Template:Are You Sure/April 7

• ... that today 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 physicist Ernst Ruhmer (15 April 1878 — 8 April 1913) investigated practical applications making use of the light-sensitivity properties of selenium, which he employed in developing wireless telephony using line-of-sight optical transmission, sound-on-film audio recording, and television transmission over wires?

• ... that physicist and academic Petrus Leonardus Rijke explored the physics of electricity, and is known for the Rijke tube, which turns heat into sound by creating a self-amplifying standing wave?