WEBVTT 1 00:00:00.840 --> 00:00:05.919 Section twenty two of Sun, Moon and Stars Astronomy for Beginners. 2 00:00:06.719 --> 00:00:11.119 This is a LibriVox recording. All LibriVox recordings are in 3 00:00:11.199 --> 00:00:15.720 the public domain. For more information or to volunteer, please 4 00:00:15.800 --> 00:00:21.480 visit LibriVox dot org. Read by Kyle Johnson. Sun Moon 5 00:00:21.600 --> 00:00:28.079 and Stars Astronomy for Beginners by Agnes Geburn, Part three, 6 00:00:28.320 --> 00:00:34.320 Chapter one, Many Suns, I even my hands have stretched 7 00:00:34.320 --> 00:00:37.600 out the heavens and all their host have I commanded 8 00:00:38.359 --> 00:00:43.159 Isaiah forty five twelve. Once more we have to wing 9 00:00:43.240 --> 00:00:46.359 our flight far far away from the busy Solar system 10 00:00:46.399 --> 00:00:52.000 where we live, away from whirling planets, moons, meteorites, all 11 00:00:52.079 --> 00:00:56.840 shining with reflected light, away from the great central Sun himself, 12 00:00:57.359 --> 00:01:01.280 our own particular bright star. Once more we have in 13 00:01:01.359 --> 00:01:06.560 imagination to cross the vast black empty space. Is it black? 14 00:01:06.840 --> 00:01:10.239 And is it empty? Had we sight to see things 15 00:01:10.280 --> 00:01:15.000 as they are separating our Sun from other suns, our 16 00:01:15.079 --> 00:01:19.280 star from other stars. For the Sun is a star 17 00:01:20.040 --> 00:01:25.159 only a star, and stars are suns, big blazing suns. 18 00:01:25.840 --> 00:01:29.599 One is near and the others far away. That is 19 00:01:29.680 --> 00:01:33.519 the main difference. We have no longer to do with 20 00:01:33.599 --> 00:01:38.200 bodies merely reflecting another's light, always dark on one side 21 00:01:38.200 --> 00:01:42.319 and bright on the other. But with burning bodies shining 22 00:01:42.359 --> 00:01:46.040 all around by their own light, we have no longer 23 00:01:46.079 --> 00:01:49.519 to picture just one single star with his surrounding worlds. 24 00:01:50.280 --> 00:01:53.280 But we have to fix our thoughts upon the great 25 00:01:53.439 --> 00:01:58.680 universe of stars or suns in countless millions. The Sun 26 00:01:58.920 --> 00:02:03.000 is center and ruler and king in his own system, 27 00:02:03.359 --> 00:02:07.959 but as a star, he is only one among many stars, 28 00:02:08.000 --> 00:02:15.280 some greater, some less than himself. Thought travels fast, faster 29 00:02:15.400 --> 00:02:19.280 than a comet, faster than light. A rushing comet would, 30 00:02:19.479 --> 00:02:23.360 it is believed, take eight millions of years to cross 31 00:02:23.400 --> 00:02:27.719 the chasm between the nearest known fixed star and us. 32 00:02:28.800 --> 00:02:31.680 Light flashing along at the rate of about one hundred 33 00:02:31.719 --> 00:02:35.639 eighty six thousand, three hundred miles. A second will perform 34 00:02:35.719 --> 00:02:39.800 the same journey in four years and one third, But 35 00:02:39.960 --> 00:02:45.639 Thought overleaps the boundary in less than four minutes. Each 36 00:02:45.719 --> 00:02:48.039 star that we see in the heavens is, to our 37 00:02:48.120 --> 00:02:52.199 eye sight, simply one point of light. The brighter stars 38 00:02:52.240 --> 00:02:55.159 are said to be of greater magnitude, and the fainter 39 00:02:55.319 --> 00:02:59.360 stars of lesser magnitude. Yet one and all, they have 40 00:02:59.439 --> 00:03:04.520 no apparent size. The most powerful telescope, though it can 41 00:03:04.520 --> 00:03:09.479 increase their brilliancy, cannot add to their size. A planet, 42 00:03:09.520 --> 00:03:11.759 which to the naked eye may look like a star, 43 00:03:12.000 --> 00:03:15.560 will under a telescope show a disc, the breadth of 44 00:03:15.599 --> 00:03:19.639 which can be measured or divided. But no star has 45 00:03:19.719 --> 00:03:24.840 any real sensible disc in the most powerful telescope yet constructed. 