A JOURNEY THROUGH SPACE
To most people Fabre is the observer, moving with head bent to study the secrets of the insect world. They are not aware that this interest was only part of that comprehensive passion which drove this great Frenchman to a clear and ordered conception of the Universe. Underlying all his local interests was an in- satiable curiosity about the mystery of Number. There is a poem by him which begins :- " Nombre ! Regulateur des effets of des causes ;
Qui donne le comment et le pourquoi des choses, Que me veux tu, Nombre imposant ? "
He knew quite well what it demanded. He knew that it called upon him to master it, and so reveal the anatomy of Life.
Now no man can feel this urge without being attracted sooner or later by astronomy, that great field where Number is put to its most athletic performance. So was Fabre attracted ; and in The Heavens (Fisher Unwin, 15s.) he has, in his characteristic paternal way, attempted to share his awful worship with young readers. To a grown-up, too, this story is so full of clearly exposed matter that the mind is strained to 'exhaustion in trying to realize, to absorb into One's bones, `the significance of it all.
First, he shows us the instruments which are to aid us in our starry travel. He explains roughly the geometry of the triangle, whose laws contain the principles of all sidereal measurement. He then examines the curtain of atmosphere through which we have to force our way before we can reach our nearest neighbour, the Moon. We learn how this atmosphere acts as a prism, breaking up and spreading the arrowy fire of the Sun, and con. verting it into the tempered and percolative daylight which is our life-stuff. We see that our blue sky is really a canopy of diffused luminosity that deceives us with its blue tranquillity, " which to such countless orbs has made us blind." For beyond this veil the Sun and stars blaze simultaneously, savage and rushing light, con- tracted to a cruel economy of intensity, stabbing through the muffling blackness of nothingness.
After having weighed and measured our Earth, we make our departure to the Moon, and see there the effect of that untempered light. For fourteen days one hemisphere of that airless and waterless world is submitted to the naked fury of the Sun ; a blaze that would annihilate any organic life. Then for another fourteen days that hemisphere is turned to the steel-cold, stars which must prick rather than shine through the intense and absolute darkness. There is nothing to prevent the complete radiation of all heat, and so that side of the Moon knows the true zero of cold, minus 270° C.
Having explored the dykes and disproportionately high volcanic ranges of the Moon—travelling very comfortably, since, owing to the gravity of that small sphere, ow weight is only one-sixth of what it is on Earth—we then measure our distance from the Sun. This we do by the elementary method of Aristarchus of Samos, who drew the base line of his celestial triangle between the Earth and the Moon at her first quarter. He knew that at this period the angle between the base- and the line of light reaching the Moon from the Sun would be a right-angle. He had only to measure the angle made by the Sun's ray meeting the base at our end of it. He then had the two angles of his triangle, and so was able to compute the hypotenuse, which was the distance between • us and the Sun.
We proceed to the Sun, travelling in an express train at sixty-three miles an hour, and reaching our destination after a non-stop run of 175 years ; a distance covered by the Sun's rays in eight minutes. We then measure and weigh the daystar, taking special note of the minor irregularities of flame which leap out to the extent of few hundred thousand miles. One of these tongues of flame would lick up the. Earth as though it were a postage stamp thrown into a blast-furnace. We then examine that fiery heart more closely, by means of the spectrum, whose machinery is explained to us.
Leaving the Sun, we turn to the rest of the Solar family, our brothers and sisters the planets. Mercury and Venus are the two nearest, and we notice a singular thing about them both. While the axis on which the Earth rotates is inclined at an angle of .23+ degrees so that we may have our life-giving variety .of seasons, these two smaller planets are inclined almost horizontally. Consequently their short " years," of three and eight months respectively, are divided into two equal seasons, one of complete darkness, the other of merciless light from a sun riding in giddy concentric circles above the exposed polar regions of these planets. Both these bodies are very irregular on their surface. Venus, for example, has mountains that, according to an Earthly proportion, would be thirty miles high. The scenery there must out- rival even a Max Rheinhardt production. Earth and Mars, the only two planets which have similarly sloped axes and approximately like conditions of climate, atmosphere, and surface, are the next in order of distance from the Sun. Of all the bodies in the Solar System, we two alone are capable of sustaining animal fife. It is a lonely thought : for if Mars is uninhabited, our next possible neighbours must dwell in some other System. But beyond the outposts of our planetary camp there is nothing until we have traversed a space which makes that camp appear as a wisp of luminous dust, with the Sun a point of light in the centre.
So in turn we visit the asteroids, that belt of. tiny worldlets flinging round the Sun on a path between those of Mars and Jupiter. At last we reach Neptune, the most distant of the Solar family. He is 2,793 million miles from the Sun, and revolves round him in 164 years. But the Sun is no light-giver to him, appearing only as an inconspicuous star. Does he then have any light and warmth ? We do not know, for though he is 110 times larger than Earth, his great distance makes him invisible to the naked eye, and difficult to observe through a telescope. If that is so, what must be the bulk of the nearest star, who lies beyond the Solar System over an abysm of nothingness which is 200,000 times our distance from the Sun ?
Coming now to the great distances, we are introduced to the " light-year," the sidereal- unit of measurement. This is the distance covered in a year by light travelling at 182,000 miles a second. We learn that some of the bright luminaries are 12, and 22, and even 72 light-years away. So we begin to get some idea of the proportions of this universe of suns and satellites which we see dis- appearing in perspective through the Milky Way. Out- side this universe we find that others begin, 32,000 light- years away ; other vast celestial precisions and groupings.
As an epilogue to this tale of the harmonies, we are told something of the comets, those contrapuntal monsters who come flaming through the rhythm of the heavens. Some of them are wide enough to fill the space between us and the Moon. Yet they rush past the planets without attracting them from their gravitational habits. The comets themselves, however, are affected, deviating a little in their courses at the pull of Earth, or Mars, or whatever substantial body they are passing. Since they are so vast, why do they not work widespread ruin ? The reason is, that they are the merest ghosts,. -whom even a star-ray can pass through without being deflected, as it would through air. These harmless giants are composed of an incandescent meteoric dust which is finer than our atmosphere. They come sweeping in towards the Sun, pass round him, and rush off again, completing some orbit whose further curve is lost in space far beyond the path of the lonely outrider, Neptune.
So, equally irresponsibly, we must leave this descriptive cosmology ; for reviewers, like astronomers, are troubled by space. But we must not do so without warning the reader that Fabre's story of the heavens is still in the great astronomic tradition which unconsciously bears traces of the Heracleitan theory that all things are fire ; and which also has conventional ideas on direction that are rapidly dissolving in the relativity theory. Einstein tells us that it is equally right to say that the Sun revolves round the Earth as to say the opposite. But we must prevent ourselves from this tempting discussion.
RICHARD CHURCII.
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