WEBVTT 1 00:00:00.560 --> 00:00:05.879 Section one of the Einstein Theory of Relativity. This is 2 00:00:05.919 --> 00:00:10.000 a LibriVox recording. All LibriVox recordings are in the public domain. 3 00:00:10.480 --> 00:00:14.759 For more information, ought to volunteer, please visit liprivox dot org. 4 00:00:15.640 --> 00:00:21.800 Recording by Avai in January twenty twenty The Einstein Theory 5 00:00:21.839 --> 00:00:30.480 of Relativity by Hendrik A. Lwentz, Section one. Note. Whether 6 00:00:30.519 --> 00:00:33.000 it is true or not that not more than twelve 7 00:00:33.079 --> 00:00:37.320 persons in all the world are able to understand Einstein's theory, 8 00:00:37.960 --> 00:00:40.560 it is nevertheless a fact that there is a constant 9 00:00:40.640 --> 00:00:44.719 demand for information about this much debated topic of relativity. 10 00:00:45.719 --> 00:00:48.920 The books published on the subject are so technical that 11 00:00:49.039 --> 00:00:52.640 only a person trained in pure physics and higher mathematics 12 00:00:52.679 --> 00:00:56.320 is able to fully understand them. In order to make 13 00:00:56.359 --> 00:01:00.560 a popular explanation of this far reaching theory available, the 14 00:01:00.600 --> 00:01:05.840 present book is published. Professor Lawrence is credited by Einstein 15 00:01:06.000 --> 00:01:10.079 with sharing the development of his theory. He is doubtless 16 00:01:10.079 --> 00:01:13.879 better able than any other man except the author himself, 17 00:01:14.319 --> 00:01:19.640 to explain this scientific discovery. The publishers wish to acknowledge 18 00:01:19.640 --> 00:01:23.959 their indebtedness to The New York Times, The Review of Reviews, 19 00:01:24.400 --> 00:01:29.040 and the Athenaeum for courteous permission to reprint articles from 20 00:01:29.079 --> 00:01:34.959 their pages. Professor Lawrence's article appeared originally in the Newer 21 00:01:35.040 --> 00:01:45.519 Rotterdam's Recurrant of November nineteen, nineteen nineteen introduction. The action 22 00:01:45.680 --> 00:01:48.840 of the Royal Society at its meeting in London on 23 00:01:48.879 --> 00:01:54.599 November six in recognizing doctor Albert Einstein's theory of relativity 24 00:01:55.159 --> 00:01:58.680 has caused a great stir in scientific circles on both 25 00:01:58.760 --> 00:02:03.799 sides of the Atlantic. Doctor Einstein propounded his theory nearly 26 00:02:03.879 --> 00:02:08.400 fifteen years ago. The present revival of interest in it 27 00:02:08.439 --> 00:02:11.879 is due to the remarkable confirmation which it received in 28 00:02:11.919 --> 00:02:16.080 the report of the observations made during the Sun's eclipse 29 00:02:16.120 --> 00:02:20.039 of last May to determine whether rays of light passing 30 00:02:20.120 --> 00:02:24.439 close to the Sun are deflected from their course. The 31 00:02:24.479 --> 00:02:27.520 actual deflection of the rays that was discovered by the 32 00:02:27.639 --> 00:02:32.840 astronomers was precisely what had been predicted theoretically by Einstein 33 00:02:33.000 --> 00:02:38.240 many years since. This striking confirmation has led certain German 34 00:02:38.319 --> 00:02:43.039 scientists to assert that no scientific discovery of such importance 35 00:02:43.120 --> 00:02:47.560 has been made since Newton's theory of gravitation was promulgated. 36 00:02:48.560 --> 00:02:52.759 This suggestion, however, was put aside by doctor Einstein himself 37 00:02:53.199 --> 00:02:56.039 when he was interviewed by a correspondent of the New 38 00:02:56.159 --> 00:03:00.560 York Times at his home in Berlin. To this core respondent, 39 00:03:00.719 --> 00:03:04.560 he expressed a difference between his conception and the law 40 00:03:04.599 --> 00:03:10.520 of gravitation in the following terms. Please imagine the Earth removed, 41 00:03:10.919 --> 00:03:13.919 and in its place suspended a box as big as 42 00:03:13.960 --> 00:03:17.840 a room or a whole house, and inside a man 43 00:03:18.159 --> 00:03:21.919 naturally floating in the center, there being no force whatever 44 00:03:22.080 --> 00:03:27.120 pulling him. Imagine further this box, being by a rope 45 00:03:27.280 --> 00:03:31.759 or other contrivance, suddenly jerked to one side, which is 46 00:03:31.800 --> 00:03:38.560 scientifically termed deform motion as opposed to uniform motion. The 47 00:03:38.599 --> 00:03:42.319 person would then naturally reach bottom on the opposite side. 48 00:03:43.280 --> 00:03:46.159 The result would consequently be the same as if he 49 00:03:46.280 --> 00:03:50.599 obeyed Newton's law of gravitation, while in fact there is 50 00:03:50.639 --> 00:03:55.560 no gravitation exerted whatever, which proves that deformed motion will 51 00:03:55.599 --> 00:04:00.280 in every case produce the same effects as gravitation. I 52 00:04:00.319 --> 00:04:03.840 have applied this new idea to every kind of deformed motion, 53 00:04:04.400 --> 00:04:08.439 and have thus developed mathematical formulas which I am convinced 54 00:04:08.520 --> 00:04:12.639 give more precise results than those based on Newton's theory. 