- are my own, either replacing or amplifying those of the author cited. - 369a being an update of the original § 369.. - 7.5.3 The structure of the universe. - 9.1.3 Summary of the new book. - 10.4 The Milky Way and the nature of the nebulae. - 13.4 Summary of the fourth edition. - And this idea of the stars being attached to a. - and the position of the star in question.. - 2.4 The principle of the transit circle. - It swings at the axis of the wheel, rotating only in one line. - For instance, the axis of the Earth changes its direction with time. - One of the most annoying of these is the Earth’s atmosphere. - For the Solar System, the Sun occupies one of the foci (and nothing special happens at the other). - This is the cause of the seasons (see Fig. - Even the absolute size of the System as a whole can be figured (with a little less accuracy). - 2.9, notice that the direction from the Earth to a star on one side of the orbit (say, about September) is different from that on the other side (March). - And it gives very good results — most of the time.. - You have to assume (and justify it when and as you can) that the first term in the sum is most of the sum, and the second term takes up. - If any of the modes are unstable, the whole situation is unstable. - One of the latter has just brought out a book on astronomy for the public.. - sections of the Principia are referred to where appropriate. - Of the Nature of Astronomical Instruments 43. - Of the Sun’s Motion 29. - Of the Moon 19. - Of the Solar System 45. - Of the Satellites 12. - 11) of celestial bodies is a part of the science of astronomy.. - As to the source of the Sun’s energy, we are “completely at a loss” (p. - Of the planets, they are certainly opaque bodies shining by reflected sunlight. - Examples are given, among others, in the case of the refinement of the “solar motion”. - Sir John summarized his view of the situation this way:. - There is no doubt that this is the center of the science and its pride. - depend on the distance-scale of the Solar System. - [precipitate] them, unbroken, on the surface of the planet.”. - We are looking down from one pole of the planet, with the ring (which we assume to be solid) beginning by being exactly centered (thick line). - First, there is no mention at all of the possible motion of the ring. - However, Herschel (as well as six of the seven other observers) remained convinced that the eastern side of the rings looked farther from the planet.. - It is possible (again, this is only my speculation) that Herschel was thinking of some of the results of planetary perturbations. - To this end Herschel gives two results of the French mathematician Lagrange (as pre- sented by Laplace). - The result thus guar- antees “the stability of the orbits of the greater planets” (p. - So the stability of the Solar System was not proved after all. - Seduction of the elegant result. - Two years before, astronomy had produced a major triumph in the prediction and discovery of the planet Neptune.. - plus as much of the “working-man” as he can reach. - The subjects of the lectures break down in this way:. - II size and shape of the Earth, rotation, 42. - III motions of the planets, parallax 37. - IV parallax of the Moon, 44. - only one lecture of the six (though it appears to be a double-length one) is devoted to weights. - that Ptolemy had no idea of the size of the Earth (p. - 2 For the number of epicycles and the size of the Earth, see (Hoskin, 1997), especially chapters 2 and 4. - For the “demotion” of the Earth, Danielson (2009) is an excellent exposition.. - you have to get rid of the physics and the cosmology together.. - Note that there are areas to the right of the barrier that feel the wave in Fig. - A particle would go through one of the holes (or neither). - I’m leaving out a lot of the caveats to keep things simple.. - Now we add heat energy through the sides of the cylinder (which can be made insulating or not, as we choose).. - temperature rises, the kinetic energy of the molecules increases, pressure increases. - Look at the areas under the curves to the right of the vertical line.. - The particular wavelengths are characteristic of the gas’s composition. - you can trace that to a close pair of emission lines in the orange part of the spectrum.. - I will use my favorite illustration of the poorly-shooting duck hunters. - (Now put together the Maxwellian distribution, above, with the idea of the escape speed. - But suppose it makes a close passage by one of the main planets. - 877), with Struve on the form of the Milky Way (p. - The lion’s share of the expansion, though, consists of observations.. - The expansion of the chapter on the calendar has no obvious astronom- ical explanation. - On the matter of the stability of the Solar System there is no change.. - The craters of the Moon are still identified as volcanoes (p. - The situation on the stability of the rings of Saturn is still somewhat confused. - but nothing of the sort has been done.. - But there are new and wonderful observations of the Sun being made (pp. - We saw Airy’s evaluation of the first results in Section 4.2. - Second, this vaporization takes place on the side of the comet nearest the Sun;. - Examples are the nature of the Milky Way as determined by star counts (where Herschel is mistaken) and the reasons for not seeing a central star in planetary nebulae (in which Herschel and Arago could both be considered right and wrong, but for reasons neither could know).. - At the same time, most of the observations are accurate and correctly interpreted. - Part I The System of the World Historically Developed 102 [The apparent sky through Newtonian gravity]. - II The Application of the Telescope to Celestial 19 Measurements. - The Structure of the Universe 31. - Later on he states, from some considerations of the distribution of irresolvable nebulae on the sky, “The most probable. - The “willow-leaf” structure of the solar photosphere similarly is discarded (p. - We can see some instances of the latter here.. - I think this is simply a slip of the pen (Saturn would float on water. - maybe he was thinking of the wrong planet). - The Sun is about in the center of the picture.. - and in fact we are well off-center, with most of the stars invisible. - two of the first. - four of the second. - in fact it is very firmly part of the object. - In the case of Theta Orionis, his formulation of the problem involves an error (of a type that is fairly well known). - Ball has written a book making a mockery of the process.. - A View of the Universe 6. - Aspects of the Heavens 10. - Eclipses of the Moon 6. - Eclipses of the Sun 12. - Aspects of the Sky 6. - There is proportionately (not absolutely) more on observations of the Solar System and on the fixed stars.. - identify them with any of the nebulae we can see. - it is found in the nuclei of atoms, making up a good part of the mass. - The first is the size and shape of the “stellar universe,” the Milky Way.