46 00:03:26.199 --> 00:03:29.479 The reason of this is the enormous distance of the 47 00:03:29.520 --> 00:03:34.120 stars far off as many of the planets lie, Yet 48 00:03:34.199 --> 00:03:36.800 the farthest of them is a member of our own 49 00:03:36.840 --> 00:03:41.960 household compared with the nearest star. I have already tried 50 00:03:42.000 --> 00:03:45.840 to make clear the fact of their vast distance. Light, 51 00:03:46.240 --> 00:03:48.520 which comes to us from the Sun in less than 52 00:03:48.599 --> 00:03:52.840 nine minutes, takes four years and four months to reach 53 00:03:52.960 --> 00:03:57.080 us from Alpha Centauri. From this four years and a 54 00:03:57.120 --> 00:04:00.360 half length of journey between Alpha Centauri and other Earth, 55 00:04:01.000 --> 00:04:06.280 the numbers rise rapidly to twenty years, fifty years, hundreds 56 00:04:06.319 --> 00:04:11.680 of years, even thousands of years. The distances of most 57 00:04:11.680 --> 00:04:15.319 of the stars are completely beyond our power to measure 58 00:04:16.160 --> 00:04:19.319 the whole orbit of our Earth. Nay, the whole wide 59 00:04:19.480 --> 00:04:22.879 orbit of the far off Neptune would dwindle down to 60 00:04:23.040 --> 00:04:26.839 one single point if seen from the greater number of 61 00:04:26.920 --> 00:04:31.680 the stars it used to be believed that taking the 62 00:04:31.680 --> 00:04:35.920 stars generally, there was probably no very marked difference in 63 00:04:36.000 --> 00:04:40.480 their size, their kind, their brightness. Some of course would 64 00:04:40.480 --> 00:04:44.360 be rather larger, and others rather smaller. Still, it was 65 00:04:44.399 --> 00:04:47.920 supposed that they might be roughly classed as formed much 66 00:04:47.959 --> 00:04:51.399 on the same scale and the same plan. But of 67 00:04:51.519 --> 00:04:56.079 late years this notion has been utterly given up. A 68 00:04:56.199 --> 00:04:59.079 very similar idea used to be held with regard to 69 00:04:59.160 --> 00:05:04.040 the solar system. The wonderful variety of form and richness 70 00:05:04.079 --> 00:05:08.000 in numbers now known to abound within its limits are 71 00:05:08.079 --> 00:05:12.399 discoveries of later years. And now the same variety in 72 00:05:12.519 --> 00:05:16.839 kind and size is found also among the stars. The 73 00:05:16.879 --> 00:05:20.079 more we look into the heavens, the more we see 74 00:05:20.480 --> 00:05:24.160 that dull, blank uniformity is not to be found there. 75 00:05:25.480 --> 00:05:29.279 It is the same upon earth. Man builds his little 76 00:05:29.399 --> 00:05:32.879 rows of box like houses side by side, each one 77 00:05:32.920 --> 00:05:37.319 exactly like all the rest, Or dresses his thousand soldiers 78 00:05:37.319 --> 00:05:40.639 in coats of the same cut and color, or repeats 79 00:05:40.680 --> 00:05:44.680 a neat leaf design hundreds of times on carpets or wallpapers. 80 00:05:45.759 --> 00:05:49.000 But God never makes two leaves or two blades of 81 00:05:49.040 --> 00:05:54.040 grass alike wholesale, turning out of things after one pattern 82 00:05:54.800 --> 00:06:00.399 is quite a human idea, not divine. We know so 83 00:06:00.480 --> 00:06:03.279 much about the stars as that some are at least 84 00:06:03.319 --> 00:06:09.000 considerably larger and some considerably smaller than others. When one 85 00:06:09.040 --> 00:06:12.519 star is seen to shine brightly and another beside it 86 00:06:12.600 --> 00:06:16.079 shines dimly, we are apt to think that the brightest 87 00:06:16.199 --> 00:06:20.000 must be the nearest. Yet it is often impossible for 88 00:06:20.120 --> 00:06:22.920 us to say how much of the difference is owing 89 00:06:22.959 --> 00:06:26.160 to the