55 00:04:13.560 --> 00:04:18.079 Newton's formulas however, are such close approximations that it was 56 00:04:18.199 --> 00:04:23.399 difficult to find by observation any obvious disagreement with experience. 57 00:04:25.399 --> 00:04:29.639 Doctor Einstein, it must be remembered, is a physicist and 58 00:04:29.839 --> 00:04:34.959 not an astronomer. He developed his theory as a mathematical formula. 59 00:04:35.720 --> 00:04:40.040 The confirmation of it came from the astronomers, As he 60 00:04:40.199 --> 00:04:43.800 himself said, The crucial test was supplied by the last 61 00:04:43.920 --> 00:04:48.959 total solar eclipse. Observations then proved that the rays of 62 00:04:49.040 --> 00:04:52.439 fixed stars, having to pass close to the Sun to 63 00:04:52.519 --> 00:04:56.720 reach the Earth were deflected the exact amount demanded by 64 00:04:56.720 --> 00:05:01.040 Einstein's formulas. The deflexion was all so in the direction 65 00:05:01.240 --> 00:05:05.879 predicted by him. The question must have occurred to many, 66 00:05:06.480 --> 00:05:10.000 what has all this to do with relativity? When this 67 00:05:10.120 --> 00:05:14.120 query was propounded by the Times correspondent to doctor Einstein, 68 00:05:14.519 --> 00:05:19.800 he replied as follows. The term relativity refers to time 69 00:05:19.959 --> 00:05:25.079 and space. According to Galileo and Newton, time and space 70 00:05:25.199 --> 00:05:29.399 were absolute entities, and the moving systems of the universe 71 00:05:29.480 --> 00:05:34.040 were dependent on this absolute time and space. On this 72 00:05:34.160 --> 00:05:39.079 conception was built the science of mechanics. The resulting formulas 73 00:05:39.199 --> 00:05:43.680 sufficed for all motions of a slow nature. It was found, however, 74 00:05:44.120 --> 00:05:47.360 that they would not conform to the rapid motions apparent 75 00:05:47.519 --> 00:05:53.959 in electrodynamics. This led the Dutch professor Laurentz and myself 76 00:05:54.439 --> 00:06:00.000 to develop the theory of special relativity. Briefly, it discovered 77 00:06:00.000 --> 00:06:03.480 Cauard's absolute time and space and makes them in every 78 00:06:03.519 --> 00:06:08.800 instance relative to moving systems. By this theory, all phenomena 79 00:06:08.920 --> 00:06:14.000 in electrodynamics as well as mechanics hitherto irreducible by the 80 00:06:14.040 --> 00:06:21.199 old formulae and there are multitudes was satisfactorily explained. Till now, 81 00:06:21.240 --> 00:06:25.040 it was believed that time and space existed by themselves 82 00:06:25.600 --> 00:06:29.120 even if there was nothing else, no Sun, no Earth, 83 00:06:29.439 --> 00:06:32.879 no stars, while now we know that time and space 84 00:06:32.959 --> 00:06:35.920 are not the vessel for the universe, but could not 85 00:06:36.079 --> 00:06:40.560 exist at all if there were no contents, namely no Sun, 86 00:06:40.920 --> 00:06:47.199 Earth and other celestial bodies. This special relativity forming the 87 00:06:47.240 --> 00:06:51.360 first part of my theory, relates to all systems moving 88 00:06:51.480 --> 00:06:55.800 with uniform motion, that is, moving in a straight line 89 00:06:55.920 --> 00:07:00.680 with equal velocity Gradually. I was led to the idea, 90 00:07:01.240 --> 00:07:04.800 seeming a very paradox in science, that it might apply 91 00:07:05.000 --> 00:07:10.160 equally to all moving systems, even of deformed motion, and 92 00:07:10.240 --> 00:07:14.720 thus I developed the conception of general relativity, which forms 93 00:07:14.759 --> 00:07:19.959 the second part of my theory, as summarized by an 94 00:07:19.959 --> 00:07:24.800 American astronomer, Professor Henry Norris Russell of Princeton, in the 95 00:07:24.839 --> 00:07:30.480 Scientific American for November twenty nine. Einstein's contribution amounts to this. 96 00:07:31.759 --> 00:07:34.959 The central fact which has been proved, and which is 97 00:07:35.000 --> 00:07:39.959 of great interest and importance, is that the natural phenomena 98 00:07:40.160 --> 00:07:45.199 involving gravitation and inertia, such as the motions of the planets, 99 00:07:45.639 --> 00:07:50.680 and the phenomena involving electricity and magnetism, including the motion 100 00:07:50.800 --> 00:07:54.680 of light, are not independent of one another, but are 101 00:07:54.720 --> 00:07:58.800 intimately related, so that both sets of phenomena should be 102 00:07:58.879 --> 00:08:03.480 regarded as parts of one vast system embracing all nature. 