Axiom of Choice

In mathematics, the axiom of choice, abbreviated AC or AoC, is an axiom of set theory equivalent to the statement that a Cartesian product of a collection of non-empty sets is non-empty. Informally put, the axiom of choice says that given any collection of sets, each containing at least one element, it is possible to construct a new set by choosing one element from each set, even if the collection is infinite.

High Altitude Observatory

The High Altitude Observatory (HAO) conducts research. It provides support and facilities for the solar-terrestrial physics research community in solar and heliospheric physics, and the effects of solar variability on the Earth's magnetosphere, ionosphere, and upper atmosphere. HAO's mission is to understand the behaviour of the Sun and its impact on the Earth, to support, enhance, and extend the capabilities of the university community and the broader scientific community.

Dungeons and Dragons

Dungeons & Dragons (commonly abbreviated as D&D or DnD) is a fantasy tabletop role-playing game (RPG) created and designed by Gary Gygax and Dave Arneson. The game was first published in 1974 by Tactical Studies Rules, Inc. (TSR). It has been published by Wizards of the Coast, now a subsidiary of Hasbro, since 1997. D&D's publication is commonly recognized as the beginning of modern role-playing games and the role-playing game industry, and also deeply influenced video games.