Part 30 (1/2)
”I. External causes of error, comprehending such as depend on external uncontrollable circ.u.mstances; such as fluctuations of weather, which disturb the amount of refraction from its tabulated value, and being reducible to no fixed laws, induce uncertainty to the amount of their own possible magnitude.
”II. Errors of observation; such as arise for instance from inexpertness, defective vision, slowness in seizing the exact instant of the occurrence of a phenomenon, or precipitancy in antic.i.p.ating it; from atmospheric indistinctness, insufficient optical power in the instrument, and the like.
”III. The third, and by far the most numerous cla.s.s of errors, arise from causes which may be deemed instrumental, and which may be divided into two cla.s.ses.
”The first arises from an instrument not being what it professes to be, which is _error of workmans.h.i.+p_. Thus if an axis or pivot, instead of being as it ought, exactly cylindrical, be slightly flattened or elliptical--if it be not exactly concentric with the circle which it carries--if this circle so called be in reality not exactly circular--or not in one plane--if its divisions, intended to be precisely equidistant, shall be in reality at unequal intervals--_and a hundred other things of the same sort_.
”The other subdivision of instrumental errors comprehends such as arise from an instrument not being placed in the position it ought to have; and from those of its parts which are made purposely movable not being properly disposed, _inter se_.
These are _errors of adjustment_. Some are unavoidable, as they arise from a general unsteadiness of the soil or building in which the instruments are placed.[334] Others again are consequences of imperfect workmans.h.i.+p; as when an instrument, once well adjusted, will not remain so. But the most important of this cla.s.s of errors arise from the non-existence of natural indications other than those afforded by astronomical observations themselves, whether an instrument has, or has not, the exact position with respect to the horizon, and the cardinal points, etc., which it ought to have, properly to fulfill its object.
”Now, with regard to the first two cla.s.ses of error, it must be observed, that in so far as they can not be reduced to known laws, and thereby become the subjects of calculation and due allowance, _they actually vitiate in their full extent the results of any observations in which they subsist_. With regard to errors of adjustment, not only the possibility, _but the certainty of their existence in every imaginable form, in all instruments_, must be contemplated. _Human hands or machines never formed a circle, drew a straight line, or executed a perpendicular, nor ever placed an instrument in perfect adjustment, unless accidentally, and then only during an instant of time._”
The bearing of these important and candid admissions of error in astronomical observations upon all kinds of other observations made by mortal eyes, and with instruments framed by human hands, in every department of science, is obvious. No philosophical observation or experiment is absolutely accurate, or can possibly be more than tolerably near the truth. The error of a thousandth part of an inch in an instrument will multiply itself into thousands, and millions of miles, according to the distance of the object, or the profundity of the calculation. Our faith in the absolute infallibility of scientific observers, and consequently in the absolute certainty of science, being thus rudely upheaved from its very foundations by Sir John Herschel's crowbar, we are prepared to learn that scientific men have made errors great and numerous.
To begin at home, with our own little globe, where certainty is much more attainable than among distant stars, we have seen that astronomers of the very highest rank are by no means agreed as to its diameter. Its precise form is equally difficult to determine. Newton showed that an ellipsoid of revolution should differ from a sphere by a compression of 1/230. The mean of a number of varying measurements of arcs, in five different places, would give 1/299. The pendulum measurement differs very considerably from both, and ”no two sets of pendulum experiments give the same result.”[335] The same liability to error, and uncertainty of the actual truth, attends the other modes of ascertaining this fundamental measurement. A very small error here will vitiate all other astronomical calculations; for the earth's radius, and the radius of its...o...b..t, are the foot-rule and surveyor's chain with which the astronomer measures the heavens. But this last and most used standard is uncertain; and of the nine different estimates, it is certain that eight must be wrong; and probably that all are erroneous. For example, Encke, in 1761, gives the earth's distance from the sun at
95,141,830 Encke, in 1769, 95,820,610 Lacaille, 76,927,900 Henderson, 90,164,110 Gillies and Gould, 96,160,000 Mayer, 104,097,100 Le Verrier, 91,066,350 Sir John Herschel, 91,718,000 Humboldt, 82,728,000[336]
Here now is the fundamental standard measure of astronomy; and nine first-cla.s.s astronomers are set to determine its length; but their measurements range all the way from seventy-seven to one hundred and four millions of miles--a difference of nearly one-fourth. Why the old-fas.h.i.+oned finger and thumb measure used before the carpenter's two-foot rule was invented never made such discrepancies; it could always make a foot within an inch more or less; but our scientific measurers, it seems, can not guess within two inches on the foot.
Their smaller measurements are equally inaccurate. Lias says the Aurora Borealis is only two and a half miles high; Hood and Richardson make its height double that, or five miles; Olmsted and Twining run it up to forty-two, one hundred, and one hundred and sixty miles![337] When they are thus inaccurate in the measurement of a phenomenon so near the earth, how can we believe in the infallibility of their measurements of the distances of the stars and the nebulae in the distant heavens?