103 00:08:04.439 --> 00:08:07.399 The relation of the two is, however, of such a 104 00:08:07.519 --> 00:08:11.959 character that it is perceptible only in a very few instances, 105 00:08:12.639 --> 00:08:18.240 and then only to refined observations. Already before the war, 106 00:08:18.519 --> 00:08:22.680 Einstein had immense fame among physicists and among all who 107 00:08:22.720 --> 00:08:26.319 are interested in the philosophy of science because of his 108 00:08:26.519 --> 00:08:32.840 principle of relativity. Clark Maxwell had shown that light is electromagnetic, 109 00:08:33.320 --> 00:08:37.120 and had reduced the whole theory of electromagnetism to a 110 00:08:37.159 --> 00:08:41.919 small number of equations, which are fundamental in all subsequent work. 111 00:08:43.000 --> 00:08:46.720 But these equations were entangled with the hypothesis of the ether, 112 00:08:47.440 --> 00:08:50.480 and was the notion of motion relative to the ether. 113 00:08:51.480 --> 00:08:54.840 Since the Ether was supposed to be at rest, such 114 00:08:54.919 --> 00:08:59.679 motion was indistinguishable from absolute motion. The motion of the 115 00:08:59.679 --> 00:09:03.279 Earth relatively to the Ether should have been different at 116 00:09:03.399 --> 00:09:07.360 different points of its orbit, and measurable phenomena should have 117 00:09:07.440 --> 00:09:12.440 resulted from this difference, but none did, and all attempts 118 00:09:12.480 --> 00:09:16.320 to detect defects of motions relative to the ether failed. 119 00:09:17.399 --> 00:09:21.279 The theory of relativity succeeded in accounting for this fact, 120 00:09:22.039 --> 00:09:26.000 but it was necessary, incidentally, to throw over the one 121 00:09:26.200 --> 00:09:31.840 universal time and substitute local times attached to moving bodies 122 00:09:31.879 --> 00:09:36.440 and varying according to their motion. The equations on which 123 00:09:36.440 --> 00:09:40.039 the theory of relativity is based are due to Laurents, 124 00:09:40.639 --> 00:09:45.240 but Einstein connected them with his general principle, namely that 125 00:09:45.320 --> 00:09:49.240 there must be nothing in observable phenomena which could be 126 00:09:49.320 --> 00:09:56.639 attributed to absolute motion of the observer. In orthodox Newtonian dynamics, 127 00:09:56.679 --> 00:10:00.519 the principle of relativity had a simpler form, which did 128 00:10:00.559 --> 00:10:04.159 not require the substitution of local time for general time. 129 00:10:05.120 --> 00:10:08.720 But it now appeared that Newtonian dynamics is only valid 130 00:10:08.879 --> 00:10:13.039 when we confine ourselves to velocities much less than that 131 00:10:13.159 --> 00:10:17.879 of light. The whole Galileo Newton system thus sank to 132 00:10:17.960 --> 00:10:22.799 the level of a first approximation, becoming progressively less exact 133 00:10:23.200 --> 00:10:30.039 as the velocities concerned approached that of light. Einstein's extension 134 00:10:30.039 --> 00:10:33.320 of his principle so as to account for gravitation was 135 00:10:33.360 --> 00:10:37.279 made during the war, and for a considerable period our 136 00:10:37.320 --> 00:10:41.639 astronomers were unable to become acquainted with it, owing to 137 00:10:41.679 --> 00:10:47.360 the difficulty of obtaining German printed matter. However, copies of 138 00:10:47.399 --> 00:10:51.600 his work ultimately reached the outside world and enabled people 139 00:10:51.679 --> 00:10:56.639 to learn more about it. Gravitation. Ever since Newton had 140 00:10:56.679 --> 00:11:01.279 remained isolated from other forces in nature. Various attempts had 141 00:11:01.320 --> 00:11:05.480 been made to account for it, but without success. The 142 00:11:05.559 --> 00:11:11.360 immense unification effected by electromagnetism apparently left gravitation out of 143 00:11:11.440 --> 00:11:15.759 its scope. It seemed that nature had presented a challenge 144 00:11:15.799 --> 00:11:19.159 to the physicists which none of them were able to meet. 145 00:11:20.879 --> 00:11:26.039 At this point, Einstein intervened with a hypothesis which, apart 146 00:11:26.200 --> 00:11:30.799 altogether from subsequent verification deserves to rank as one of 147 00:11:30.840 --> 00:11:36.039 the great monuments of human genius. After correcting Newton, it 148 00:11:36.159 --> 