# Talk:Pierre-Simon Laplace

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## Untitled

Can we see his calculation of the mass of Saturn?

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## Pronunciation

How do you pronounce his name? "Lap-lace", or "law-plause"? Anyone trying to record the Featured article on Free Will needs to know this. -William Morgan

it's pronounced "la" (the a is sounded as in father) - "plass" (rhymes with glass) --Sysys 00:46, 6 March 2006 (UTC)

You are correct on the first syllable, but not the second. The "a" in both syllables rhymes with the a in "father." So the correct pronunciation is "Lahh - plahhss". -- Metacomet 01:55, 6 March 2006 (UTC)
I can't imagine any French-speaking person pronouncing it that way. If split into the root words "la" and "place" ("the" and "place" in English), both a's are pronounced as the one in "glass". Dictionary.com seems to disagree, but I can't see why the name would have such an odd pronunciation given that it's constructed from such simple words (unless they're unrelated, which would seem bizarre). -- 70.81.118.123 09:28, 28 April 2006 (UTC)
A French dictionnary gives the pronunciation in international phonetic spelling (for both root words) [la] [plas]. It is not Lap-lace but La-place (two syllables with a close to "glass" — although I don't know the difference between the "a" in "father" and in "glass"...) Santa Sangre 15:57, 4 June 2006 (UTC)
The problem with your discussion on how the 'a' in glass should sound probably lies with the fact that one of you two is american, the other british? Both a's in laplace are pronounced as they are in father, or the british pronunciation of glass —Preceding unsigned comment added by 130.89.192.56 (talk) 13:37, 26 June 2006
F(AW)ther... Gl(AH)ss... I guess it depends on how you normally pronounce the words. - 70.81.118.123 15:12, 26 June 2006 (UTC)
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## Rule of succession promenence

It is weird that so MUCH of this article is about the rule of succession, one of the less well-known things associated with Laplace, and so little about the many other things associated with him. Michael Hardy 00:10, 10 Jul 2004 (UTC)

Thanks for volunteering to rewrite it. :-) -- Curps 19:23, 10 Jul 2004 (UTC)
I've noticed that there are a lot of active Bayesians writing here at wikipedia and that's cool. But to call Laplace a Bayesian is an anachronism that is a little too much I think. Laplace did so much so it can be hard for a mere mortal to grasp, but the induction rule referred to in the article was definitely not on of his greatest achievements. INic 22:13, 18 October 2005 (UTC)

This statement is conceptually narrow and potentially false: "The discoveries of modern physics, especially quantum physics and uncertainty principle proved that the existence of such an intellect is not possible even in principle." As displayed in Interpretation of quantum mechanics, quantum theory has not ruled out causal determinism and only interpretations of it make Laplace's demon impossible. --Psients 10:17, 18 Aug 2004 (UTC)

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## celestial mechanics

Could we have more on his celestial mechanics? Charles Matthews 15:21, 22 Nov 2004 (UTC)

Express evidence that Laplace saw himself as an atheist, rather than a deist or agnostic. for example, should be supplied. It will be difficult to come by for anyone favored by the Restoration Bourbons, of course...

The famous anecdote about Napoleon and the Celestial Mechanics is not sufficient. Septentrionalis 15:35, 9 Jun 2005 (UTC)

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## creationist slant?

The last paragraph seems a bit off-topic and seems to be trying to inject a creationist argument.Blaise 08:28, September 6, 2005 (UTC)

You mean, I suppose, the following sentence, which is unsourced, unevidenced, and (to my mind) unlikely. I have removed it:
Predicting the rise of life in the universe, for example, requires vastly more data than this, and so, according to the theory, is computationally infeasible to predict.
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## Confused

It says in the Catholic Encyclopedia[[1]] (please click here for more info) that "Laplace was born and died a Catholic," and that it is mistaken that he had a determinist slant. Here, it says that he was a determinist. Can anyone help me? I'm obviously confused. Oh, and what about this source;[[2]] (this link) also says that it is mistaken that he was on an atheistic slant. I'm just supplying you with more evidence so you can help me answer!

