Science.

Poverty Bay Standard, Volume X, Issue 1193, 4 November 1882, Page 4 (Supplement)

Science.

AN INTERSTELLAR RESISTING MEDIUM. 0. Buckland recently made a brief report to the St. Petersburg Academy, on his investigation of the hypothesis of a resisting medium in space, from which the Naturforschcr extracts the following: Encke’s hypothesis of a medium filling interstellar space, has met with no serious opposition from scientific men. Encke himself thought that it received strong confirmation from the theory of the comet that also bears his name. Asten, who has continued the theory of the comets since 1848, advocated Encke’s hypothesis, and believed that his results offered a still stronger proof of the correctness of the hypothesis. Encke first found that the periodic time of the comet referred to, decreased by time proportional to the square of the time, and he proposed this hypothesis. Interstellar (or interplanetary) space is filled with some substance that gravitates toward the sun, and its density decreases inversely as the square of the distance ; it therefore offers resistance to the motion of the heavenly bodies, which is proportional to the square of their velocity. It can be proven

mathematically that such a medium must cause secular as well as periodical disturbances in their mean motions and eccentricity, but only a periodical one in the length of the perihelion. The period of the periodical disturbance agrees with the orbit, but such a medium has no effect ’on the inclination of the orbit or on the nodes.

Since Encke only took strictly into account the disturbance that took place in its mean motion, and did not investigate the periodical members of this disturbance, the theory of the comet named after him afforded no proof of the correctness of the hypothesis ; for, if we are to adhere to the existence of a resisting medium, an infinite number of suppositions can be made concerning the properties of this medium, all of which shall fulfil the requirements mentioned. An essential limitation of the possible number of hypotheses has been established by Asten’s investigation, inasmuch as he inde-

pendently deduced the secular disturbance in its mean motion, and eccentricity from the observations. The results of my investigations regarding this resisting medium are of a negative character, and can be summarised as follows: As yet the treatment of the theory of Encke’s comet has really proved nothing regarding the existence of a resisting medium in space. If anyone should succeed, on any hypothesis whatever, in explaining the increased mean motion, and the decreased eccentricity, during the interval between 1319 and 1848, so simple a hppothesis will not suffice to explain the course of the comet of 1865, inasmuch as the mean motion has very probably changed since that time. After the phenomena from 1865 to 1881 have been fully worked out, and their relation to former phenomena ascertained, it will probably be impossible to find out the nature of the hitherto unknown forces acting upon comets. —(Scientific American.)