greater distance of one or the other, or 90 00:06:26.199 --> 00:06:29.240 to the greater size of one or the other, or 91 00:06:29.279 --> 00:06:33.639 to the greater brilliancy of one or the other. In 92 00:06:33.720 --> 00:06:36.600 many instances we do not know enough to be quite 93 00:06:36.600 --> 00:06:39.879 sure that there is a great difference not only in 94 00:06:39.959 --> 00:06:43.560 the distance of the stars, but in their size, their kind, 95 00:06:43.920 --> 00:06:49.040 their brightness. The stars have been sometimes classified into four 96 00:06:49.120 --> 00:06:54.920 distinct orders or degrees, partly depending on their color. The 97 00:06:54.959 --> 00:06:58.920 first class is that of the white suns. These are 98 00:06:58.959 --> 00:07:02.399 generally held to be the grandest and mightiest of all 99 00:07:03.240 --> 00:07:06.920 the stars. Serious belongs to the order of white suns. 100 00:07:08.680 --> 00:07:13.399 Secondly comes the class of golden suns. To these blazing 101 00:07:13.519 --> 00:07:16.720 orbs of yellow light, said to be second only to 102 00:07:16.800 --> 00:07:23.439 the white light stars, belongs our own sun. Thirdly, there 103 00:07:23.480 --> 00:07:27.560 are numbers of stars called variable stars, the light of 104 00:07:27.600 --> 00:07:34.480 which is constantly changing, now becoming greater, now becoming less. Fourthly, 105 00:07:35.040 --> 00:07:38.839 there is the class of small red suns, about which 106 00:07:38.959 --> 00:07:43.720 not so much is known. These four orders or divisions 107 00:07:43.759 --> 00:07:46.720 do not, by any means include all the stars, or 108 00:07:46.800 --> 00:07:51.399 even all the single stars. Roughly speaking, however, the greater 109 00:07:51.519 --> 00:07:55.079 number of single stars, and many also of the double stars, 110 00:07:55.600 --> 00:08:00.199 belong to one or another of the above classes. When 111 00:08:00.240 --> 00:08:03.560 we talk of the different sizes of the different stars, 112 00:08:03.600 --> 00:08:07.040 it should be plainly understood that we have no means 113 00:08:07.040 --> 00:08:11.360 of directly measuring them. A point of light showing no disk, 114 00:08:11.879 --> 00:08:16.360 no surface, no breadth, cannot be measured, for there is 115 00:08:16.399 --> 00:08:21.079 nothing to measure. In certain cases, we are not entirely 116 00:08:21.160 --> 00:08:24.879 without the power of judging. The distances of some of 117 00:08:24.920 --> 00:08:28.560 the stars from us have been found out. Knowing how 118 00:08:28.600 --> 00:08:32.720 far off any particular star is, astronomers are able to 119 00:08:32.799 --> 00:08:36.840 calculate exactly how bright our own sun would look at 120 00:08:36.879 --> 00:08:40.399 that same distance. If they find that our sun would 121 00:08:40.440 --> 00:08:44.039 shine just as the star in question shines, there is 122 00:08:44.080 --> 00:08:47.679 some reason for supposing that our sun and yonder star 123 00:08:48.320 --> 00:08:51.960 may be of the same size. If our sun would 124 00:08:51.960 --> 00:08:55.480 shine more brightly than the star shines, there is some 125 00:08:55.639 --> 00:08:59.039 reason for supposing that the star may be smaller than 126 00:08:59.039 --> 00:09:02.879 our sun. If our sun would shine more dimly than 127 00:09:02.879 --> 00:09:06.840 the star shines, there is some reason for supposing that 128 00:09:06.879 --> 00:09:12.440 the star may be larger than our sun. Other matters, however, 129 00:09:12.559 --> 00:09:16.399 have to be considered. Suppose we find a star at 130 00:09:16.440 --> 00:09:19.919 a certain distance shining twice as brilliantly as our own 131 00:09:19.960 --> 00:09:24.279 sun would shine at that same distance. Naturally, then we 132 00:09:24.320 --> 00:09:27.360 say that star must be much larger than our sun. 133 00:09:28.919 --> 00:09:33.000 The reasoning may be mistaken. We do not know the fact. 134 00:09:34.000 --> 00:09:37.200 What if, instead of being a much larger sun, it 135 00:09:37.279 --> 00:09:42.039 is only a much brighter sun. This is more than possible. 