What more convincing than the epicyclic theory of Ptolemy, buttressed by figures so ingenious and convincing, that the theory might have lasted till now except for the truer understanding of planetary movements in relation to that of the Earth? All through this history are found traces of the barriers erected by prejudiced conservatives, of which the attitude of Tycho Brahe is a good example, though in this case it was probably his belief in the Hebraic conception of the universe which excited his opposition to Kepler's views, a conception which, unfortunately for the progress of astronomical research, still lingers among certain observers to-day and places them in precisely the same category with Tycho Brahe. With the gradual accumulation of knowledge it was found that of all the innumerable illuminated bodies in the heavens, only one,--just one,--the Moon, revolved around the Earth, and that the Earth instead of being all dominant in the affairs of the universe, played a very minor part, and, instead of being master, was a very humble midget revolving around the Sun; that, indeed, with the exception of the Moon, there were visible to the naked eye only three bright points of light in the whole range of the heavens more insignificant in size,--Mercury, Venus, and Mars,--while the other planets were vastly larger, and had many more satellites revolving around them. Then it was found that, with the exception of the few planets, the myriad stars had no connection with the Sun whatsoever, that the Sun was no longer the centre of a great universe. Later it was discovered through spectroscopic analysis that all the myriad of stars were composed of chemical elements similar to our Sun. Here, then, was the startling revelation that our Sun was simply a star, and that the stars represented a "universe of Suns," and, if we could get near any one star of the millions that sparkle in the heavens telescopically, we should see it as a round ball emitting light and heat. It was perhaps humiliating to find that our Sun was so insignificant in size that from Sirius, for example, it could not be seen with the naked eye, so small indeed that in the close companionship of other stars it would be swallowed up by their greater size and brilliancy.