Sense 6 (“mathematical constant equal to 2π”) was used by Joseph M. Lindenberg in 1991, and popularized by the American educator and entrepreneur Michael Hartl in a 2010 paper which explains thatτ resemblesπ; and thatτ is the Greek equivalent oft, the first letter ofturn, and 2π corresponds to one turn of a circle with a radius of one unit.[1]
Sense 8.1 (“short for tau leptonor tau particle”) wascoined by the American physicistMartin Lewis Perl (1927–2014) after the first letter ofAncient Greekτρίτον(tríton,“third”), since the tau lepton or tauon was the third charged lepton discovered.[2]
1847, Richard Edmund Tyrwhitt,Sermons Chiefly Expository, volume I, Oxford: John Henry Parker;F[rancis] and J[ohn] Rivington, London, page366:
Hence it appears that the spits, or skewers, on which and to which the lamb was fixed and fastened in order to be roasted, assumed the form of across, not such atau-cross as is engraved in Dr. Oliver’s Historical Landmarks of Freemasonry, vol. i. p. 80. having three arms only like theGreek lettertau; but a cross like the ancientHebrewtau, with four arms, though not necessarily all of equal length.
1851,D[aniel] Rock,Hierurgia; or Transubstantiation, Invocation of Saints, Relics, and Purgatory, Besides Those Other Articles of Doctrine Set Forth in the Holy Sacrifice of the Mass, Expounded;[…], 2nd edition, London: C. Dolman,[…], page350:
In the Spanish translation of Sallust, by the Infant Don Gabriel in 1772, called the Infant Sallust, there is a curious dissertation by Father Perez Bayer on the resemblance between the ancient Hebrew and Phœnician alphabets, in which it is observed that the HebrewTau was written in pure Phœnician,[…]
2017, Piers Vaughan,Capitular Development Course, 2nd edition, Rose Circle Publications,→ISBN, page135:
Thetau is both the 19th letter of the Greek alphabet, and also the 22nd letter of the Hebrew alphabet. In this context, the Hebrewtau ortav is more pertinent.
Nor ſhall we take in the myſticallTau, or the Croſſe of our bleſſed Saviour, which having in ſome deſcriptions anEmpedon or croſſing foot-ſtay, made not one ſingle tranſverſion.
Quite what that job is remains obscure, but one theory is that it is to stabilise another protein calledtau, which is supposed in turn to keep in shape the tubular ‘skeleton’ of a neuron.
^Michael Hartl (2010 June 28) “The Tau Manifesto”, inTauday.com[1], archived fromthe original on30 January 2022, section 4.1 (One Turn):
There are two main reasons to useτ for the circle constant. The first is thatτ visually resembles π: after centuries of use, the association of π with the circle constant is unavoidable,[…] The second reason is thatτ corresponds to oneturn of a circle, and you may have noticed that “τ” and “turn” both start with a “t” sound.
^Martin L[ewis] Perl (1977 April)Evidence for, and Properties of, the New Charged Heavy Lepton (SLAC-PUB-1923)[2], archived fromthe original on9 July 2021, section 1 (Introduction), page 3; published inTrần Thanh Vân, editor,Proceedings of the Twelfth Rencontre de Moriond: Flaine, Haute-Savoie, France, March, 6–18, 1977 (Moriond Proceedings;19), volumes 1 (Leptons and Multileptons), Orsay, Paris: Laboratoire de Physique Théorique et Particules Elémentaires [Laboratory of Theoretical Physics and Elementary Particles],Université de Paris-Sud,1977,→OCLC, pages75–97:
Since there is now substantial evidence that it [the new elementary particle] is a lepton, we wish to designate it by a lower case Greek letter. We use because it appears to be the third charged lepton to be found andτριτον means third in Greek. We feel the old use of to designate the three pion decay mode of the K is now obsolete.
“tau”, inKielitoimiston sanakirja [Dictionary of Contemporary Finnish][3] (in Finnish) (online dictionary, continuously updated), Kotimaisten kielten keskuksen verkkojulkaisuja 35, Helsinki:Kotimaisten kielten tutkimuskeskus (Institute for the Languages of Finland),2004–, retrieved2023-07-03
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tau: The letterΤ/τ in the Greek, Hebrew and ancient Semitic alphabets, being the nineteenth letter of theClassical andModern Greek, the twenty-first letter ofOld andAncient Greek.
2003, Alexander Lubotsky, Sergey Starostin, “Turkic and Chinese loan words in Tocharian”, in Bauer, Brigitte L.M., Pinault, Georges-Jean, editors,Language in Time and Space: A Festschrift for Werner Winter on the Occasion of his 80th Birthday, pages257-269: