sea, so that moisture can be considered the first requirement for its appearance on the earth.85 As to heat, life is destroyed by frost and favoured by increased warmth, at least to a certain point, about 35° to 40° C. (95° to 104° Fahrenheit) , which temperature is most propitious to the development of life, while a further increase is detrimental, so that already below the boiling point of water life suffers more harm than at temperatures below freezing. ”

“ If we wish to picture to us the future fate249 of our Earth when it gradually enters the reign of darkness and cold in consequence of the enfeebling of the Sun, we must seek our illustration on Mars and not on the Moon. Slowly are the oceans going to freeze, finally down to their bottom, the abundance of the rainfalls will diminish, only light snow will now and then bring change to a surface evermore transformed into a sand desert as far as the continents reach. Rents in the rocky substrata of the latter will appear as dark lines, caused by the gases rising from the interior. ”

“ As we shall see later, free oxygen cannot be present on the planets until a solid crust has been formed. We may therefore state that the conditions for the existence of life on a planet are fulfilled when a true atmosphere containing oxygen and water surround its body. ”

“ No doubt, the facts that the intensity of gravity on Mars is only three-eights of its intensity on the Earth and that the curvature of the Martian surface is twice as sharp as the Earth’s contribute to this result. ”

“ As far as we know none but gravitation. It appears therefore as if the gaseous primeval substance of the stars were not governed by this force. It might prove hazardous, however, to make this assumption as gases also possess weight and even the most rarefied strata of the Earth’s atmosphere exert barometric pressure by virtue of their attraction to the mass of the earth. Rather the immobility of the nebulæ is due to the frequent collisions between the molecules in any quantity of gas even if it be attenuated to such a high degree as in the nebulæ. ”

“ In a certain sense, we are justified in speaking of an atmosphere of suns and stars. These bodies consist mainly of a comparatively dense mass surrounded by a layer of very attenuated gas. The density of our Sun is about 1.4 times that of water. In other stars it is considerably lower, in some cases only a few hundredths of the density of water. This applies particularly to those stars of variable magnitude, the Cepheid type, named after their longest and best known representative, the mysterious star Delta in the constellation Cepheus, and in general to young stars. ”

“ This is the case also with those parts of astronomy which, because of their practical importance at the outset, gave rise to the science itself.
The growing knowledge about the stars, like all higher insight, became among primitive peoples the private possession of their leaders, was by these kept a secret and made a part of the venerable realm of religion. We find that a majority of these old peoples rendered worship to the stars, believing them to govern the fates of human beings. ”

“ When the Sun after the oppressive day sinks behind the horizon, it is well known that a sharp fall of temperature occurs, particularly in arid zones, but also in humid regions within the tropics where this very phenomenon is utilized for the production of ice. He who exposes himself to the sudden cold of the night falls an easy prey to illness. Particularly is this true under a clear sky—primitive people say “when the Moon shines”—because of the strong radiation. ”

“ No sheet of snow covers the ground in winter-time, kills the vegetation, or decimates the supply of nourishment for animals and men. Indeed, contrary to our experience, a suppression of growth often accompanies a high altitude of the Sun due to the drought which simultaneously occurs. The altitude and luminosity of the Sun change altogether too slightly in the course of the year to15 attract the attention of primitive man. The light of the Moon, on the other hand, varies from full intensity to nothing and this takes place in periods so short that memory has no time to forget the cycle. ”

“ Life is, at least on Earth, tied to certain so-called compounds, in which carbon is the essential common element, while hydrogen, nitrogen, and oxygen together with sulphur, phosphorus, iron, magnesium, and a few other less important elements also enter therein. No substance but carbon possesses this quality of being a prerequisite of life. Silica is a close kin to carbon and a substitute in certain organic compounds, but protoplasm, the main constituent of the living cell, cannot159 be built without carbon. ”

“ As the Algonkian time belongs to the oldest epochs of geological history it appears that the temperature on the Earth as long as life has existed on our planet on the whole has been nearly constant, with important alternations, however, of warm and cold periods. For an explanation of these fluctuations, our well-nigh only recourse is the assumption that the heat-conserving quality of the atmosphere has changed by virtue of a varying composition. ”

“ Withal the most intense facts of astronomical knowledge and discovery are given beside the tapestried romance which earlier peoples wove with star-stuff as the medium of their art. It is a book delightful to the eye, scholarly in conception and treatment, and charming to the inner sense.”—From Scientific American. ”

“ It is often stated that the assurance of the return of sunlight after the darkness of night enabled humanity with greater equanimity to acquiesce in the loss of light during one half of its existence and that worship was rendered to the Sun in gratitude therefor. ”

“ There is then no reason to doubt that the material of which the planets are built essentially is the same throughout the universe.158 Their interior should, like that of our Earth, consist of the heavy metals, principally iron,—strongly prevalent also in the Sun and in the meteors,—and this metallic nucleus should be clothed with the silicates, oxides, carbonates, sulphides, and hydrates of all metals, particularly aluminum, and among the metals we may also count hydrogen. ”

“ Since I presented Worlds in the Making and Life of the Universe as Conceived by Man from Earliest Ages to the Present Time to the public—which received them with far greater interest and appreciation than I could foresee—I have had repeated occasions to treat new questions of a cosmological nature, questions largely arisen from new discoveries and observations within the scope of astronomy. ”

“ In poetic flight he does not hesitate to endow the Milky Way organism with life. Its evolution cannot be denied a certain similarity to the processes of life. The great nebula owes its origin to the union of two individuals, two nebulosities, who met in their course through boundless space. ”

“ According to the great Kant, conditions on the wandering stars outside of the Earth’s orbit were so favourable to life that their inhabitants ought to have reached a far higher development than beings on the Earth. The last remnant of this conception lives in the speculations about the marvellously proficient engineers who built the magnificent system of giant canals on Mars. ”

“ The rare gases of the air especially should originally have come from the exterior parts of the sun, as did the nitrogen.
An atmosphere of such a composition would be utterly unendurable to living beings. It must, if organisms are going to thrive therein, be purified from such poisons as carbon dioxide, gaseous sulphur, cyanogen, and sulphurous acid. We know that such a process has taken place and that the sunlight has been the great chemist who produced oxygen and carbon from the carbon dioxide. ”

“ The compound substances of the Earth, like those of162 the Sun, are also strongly reducing, so that we must infer that free oxygen did not enter into the gas covering of the Earth at the time when its solid crust was formed. We may gain a conception of the gases which then existed in the outmost layers of the Earth by studying the gases on the Sun and on other stellar bodies, particularly the comets, and also by investigating the gases absorbed by the molten interior of the Earth. ”

“ The opposite extremity, the dry desert climate, is far more pronounced in the present time. This condition is well known in all continents except Europe, where we hardly93 can claim a desert but instead have steppes, with a vegetation abundant after the spring rains but fast disappearing with the arrival of the burning summer heat. A particular type of plant life has adapted itself to this periodic change from rain to drought, from bitter cold during the winter to parching sun during the summer. Perennial plants, and particularly trees, can rarely endure the rigors of such climatic upheavals. ”

“ With growing civilization all people learn to understand, as have the Japanese, the superior importance of the Sun. The Incas of Peru, who reached a very high grade of culture, were sun-worshippers and called themselves children of the Sun, although they lived near the equator where the Moon-cult, as we presently shall see, owns its most faithful adherents.
In the neighbourhood of the equator, winter and summer differ very slightly with respect to temperature and altitude of the Sun. ”