What Is an Imaginary Number?

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What Is an Imaginary Number? · 1:31 · Intellect Plus

In short: How the square root of a negative number went from a 'mental torture' in Cardano's 1545 algebra to a tool for electrical engineering and a testable question in quantum theory.

A 1:31 short film in the series “From Fingers to Qubits”.

Sources used in this film: Cambridge University Press & Assessment (Cambridge Dictionary), “imaginary number”; Encyclopedia.com (entries from UXL Encyclopedia of Science, The Gale Encyclopedia of Science and World Encyclopedia), “Imaginary Number | Encyclopedia.com”; Orlando Merino, University of Rhode Island (hosted on MIT Mathematics course pages), “ShortHistoryComplexNumbers2006.dvi”; Mathematical Institute, University of Oxford (article by Richard Earl, July 2004), “complex.dvi”; MacTutor History of Mathematics, University of St Andrews, “Girolamo Cardano - Biography”; MacTutor History of Mathematics, School of Mathematics and Statistics, University of St Andrews, “Rafael Bombelli - Biography”; MacTutor History of Mathematics, School of Mathematics and Statistics, University of St Andrews, “Bombelli: "Algebra" - MacTutor History of Mathematics”; MacTutor History of Mathematics, University of St Andrews, “Caspar Wessel (1745 - 1818) - Biography - MacTutor History of Mathematics”; Springer (Lettera Matematica), “I for Imaginary numbers”; Internet Archive (digitised copy of Charles Proteus Steinmetz, 'Theory and Calculation of Alternating Current Phenomena', The W. J. Johnston Company, New York, 1897), “Internet Archive (digitised copy of Charles Proteus Steinmetz, 'Theory and Calculation of Alternating Current Phenomena', The W. J. Johnston Company, New York, 1897)”; Internet Archive (scan contributed by University of California Libraries), “Theory and calculation of alternating current phenomena : Steinmetz, Charles Proteus, 1865-1923 : Free Download, Borrow, and Streaming : Internet Archive”; Nature (Springer Nature); article by Marc-Olivier Renou, David Trillo, Mirjam Weilenmann, Thinh P. Le, Armin Tavakoli, Nicolas Gisin, Antonio Acín & Miguel Navascués, published 15 December 2021, “Quantum theory based on real numbers can be experimentally falsified”; arXiv (Cornell University); paper by Marc-Olivier Renou, David Trillo, Mirjam Weilenmann, Le Phuc Thinh, Armin Tavakoli, Nicolas Gisin, Antonio Acin, Miguel Navascues, “Quantum physics needs complex numbers”.

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