Myths and Marvels of Astronomy
planets revolving round the sun, and a contest arose for the possession
of these mythical planets. Tarde maintained that they should be called
_Astra Borbonia_, in honour of the royal family of France; but C.
Malapert insisted that they should be called _Sidera Austriaca_.
Meantime the outside world laughed at the spots, and their names, and
the astronomers who were thought to have invented both. 'Fabritius puts
only three spots,' wrote Burton in his 'Anatomy of Melancholy,' 'and
those in the sun; Apelles 15, and those without the sun, floating like
the Cyanean Isles in the Euxine Sea. Tarde the Frenchman hath observed
33, and those neither spots nor clouds as Galileus supposed, but planets
concentric with the sun, and not far from him, with regular motions.
Christopher Schemer' [a significant way of spelling Scheiner's name], 'a
German Suisser Jesuit, divides them _in maculas et faculas_, and will
have them to be fixed _in solis superficie_ and to absolve their
periodical and regular motions in 27 or 28 dayes; holding withall the
rotation of the sun upon his centre, and are all so confident that they
have made schemes and tables of their motions. The Hollander censures
all; and thus they disagree among themselves, old and new,
irreconcilable in their opinions; thus Aristarchus, thus Hipparchus,
thus Ptolomaeus, thus Albategnius, etc., with their followers, vary and
determine of these celestial orbs and bodies; and so whilst these men
contend about the sun and moon, like the philosophers in Lucian, it is
to be feared the sun and moon will hide themselves, and be as much
offended as she was with those, and send another message to Jupiter, by
some new-fangled Icaromenippus, to make an end of all these curious
controversies, and scatter them abroad.'
It is well to notice how in this, as in many other instances, the very
circumstance which makes scientific research trustworthy caused the
unscientific to entertain doubt. If men of science were to arrange
beforehand with each other what observations they should publish, how
their accounts should be ended, what theories they would endeavour to
establish, their results would seem far more trustworthy, their theories
far more probable, than according to the method actually adopted.
Science, which should be exact, seems altogether inexact, because one
observer seems to obtain one result, another a different result.
Scientific theories seem unworthy of reliance because scientific men
entertain for a long time rival doctrines. But in another and a worthier
sense than as the words are used in the 'Critic,' when men of science do
agree their agreement is wonderful. It _is_ wonderful, worthy of all
admiration, because before it has been attained errors long entertained
have had to be honestly admitted; because the taunt of inconsistency is
not more pleasant to the student of science than to others, and the man
who having a long time held one doctrine adopts and enforces another
(one perhaps which he had long resisted), is sure to be accused by the
many of inconsistency, the truly scientific nature of his procedure
being only recognised by the few. The agreement of men of science ought
to be regarded also as most significant in another sense. So long as
there is room for refusing to admit an important theory advanced by a
student of science, it is natural that other students of science should
refuse to do so; for in admitting the new theory they are awarding the
palm to a rival. In strict principle, of course, this consideration
ought to have no influence whatever; as a matter of fact, however, men
of science, being always men and not necessarily strengthened by
scientific labours against the faults of humanity, the consideration has
and must always have influence. Therefore, when the fellow-writers and
rivals of Newton or of his followers gave in their adhesion to the
Newtonian theory; when in our own time--but let us leave our own time
alone, in this respect--when, speaking generally, a novel doctrine, or
some new generalisation, or some great and startling discovery, is
admitted by rival students of the branch of astronomy to which it
belongs, the probability is great that the weight of evidence has been
found altogether overwhelming.
Let us now, however, turn to cases in which, while many observations
seem to point to some result, it has appeared that, after all, those
observations must have been illusory.
A striking instance in point is found in the perplexing history of the
supposed satellite of Venus.
On January 25, 1672, the celebrated astronomer, J.D. Cassini saw a
crescent shaped and posited like Venus, but smaller, on the western side
of the planet. More than fourteen years later, he saw a crescent east of
the planet. The object continued visible in the latter case for half an
hour, when the approach of daylight obliterated the planet and this
phantom moon from view. The apparent distance of the moon from Venus was
in both cases small, viz., only one diameter of the planet in the former
case, and only three-fifths of that diameter in the latter.
Next, on October 23, 1740, old style, the optician Short, who had had
considerable experience in observation, saw a small star perfectly
defined but less luminous than Venus, at a distance from the planet
equal to about one-third of the apparent diameter of our moon. This is a
long distance, and would correspond to a distance from Venus certainly
not less than the moon's distance from the earth. Short was aware of the
risk of optical illusion in such matters, and therefore observed Venus
with a second telescope; he also used four eye-pieces of different
magnifying power. He says that Venus was very distinct, the air very
pure, insomuch that he was able to use a power of 240. The seeming moon
had a diameter less than a third of Venus's, and showed the same phase
as the planet. Its disc was exceedingly well defined. He observed it
several times during a period of about one hour.
