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enter image description here Hi guys, I've been reading about the wave-particle duality of matter, and I came across this statement that said de Broglie was a prince. Is that true?

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  • $\begingroup$ He was the seventh duc de Broglie, and so a nobleman, not a prince. $\endgroup$
    – Mary
    Commented Sep 14, 2020 at 1:20
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    $\begingroup$ Unless de Broglie's title has a tangible connection to his scientific work this question is off-topic here. $\endgroup$
    – Conifold
    Commented Sep 14, 2020 at 4:04

1 Answer 1

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Wikipedia describes the House of Broglie:

Broglia [it] (pronounced [ˈbrɔʎʎa]) was the name of an old Piedmontese family, from which were descended the counts of Casalborgone, Mombello and Revello, and the lords of Arignano, Cortandone, Fontanetto Po, Chieri, Cocconato, Monale, Montaldo,[8] Pont Canavese and Santena. The first reference to the name is dated 1245, mentioning one Ardizzone Broglia, father of Guglielmo, decurione of Chieri.[9]

The founder of the French de Broglie line was Francesco Maria, count of Revello, of the Broglia di Chieri family. Born in 1611 in Piedmont, he took service in the French army in the Thirty Years' War and was naturalized in France after 1643. He is now known as François-Marie, comte de Broglie. After distinguishing himself as a soldier, he died, a lieutenant-general, at the siege of Valenza on 2 July 1656.[7]

His son, Victor-Maurice, comte de Broglie (1647–1727), served under Condé, Turenne and other great commanders of the age of Louis XIV. He became maréchal de camp in 1676, lieutenant-general in 1688, and finally marshal of France in 1724.[7]

His grandson, François-Marie, was made duc de Broglie and a peer of France in 1742. His great-grandson, Victor-François, 2nd duc de Broglie, was created prince of the Holy Roman Empire in 1759 by Emperor Francis I.

All junior members of the House of Broglie bear the title of prince de Broglie, while the head of the family is the duc de Broglie. A junior line used the title of prince de Broglie-Revel, after one of its lordships.[7]

Louis, 7th duc de Broglie (1892–1987), a physicist and Nobel laureate, was one of the founders of quantum theory.

https://en.wikipedia.org/wiki/House_of_Broglie[1]

Louis de Broglie (1892-1987), 7th Duke of Broglie, was the youngest child of Louis-Alphonse-Victor, (1846-1906), 5th Duke of Broglie, and the younger brother of Maurice de Broglie (1875-1960) 6th Duke of Broglie.

So he didn't become the 7th Duke of Broglie until he was 68 years old. So when he was a student he was not yet the Duke of Broglie.

What does the Wikipedia quote above say:

All junior members of the House of Broglie bear the title of prince de Broglie, while the head of the family is the duc de Broglie.

So apparently the title of Duc de Broglie descends by primogeniture, while the lesser title of Prince of Broglie is shared by all male members of the family. The second Duc de Broglie was made a Prince of the Holy Roman Empire by Emperor Francis I in 1759, and possibly that title is shared by all of his male line descendants.

The English word prince has several different meanings, as did the Latin word princeps which it is based on. In fact, the German language has two different words which are translated into English as prince - Fürst and Prinz.

In the Holy Roman Empire, the word Fürst itself had two meanings, one a subset of the other meaning. A Fürst was the "first" man in in his principality, and collectively the Fürsten were the first men in the empire. The princes of the Empire included rulers who used a number of different titles. From the lowest to the highest the titles used by princes or Fürsten of the empire included princely count, landgrave, margrave, count palatine, prince (Fürst), duke, and the rare titles of grand duke and archduke. Thus the princes of the Empire whose German title was Fürst (prince) were a subcategory of the princes of the Empire.

The German word Prinz is used for the sons or grandsons,etc. of a king, royal princes.

The Emperor also granted titles, such as Fürst, to persons who did not rule fiefs or principalities in the Empire and thus did not have votes in the imperial Reichstag. The de Broglie title of Prince of the Holy Roman Empire would thus be one of those titular prince titles without a functioning principality.

The title of Prince of Broglie used by junior members of the Broglie family is obviously a French or Holy Roman Empire noble title that was granted to all male descendants of the orginal grantee, and thus would be Fürst von Broglie in German, while the title of Duke of Broglie is a French title and descends to only the head of the Broglie family.

So The 7th Duke of Broglie was apparently entitled to the title of Prince of Broglie all his life if that title was granted to all members of the Broglie family, while he didn't inherit the title of Duke of Broglie until his older brother died without sons.

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