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The Ricci calculus has influenced Einstein only more than a decade later, in the development of the General Relativity (1917), for which tensor calculus was indispensable. It had no influence on the theory of Special Relativity (1905). Einstein is the one who changed the meaning of the word "tensor" to the meaning used today in most cases, when tensor means a general multi-dimensional quantity. I could not find any information about the reason why Einstein has chosen to make this change in terminology. Before Einstein, "tensor" (a term introduced by Hamilton) was applied only to symmetric matrices (because general matrices can be decomposed into "versors", i.e. rotation matrices that rotate vectors and a "tensor", i.e. a symmetric matrix that stretches vectors). While Ricci has invented the concept of tensor, he has not used the word "tensor". Nevertheless, because Einstein's theory had become extremely fashionable at the end of WWI, when Ricci's work has been translated and published in USA, the American editor has introduced the word "tensor" everywhere in the book and they added on the covers that this is the book needed to understand Einstein's tensor theory, in order to promote the sales of the book. Thus, Ricci's calculus became known as tensor calculus, first in USA, then everywhere. |