00:11:39.480 remained to correct Euclid, and it was in terms of 149 00:11:39.559 --> 00:11:44.399 non Euclidean geometry that he stated his new theory. Non 150 00:11:44.440 --> 00:11:48.279 Euclidean geometry is a study of which the primary motive 151 00:11:48.480 --> 00:11:53.240 was logical and philosophical. Few of its promoters ever dreamed 152 00:11:53.360 --> 00:11:56.840 that it would come to be applied in physics. Some 153 00:11:56.919 --> 00:12:01.080 of Euclid's axioms were felt to be not neces serie truths, 154 00:12:01.600 --> 00:12:05.919 but mere empirical laws. In order to establish this view, 155 00:12:06.360 --> 00:12:11.159 self consistent geometries were constructed upon assumptions other than those 156 00:12:11.200 --> 00:12:15.840 of Euclid. In these geometries, the sum of the angles 157 00:12:15.879 --> 00:12:19.799 of a triangle is not two right angles, and the 158 00:12:19.879 --> 00:12:23.840 departure from two right angles increases as the size of 159 00:12:23.879 --> 00:12:28.240 the triangle increases. It is often said that in non 160 00:12:28.279 --> 00:12:32.519 Euclidean geometry, space has a curvature, but this way of 161 00:12:32.600 --> 00:12:36.120 stating the matter is misleading, since it seems to imply 162 00:12:36.240 --> 00:12:40.279 a fourth dimension which is not implied by these systems. 163 00:12:41.799 --> 00:12:46.000 Einstein supposes that space is Euclidean where it is sufficiently 164 00:12:46.120 --> 00:12:49.840 remote from matter, but that the presence of matter causes 165 00:12:49.879 --> 00:12:54.120 it to become slightly non Euclidean. The more matter there 166 00:12:54.200 --> 00:12:57.399 is in the neighborhood, the more space will depart from 167 00:12:57.440 --> 00:13:02.000 euclid By the help of this hypothesis, together with his 168 00:13:02.159 --> 00:13:08.320 previous theory of relativity, he deduces gravitation very approximately but 169 00:13:08.440 --> 00:13:13.440 not exactly according to the Newtonian law of the inverse square. 170 00:13:15.159 --> 00:13:19.159 The minute differences between the effects deduced from his theory 171 00:13:19.639 --> 00:13:24.000 and those deduced from Newton are measurable in certain cases. 172 00:13:24.720 --> 00:13:28.600 There are so far three crucial tests of the relative 173 00:13:28.679 --> 00:13:34.720 accuracy of the new theory and the old one. The 174 00:13:34.759 --> 00:13:40.039 perihelion of mercury shows a discrepancy which has long puzzled astronomers. 175 00:13:40.919 --> 00:13:45.440 This discrepancy is fully accounted for by Einstein. At the 176 00:13:45.519 --> 00:13:48.679 time when he published his theory, this was its only 177 00:13:48.799 --> 00:13:56.559 experimental verification. Two modern physicists were willing to suppose that 178 00:13:56.720 --> 00:14:01.000 light might be subject to gravitation, i e. That a 179 00:14:01.120 --> 00:14:03.960 ray of light passing near a great mass like the 180 00:14:04.080 --> 00:14:07.600 Sun might be deflected to the extent to which a 181 00:14:07.759 --> 00:14:12.639 particle moving with the same velocity would be deflected according 182 00:14:12.679 --> 00:14:18.279 to the orthodox theory of gravitation. But Einstein's theory required 183 00:14:18.559 --> 00:14:21.840 that the light should be deflected just twice as much 184 00:14:21.960 --> 00:14:25.919 as this. The matter could only be tested during an 185 00:14:25.919 --> 00:14:31.240 eclipse among a number of bright stars. Fortunately, a peculiarly 186 00:14:31.320 --> 00:14:36.200 favorable eclipse occurred last year. The results of the observations 187 00:14:36.240 --> 00:14:40.600 have now been published and are found to verify Einstein's prediction. 188 00:14:41.600 --> 00:14:46.279 The verification is not, of course quite exact. With such 189 00:14:46.360 --> 00:14:50.279 delicate observations, that was not to be expected. In some 190 00:14:50.480 --> 00:14:55.600 cases the departure is considerable, but taking the advantage of 191 00:14:55.639 --> 00:14:59.559 the best series of observations, the deflection at the Sun's 192 00:14:59.600 --> 00:15:03.559 limb is found to be one point nine eight seconds, 193 00:15:03.600 --> 00:15:07.440 with a probable error of about six percent, whereas the 194 00:15:07.519 --> 00:15:12.720 deflection calculated by Einstein's theory should be one point seventy 195 00:15:12.840 --> 00:15:17.679 five seconds. It will be noticed that Einstein's theory gave 196 00:15:17.679 --> 00:15:20.840 a deflection twice as large as that predicted by the 197 00:15:20.960 --> 00:15:25.720 orthodox theory, and that the observed deflection is slightly larger 198 00:15:25.759 --> 00:15:30.440 than Einstein predicted. The discrepancy is well within what might 199 00:15:30.480 --> 00:15:34.240 be expected in view of the minuteness of the measurements. 