Template:Selected anniversaries/April 28

• 

  1402: Aztec philosopher, warrior, architect, poet, and ruler Nezahualcoyotl born. He will have an experience of an "Unknown, Unknowable Lord of Everywhere" to whom he will build an entirely empty temple in which no blood sacrifices of any kind will be allowed.

• 

  1693: Gottfried Wilhelm Leibniz writes to L'Hospital, announcing his discovery of determinants fifty years before Cramer, who was the real driving force in the development of determinants. Leibniz's work had little or no influence because it was not published until 1850 in his Mathematische Schriften.

• 

  1774: Astronomer Francis Baily born. He will observe "Baily's beads" during an annular eclipse (1836).

• 

  1817: Carl Friedrich Gauss writes to the astronomer H. W. M. Oblers, saying, "I am becoming more and more convinced that the necessity of our (Euclidean) geometry cannot be proved, at least not by human intellect nor for the human intellect."

• 

  1847: Mathematician Leopold Kronecker uses number theory to predict and prevent crimes against mathematical constants.

• 

  1868: Mathematician Georgy Voronoy born. He will invent what are today called Voronoi diagrams or Voronoi tessellations.

• 

  1906: Mathematician, philosopher, and academic Kurt Gödel born. His two incompleteness theorems will have an immense impact upon scientific and philosophical thinking in the 20th century.

• 

  1928: Geologist and astronomer Eugene Merle Shoemaker born. Shoemaker will be the first scientist to conclude that Barringer Meteor Crater in Arizona, and similar craters, were caused by meteor impact.

• 

  1985: A brief, transient outbreak of Geometrical frustration affects nuclear reactors around the world. The outbreak will last only a few microseconds, and there will be no signs of damage to any of the reactors. The event will later be recognized as a precursor to the Chernobyl disaster.

• 

  1986: High levels of radiation resulting from the Chernobyl disaster are detected at a nuclear power plant in Sweden, leading Soviet authorities to publicly announce the accident.

• 

  1986: Celebrity time-traveller Radium Jane visits the stricken Chernobyl reactor, calls it "a waste of good fissionable material."

• 

  2017: New survey shows that Fantasy Voronoi diagram is more popular than Fantasy Football.

• 

  2018: Steganographic analysis of Spiral Rings 2 reveals "at least five hundred megabytes of encrypted data." Cryptographer Janet Beta calls it "a completely unexpected treasure-trove of archaic Gnomon algorithm functions, some of them timestamped centuries ago, which raises interesting questions of provenance."