Still more convincing, to all appearance, is the account of the
observations made by M. Montaigne, as presented to the Academy of
Sciences at Paris by M. Baudouin in 1761. The transit of Venus which was
to take place on June 6 in that year led to some inquiry as to the
satellite supposed to have been seen by Cassini and Short, for of course
a transit would be a favourable occasion for observing the satellite. M.
Montaigne, who had no faith in the existence of such an attendant, was
persuaded to look for it early in 1761. On May 3 he saw a little
crescent moon about twenty minutes of arc (nearly two-thirds the
apparent diameter of our moon) from the planet. He repeated his
observation several times that night, always seeing the small body, but
not quite certain, despite its crescent shape, whether it might not be a
small star. On the next evening, and again on May 7 and 10, he saw the
small companion apparently somewhat farther from Venus and in a
different position. He found that it could be seen when Venus was not in
the field of view. The following remarks were made respecting these
observations in a French work, 'Dictionnaire de Physique,' published in
1789:--'The year 1761 will be celebrated in astronomy in consequence of
the discovery that was made on May 3 of a satellite circulating round
Venus. We owe it to M. Montaigne, member of the Society of Limoges. M.
Baudouin read before the Academy of Sciences at Paris a very interesting
memoir, in which he gave a determination of the revolution and distance
of the satellite. From the calculations of this expert astronomer we
learn that the new star has a diameter about one-fourth that of Venus,
is distant from Venus almost as far as the moon from our earth, has a
period of nine days seven hours' [much too short, by the way, to be
true, expert though M. Baudouin is said to have been], 'and its
ascending node'--but we need not trouble ourselves about its ascending
node.
Three years later Roedkier, at Copenhagen, March 3 and 4, 1764, saw the
satellite of Venus with a refracting telescope 38 feet long, which
should have been effective if longitude has any virtue. He could not see
the satellite with another telescope which he tried. But several of his
friends saw it with the long telescope. Amongst others, Horrebow,
Professor of Astronomy, saw the satellite on March 10 and 11, after
taking several precautions to prevent optical illusion. A few days later
Montbaron, at Auxerre, who had heard nothing of these observations, saw
a satellite, and again on March 28 and 29 it appeared, always in a
different position.
It should be added that Scheuten asserted that during the transit of
1761 Venus was accompanied by a small satellite in her motion across the
sun's face.
So confidently did many believe in this satellite of Venus that
Frederick the Great, who for some reason imagined that he was entitled
to dispose as he pleased of the newly discovered body, proposed to
assign it away to the mathematician D'Alembert, who excused himself from
accepting the questionable honour in the following terms:--
'Your Majesty does me too much honour in wishing to baptize this new
planet with my name. I am neither great enough to become the satellite
of Venus in the heavens, nor well enough (_assez bien portant_) to be so
on the earth, and I am too well content with the small place I occupy in
this lower world to be ambitious of a place in the firmament.'
It is not at all easy to explain how this phantom satellite came to be
seen. Father Hell, of Vienna--the same astronomer whom Sir G. Airy
suspects of falling asleep during the progress of the transit of Venus
in 1769--made some experiments showing how a false image of the planet
might be seen beside the true one, the false image being smaller and
fainter, like the moons seen by Schort (as Hell called Short), Cassini,
and the rest. And more recently Sir David Brewster stated that Wargentin
'had in his possession a good achromatic telescope, which always showed
Venus with such a satellite.' But Hell admitted that the falsehood of
the unreal Venus was easily detected, and Brewster adds to his account
of Wargentin's phantom moon, that 'the deception was discovered by
turning the telescope about its axis.' As Admiral Smyth well remarks, to
endeavour to explain away in this manner the observations made by
Cassini and Short 'must be a mere pleasantry, for it is impossible such
accurate observers could have been deceived by so gross a neglect.'
Smyth, by the way, was a believer in the moon of Venus. 'The contested
satellite is perhaps extremely minute,' he says, 'while some parts of
its body may be less capable of reflecting light than others; and when
the splendour of its primary and our inconvenient station for watching
it are considered, it must be conceded that, however slight the hope may
be, search ought not to be relinquished.'
Setting aside Scheuten's asserted recognition of a dark body near Venus
during the transit of 1761, Venus has always appeared without any
attendant when in transit. As no one else claimed to have seen what
Scheuten saw in 1761, though the transit was observed by hundreds, of
whom many used far finer telescopes than he, we must consider that he
allowed his imagination to deceive him. During the transit of 1769, and
again on December 8-9, 1874, Venus certainly had no companion during her
transit.
What, then, was it that Cassini, Short, Montaigne, and the rest supposed
they saw? The idea has been thrown out by Mr. Webb that mirage caused
the illusion. But he appears to have overlooked the fact that though an
image of Venus formed by mirage would be fainter than the planet, it
would not be smaller. It might, according to the circumstances, be above
Venus or below, or even somewhat towards either side, and it might be