In 1835 a French philosopher, Auguste Comte, considered the limits of human knowledge. In his book Positive Philosophy, Comte wrote of the stars,
``Any research that cannot be reduced to actual visual observation is excluded where the stars are concerned...We can see the possibility of determining their forms, their distances, their magnitudes, and their movements, but it is inconceivable that we should ever be able to study, by any means whatsoever, their chemical or mineralogical structure...''
Well, little did Mr. Comte know that 33 years earlier William Wollaston had discovered a number of ``spectral lines'' in the spectrum of the Sun. By 1814 Joseph Frauenhofer had catalogued 475 of these dark lines in the solar spectrum, and had identified one such line belonging to the element sodium. By 1860 Robert Bunsen and Gustav Kirchhoff had identified most of the dark lines, or absorption lines, in the Sun's spectrum with their elemental origin. Throughout the second half of the 19th century, William Huggins identified the spectral lines in other stars, as well as the gaseous ``nebulae'' - demonstrating that the celestial objects were composed of the same elements as found on Earth. Today, astronomers regularly identify and quantitatively measure the abundances of the elements in stars and gas clouds throughout the observable universe. You can throw in planets, moons, asteroids, and comets in our own Solar System for good measure.
Every so often somebody writes a book either declaring
what we cannot ever know or that we now know all there is to know. Both
are soon shown to be wrong. Science is progressive and incomplete by its
very nature. It can never become static or complete. Ponder that for a
thanks for your interest,