National Geographic : 1925 Jan
INTERVIEWING TIIE STARS 107 orbit to another creates waves in the ether, and the length of the waves depends on the length of the hops. The shortest jumps are apparently most frequent, and the longest most rare. As the waves engendered by these hops come into the spectroscope, it classifies them, each class making its own particular line. In this way each line in the spectrum of hydrogen is a summary of all the orbital hops of a given type occurring in the atoms from which the light comes. The frequent jumps make the clear lines and the rare ones give the faint lines. Heat, magnetism, pressure, and other things affect the orbital behavior of the electrons. In the explosion of calcium with his giant transformer, Dr. Anderson got 8oo new lines, showing that its elec trons exhibited hundreds of new kinds of orbital behavior under the fierce punish ment to which he subjected the calcium atoms. A PROBE THAT SOLVES THE MYSTERY OF TIHE COMPOSITION OF STARS Having seen what causes the lines in the spectroscope, let us see how the astron omer makes use of them in interviewing the stars. Every element has its own particular .... group of lines, and no bank cashier or United States Treasurer ever had a signa ture more certainly his own than each ele ment writes in the spectroscope. So when an astronomer finds a given set of lines in a star he knows that the element whose signature those lines con stitute is found there. When a hitherto unknown group of lines appears, he knows that a new element has been found, as in the case of helium. Therefore, hitching his spectroscope to his telescope, the astronomer gets a Brob dingnagian probe with which he can reach out through the vast stretches of space and not only lay bare the materials of which the well-nigh infinitely remote stars and nebule are made, but even many of the conditions with which they are sur rounded. Photograph from Mt. Wilson Observatory Everyone has noticed in traveling on a TOWER TELESCOPE USEDI) AT MT. WILSON double-track railroad and passing a train TO STUDY TIE SUN running in the opposite direction that the pitch of the sound of the bell of the pass- \Vith this 15o-foot tower and a 75-foot well beneath, the sunspots and the great flames, or ing locomotive goes from high to low as prominences, on the edge of the sun are made the train changes from an approaching to to tell their story.