136 00:09:42.960 --> 00:09:46.919 Some doubts have been indeed expressed whether the surface of 137 00:09:47.039 --> 00:09:50.519 any star could exceed that of our sun in radiance. 138 00:09:51.360 --> 00:09:54.399 But we have really no reason to suppose that our 139 00:09:54.480 --> 00:09:58.559 son is a king of sons in brilliance, since certainly 140 00:09:58.639 --> 00:10:04.120 he is not so inside in speed. When we picture 141 00:10:04.159 --> 00:10:08.919 to ourselves the star depths the boundless reaches of heavenly space. 142 00:10:09.000 --> 00:10:14.000 With these countless blazing suns scattered broadcast throughout, we have 143 00:10:14.080 --> 00:10:18.480 not to picture a universe in repose. On the contrary, 144 00:10:19.080 --> 00:10:24.120 all is life, stir energy, Just as in the busy 145 00:10:24.240 --> 00:10:27.320 whirl of our solar system knows such thing as rest 146 00:10:27.440 --> 00:10:30.639 is to be found, so also it seems to be 147 00:10:30.919 --> 00:10:36.799 in the wide universe. Every star is in motion, fixed 148 00:10:36.840 --> 00:10:40.960 as we call them. They are not fixed invisible, as 149 00:10:41.000 --> 00:10:45.159 their movements are to our eyes through immensity of distance. 150 00:10:45.759 --> 00:10:50.840 Yet all are moving. Those silent, placid, twinkling specks of 151 00:10:50.919 --> 00:10:57.120 light are in reality huge, roaring, seething, tumultuous furnaces of 152 00:10:57.200 --> 00:11:02.679 fire and flame, heat and radiance. Each too is hurrying 153 00:11:02.720 --> 00:11:07.480 along his appointed pathway in space. Some move faster, some 154 00:11:07.559 --> 00:11:11.960 move more slowly. One mile per second, ten miles per second, 155 00:11:12.519 --> 00:11:17.679 twenty fifty hundreds of miles per second. Thus varying are 156 00:11:17.720 --> 00:11:23.080 their rates of speed, but rather fast or whether slowly still? 157 00:11:23.159 --> 00:11:27.960 Onward and ever onward they press. Some are rushing towards us, 158 00:11:28.480 --> 00:11:32.000 Some are rushing away from us. Some are speeding to 159 00:11:32.039 --> 00:11:36.559 the right, some are speeding to the left. Where are 160 00:11:36.600 --> 00:11:40.320 they going? Does any single star ever return to his 161 00:11:40.399 --> 00:11:44.879 starting point? Wherever that starting point may have been? Do 162 00:11:44.919 --> 00:11:48.840 they journey in vast circles or ellipses round some far 163 00:11:48.960 --> 00:11:53.799 distant center. What controls them all? Is it the mighty 164 00:11:53.879 --> 00:11:57.399 power of some such center, Or does each star, by 165 00:11:57.440 --> 00:12:00.679 his faint and distant attraction, help to contryro all his 166 00:12:00.799 --> 00:12:04.799 brother stars, to guide them on their appointed path, to 167 00:12:04.919 --> 00:12:09.559 preserve the delicate balance of a universe. How little we 168 00:12:09.679 --> 00:12:14.120 know about the matter, Only so much we can tell 169 00:12:14.720 --> 00:12:18.320 that the controlling and restraining hand of God is over 170 00:12:18.360 --> 00:12:22.440 the whole, Whether by the attraction of one great center 171 00:12:23.240 --> 00:12:27.720 or by the united influences of a thousand fainter attractions. 172 00:12:27.759 --> 00:12:32.639 He steers each radiant sun upon its heavenly path, upholding 173 00:12:32.720 --> 00:12:36.440 all things by the word of His power. There is 174 00:12:36.440 --> 00:12:42.639 no blundering, no confusion, no entanglement. All is perfect order, 175 00:12:43.440 --> 00:12:53.519 calm arrangement, restrained energy. End of Section twenty two.