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
- 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
- SECTION I WHAT IS A COMET?
- SECTION II CARDAN'S HYPOTHESIS
- SECTION III THEORY OF THE IMPULSION OF THE SOLAR BAYS
- SECTION IV HYPOTHESIS OF AN APPARENT REPULSION
- SECTION V THEORY OF OLBERS AND BESSEL
- SECTION VI THEORY OF COMETARY PHENOMENA
- SECTION VII THE REPULSIVE FORCE A REAL PHYSICAL FORCE
- SECTION VIII THEORY OF THE ACTINIC ACTION OF THE SOLAR RAYS
- SECTION IX COMETS AND THE RESISTANCE OF THE ETHER
- 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 II - CARDAN'S HYPOTHESIS
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
- 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
- SECTION I WHAT IS A COMET?
- SECTION II CARDAN'S HYPOTHESIS
- SECTION III THEORY OF THE IMPULSION OF THE SOLAR BAYS
- SECTION IV HYPOTHESIS OF AN APPARENT REPULSION
- SECTION V THEORY OF OLBERS AND BESSEL
- SECTION VI THEORY OF COMETARY PHENOMENA
- SECTION VII THE REPULSIVE FORCE A REAL PHYSICAL FORCE
- SECTION VIII THEORY OF THE ACTINIC ACTION OF THE SOLAR RAYS
- SECTION IX COMETS AND THE RESISTANCE OF THE ETHER
- 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
Cometary tails considered as effects of optical refraction–Objections made by Newton and Gregory–New theory of Gergonne : ideas of Saigey on the subject of planetary tails–Difficulties and lacunae in this theory.
Panætius, a philosopher of antiquity, held the belief that comets did not really exist, but were false appearances. ‘They are,’ he says, ‘ images formed by the reflexion, in the heavenly expanse, of the rays of the sun.’ In the opinion of Cardan and some astronomers and physicists, Apian, Tycho Brahe, in the Renaissance, and Gergonne and Saigey, in our time; the tails of comets are simple optical appearances.
The following is the passage in Cardan's work (De Subtilitate) which relates to this question : ‘It is, therefore, evident that a comet is a globe situated in the heavens and rendered visible by the illumination of the sun ; the rays which pass through it form the appearance of a beard or tail.’ The Milanese doctor has entered into no particulars respecting the manner in which these appearances are formed, which, in his opinion, were doubtless analogous to the effects of refraction produced by the convergence of luminous rays passing through a lenticular glass or globe filled with water; such as were formerly employed by artisans for concentrating the light upon their work.
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- Information
- The World of Comets , pp. 361 - 364Publisher: Cambridge University PressPrint publication year: 2010