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Page 35
At the close of the eighteenth century, mankind were acquainted with
all the major planets except Neptune. Uranus, the last of the group,
was discovered by the Elder Herschel, on the night of the thirteenth
of March, 1781. True, this planet had been seen on twenty different
occasions, by other observers; but its character had not been
revealed. Sir William called his new world Georgium Sidus, that is,
the George Star, in honor of the King of England. The world, however,
had too much intelligence to allow the transfer of the name of George
III. from earth to heaven. Such nomenclature would have been unpopular
in America! The name of the king was happily destined to remain a part
of terrestrial history!
For a while it was insisted by astronomers and the world at large that
the new globe, then supposed to bound the solar system on its outer
circumference, should be called Herschel, in honor of its discoverer.
But the old system of naming the planets after the deities of
classical and pagan mythology prevailed; and to the names of Mercury,
Venus, Mars, Jupiter, Saturn, was now added the name Uranus, that is,
in the language of the Greeks, _Heaven_.
Piazzi, scanning the zodiac from his observatory in Palermo, in the
early hours of that first night of the century, noticed a hitherto
unobserved star, which under higher power proved to be a planet. It
presented a small irregular disc, and a few additional observations
showed that it was progressing in the usual manner from west to east.
For some time such a revelation had been expected; but the result did
not answer to expectation in one particular; for the new body seemed
to be too insignificant to be called a world. It appeared rather to be
a great planetary boulder, as if our Mount Shasta had been wrenched
from the earth and flung into space. Investigation showed that the new
body was more than a hundred miles in diameter; but this, according to
planetary estimation, is only the measurement of a clod.
There had been, as we say, expectation of a discovery in the region
where the first asteroid was found. Kepler had declared his belief
that in this region of space a new world might be discovered.
Following this suggestion, the German astronomer Olbers, of Bremen,
had formed an association of twenty-four observers in different parts
of Europe, who should divide among themselves the zodiacal band, and
begin a system of independent scrutiny, either to verify or disprove
Kepler's hypothesis.
There was another reason also of no small influence tending to the
same end. Johann Elert Bode, another German astronomer, born in 1747
and living to 1826, had propounded a mathematical formula known as
Bode's Law, which led those who accepted it to the belief that a
planet would be found in what is now known as the asteroidal space.
Bode's Law, so-called, seems to be no real law of planetary
distribution; and yet the coincidences which are found under the
application of the law are such as to arouse our interest if not to
produce a conviction of the truth of the principle involved. Here,
then, is the mathematical formula, which is known as Bode's Law:
Write from left to right a row of 4's and under these, beginning with
the second 4, place a geometrical series beginning with 3 and
increasing by the ratio of 2; add the two columns together, and we
have a series running 4, 7, 10, etc.; and this row of results has an
astonishing coincidence, or approximate coincidence with the relative
distances of the planets from the sun--thus:
4 4 4 4 4 4 4 4 4
3 6 12 24 48 96 192 384
-- -- -- -- -- -- --- --- ---
4 7 10 16 28 52 100 196 388
The near agreement of this row of results with the row containing the
_actual_ relative distances of the planets from the sun may well
astonish, not only the astronomer, but the common reader. Those
distances--making 10 to represent the distance of the earth--are as
follows:
Mercury, 3.9; Venus, 7.2; Earth, 10; Mars, 15.2; Asteroids, 27.4;
Jupiter, 52; Saturn, 95.4; Uranus, 192; Neptune, 300.
In addition to Kepler's prediction and the indications of Bode's Law,
there was a _general_ reason for thinking that a planetary body of
some kind should occupy the space between the orbits of Mars and
Jupiter. The mean distance of Mars from the sun is about 141,500,000
miles; that of Jupiter, is about 483,000,000 miles. The distance from
one orbit to the other is therefore about 341,500,000 miles. Conceive
of an infinite sheet of tin. Mark thereon a centre for the sun.
Measure out a hundred and forty millions of miles, and with that
radius strike a circle. From the same centre measure out four hundred
and eighty-three millions of miles, and with that radius strike a
circle. Cut out the sheet between the two circles, and the vast space
left void will indicate the vacant area in the mighty disc of our
solar system. That this space should be occupied with _something_
accords with the plan of nature and the skill of the Builder.
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