200 00:15:34.840 --> 00:15:39.080 It is therefore generally acknowledged by astronomers that the outcome 201 00:15:39.240 --> 00:15:46.080 is a triumph for Einstein. Three. In the excitement of 202 00:15:46.120 --> 00:15:50.559 this sensational verification, there has been a tendency to overlook 203 00:15:50.600 --> 00:15:54.840 the third experimental test to which Einstein's theory was to 204 00:15:54.879 --> 00:15:59.159 be subjected. If his theory as correct as it stands, 205 00:15:59.399 --> 00:16:03.440 there odd in a gravitational field to be a displacement 206 00:16:03.519 --> 00:16:07.200 of the lines of the spectrum towards the red. No 207 00:16:07.360 --> 00:16:12.840 such effect has been discovered. Spectroscopists maintain that, so far 208 00:16:12.879 --> 00:16:15.600 as can be seen at present, there is no way 209 00:16:15.639 --> 00:16:19.200 of accounting for this failure if Einstein's theory in its 210 00:16:19.200 --> 00:16:24.639 present form is assumed. They admit that some compensating cause 211 00:16:24.840 --> 00:16:28.840 may be discovered to explain the discrepancy, but they think 212 00:16:28.879 --> 00:16:36.120 it far more probable that Einstein's theory requires some essential modification. Meanwhile, 213 00:16:36.360 --> 00:16:40.200 a certain suspense of judgment is called for. The new 214 00:16:40.279 --> 00:16:43.440 law has been so amazingly successful in two of the 215 00:16:43.519 --> 00:16:47.120 three tests that there must be something valid about it, 216 00:16:47.720 --> 00:16:53.320 even if it is not exactly right. As yet, Einstein's 217 00:16:53.360 --> 00:16:57.679 theory has the very highest degree of esthetic merit. Every 218 00:16:57.759 --> 00:17:01.080 lover of the beautiful must wish it to be true. 219 00:17:01.879 --> 00:17:05.240 It gives a vast, unified survey of the operations of 220 00:17:05.359 --> 00:17:10.160 nature with a technical simplicity in the critical assumptions, which 221 00:17:10.200 --> 00:17:14.240 makes the wealth of deductions astonishing. It is a case 222 00:17:14.279 --> 00:17:18.240 of an advance arrived at by pure theory. The hole 223 00:17:18.279 --> 00:17:22.119 effect of Einstein's work is to make physics more philosophical 224 00:17:22.720 --> 00:17:25.839 in a good sense, and to restore some of that 225 00:17:26.000 --> 00:17:30.279 intellectual unity which belonged to the great scientific systems of 226 00:17:30.319 --> 00:17:34.839 the seventeenth and eighteenth centuries, but which was lost through 227 00:17:34.920 --> 00:17:40.920 increasing specialization and the overwhelming mass of detailed knowledge. In 228 00:17:40.960 --> 00:17:43.400 some ways, our age is not a good one to 229 00:17:43.480 --> 00:17:46.839 live in, but for those who are interested in physics 230 00:17:47.119 --> 00:18:00.359 there are great compensations. End of section one Section two 231 00:18:00.400 --> 00:18:05.240 of The Einstein Theory of Relativity by Hendrik A. Laurentz. 232 00:18:06.200 --> 00:18:10.079 This LibriVox recording is in the public domain. Recording by 233 00:18:10.240 --> 00:18:16.279 ABAI in February twenty twenty The Einstein Theory of Relativity 234 00:18:16.920 --> 00:18:21.160 a concise statement by Professor H. A. Lorentz of the 235 00:18:21.279 --> 00:18:27.160 University of Leiden. The total eclipse of the Sun on 236 00:18:27.279 --> 00:18:31.160 May twenty ninth resulted in a striking confirmation of the 237 00:18:31.240 --> 00:18:36.200 new theory of the universal attractive power of gravitation developed 238 00:18:36.240 --> 00:18:41.079 by Albert Einstein, and thus reinforced the conviction that the 239 00:18:41.160 --> 00:18:44.680 defining of this theory is one of the most important 240 00:18:44.720 --> 00:18:49.359 steps ever taken in the domain of natural science. In 241 00:18:49.400 --> 00:18:52.680 response to a request by the editor, I will attempt 242 00:18:52.720 --> 00:18:57.519 to contribute something to its general appreciation in the following lines. 243 00:18:59.279 --> 00:19:03.799 For centuries, Newton's doctrine of the attraction of gravitation has 244 00:19:03.880 --> 00:19:07.599 been the most prominent example of a theory of natural science. 