Galileo

From Walter W. Bryant's "A History of Astronomy."

Of undying fame in [physical and descriptive] astronomy was Galileo Galilei, more commonly known by his first name. Born at Florence in 1564, and educated at Venice and Pisa, he became a professor at Padua, after a brief and meagre appointment at Pisa, until induced by Cosmo de' Medici (Cosmo II.) to remove to Florence. His discoveries in mechanics were of far-reaching importance. By experiments carried out at the celebrated leaning tower of Pisa, he established the law of acceleration of falling bodies, and by observation of a swinging lamp during some long cathedral sermon he was led to the principle of the isochronism of the vibrations of a common pendulum-i.e. that a pendulum of a given length has its time of swing independent of the extent of swing, a principle which rendered immense service to astronomy by making accurate clock-driving possible. But he is chiefly celebrated for reasons of a totally different kind. The combination of a convex and a concave lens to magnify distant objects had been accidentally discovered in Holland, and Galileo heard of it, and at once set to work to try his hand with lenses in a leaden tube. He soon constructed a telescope which magnified 32 times, and turning it towards the moon, discovered the irregularity of its surface. Turning next to the planets, he discovered that Venus exhibited phases similar to those of the moon (just as Copernicus had predicted would be the case, according to his system by which Venus revolved about the sun), that Jupiter was accompanied by four moons, moving round the great planet just as our moon does round the earth, which, in compliment to Cosmo, he named the "Medicean stars," and that Saturn at times appeared like three stars joined together and at other times only one. He also was the first to record spots on the sun, and to deduce its time of rotation from their motion. These discoveries, marvellous as they must have appeared, were, of course, a necessary consequence of the invention of the telescope, which was not due to Galileo, although his particular form of telescope was worked out by himself...He was the first to suggest eclipses of Jupiter's satellites as a means for determining differences of longitude, the difference between the local time at two different stations of an instantaneous phenomenon visible at both being, of course, the difference of longitude. He also discovered the "libration" of the moon, by which, according to its position in its orbit, we sometimes see a little way round the corner, so to speak, in different parts of the moon's apparent edge. The sentences passed against him by the Inquisition on account of his so-called heretical opinions as to the motion of the earth and the similarity to it of the other planets, which Aristotle had maintained to be divine and incorruptible essences, were not strictly enforced. He was imprisoned, but his patron procured his release on condition of perpetual exile from Florence. He unfortunately became blind before his tables of Jupiter's satellites were completed, and died a few years later, in 1642.

The Discovery of Radium and Radioactivity

This account is taken from the translation of Madame Curie's lecture at the Sorbonne on November 5, 1906, to be found in the "Annual Report" of the Smithsonian Institution, volume sixty-one.

A new property of matter has been discovered which has received the name of radioactivity. Radioactivity is the property which the atoms of certain substances possess of shooting off particles, some of which have a mass comparable to that of the atoms themselves, while the others are the electrons. This property, which uranium and thorium possess in a slight degree, has led to the discovery of a new chemical element, radium, whose radioactivity is very great. Among the particles expelled by radium are some which are ejected with great velocity, and their expulsion is accompanied with a considerable evolution of heat. A radioactive body constitutes then, a source of

energy.

According to the theory which best accounts for the phenomena of radioactivity, a certain proportion of the atoms of a radioactive body is transformed in a given time, with the production of atoms of less atomic weight, and in some cases with the expulsion of electrons. This is a theory of the transmutation of elements, but differs from the dreams of the alchemists in that we declare ourselves, for the present at least, unable to induce or influence the transmutation. Certain facts go to show that radioactiviy appertains in a slight degree to all kinds of matter. It may be, therefore, that matter is far from being as unchangeable or inert as it was formerly thought; and is, on the contrary, in continual transformation, although this transformation escapes our notice by its relative slowness...

Among the radioactive elements, some appear to be permanently active (uranium, thorium, radium, actinium) while others lose their radioactivity little by little (polonium). The most powerful representative of the permanently radioactive substances is radium. According to the theory of transformation this substance changes very slowly, so that a given mass of radium would lose half its weight only in several thousand years. Consequently the quantity of radium which disappears from a gram of this substance in an hour is absolutely inaccessible to experiments. However, a gram of radium disengages each hour about 100 calories of heat. To conceive how enormous this disengagement of heat is, we remark that during the life attributable to radium the complete transformation of a gram of this substance would produce as much heat as the combustion of a ton of coal. The transformation of radium, then, if transformation there be, is not to be regarded as an ordinary chemical reaction, for the quantity of heat involved is of a far higher order. One is led to conceive, rather, that the

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atoms themselves are transformed, for the quantities of energy put in play in the formation of atoms are probably considerable.

