## History of Astronomy |

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Page 18

The line from the earth to the “ excentric ” was called the line of apses . A circle

having this centre was called the equant , and he supposed that a radius drawn

to the sun from the excentric passes over

.

The line from the earth to the “ excentric ” was called the line of apses . A circle

having this centre was called the equant , and he supposed that a radius drawn

to the sun from the excentric passes over

**equal**arcs on the equant in**equal**times.

Page 42

His second law ( a far more difficult one to prove ) states that a line drawn from a

planet to the sun sweeps over

published in his great work , Astronomia Nova , seu Physica Cælestis tradita ...

His second law ( a far more difficult one to prove ) states that a line drawn from a

planet to the sun sweeps over

**equal**areas in**equal**times . These two laws werepublished in his great work , Astronomia Nova , seu Physica Cælestis tradita ...

Page 135

From this it has been calculated that the mass of Sirius

and its intrinsic brightness

mass

From this it has been calculated that the mass of Sirius

**equals**two of our suns ,and its intrinsic brightness

**equals**twenty suns ; but the companion , having amass

**equal**to our sun , has only a five - hundredth part of the sun ' s brightness .### What people are saying - Write a review

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### Contents

ANCIENT GREEK ASTRONOMY | 3 |

GALILEO AND THE TELESCOPENOTIONS OF GRAVITY | 46 |

NEWTONS SUCCESSORS HALLEY EULER | 60 |

### Other editions - View all

### Common terms and phrases

accepted accurate ancient appear astronomers attraction bodies bright calculations called catalogue cause centre century Chinese circle comet compared complete Copernicus determined diameter direction discovered discovery distance earth eclipse effect elements enabled epicycles equal error explain fact fixed follow force four Galileo gave give given gravitation heavens held Herschel increased interesting Jupiter Kepler knowledge known later light lunar Mars mass mathematical mean measured method miles moon moon's motion move nebulæ Newton noted noticed object observations Observatory opposition orbit original parallax pass period photographic physical planet planetary pole position predicted progress proper motion proved records researches revolve ring rotation round Royal satellites seems seen showed solar system spectroscope spectrum stars studied sun's supposed surface tables telescope theory tion trace true Tycho Brahe UNIVERSITY