Helping San Diego, California and beyond since 1997.
Do you need
volunteer, community service, work, military or court hours?
|
|
Helping San Diego, California and beyond since 1997.
|
|
Click here and add this page to your favorites!
|
Encyclopedia Britannica - Main :: ARN-AUD |
|
|
ASTROPHYSICS , the branch of astronomical science which treats of the physical constitution of the heavenly bodies. So long as these bodies could be known to men only as points or disks of light in the sky, no such science was possible. Even later, when the telescope was the only instrument of research, knowledge on this subject was confined to the appearances presented by the planets, supplemented by more or less probable inferences as to the nature of their surfaces. When, in the third quarter of the loth century, spectrum analysis was applied to the light coming to us from the heavenly bodies, a new era in astronomical science was,opened up of such importance that the body
auxiliary
work
recent
, astronomical science, to the combination of the processes involved in the three arts of spectroscopy, photography and photometry. The most general conclusions reached by this combination may be summed up as follows: I. The heavenly bodies are composed of like matter with that which we find to make up our globe. The sun and stars are found to contain the more important elements with . which chemistry has made: us acquainted. , Iron, calcium and hydrogen may be especially mentioned as three familiar chemical elements which enter largely into the constitution of all the matter of the heavens. It would be going too far to say that all the elements known to us exist. in the sun or 'the s-tars;- nor is the question whether the rarer ones can or cannot be found there of prime importance. The general fact of identity in the main constituents is the one of most fundamental importance. ` It would be going too far in the other direction' to claim that all the elements which compose the heavenly bodies are found on the earth. There are many lines in the spectra of the stars, as well as of the nebulae, which are not certainly identified with those belonging to any elements known to our chemistry. The recent
element
2. The second conclusion is that, as ageneral rule, the incandescent heavenly bodies are not masses of solid or liquid matter as formerly assumed, but mainly masses either of gas, or of substances gaseous in their- nature, so compressed by the gravitation of their superincumbent parts toward a common centre that their properties combine those of the three forms of matter known to us. We have strong reason to believe that even the sun, though much denser than the general average of819 the stars, may possibly be characterized as gaseous rather than solid. Probabilities also seem to favour the view that this-may, to a certain extent, be true of the four great
3. A third characteristic which seems to belong to the great
A limit is placed on our knowledge of astrophysics which, up to the present time, we have found no means of overstepping. This is imposed upon us by the fact that it is only when matter is in agaseous form that the spectroscope can give us certain knowledge as to its physical condition. So long as bodies are in the solid state the light which they emit, though different in different substances, has no characteristic so precisely marked that detailed conclusions can be drawn
body
drawback
drawn
When the spectroscope was first applied in astronomy, it was hoped that the light reflected from living matter might be found to possess some property different from that found in light reflected from non-living -natter, and that we might thus detect the presence of life on the surface of a planet by a study of its spectrum; but no hope of this kind has so far been realized. We have, in this brief view of the subject, referred mainly to the results of spectrum analysis. Growing out of, but beyond this method is the beginning of a great branch of research which may ultimately explain many heretofore enigmatical phenomena of nature. The discovery of radio-activity may, by explaining the interior heat of the great bodies of the universe, solve a ;difficulty which since the middle of the 19th century has been discussed by physicists and geologiststhat of reconciling the long duration which geologists claim for the crust of the earth with the period during which physicists have deemed it possible that the sun should have radiated heat. Evidence is also accumulating to show that the sun and stars are radio-active bodies, and that emanations proceeding from the sun, and reaching the earth, have important relations to the phenomena of Terrestrial Magnetism and the Aurora. The subject of Astrophysics does not admit of so definite a sub-division as that of Astrometry. The conclusions which researches relating to it have so far reached are treated in the articles STAR
End of Article: ASTROPHYSICS If you wish, you can link directly to this article.
<a href="http://jcsm.org/StudyCenter/Encyclopedia/ARN_AUD/ASTROPHYSICS.html"> ASTROPHYSICS </a> |
|
|
(Previous) ASTROPALIA (classical Astypalaea) |
(Next) ASTRUC, JEAN (1684-1766) |
|
Sponsored Advertisements