245 00:19:08.640 --> 00:19:12.920 Through the simplicity of its basic idea, an attraction between 246 00:19:13.000 --> 00:19:17.319 two bodies proportionate to their mass and also proportionate to 247 00:19:17.400 --> 00:19:21.640 the square of the distance, through the completeness with which 248 00:19:21.680 --> 00:19:25.480 it explained so many of the peculiarities in the movement 249 00:19:25.599 --> 00:19:29.680 of the bodies making up the Solar System, and finally, 250 00:19:29.880 --> 00:19:33.359 through its universal validity even in the case of the 251 00:19:33.400 --> 00:19:38.319 far distant planetary systems. It compelled the admiration of all. 252 00:19:39.720 --> 00:19:43.440 But while the skill of the mathematicians was devoted to 253 00:19:43.519 --> 00:19:48.079 making more exact calculations of the consequences to which it led, 254 00:19:48.839 --> 00:19:52.079 no real progress was made in the science of gravitation. 255 00:19:53.279 --> 00:19:56.480 It is true that the inquiry was transferred to the 256 00:19:56.480 --> 00:20:02.000 field of physics following Cavendish's success in demonstrating the common 257 00:20:02.039 --> 00:20:06.640 attraction between bodies with which laboratory work can be done. 258 00:20:07.200 --> 00:20:10.960 But it always was evident that natural philosophy had no 259 00:20:11.079 --> 00:20:16.400 grip on the universal power of attraction. While in electric effects, 260 00:20:16.440 --> 00:20:20.680 an influence exercised by the matter placed between bodies was 261 00:20:20.839 --> 00:20:25.000 speedily observed the starting point of a new and fertile 262 00:20:25.039 --> 00:20:29.519 doctrine of electricity. In the case of gravitation, not a 263 00:20:29.680 --> 00:20:33.920 trace of an influence exercised by intermediate matter could ever 264 00:20:33.960 --> 00:20:40.960 be discovered. It was and remained inaccessible and unchangeable, without 265 00:20:41.079 --> 00:20:47.960 any connection, apparently with other phenomena of natural philosophy. Einstein 266 00:20:48.039 --> 00:20:51.160 has put an end to this isolation. It is now 267 00:20:51.200 --> 00:20:56.519 well established that gravitation effects not only matter but also light. 268 00:20:57.720 --> 00:21:02.000 Thus strengthened in the face that his theory already has inspired, 269 00:21:02.519 --> 00:21:05.039 we may assume with him that there is not a 270 00:21:05.079 --> 00:21:10.119 single physical or chemical phenomenon which does not feel, although 271 00:21:10.240 --> 00:21:15.000 very probably in an unnoticeable degree, the influence of gravitation, 272 00:21:15.839 --> 00:21:19.799 and that, on the other side, the attraction exercised by 273 00:21:19.839 --> 00:21:22.880 a body is limited in the first place by the 274 00:21:23.000 --> 00:21:27.559 quantity of matter it contains, and also to some degree 275 00:21:27.880 --> 00:21:32.119 by motion, and by the physical and chemical condition in 276 00:21:32.200 --> 00:21:37.200 which it moves. It is comprehensible that a person could 277 00:21:37.200 --> 00:21:40.240 not have arrived at such a far reaching change of 278 00:21:40.319 --> 00:21:44.799 view by continuing to follow the old beaten paths, but 279 00:21:44.960 --> 00:21:50.440 only by introducting some sort of new idea. Indeed, Einstein 280 00:21:50.559 --> 00:21:53.559 arrived at his theory through a train of thought of 281 00:21:53.640 --> 00:21:59.759 great originality. Let me try to restate it in concise terms. 282 00:22:02.519 --> 00:22:12.119 End of section two Section three of the Einstein Theory 283 00:22:12.160 --> 00:22:17.319 of Relativity by Hendrik A. Lorentz. This LibriVox recording is 284 00:22:17.359 --> 00:22:21.400 in the public domain. Recording by A. Vai in February 285 00:22:21.480 --> 00:22:28.279 twenty twenty. The Earth as a moving car. Everyone knows 286 00:22:28.319 --> 00:22:30.960 that a person may be sitting in any kind of 287 00:22:31.000 --> 00:22:35.359 a vehicle without noticing its progress, so long as the 288 00:22:35.440 --> 00:22:39.559 movement does not vary in direction or speed. In a 289 00:22:39.640 --> 00:22:43.400 car of a fast express train, objects fall in just 290 00:22:43.519 --> 00:22:46.480 the same way as in a coach that is standing still. 