Indeed, the phenomena of radioactivity has a palpably atomic character which was brought to light in the beginning of researches on the subject. It was precisely the absolute conviction that we were dealing with an atomic phenomenon which led M. Curie and me to the discovery of radium. If the radioactivity can not be separated from the atom it is very difficult to conceive anything but the atom itself involved in the transformation.

The effects produced by radium are very powerful considering how small is the quantity of this substance at disposal for experiments. There is a spontaneous and continous emission of rays, analogous to those which we know are produced by means of an induction coil in a Crookes tube, and these rays produce ionization of gas in the same manner. They are able, for example, to produce the rapid discharge of an electroscope. The energy of the rays is so great that the discharge is produced even across a thick metallic screen, for the rays can traverse such a screen...

The energy of the rays of radium is also manifested by their capacity for exciting the luminosity of various phosphorescent substances. Radium salts are, indeed, themselves luminous, and the light is readily visible in certain conditions.

A Misstatement

The misstatements which appear in print would fill volumes, libraries of volumes, in fact, and are in most cases to be relegated to the large class of things in the world which are regrettable but unimportant. Sometimes, however, such misstatements are so ludicrously far from the truth that one wonders why the author does not ascertain at least the fundamental basis of fact even if he does not care about exactness of detail. Of the latter class of misstatements is the one in Upton Sinclair's "The Brass Check" which says that the Pittsburgh library has barred Jack London's books from its shelves. Nothing more than a glance at the shelves, or for that matter, at the printed catalogues of this library, is necessary to show that the Pittsburgh library has for circulation many of London's books.

Let us hope that Mr. Sinclair's statements are not always so unreliable as this would lead one to suppose.

A New Gift Fund

The Pittsburgh section of the American Chemical Society recently turned over to the Carnegie Library of Pittsburgh two thousand dollars which has been given by various industrial firms as the initial installment of a fund which the society is raising for use in extending the resources of the Technology Department of the Library. The contributions to the fund are due largely to the disinterested testimony of the society as to the value of the Technology Department to the industries.

The fact that Pittsburgh is an industrial center was responsible in the first place for the establishing of the Technology Department, and makes imperative its maintenance to meet the rapidly expanding needs and demands of the industries and their workers, so that the source of the gift, as well as its purpose, seems particularly appropriate.

The gift makes possible an immediate increase in the usefulness of the department by allowing a more extensive purchase of scientific literature than would otherwise be possible at the present time when the cost of all books, and especially of technical books, has increased so materially.

The Library already has a few funds for the purchase of books on special subjects; among them the Bernd Fund for books on architecture, the Schwartz Fund for books on ethics, the Stuart Fund for books on single tax, and four funds given by Mr. Charles C. Mellor for books for children, books relating to history, books on biography, and books relating to woman. These have proved very valuable and have made possible the building up of more extensive collections on their subjects than could otherwise have been made available. It is hoped that the number and scope of special funds will increase so that they will cover many subjects and interests. At the present time, however, no gift could be more welcome to the Library, nor more fitted to its needs, than this one for the Technology Department.

The public spirited attitude of the society which is raising the fund will meet with the approval of both those who are interested in making information available to everyone who needs it, and those who depend upon the Library to supply their needs.

Vacation Book Privileges

Beginning with the first of June, regular borrowers may take books out of town for the summer on the following conditions:

Not more than ten books may be issued on one card. Four of these may be fiction.

Books will be stamped due October 1, 1921, from which date a fine of two cents a day will accrue on each. The books may be returned at any time before the first of October.

Any transportation charges on books returned must be prepaid.

Borrowers will be asked to give their out of town addresses and their cards will be held at the Library.

The Library reserves the right to refuse to lend by this method any books which it seems unwise to take out of general circulation for so long a time.

New Publications of the Library

Carnegie Institute and Carnegie Library of Pittsburgh

The first edition of the handbook "Carnegie Institute and Carnegie Library of Pittsburgh" was exhausted within a few months of the time it was issued. A second edition, slightly revised, has recently taken its place. On account of the increased cost of production, it has been necessary to raise the price on this edition to thirty-five cents; postpaid, forty cents.

Periodicals and Other Serials

The eighth edition of the list "Periodicals and Other Serials Currently Received by the Carnegie Library of Pittsburgh" is off the press and may be obtained free at the Library, or by mail for five cents.