Book contents
- Frontmatter
- EDITOR'S PREFACE
- PREFACE
- Contents
- LIST OF ILLUSTRATIONS
- CHAPTER I BELIEFS AND SUPERSTITIONS RELATIVE TO COMETS
- CHAPTER II COMETARY ASTRONOMY UP TO THE TIME OF NEWTON
- CHAPTER III THE MOTIONS AND ORBITS OF COMETS
- CHAPTER IV PERIODICAL COMETS
- CHAPTER V PERIODICAL COMETS
- CHAPTER VI THE WORLD OF COMETS AND COMETARY SYSTEMS
- SECTION I THE NUMBER OF COMETS
- SECTION II COMETS WITH HYPERBOLIC ORBITS
- SECTION III REMARKS ON THE ORIGIN OF COMETS
- SECTION IV SYSTEMS OF COMETS
- SECTION V COMETARY STATISTICS
- CHAPTER VII PHYSICAL AND CHEMICAL CONSTITUTION OF COMETS
- CHAPTER VIII PHYSICAL TRANSFORMATIONS OF COMETS
- CHAPTER IX MASS AND DENSITY OF COMETS
- CHAPTER X THE LIGHT OF COMETS
- CHAPTER XI THEORY OF COMETARY PHENOMENA
- CHAPTER XII COMETS AND SHOOTING STARS
- CHAPTER XIII COMETS AND THE EARTH
- CHAPTER XIV PHYSICAL INFLUENCES OF COMETS
- CHAPTER XV SOME QUESTIONS ABOUT COMETS
- I ELLIPTIC ELEMENTS OF THE RECOGNISED PERIODICAL COMETS OF THE SOLAR SYSTEM
- II GENERAL CATALOGUE OF THE ORBITS OF COMETS
- Plate section
SECTION III - REMARKS ON THE ORIGIN OF COMETS
Published online by Cambridge University Press: 05 March 2012
- Frontmatter
- EDITOR'S PREFACE
- PREFACE
- Contents
- LIST OF ILLUSTRATIONS
- CHAPTER I BELIEFS AND SUPERSTITIONS RELATIVE TO COMETS
- CHAPTER II COMETARY ASTRONOMY UP TO THE TIME OF NEWTON
- CHAPTER III THE MOTIONS AND ORBITS OF COMETS
- CHAPTER IV PERIODICAL COMETS
- CHAPTER V PERIODICAL COMETS
- CHAPTER VI THE WORLD OF COMETS AND COMETARY SYSTEMS
- SECTION I THE NUMBER OF COMETS
- SECTION II COMETS WITH HYPERBOLIC ORBITS
- SECTION III REMARKS ON THE ORIGIN OF COMETS
- SECTION IV SYSTEMS OF COMETS
- SECTION V COMETARY STATISTICS
- CHAPTER VII PHYSICAL AND CHEMICAL CONSTITUTION OF COMETS
- CHAPTER VIII PHYSICAL TRANSFORMATIONS OF COMETS
- CHAPTER IX MASS AND DENSITY OF COMETS
- CHAPTER X THE LIGHT OF COMETS
- CHAPTER XI THEORY OF COMETARY PHENOMENA
- CHAPTER XII COMETS AND SHOOTING STARS
- CHAPTER XIII COMETS AND THE EARTH
- CHAPTER XIV PHYSICAL INFLUENCES OF COMETS
- CHAPTER XV SOME QUESTIONS ABOUT COMETS
- I ELLIPTIC ELEMENTS OF THE RECOGNISED PERIODICAL COMETS OF THE SOLAR SYSTEM
- II GENERAL CATALOGUE OF THE ORBITS OF COMETS
- Plate section
Summary
Have all the known comets of the solar world always belonged to it?–Probable modification of their original orbits through the planetary perturbations–Cause of the gradual diminution of the periods of certain comets.
The origin of comets is a question equally interesting and difficult.
On comparing all the orbits that have been calculated we find that they pass by almost imperceptible gradations from comets of short period to comets of periods of immense length, and thence to others the major axes of which are of infinite dimensions. If we suppose the latter to be strangers to our solar system, have the former, we may ask, always formed a part of it? In which case why should periodical comets in the elements of their orbits and their physical constitution differ so essentially from planets? Why do they cut the plane of the ecliptic at all inclinations, and why are their movements sometimes direct and sometimes retrograde? Why are their masses so small, and why do they exhibit such vaporous appearances, such rapid changes of aspect, and the phenomenon of tails?
On the other hand, if comets are all of extra-solar origin, why have not all cometary orbits a major axis equal at least to the radius of the sphere of the sun's activity?
The reply to the first questions would be difficult on the hypothesis of comets having the same origin as the planets.
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- The World of Comets , pp. 171 - 173Publisher: Cambridge University PressPrint publication year: 2010First published in: 1877