- The Axiom of Choice (AC) was formulated about a century ago, and it was controversial for a few of decades after that; it might be considered the last great controversy of mathematics. It is now a basic assumption used in many parts of mathematics.
- Gacrux (Wikipedia)
Gacrux is the third-brightest star in the southern constellation of Crux, the Southern Cross. It has the Bayer designation Gamma Crucis, which is Latinised from γ Crucis and abbreviated Gamma Cru or γ Cru. With an apparent visual magnitude of +1.63, it is the 26th brightest star in the night sky. A line from the two “Pointers”, Alpha Centauri through Beta Centauri, leads to within 1° north of this star. Using parallax measurements made during the Hipparcos mission, it is located at a distance of 88.6 light-years (27.2 parsecs) from the Sun. It is the nearest M-type red giant star to the Sun.