The moon is the nearest to us of all the heavenly bodies, and exercises the greatest influence of any, save the sun, upon our crops, s.h.i.+ps, health and lives, and consequently has had a larger share of astronomical attention than any other celestial body. But the most conflicting statements are made by astronomers regarding her state and influences. There is no end to the controversy whether the moon influences the weather; though one would think that question, being rather a terrestrial one, could easily be decided. Schwabe says Herschel is wrong in saying that the years of most solar spots were fruitful; but Wolf looks up the Zurich meteorological tables, and confirms Herschel.
In _Ferguson's Astronomy_, the standard text-book of its day, we are informed that ”Some of her mountains (the moon's) by comparing their height with her diameter, are found to be three times higher than the highest hills on earth.” They would thus be over fifteen miles high. But Sir Wm. Herschel a.s.sures us that ”The generality do not exceed half a mile in their general elevation.” _Transactions of the Royal Society_, May 11, 1780. Beer and Madler have measured thirty-nine whose height they a.s.sure us exceed Mont Blanc. But M. Gussew, of the Imperial Observatory at Wilna, describes to us, ”a mountain ma.s.s in the form of a meniscus lens, rising in the middle to a height of seventy-nine English miles.”[338] As this makes the moon lopsided, with the heavy side toward the earth, the question of an atmosphere, and of the moon's inhabitability is reopened; and the discussion seems to favor the man in the moon; only he keeps on the other side always, so that we can not see him.
The best astronomers have gravely calculated the most absurd problems--for instance the projection of meteorites from lunar volcanoes; Poisson calculated that they would require an initial velocity of projection of seven thousand nine hundred and ninety-five feet per second; others demanded eight thousand two hundred and eighty-two; Olbers demanded fourteen times as much; but La Place, the great inventor of the nebular theory, after thirty years' study fixed it definitely at seven thousand eight hundred and sixty-two! It appears that the absurdity of the discharging force of a part greater than the attracting force of the whole never occurred to him.[339]
This same La Place supposed, that he could have placed the moon in a much better position for giving light than she now occupies; and that this was the only object of her existence. As this was not done he argued that her waxing and waning light was a proof that she was not located by an Omniscient Creator. He says he would have placed her in the beginning in opposition to the sun, in the plane of the ecliptic, and about four times her present distance from us, with such a motion as would ever maintain that position, thus securing full moon from sunset to sunrise, without possibility of eclipse. But Lionville demonstrates that ”if the moon had occupied at the beginning the position a.s.signed her, by the ill.u.s.trious author of the _Mecanique Celeste_, she could not have maintained it but a very short time.”[340] In short, La Place's hypothetical calculations generally have proved erroneous when applied to any existing facts; and we have no reason to attach more value to his nebular theory calculations.
The sun is the princ.i.p.al orb of our system, and by far the most conspicuous, and the most observed of all observers, astronomers included. But we have seen already how contradictory their measurements of his distance, and their observations of the influence of his spots.
Far more conflicting are the theories as to his const.i.tution, of which indeed we may truly say very little was known before the application of photography and the spectroscope to heliography within the last seven years. One astronomer fixed the period of his rotation at twenty-five days, fourteen hours, and eight minutes; another at twenty-six days, forty-six minutes; another at twenty-four days, twenty-eight minutes.[341]
In regard to the sun's heat, a matter fundamental to the nebular theory, the calculations differ widely, and some of them must be grossly erroneous. M. Vicaire called the attention of the French Academy, at a recent meeting, to this unsatisfactory condition of science. Father Secchi estimates it at eighteen million Fahrenheit; while Pouillet says it ranges from two thousand six hundred and sixty-two to three thousand two hundred and one; and others range from two hundred thousand downward. The most singular thing is that these results are derived from observations or radiations made by apparatus identical in principle.[342] But Waterston calculates the temperature of the solar surface at above ten, and probably twelve million Fahrenheit.[343]
Now what feeds these enormous fires? The old opinion of astronomy, that the sun was a ma.s.s of fire, was a.s.sailed by Sir Wm. Herschel, who maintained that it was in the condition of a perpetual magnetic storm.
This notion was altered into the belief of a central dark body, surrounded by a stratum of clouds, outside of which is a photosphere of light and heat; which some made one thousand five hundred miles in depth, others four thousand. Outside of this was another layer of rose-colored clouds. To this theory Arago, Sir John Herschel and Humboldt a.s.sented. But Le Verrier declares that the facts observed during late eclipses are contrary to this theory, and a new theory is slow in process of construction, to be demolished in its turn by later observations.[344]
One of the most recent theories is that the fuel is furnished by a stream of meteorites, planetoids, and comets, falling in by the power of attraction, and being speedily converted into gas flames; a process the very reverse of the theory of the evolution of the solid celestial bodies from gas. But it is pretty evident from these conflicting theories that n.o.body knows anything certainly as to the materials of the sun, or the fuel which feeds his flames. But if the very best astronomers do not know of what he is made, is it not too great a demand upon our credulity to ask us to believe that they can tell how he was made?
