All sciences are making an advance, but Astronomy is moving at high speed. Since the principles of this science were settled by Copernicus, four hundred years ago, it has never had to beat a retreat. It is rewritten not to correct material errors, but to incorporate new discoveries.
At one time, Astronomy studied mostly tides, seasons, and telescopic aspects of the planets; now these are only primary matters. Once it considered stars as mere fixed points of light; now it studies them as suns, determines their age, size, color, movements, chemical constitution, and the revolution of their planets. Once it considered space as empty; now it knows that every cubic inch of it quivers with greater intensity of force than that which is visible in Niagara.
Every inch of surface that can be conceived of between suns is more wavetossed than the ocean in a storm.
The invention of the telescope constituted one era in Astronomy; its perfection in our day, another; and the discoveries of the spectroscope a third—no less important than either of the others. New discoveries are made every day with the advancement of telescopes.
The Hubble space telescope has let man see further into the universe then ever before. Astronomy and space science is an ever changing study, and possibly the most exciting of the sciences. It is for one reason that this course was written, to hopefully interest more people in the exciting study of the universe around us.