- Algebra is a branch of mathematics sibling to geometry, analysis (calculus), number theory, combinatorics, etc. Although algebra has its roots in numerical domains such as the reals and the complex numbers, in its full generality it differs from its siblings in serving no specific mathematical domain. Whereas geometry treats spatial entities, analysis continuous variation, number theory integer arithmetic, and combinatorics discrete structures, algebra is equally applicable to all these and other mathematical domains.
- Messier 12 (Wikipedia)
Messier 12 or M 12 (also designated NGC 6218) is a globular cluster in the constellation of Ophiuchus. It was discovered by the French astronomer Charles Messier on May 30, 1764, who described it as a “nebula without stars”. In dark conditions this cluster can be faintly seen with a pair of binoculars. Resolving the stellar components requires a telescope with an aperture of 8 in (20 cm) or greater. In a 10 in (25 cm) scope, the granular core shows a diameter of 3′ (arcminutes) surrounded by a 10′ halo of stars.
stanford encyclopedia of philosophy of