- Messier 73 (M73, also known as NGC 6994) is an asterism of four stars in the constellation Aquarius which was long thought to be a small open cluster. It lies several arcminutes east of globular cluster M72. According to Gaia EDR3, the stars are 1030±9, 1249±10, 2170±22, and 2290±24 light-years from the Sun, with the second being a binary star.
- René Descartes (plato.standford.edu)
René Descartes (1596–1650) was a creative mathematician of the first order, an important scientific thinker, and an original metaphysician. During the course of his life, he was a mathematician first, a natural scientist or “natural philosopher” second, and a metaphysician third. In mathematics, he developed the techniques that made possible algebraic (or “analytic”) geometry. In natural philosophy, he can be credited with several achievements: the first to publish the sine law of refraction; developer of an important empirical account of the rainbow; and proposer of a naturalistic account of the formation of the earth and planets (a precursor to the nebular hypothesis, that the planets formed from loose matter orbiting the sun). More importantly, he offered a new vision of the natural world, which shaped modern physics: a world of matter possessing a few fundamental properties and interacting according to a few universal laws. This natural world included an immaterial mind that, in human beings, was directly related to the brain, a position that led to the modern mind–body problem. In metaphysics (the search for the basic principles of everything there is), Descartes provided arguments for the existence of God and to show that the essence of matter is to be spatially extended, and that the essence of mind is thought (where “thought” includes sensory images as well as rational discourse). Descartes claimed early on to possess a special method, which was variously exhibited in mathematics, natural philosophy, and metaphysics, and which came to include, or to be supplemented by, a method of doubt.