291 00:22:47.640 --> 00:22:51.240 Only when we look at objects outside the train, or 292 00:22:51.319 --> 00:22:54.400 when the air can enter the car, do we notice 293 00:22:54.480 --> 00:22:59.000 indications of the motion. We may compare the Earth with 294 00:22:59.279 --> 00:23:02.720 such a movie vehicle, which, in its course around the 295 00:23:02.759 --> 00:23:06.559 Sun has a remarkable speed, of which the direction and 296 00:23:06.680 --> 00:23:11.279 velocity during a considerable period of time may be regarded 297 00:23:11.440 --> 00:23:15.960 as constant In place of the air now comes. So 298 00:23:16.160 --> 00:23:20.359 it was reasoned formally the ether which fills the spaces 299 00:23:20.359 --> 00:23:23.559 of the universe and is the carrier of light and 300 00:23:23.640 --> 00:23:28.240 of electromagnetic phenomena. There were good reasons to assume that 301 00:23:28.279 --> 00:23:31.960 the Earth was entirely permeable for the ether, and could 302 00:23:32.000 --> 00:23:36.319 travel through it without setting it in motion. So here 303 00:23:36.440 --> 00:23:39.759 was a case comparable with that of a railroad coach 304 00:23:40.039 --> 00:23:44.200 open on all sides. There certainly should have been a 305 00:23:44.359 --> 00:23:49.079 powerful ether wind blowing through the Earth and all our instruments, 306 00:23:49.640 --> 00:23:52.640 and it was to have been expected that some signs 307 00:23:52.680 --> 00:23:56.200 of it would be noticed in connection with some experiment 308 00:23:56.480 --> 00:24:02.240 or other. Every attempt along that line, however, has remained fruitless. 309 00:24:02.880 --> 00:24:07.240 All the phenomena examined were evidently independent of the motion 310 00:24:07.440 --> 00:24:10.519 of the Earth. That this is the way they do 311 00:24:10.680 --> 00:24:14.000 function was brought to the front by Einstein in his 312 00:24:14.240 --> 00:24:19.640 first or special theory of relativity. For him, the ether 313 00:24:19.880 --> 00:24:23.119 does not function, And then the sketch that he draws 314 00:24:23.119 --> 00:24:27.279 of natural phenomena, there is no mention of that intermediate matter. 315 00:24:28.680 --> 00:24:32.039 If the spaces of the universe are filled with an ether, 316 00:24:32.720 --> 00:24:36.519 let us suppose with the substance in which, aside from 317 00:24:36.599 --> 00:24:41.160 eventual vibrations and other slight movements. There is never any 318 00:24:41.240 --> 00:24:46.079 crowding or flowing of one part alongside of another. Then 319 00:24:46.119 --> 00:24:50.319 we can imagine fixed points existing in it. For example, 320 00:24:50.799 --> 00:24:55.559 points in a straight line located one meter apart, points 321 00:24:55.640 --> 00:24:59.240 in a level plane like the angles or squares on 322 00:24:59.279 --> 00:25:04.519 a chessboard word extending out into infinity, and finally points 323 00:25:04.599 --> 00:25:08.480 in space, as they are obtained by repeatedly shifting that 324 00:25:08.599 --> 00:25:11.599 level spot a distance of a meter in the direction 325 00:25:11.799 --> 00:25:17.319 perpendicular to it. If consequently one of the points is 326 00:25:17.440 --> 00:25:22.799 chosen as an original point, we can, proceeding from that point, 327 00:25:23.319 --> 00:25:26.839 reach any other point through three steps in the common 328 00:25:26.880 --> 00:25:32.319 perpendicular directions in which the points are arranged. The figures 329 00:25:32.400 --> 00:25:35.559 showing how many meters are comprised in each of the 330 00:25:35.640 --> 00:25:40.000 steps may serve to indicate the place reached and to 331 00:25:40.119 --> 00:25:43.960 distinguish it from any other these are as. Is said, 332 00:25:44.319 --> 00:25:49.480 the coordinates of these places comparable, for example, with the 333 00:25:49.559 --> 00:25:54.960 numbers on a map giving the longitude and latitude. Let 334 00:25:55.039 --> 00:25:58.279 us imagine that each point has noted upon it the 335 00:25:58.359 --> 00:26:01.720 three numbers that give its place position. Then we have 336 00:26:01.839 --> 00:26:06.799 something comparable with a measure with numbered subdivisions. Only we 337 00:26:06.920 --> 00:26:10.079 now have to do, one might say, with a good 338 00:26:10.119 --> 00:26:15.720 many imaginary measures in three common perpendicular directions. In this 339 00:26:16.200 --> 00:26:20.039 system of coordinates, the numbers that fix the position of 340 00:26:20.200 --> 00:26:23.079 one or the other of the bodies may now be 341 00:26:23.160 --> 00:26:27.519 read off at any moment. This is the means which 342 00:26:27.559 --> 00:26:32.519 the astronomers and their mathematical assistance have always used in 343 00:26:32.599 --> 00:26:36.559 dealing with the movement of the heavenly bodies. At a 344 00:26:36.640 --> 00:26:40.559 determined moment, the position of each body is fixed by 345 00:26:40.599 --> 00:26:45.319 its three coordinates. If these are given, then one knows 346 00:26:45.359 --> 00:26:49.680 also the common distances, as well as the angles formed 347 00:26:49.720 --> 00:26:53.200 by the connecting lines, and the movement of a planet 348 00:26:53.319 --> 00:26:56.000 is to be known as soon as one knows how 349 00:26:56.039 --> 00:27:01.359 its coordinates are changing from one moment to the