问答题
Much has been made of the 400th anniversary this
year of Galileo pointing a telescope at the moon and jotting down what he saw.
But 2009 is also the 400th anniversary of the publication by Johannes Kepler, a
German mathematician and astronomer, of "Astronomia Nova". {{U}} {{U}}
1 {{/U}} {{/U}}{{U}}This was a book that contained an account of his
discovery of how the planets move around the sun, correcting Copernicus's own
more famous but incorrectly formulated description of the solar system.{{/U}} And
it established the laws for planetary motion on which Isaac Newton based his
work. Four centuries ago the received wisdom was that of
Aristotle, who asserted that the Earth was the centre of the universe, and that
it was encircled by the spheres of the moon, the sun, the planets and the stars
beyond them. Copernicus had noticed inconsistencies in this theory and had
placed the san at the centre, with the Earth and the other planets travelling
around the sun. {{U}} {{U}} 2 {{/U}}
{{/U}}{{U}}Some six decades later when Kepler tackled the motion of Mars, he
proposed a number of geometric models, checking his results against the position
of the planet as recorded by his boss{{/U}}. Kepler repeatedly found that his
model failed to predict the correct position of the planet. He altered it and,
in so doing, created first egg-shaped "orbits" and, finally, an ellipse (椭圆)
with the sun placed at one focus. {{U}} {{U}} 3 {{/U}}
{{/U}}{{U}}Kepler went on to show that an elliptical orbit is sufficient to explain
the movement of the other planets and to devise the laws of planetary, motion
that Newton built on.{{/U}} A.E.L. Davis this week told
astronomers and historians that it was the rotation of the sun that provide
Kepler with what he thought was one of the causes of the planetary motion that
his laws described, although his reasoning would today be considered entirely
wrong. {{U}} {{U}} 4 {{/U}} {{/U}}{{U}}In 1609
astronomy and astrology were seen as intimately related; mathematics and natural
philosophy, meanwhile, were quite separate areas of endeavor; however, Kepler
sought physical mechanisms to explain his mathematical result.{{/U}} He wanted to
know how it could be that the planets orbited the sun. {{U}} {{U}}
5 {{/U}} {{/U}}{{U}}Once he learned that the sun rotated, he comforted
himself with the thought that the sun's rays must somehow sweep the planets
around it while some magnetism accounted for the exact elliptical path.{{/U}} As
today's astronomers struggle to determine whether they can learn from the past,
Kepler's tale provides a salutary reminder that only some explanations stand the
test of time.