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I've encountered the claim that around the end of the 19th century, physicists believed that their understanding of the physical world was close to being complete.

One example of this claim can be found in Wikipedia's article on History of physics

... So profound were these and other developments that it was generally accepted that all the important laws of physics had been discovered and that, henceforth, research would be concerned with clearing up minor problems and particularly with improvements of method and measurement.

Was this really generally accepted? What sources support that?

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    $\begingroup$ I add it as a comment as it is just another quote (but it is quite fun). Planck was told around 1875 by one of his teachers (von Jolly) not to go into physics as there almost everything is already discovered, and all that remains is to fill a few unimportant holes. $\endgroup$ – quid Nov 2 '14 at 18:21
  • $\begingroup$ @quid Interesting. Do you know of a credible source for that? $\endgroup$ – Ofri Raviv Nov 2 '14 at 18:44
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    $\begingroup$ The story was told by Planck himself in a talk decades latter (mid twenties) and this account is published see de.wikipedia.org/wiki/Philipp_von_Jolly#cite_note-5 The paraphrase I gave is from the English version of the same page. $\endgroup$ – quid Nov 2 '14 at 19:24
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On the other hand, consider this quote from The Feynman Lectures on Physics

[In 1869], in a lecture, [Maxwell] said, “I have now put before you what I consider to be the greatest difficulty yet encountered by the molecular theory.” These words represent the first discovery that the laws of classical physics were wrong. This was the first indication that there was something fundamentally impossible, because a rigorously proved theorem did not agree with experiment. About 1905, Sir James Hopwood Jeans and Lord Rayleigh (John William Strutt) were to talk about this puzzle again. One often hears it said that physicists at the latter part of the nineteenth century thought they knew all the significant physical laws and that all they had to do was to calculate more decimal places. Someone may have said that once, and others copied it. But a thorough reading of the literature of the time shows they were all worrying about something. Jeans said about this puzzle that it is a very mysterious phenomenon, and it seems as though as the temperature falls, certain kinds of motions “freeze out.”

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    $\begingroup$ Thanks. I had a feeling that claim was just a fairytale physics professors tell their students to teach them humbleness. I'm glad to see I'm not the only one that feels that way... $\endgroup$ – Ofri Raviv Nov 2 '14 at 19:04
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According to (the late) William Strauss and Neil Howe in Generations, there are periodic episodes of scientific exhaustion, at least in the United States. For instance, around 1910, the head of the U.S. patent office was (mis)quoted as saying: "Everything that can be invented has been invented." In 1992, Francis Fukuyama famously opined about "the end of history." These "periods" occur roughly eighty years, or four generations apart.

What really happened was that these remarks followed a recent burst of scientific achievement; the space program and "star wars" in Fukuyama's case, and the industrialization of America, in the earlier case. At one level, such people are "right;" the recent pace of scientific achievement can't be maintained. But they then wrongly conclude that scientific progress has "come to an end."

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  • $\begingroup$ I fail to see how this answers my question. Aside from being US-centric (as opposed to the advances in physics at the time, which were primarily in Europe), this answer relates to why people would believe that everything has been discovered, and not to what I asked - did they really believe that? $\endgroup$ – Ofri Raviv Nov 2 '14 at 18:56
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    $\begingroup$ @OfriRaviv: Actually, Strauss and Howe (S&H) is an ANGLO-American model, beginning in 1584 in ENGLAND, and it basically applies to the Anglo-American world. Lord Kelvin was an Englishman, meaning that his sentiments could be explained by (S&H). That said, "answering "why" supports the answer of "what," given by someone else. (The weakness of S&H is that it does not explain sentiments on Continental Europe, Asia, or Africa.You asked if this theory was generally accepted, and asked for sources. I answered that it had (at least) limited (e.g. U.S.) acceptance and gave you my source. $\endgroup$ – Tom Au Nov 2 '14 at 19:27
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See, for instance, A. A. Michelson's claim in the second lecture of his 1899 (pub. 1903) lectures Light Waves and Their Uses:

Before entering into these details, however, it may be well to reply to the very natural question: What would be the use of such extreme refinement in the science of measurement? Very briefly and in general terms the answer would be that in this direction the greater part of all future discovery must lie. The more important fundamental laws and facts of physical science have all been discovered, and these are now so firmly established that the possibility of their ever being supplanted in consequence of new discoveries is exceedingly remote. Nevertheless, it has been found that there are apparent exceptions to most of these laws, and this is particularly true when the observations are pushed to a limit, i. e., whenever the circumstances of experiment are such that extreme cases can be examined. Such examination almost surely leads, not to the overthrow of the law, but to the discovery of other facts and laws whose action produces the apparent exceptions.

It is unclear to me whether this was merely an unpopular, optimistic bluster, or whether this quote represents an entire school of thought at the time. Especially troublesome to me is Michelson's involvement in the famous 1880s experiments on light and ether... surely the conflicting results gave him some pause?

On the other hand, note his last two sentences above - Michelson is clearly not positing that all of physics is "done" per se. Instead, his view seems to be that "the more important fundamental laws" are correct, modulo certain small improvements that can still be made.

Perhaps it is this bolded statement that represented the general attitude of the time, and not the statement that physics was "finished." Of course, while this quote does not conclusively answer your first question, it does provide another data point towards the second.

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  • $\begingroup$ +1 This quote certainly does seem to be indicative of the academic attitudes of the age. $\endgroup$ – user22 Nov 3 '14 at 5:51
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    $\begingroup$ What strikes me is the last sentence of the quote, "leads... to the discovery of other facts and laws..." Michelson, the consummate experimentalist and measurer of constants, argues that the path forward is through measurement, especially beyond the limits of the currently verified regime. I think there is considerable merit in his position, even viewed with 20/20 hindsight. $\endgroup$ – Michael Weiss Nov 3 '14 at 17:18
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I'll add more later, but for now consider this quote by Lord Kelvin:

There is nothing new to be discovered in physics now. All that remains is more and more precise measurement.

I believe this is what the Wikipedia article you found is talking about. Wikipedia also references this. Note, though, that its accuracy is disputed. However, it still sums up the feelings of some at the time.

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    $\begingroup$ As the author of the website you reference states: "Webmaster has searched for a primary print source without success. Walter Isaacson likewise found no direct evidence, as he reports in Einstein (2007)". Furthermore, it does not even claim to represent a generally accepted view, but rather the view of one (albeit important) person. $\endgroup$ – Ofri Raviv Nov 2 '14 at 18:49
  • $\begingroup$ @OfriRaviv I know about both issues. My answer still needs improving. However, I felt it was important to include the quote because it was what the Wikipedia page alluded to. But yes, the accuracy of the quote is disputed, as wikiquote alludes to. $\endgroup$ – HDE 226868 Nov 2 '14 at 18:54
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    $\begingroup$ Kelvin also said Heavier than air flying machines are impossible $\endgroup$ – gerrit Feb 3 '15 at 20:25
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    $\begingroup$ @gerrit He was a brilliant man, but not a brilliant prophet. $\endgroup$ – HDE 226868 Feb 3 '15 at 21:50

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