Astronomy
1. ACCURATE MEASUREMENT.--Accurate measurement is the foundation of exact science, and at the very beginning of his study in astronomy the student should learn something of the astronomer's kind of measurement. He should practice measuring the stars with all possible care, and...
184. THE CONSTELLATIONS.--In the earlier chapters the student has learned to distinguish between wandering stars (planets) and those fixed luminaries which remain year after yea...
13. CHAPTER XI133. PLANETS.--Circling about the sun, under the influence of his attraction, is a family of planets each member of which is, like the moon, a dark body shining by reflected sun...
14. CHAPTER XII158. VISITORS IN THE SOLAR SYSTEM.--All of the objects--sun, moon, planets, stars--which we have thus far had to consider, are permanent citizens of the sky, and we have no reas...
12. CHAPTER Xand proceeding to depict in vivid words the consequences of this extinction. The most matter-of-fact language of science agrees with the words of the poet in declaring the earth...
10. CHAPTER VIII74. TWO FAMILIAR INSTRUMENTS.--In previous chapters we have seen that a clock and a divided circle (protractor) are needed for the observations which an astronomer makes, and it...
11. CHAPTER IX91. RESULTS OF OBSERVATION WITH THE UNAIDED EYE.--The student who has made the observations of the moon which are indicated in Chapter III has in hand data from which much may b...
5. CHAPTER IV32. THE BEGINNINGS OF CELESTIAL MECHANICS.--From the earliest dawn of civilization, long before the beginnings of written history, the motions of sun and moon and planets among...
18. Chapter XI, this ring is made up of a great number of independentparticles which move at different rates of speed, and comparing, through Kepler's Third Law, the motion of the inner edge of the ring with the known periodic time of the satelli...
16. CHAPTER XIV209. STELLAR COLORS.--We have already seen that one star differs from another in respect of color as well as brightness, and the diligent student of the sky will not fail to obs...
9. CHAPTER VII63. THE NATURE OF ECLIPSES.--Every planet has a shadow which travels with the planet along its orbit, always pointing directly away from the sun, and cutting off from a certain...
7. Chapter II, how these angles may be measured, and it is apparent fromthe figure that the difference between any two of these angles--e. g., the angles at _1_ and _2_--is equal to the angle at the center, _O_, between the points _1_ and _2_. By me...
4. CHAPTER III23. STAR MAPS.--Select from the map some conspicuous constellation that will be conveniently placed for observation in the evening, and make on a large scale a copy of all the s...
2. CHAPTER II8. THE STARS.--From the very beginning of his study in astronomy, and as frequently as possible, the student should practice watching the stars by night, to become acquainted wi...
8. CHAPTER VI52. SOLAR TIME.--To measure any quantity we need a unit in terms of which it must be expressed. Angles are measured in degrees, and the degree is the unit for angular measuremen...
17. CHAPTER XV226. NATURE OF THE PROBLEM.--To use a common figure of speech, the universe is alive. We have found it filled with an activity that manifests itself not only in the motions of t...
1. CHAPTER I1. ACCURATE MEASUREMENT.--Accurate measurement is the foundation of exact science, and at the very beginning of his study in astronomy the student should learn something of the...
3. Chapter V), these numbers all change slowly with the lapse of time, andon the average the right ascension of each star of the table must be increased by one twentieth of a minute for each year after 1900--i. e., in 1910 the right ascension of the f...
6. CHAPTER V44. THE SIZE OF THE EARTH.--The student is presumed to have learned, in his study of geography, that the earth is a globe about 8,000 miles in diameter and, without dwelling upo...