The size, density, and distances of the planets, which form such essential elements in the calculations of the nebular theory of evolution, are equally uncertain. Ten or twelve years ago Mercury was believed to be nearly three times as dense as the earth (2.94); and the theory of evolution was partly based upon this a.s.sumed fact. But Hausen now finds that it is not half so dense; that, as compared with the earth, it is only 1.22; and that its ma.s.s is less than half (5/12) of what had been confidently calculated.[345] Corrections of the ma.s.ses and densities of other planets are also offered.
Still wider differences prevail in calculating the velocities of these bodies; velocities _calculated_ and found to correspond with the theory of evolution. Bianchini gives the period of the rotation of Venus at twenty-four days, eight hours; but Schroeter says it is not as many hours as Bianchini gives days; that it is only twenty-three hours and twenty minutes. Sir Wm. Herschel can not tell which is right, or whether both are wrong.[346]
From such imperfect and erroneous calculations astronomers have deduced what they called a _law_, which holds the same place in nature that the Blue Laws of Connecticut maintain in history; and which like them have imposed upon the credulous. t.i.tius and Bode imagined that they had discovered that, ”When the distances of the planets are examined, it is found that they are almost all removed from each other by distances which are in the same proportion as their magnitudes increase.” And this _law_ played an important part in introducing the theory of evolution, which, it was alleged, exactly corresponded with such an arrangement.
But more accurate calculations and recent discoveries have dissipated the supposed order of progression. Humboldt says of it, it is ”a law which scarcely deserves this name, and which is called by Lalande and Delambre a play of numbers; by others a help for the memory. * * * In reality the distances between Jupiter, Saturn, and Ura.n.u.s approximate very closely to the duplication. Nevertheless, since the discovery of Neptune, which is much too near Ura.n.u.s, the defectiveness in the progression has become strikingly evident.” And Olbers rejects it, as ”contrary to the nature of all truths which merit the name of laws; it agrees only approximately with observed facts in the case of most planets, and what does not appear to have been once observed, not at all in the case of Mercury. It is evident that the series, 4, 4+3, 4+6, 4+12, 4+48, 4+96, 4+192, with which the distances should correspond, is not a continuous series at all. The number which precedes 4+3 should not be 4; _i. e._, 4+0, but 4+3/2. Therefore between 4 and 4+3 there should be an infinite number, or as Wurm expresses it, for _n_=1, there is obtained from 4+2^{n-2}.3; not 4, but 5-1/2.”[347] Thus this so-called law is erroneous in both ends, and defective in the middle.
Finally it has been utterly abolished by the discovery of the planet Vulcan, which does not correspond to any such law.[348] If the theory of evolution then corresponds to Bode's law, as its advocates alleged, it corresponds to a myth.
About the nebulae which have played so large a part in the atheistic world building, our astronomers are utterly at variance. Sir John Herschel says they are far away beyond the stars in s.p.a.ce. But the Melbourne astronomer, M. Le Seur, suggests that the star Eta and the nebulous matter are neighbors; that the nebulous matter formerly around it, which has recently disappeared, while the star has blazed up into flames, is being absorbed and digested by the star. This has happened before, thirty years ago, to that star. Why may not our sun also absorb and burn up nebulae. But if so, what becomes of the rings of the nebular theory?
The light of the stars is almost the only medium through which we can observe them, and it would naturally be supposed that astronomers would be at pains to have clear views of light. But the most surprising differences of statement regarding it exist among the very first astronomers. They do not see it alike. Herschel says a Herculis is red; Struve says it is yellow. They dispute about its nature, motion, and quant.i.ty. Some astronomers believe the sun to be the great source of light, at least to our system. But Nasmyth informs the Royal Astronomical Society that ”the true source of latent light is not in the solar orb, but in s.p.a.ce itself, and that the grand function of the sun is to act as an agent for the bringing forth into existence the luciferous element, which element I suppose to be diffused throughout the boundless regions of s.p.a.ce.”[349] The nature of light is however still as great a mystery as when Job demanded, ”Where is the way where light dwelleth?” The undulatory theory of light, now generally accepted, a.s.sumes that light is caused by the vibrations of the ether in a plane transverse to the direction of propagation. In order to transmit motions of this kind, the parts of the luminiferous medium must resist compression and distortion, like those of an elastic solid body; its transverse elasticity being great enough to transmit one of the most powerful kinds of physical energy, with a speed in comparison with which that of the swiftest planets of our system is inappreciable, and its longitudinal elasticity immensely greater--both of these elasticities being at the same time so weak as to offer no perceptible resistance to the motion of the planets, and other visible bodies.[350]
Is the velocity of light uniform? Or, if variable, is the variation caused by the original difference of the projectile force of the different suns, stars, comets, etc.? or by the different media through which it pa.s.ses? Arago alleges that light moves more rapidly through water than through air; but Brequet a.s.serts that the fact is just the reverse.[351] Both admit that its velocity varies with the medium.