does not appear to rotate
as a whole, so this time of rotating varies by as much as two days if we
consider a region on the sun's equator or at a distance from it of 45 deg..
The intensity of sunlight at the surface of the sun is about 190,000
times that of a candle-flame, and the effective temperature of the solar
surface is eight or ten thousand degrees centigrade.

Such are some of the facts about the sun that are received, or, as it
would be technically expressed, "adopted" to-day. Doubtless a very few
years will find them altered and rendered more accurate as observations
accumulate. In a few hundred years, knowledge of the constitution of the
sun may have so increased that these data and suggestions may seem so
erroneous as to be absurd. It is little more than a century since one of
the greatest of astronomers, Sir William Herschel, contended that the
central globe of the sun might be a habitable world, sheltered from the
blazing photosphere by a layer of cool non-luminous clouds. Such an
hypothesis was not incompatible with what was then known of the
constitution of the heavenly bodies, though it is incompatible with what
we know now. It was simply a matter on which more evidence was to be
accumulated, and the holding of such a view does not, and did not,
detract from the scientific status of Sir William Herschel.

The hypotheses of science require continual restatement in the light of
new evidence, and, as to the weight and interpretation to be given to
such evidence, there is continual conflict--if it may so be
called--between the old and the new science, between the science that is
established and the science that is being established. It is by this
conflict that knowledge is rendered sure.

Such a conflict took place rather more than 300 years ago at the opening
of the Modern Era of astronomy. It was a conflict between two schools of
science--between the disciples of Aristotle and Claudius Ptolemy on the
one hand and the disciples of Copernicus on the other. It has often been
represented as a conflict between religion and science, whereas that
which happened was that the representatives of the older school of
science made use of the powers of the Church to persecute the newer
school as represented by Galileo. That persecution was no doubt a
flagrant abuse of authority, but it should be impossible at the present
day for any one to claim a theological standing for either theory,
whether Copernican or Ptolema