-Tlozano

Laplace was obviously a determinist, that's the sense of "Laplace's demon". I don't know why you would want to oppose that to Catholic faith; both are not contradictory. Science & faith is not contradictory since Kant's critique, which limited the assertions that Reason can make to a specific field; further on from this field lies questions which science can't resolve, such as, in Kant's words, the existence (or not) of an immortal soul, the existence of God, the existence of liberty, etc. The Catholic Encyclopedia seems to be biased in claiming determinism is opposed to religion. Santa Sangre 15:49, 4 June 2006 (UTC)
ps: since Kant who resolved this conflict between science & religion, only Fundamentalists (whatever their religion) oppose both. Santa Sangre 15:59, 4 June 2006 (UTC)

If Laplace died in communion with the Church of France (as is almost certain for a Restoration civil servant) that does not mean he was not a determinist. It would not surprise me if the Catholic Encyclopedia is misleading here; nor would it surprise me if they had edifying anecdotes about Voltaire's deathbed either. None of this justifies the category atheist, or any or its subcats, without discussion and sources in the article. Septentrionalis 19:59, 16 June 2006 (UTC)

Well according to a biography of Laplace, it states: "The Catholic newspaper La Quotidienne announced that Laplace had died in the arms of two curts (priests), implying that he had a proper Catholic end, but this is not credible. To the end, he remained a skeptic, wedded to his deterministic creed and to an uncompromised ethos derived from his vast scientific experience." Roger Hahn, Pierre Simon Laplace, 1749-1827: a determined scientist, page 204. — Preceding unsigned comment added by 24.141.253.213 (talk) 22:08, 10 March 2012 (UTC)

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## Maximum computability

The article talks about the maximum data computable (at the end of the section on laplace's demon), but provides no reference. Can someone please look to providing a reference for this? 129.78.64.106 05:52, 15 September 2006 (UTC)

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## Cleanup

I am not going to attempt the article that Laplace actually deserves, I neither have the knowledge nor the particular interest, but I am going to try to establish a basis for others to build on. The article is a direct copy of the chapter from A Short Account of the History of Mathematics (4th edition, 1908) by W. W. Rouse Ball with some modern, and possibly less than felicitous, interpolations. Though Rouse Ball is out of copyright it is also out of date. I am going to start by adding in-line citations for Ball and flagging missing citations. I am going to try my best to upate what I know about (which is not much). The article then needs a layered detailing, not by me, starting with the St Andrews website then from DSB then an up to date bio. Unfortunately I suspect that there are other mathematicians in a similar state.Cutler 19:22, 24 August 2007 (UTC)

I have made a start so at least the Rouse Ball stuff is cited and the uncited stuff is flagged. The article was an odd mixture of anachronisms mixing "is there anything in the nebular hypothesis?" with "Laplace discovered black holes". I have eliminated/ revised the worst but there is much to do. Here are my thoughts on the current sections:

• Biography Need more on early life if poss. Some of this belongs in the head para, some in a new section on personality etc. Did this guy marry? Have children?
• Probability theory This looks like good NPOV stuff. It properly belongs under Analytic theory of probabilities but I have left it here as it totally lacks references. I have nothing to hand.
• Laplace's demon This needs to go to bottom of article if anywhere. It is really about other people's interpretation of Laplace or their own ideas in which they find Laplacian resonances (sic).
• Spherical harmonics and potential theory Important stuff but it should be up to the technical articles to define in detail what theses things are. Frankly I wouldn't have recognised the definition of a spherical harmonic from Rouse Ball's def but this is not really my cup of tea. Probably needs expert.
• Planetary inequalities This is where I came in. Laplace got the secular acceleration of the moon only partially right as John Couch Adams showed in 1853 (so Rouse Ball should have known!) Section needs updating - this is important. I only got involved because I was working on the Adams article and I only got involved in that because I wanted to create William Grylls Adams.
• Celestial mechanics OK as far as it goes now the anachronisms are taken out but this is a big deal and ultimately needs its own article.
• Science as prediction looks like somebody pushing a position but content it OK (once verified)
• Black hole needs verification and scrutiny from an expert.
• Analytic theory of probabilities Needs more to do it justice - see Proability theory supra. One odd contribution that I have discussed below.
• Minor discoveries and accomplishments OK but would like more on political career and relationship with Napoleon. The collaboration with Lavoisier is more important than is suggested here.
• Quotes don't think we need this as all quotes appear in narrative

