Conversations on Natural Philosophy, in which the Elements of that Science are Familiarly Explained Part 21

_Caroline._ If I dared to confess it, Mrs. B., I should say that such an inquiry indicated rather a deficiency than a superiority of intellect. I do not understand how any one can wonder at what is so natural and so common.

_Mrs. B._ It is the mark of superior genius to find matter for wonder, observation, and research, in circ.u.mstances which, to the ordinary mind, appear trivial, because they are common; and with which they are satisfied, because they are natural; without reflecting that nature is our grand field of observation, that within it, is contained our whole store of knowledge; in a word, that to study the works of nature, is to learn to appreciate and admire the wisdom of G.o.d. Thus, it was the simple circ.u.mstance of the fall of an apple, which led to the discovery of the laws upon which the Copernican system is founded; and whatever credit this system had obtained before, it now rests upon a basis from which it cannot be shaken.

_Emily._ This was a most fortunate apple, and more worthy to be commemorated than all those that have been sung by the poets. The apple of discord for which the G.o.ddesses contended; the golden apples by which Atalanta won the race; nay, even the apple which William Tell shot from the head of his son, cannot be compared to this!

Questions

1. (Pg. 80) Into what two cla.s.ses are the planets divided, and how are they distinguished?

2. (Pg. 80) By what reasoning do you prove that the sun contains a greater quant.i.ty of matter than any other body in the system?

3. (Pg. 81) What two circ.u.mstances govern the force with which bodies attract each other?

4. (Pg. 81) Were a planet removed to double its former distance from the sun, what would be the effect upon its attractive force?

5. (Pg. 81) Why would it be reduced to one-fourth?

6. (Pg. 81) What is meant by the square of a number, and what examples can you give?

7. (Pg. 81) What then would be the effect of removing it to three, or four times its former distance?

8. (Pg. 81) How is the rule upon this subject expressed?

9. (Pg. 81) Does this apply to any power excepting gravitation?

10. (Pg. 81) How is it that a secondary planet revolves round its primary, and is not drawn off by the sun?

11. (Pg. 82) What is said respecting the revolution of the moon, and of the earth, round a common centre of gravity?

12. (Pg. 82) By what law in mechanics is this explained?

13. (Pg. 82) What motions then has the earth, and are these remarks confined to it alone?

14. (Pg. 82) What effect have the planets upon the sun, and what is said of the common centre of gravity of the system?

15. (Pg. 83) What other motion has the sun, and how is it proved?

16. (Pg. 83) How may you observe the motion of a planet, by means of a fixed star?

17. (Pg. 83) What is represented by fig. 1. plate 7?

18. (Pg. 83) Why are the orbits represented as circular?

19. (Pg. 83) In what order do the planets increase in size as represented, fig. 2. plate 7?

20. (Pg. 83) What are we told respecting Mercury?

21. (Pg. 84) What respecting Venus?

22. (Pg. 84) When does Venus become a morning, and when an evening star?

23. (Pg. 84) What is said of the Earth?

24. (Pg. 84) What of Mars?

25. (Pg. 84) What four small planets follow next?

26. (Pg. 85) What is said of Jupiter?

27. (Pg. 85) What of Saturn?

28. (Pg. 85) What of Herschel?

29. (Pg. 85) Why do we conclude that the moons of Saturn afford less light than ours?

30. (Pg. 85) In what proportion will the light and heat at Saturn be diminished, and why?

31. (Pg. 86) What do the comets resemble, and what is remarkable in their orbits?

32. (Pg. 86) What is said of the number of comets?

33. (Pg. 86) What is a constellation?

34. (Pg. 86) How are the twelve constellations, or signs, called the zodiac, situated?

35. (Pg. 86) Name them.

36. (Pg. 86) What is meant by the sun being in a sign?

37. (Pg. 86) What causes the apparent change of the sun's place?

38. (Pg. 87) The stars appear of different magnitudes, by what may this be caused?

39. (Pg. 87) We are not sensible of the motion of the earth; what fact is mentioned to ill.u.s.trate this point?

40. (Pg. 87) What does this teach us?

41. (Pg. 88) Would the slowness, or the rapidity of the motion, if steady, produce any sensible difference?

42. (Pg. 88) If we do not feel the motion of the earth, how may we be convinced of its reality?

43. (Pg. 89) Were we to deny the motion of the earth upon its axis, what must we admit respecting the heavenly bodies?

44. (Pg. 89) What distance is an inhabitant on the equator carried in a minute by the diurnal motion of the earth?

45. (Pg. 89) Why is not the velocity every where equally great?