other. Thus, 350 00:27:01.400 --> 00:27:05.039 the picture that one forms of the phenomena stands there 351 00:27:05.079 --> 00:27:07.519 as if it were sketched on the canvas of the 352 00:27:07.559 --> 00:27:19.960 motionless ether. End of section three Section four of the 353 00:27:20.000 --> 00:27:25.640 Einstein Theory of Relativity by Hendrik A. Lorentz. This LibriVox 354 00:27:25.680 --> 00:27:29.759 recording is in the public domain. Recording by AVAI in 355 00:27:29.799 --> 00:27:38.480 February twenty twenty Einstein's departure. Since Einstein has cut loose 356 00:27:38.559 --> 00:27:42.960 from the ether, he lacks this canvas, and therewith at 357 00:27:43.000 --> 00:27:47.319 the first glance also loses the possibility of fixing the 358 00:27:47.359 --> 00:27:52.319 positions of the heavenly bodies and mathematically describing their movement, 359 00:27:53.000 --> 00:27:57.279 that is, by giving comparisons that define the positions at 360 00:27:57.400 --> 00:28:02.440 every moment. How einstein Lie has overcome this difficulty may 361 00:28:02.480 --> 00:28:08.279 be somewhat elucidated through a simple illustration. On the surface 362 00:28:08.319 --> 00:28:12.440 of the Earth, the attraction of gravitation causes all bodies 363 00:28:12.519 --> 00:28:17.240 to fall along vertical lines, and indeed, when one omits 364 00:28:17.319 --> 00:28:21.640 the resistance of the air with an equally accelerated movement, 365 00:28:22.359 --> 00:28:27.599 the velocity increases in equal degrees in equal consecutive divisions 366 00:28:27.640 --> 00:28:31.759 of time, at a rate that in this country gives 367 00:28:31.759 --> 00:28:35.200 the velocity attained at the end of a second as 368 00:28:35.359 --> 00:28:39.680 nine hundred eighty one centimeters thirty two point two feet 369 00:28:40.279 --> 00:28:45.319 per second. The number nine hundred eighty one defines the 370 00:28:45.839 --> 00:28:50.240 acceleration in the field of gravitation, and this field is 371 00:28:50.359 --> 00:28:54.759 fully characterized by that single number. With its help, we 372 00:28:54.839 --> 00:28:58.279 can also calculate the movement of an object hurled out 373 00:28:58.359 --> 00:29:03.440 in an arbitrary direction. In order to measure the acceleration, 374 00:29:03.920 --> 00:29:07.279 we let the body drop alongside of a vertical measure 375 00:29:07.559 --> 00:29:11.359 set solidly on the ground. On this scale, we read 376 00:29:11.400 --> 00:29:15.240 at every moment the figure that indicates the height, the 377 00:29:15.359 --> 00:29:19.759 only coordinate that is of importance in this rectilinear movement. 378 00:29:21.079 --> 00:29:23.920 Now we ask what would we be able to see 379 00:29:24.119 --> 00:29:27.240 if the measure were not bound solidly to the earth, 380 00:29:27.960 --> 00:29:31.799 if it, let us suppose, moved down or up with 381 00:29:31.960 --> 00:29:36.039 the place where it is located and where we are ourselves. 382 00:29:37.079 --> 00:29:40.960 If in this case the speed were constant, then and 383 00:29:41.279 --> 00:29:44.640 this is in accord with the special theory of relativity, 384 00:29:45.240 --> 00:29:48.279 there would be no motion observed at all. We should 385 00:29:48.279 --> 00:29:51.960 again find an acceleration of nine hundred eighty one for 386 00:29:52.079 --> 00:29:55.920 a falling body. It would be different if the measure 387 00:29:56.000 --> 00:30:00.720 moved with changeable velocity. If it went down with a 388 00:30:00.799 --> 00:30:05.240 constant acceleration of nine hundred eighty one itself, then an 389 00:30:05.240 --> 00:30:09.200 object could remain permanently at the same point on the measure, 390 00:30:10.000 --> 00:30:13.400 or could move up or down itself alongside of it 391 00:30:13.759 --> 00:30:18.680 with constant speed. The relative movement of the body with 392 00:30:18.839 --> 00:30:23.279 regard to the measure should be without acceleration. And if 393 00:30:23.319 --> 00:30:26.319 we had to judge only by what we observed in 394 00:30:26.400 --> 00:30:30.039 the spot where we were and which was falling itself, 395 00:30:30.720 --> 00:30:33.359 then we should get the impression that there was no 396 00:30:33.440 --> 00:30:37.839 gravitation at all. If the measure goes down with an 397 00:30:37.880 --> 00:30:41.680 acceleration equal to a half or a third of what 398 00:30:41.839 --> 00:30:45.720 it just was, then the relative motion of the body 399 00:30:45.799 --> 00:30:50.400 will of course be accelerated. But we should find the 400 00:30:50.519 --> 00:30:55.319 increase in velocity per second one half or two thirds 401 00:30:55.400 --> 00:31:00.720