Template:Are You Sure/April 7

• ... that April 7 is National Abuse of Notation Day in the United States; and that while Canada does not have an official Abuse of Notation Day, the phrase "Every Day is Abuse of Notation Day" is often attributed to the mathematician-comedians of New Minneapolis, Canada?

• ... that computer scientist Donald Sarason pioneered the abstract treatment of contractive containment and established a fruitful connection between the spaces Hb and the ranges of certain Toeplitz operators?

• ... that astronomer, mathematician, and philosopher Hasan Tahsini (7 April 1811 – 3 July 1881) was first rector of the newly established Istanbul University, where he gave lectures on physics, astronomy and psychology; that in one experiment, Tahsini placed a pigeon underneath a glass bell and emptied the receptacle, suffocating the pigeon; that conservatives considered Tahsini's experiment as evidence of witchcraft; and that Tahsini was declared a heretic through a fatwa, dismissed from the university, and forbidden to give lectures?

• ... that physicist and academic Petrus Leonardus Rijke (11 July 1812 – 7 April 1899) explored the physics of electricity, and is known for the Rijke tube, which turns heat into sound by creating a self-amplifying standing wave?