I will work away but it's really low on my priorities. Hope others can help.Cutler 22:17, 24 August 2007 (UTC)

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## Analytic theory of probabilities

In this section, Rouse Ball says:

In 1812, Laplace issued his Théorie analytique des probabilités. The method of estimating the ratio of the number of favourable cases, compared to the whole number of possible cases, had been previously indicated by Laplace in a paper written in 1779. It consists of treating the successive values of any function as the coefficients in the expansion of another function, with reference to a different variable. The latter is therefore called the generating function of the former. Laplace then shows how, by means of interpolation, these coefficients may be determined from the generating function. Next he attacks the converse problem, and from the coefficients he finds the generating function; this is effected by the solution of a finite difference equation.

This is, I think, a description of Laplace's development of the concept of the generating function of a probability distribution. However, somebody else had added this:

The method is cumbersome and leads most of the time to a normal probability distribution the so called Laplace-Gauss distribution.

I have no idea what this means and it is unreferenced. Any ideas? Is somebody just saying "Why bother with all that tricksy math stuff, just bung in a normal distribtion"?Cutler 22:33, 24 August 2007 (UTC)

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## Significance of scalar operator

Laplace's equation, or the more general form $\nabla^2 V=- 4 \pi \rho$, appears in all branches of mathematical physics. According to some writers this follows at once from the fact that $\nabla^2$ is a scalar operator ...

From Rouse Ball (1908) I have no idea what this can mean. I can even see that the following assertion has some sort of meaning but this quote ... . Any ideas?Cutler 12:18, 25 August 2007 (UTC)

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## Laplace's demon

As I understand it, Laplace's demon is a concept used by 20th century thinkers, articles are very unclear but I think by Suppes originally in the 1930s, in their post-Copenhagen discussions of determinism. It's not really about Laplace. Further, the quotation from Laplace in this section is misleading as it is only part of a longer quote found on pp26-27 of Gillispie (1997). I proposed:

• Rename this section "Laplace's determinism";
• As the full quote is too long for an article, move it to Wikisource and paraphrase it in the article;
• Deal properly with Laplace's complex attitudes to determinism and probability;
• Mention the demon in passing.

Discuss. I have a copy of Gillispie now and am using it to update this article though it is not an easy book.Cutler 11:33, 31 August 2007 (UTC)

Well, this quotation is definitely misleading without the other half but that would be too big an extract for the article (though still under 500 words so potentially fair use). However, it can't go to Wikisource as they no longer allow fair use and this is a modern translation of the French. I think my solution is to delete the quote and paraphrase the longer quote. I will see if anybody complains.Cutler 21:01, 3 September 2007 (UTC)
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## Laplace and Napoleon

I have removed the following as apocryphal: Laplace then declared: "Cette hypothèse, Sire, explique en effet tout, mais ne permet de prédire rien. En tant que savant, je me dois de vous fournir des travaux permettant des prédictions" ("This hypothesis, Sire, does explain everything, but does not permit to predict anything. As a scholar, I must provide you with works permitting predictions." - quoted by Ian Stewart and Jack Cohen). Laplace thus defined science as a predicting tool. I have not found it in de Morgan or anywhere else, and it has had a Fact tag since August 2007. NBeale (talk) 16:21, 5 April 2008 (UTC)

