October 27

• 

  1654: Blaise Pascal writes to Pierre de Fermat, praising him for his solution to the Problem of the Points, about which they had exchanged seven previous letters.

• 

  1675: Mathematician and academic Gilles de Roberval dies. He published a system of the universe in which he supports the Copernican heliocentric system and attributes a mutual attraction to all particles of matter.

• 

  1678: Mathematician Pierre Raymond de Montmort born. He will write Essay d'analyse sur les jeux de hazard, an influential book about probability and games of chance which will introduce the combinatorial study of derangements.

• 

  1854: Physician Golding Bird dies. He pioneered the medical use of electricity.

• 

  1972: The Mariner 9 spacecraft is switched off. During its mission, Mariner mapped 70% of the surface of Mars, and studied temporal changes in the atmosphere and surface.

• 

  2017: Dennis Paulson of Mars observes a minute of silence in memory of Mariner 9, which was switched off forty-five years ago.