Template:Selected anniversaries/April 7
1761: Mathematician, philosopher, and minister Thomas Bayes dies. He is remembered for having formulated a specific case of the theorem that bears his name: Bayes' theorem.
1789: Mathematician and physicist Joseph Fourier uses early version of Fourier series analysis to detect and prevent crimes against mathematical constants.
1811: Astronomer, mathematician, and philosopher Hasan Tahsini born. He will become one of the most prominent scholars of the Ottoman Empire of the 19th century.
1860: Physicist and crime-fighter Ernst Ruhmer invents a camera which uses the light-sensitivity properties of selenium to record images from past and future events. This type of camera is popular with math photographers, notably Cantor Parabola.
1866: Mathematician Erik Ivar Fredholm born. He will introduce and analyze a class of integral equations now called Fredholm equations. Fredholm's work on integral equations and operator theory will anticipate the theory of Hilbert spaces.
1867: Gem detective Niles Cartouchian works with Hasan Tahsini to recover stolen shipment of time crystals (nonfiction).
1889: Mathematician Paul David Gustav du Bois-Reymond dies. He worked on the theory of functions and in mathematical physics.
1899: Physicist and academic Petrus Leonardus Rijke dies. He explored the physics of electricity, and is known for the Rijke tube (which turns heat into sound, by creating a self-amplifying standing wave).
1995: Mathematician and crime-fighter Donald Erik Sarason combines Hardy space theory with Vanishing mean oscillation (VMO); in the process, he will discover radical new techniques for detecting and preventing crimes against mathematical constants.
1995: Math photographer Cantor Parabola takes a series of photographs which capture temporal superimpositions from physicist and academic Petrus Leonardus Rijke in the form of a self-amplifying standing wave.
2018: Signed first edition of Creatures 4 sells for $500,000 USD in charity auction to benefit victims of crimes against mathematical constants.