Your action was most admirable, however, you may be too late to save the truth. The "prediction" quote is plastered all over the internet. I doubt it will ever be forgotten, alas.
The Ball quote does not make it clear when Lagrange's reply was made. Some sources suggest it was all one exchange, others that Lagrange was not present at the submission and that the reply came later. It would be good to have further clarification of this. Obviously, if the reply came after, there is much less chance of the Laplace rebuttal having occurred. ObsessiveMathsFreak (talk) 15:17, 16 September 2009 (UTC)
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While what Laplace predicted about astronomical phenomena are admirable and very visionary, the text post-rationalize his theories a little too much for my taste:

1. he never conjectured black holes, he conjectured "dark stars" from which some light always can leave, but all lesser the heavier that "dark star" is. Only when adding the 20th century theory of relativity, the "dark star" becomes a black hole;
2. he conjectured one variant of the Nebular Theory that is nowadays disproven: a fastly rotating (proto)star is releasing momentum by successively releasing rings of star matter along the equator, who thereby gains momentum, while the (proto)star looses monentum; this variant works considerably worse than the earlier Kant Nebular Theory, consisting of rings of cold dust clouds in a fractally rotating circular pattern, which happen to fit very much better with the modern opinion.

That said, these theories of him were still very visionary and important for 2 centuries of coming astronomy. Said: Rursus () 19:28, 9 September 2008 (UTC)

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## Wrong translation of Napoleon quote?

In a quote about Laplace political work, the article says Napoleon said something about Laplace bringing the spirit of "infiniment petits" to his affairs. Shouldn't the translation reflect the fact that "infiniment petits" means infinitesimals? —Preceding unsigned comment added by 200.161.121.122 (talk) 22:04, 16 September 2008 (UTC)

I agree with you and edited your suggestion. I also changed the "objectively" to "from the right angle", as I felt it more closely matched what Bonaparte said. I do not find clear whether the quote is 1/ entirely from W. W. Rouse Ball, in which case it's debatable whether I should have done the change or 2/ French from Bonaparte memoirs and English provided by a wikepedian, in which case the correction was I think the right thing to do. If I am not the only one to whom this isn't clear, it should be clarified--Ptranouez (talk) 14:05, 10 February 2010 (UTC)
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## Inductive probability

The example in the last two paragraphs is really unclear. If it is 'famous' it needs a reference, and it definitely needs to be clearer. I'm also not sure that it's in the right place - surely there is another page for controversies about inductive probability? --Ac1201 (talk) 01:24, 2 April 2009 (UTC)

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## Lucien

Lucien, Napoleon's brother, was given Laplace's job. —Preceding unsigned comment added by 86.137.170.8 (talk) 13:08, 19 May 2009 (UTC) This was at the Ministry of the Interior. —Preceding unsigned comment added by 81.153.63.109 (talk) 09:32, 25 May 2009 (UTC)

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The {{skiptotoctalk}} template has been added to the top of this Talk page for those who want to "get right down to it".  .^) Paine Ellsworthdisscuss (^`.  22:11, 30 May 2009 (UTC)

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## Laplace's student

This article says that Poisson was Laplace's student yet Poisson's article claims that Lagrange was his doctoral advisor. Also, Lagrange's article says that was Poisson was his student. Can anyone clear this up please? --Hamsterlopithecus (talk) 18:01, 3 December 2009 (UTC)

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## error

probability A occurring given B has occurred (assuming they are not correlated) is not P(A)/P(B). it is P(A intersect B)/P(B). I corrected it. 99.67.184.222 (talk) 23:41, 27 March 2010 (UTC)Dan

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## What is the date of publication of the Philosophical Essay on Probabilities?

Is it 1814, 1816, or 1819? I have seen all three dates being cited! --Forich (talk) 15:40, 27 October 2010 (UTC)

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## Green citation

I tidied up the statement about the first use of the word potential - see Whittaker Volume 1. Also introduced missing reference to Green. Harry "Snapper" Organs (talk) 19:54, 13 December 2010 (UTC)

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