Page:Collier's New Encyclopedia v. 02.djvu/23

LEFT BETEL 9 BETELGETTSE allegories they contained, no less than as handbooks of zoological facts. The oldest Latin bestiaries had an early Greek original, the well known "Physiologus," under which name about 50 such al- legories were grouped. The Greek text of this famous work is found only in manuscript. There are old Syriac, Ar- menian, Ethiopic, Arabic, Icelandic, and numerous Latin versions. Editions of the Latin have been issued — Mai, Heider, and Cahier. An Old High German version was made earlier than the 11th century; in the 12th century, versions in French were made by Philippe de Thaun and Guillaume, a priest of Normandy. The "Bestiary of Love" of Richard de Fourni- val was rather a parody upon the ealier form of such books. BETEL, or BETLE, the English name of the piper betle, a shrubby plant with evergreen leaves, belonging to the typical genus of the order piperacess (pepperworts). It is extensively culti- vated in the East Indies. Its leaf is used as a wrapper to inclose a few slices of the areca palm nut with a little shell lime. The southern Asiatics are per- petually chewing it to sweeten the breath, to strengthen the stomach, and, if hunger be present, to deaden its cravings. It is called pan, or pan sooparee, BETELGEUSE, the name given to a fixed star of the Orion constellation, also known as the Alpha Orionis, whose diam- eter, according to measurements made by Professor Albert A. Michelson, of Chi- cago University, is slightly more than three hundred times that of the sun, and nearly as large as that of the orbit of the planet Mars. Professor Michelson, in 1920, by means of a device for determin- ing the actual diametrical size of a star, calculated that of Betelgeuse to be 260,- 000,000 miles. Compared with the sun in volume, this makes it 27,000,000 times as great, and if it could be placed as near to the earth as the sun, the planet would embrace the entire visible heavens. It is computed that it would take trillions of globes like the earth to equal Betelgeuse in size. The distance of this star from the earth is perhaps 150 "light" years, that is, the light which strikes the eye in looking up at Betelgeuse started on its journey from the star at the rate of 186,- 000 miles a second 150 years ago (from 1920). By Professor Michelson's device, it is believed that measurements of planets lost in space with invisible disks can be accurately determined with the aid of a simple formula. Astronomers incline to the opinion that other fixed stars, seem- ingly small by reason of their distance from the earth, are also vastly larger than the sun. The dimension created to Betelgeuse, indeed, presents the concep- tion of celestial bodies of magnitudes hitherto unmeasured and almost beyond comprehension. The size of Betelgeuse was determined by combining its approximate distance from the earth, which was known, and its angular diameter, which had to be ascer- tained by Professor Michelson. Angu- lar diameter is not the same as real or linear diameter. In the case of a star it has to be known before the real diam- eter can be calculated. The angular diameter of any object (say a house) varies according to the distance from which it is viewed; the real or linear diameter remains the same, no matter at what varying distances a spectator sees it. Only the angular diameter (or the apparent diameter) is changed by the spectator changing his distance, and the farther off he stands the smaller the angular diameter becomes. The distance of Betelgeuse from the earth is approxi- mately 1,070 trillion miles, from which dim point in the firmament is showed an angular diameter of 0.046 seconds, i. e., 46/1,000 of a second of arc, or, say, for round numbers, 1/20 of a second. The magnitude of this exceedingly small an- gle can be appreciated by the fact that it is roughly equal to that which would be shown by a pinhead at a distance of more than a thousand miles. To put an angular diameter of 1/20 of a second into miles, Professor Michelson had to combine it with the known distance of the star in miles, remembering that since an angular diameter of one second cor- responds to a distance of 206,000 times the actual or linear distance of the ob- ject, an angular diameter of only 1/20 of a second must correspond to a distance of about 4,120,000 times the object's real diameter. The actual diameter of Betel- geuse was thus found to be approximately 260,000,000 miles by dividing the 1,070 trillions (the star's distance) by 4,120,- 000, This measurement could not be made by direct observation. The small- ness of the star's image not only ren- dered such a measurement impracticable, but such effects as irradiation and twin- kling obscured the star's definition and blended the edge of the image with the diffraction rings surrounding it. These obstacles have been overcome by the use of the "interferometer," a device whose feature is parallel and movable slits of known distances separating them in a screen covering the viewing lens. By manipulating the slits the star's light becomes shed of the fringes, or inter- ference bands, which appear when the instrument is focused on the star. As the slits are moved apart the fringes