Newtonian telescope secondary mirror. This design reduces the size and cost of the telescope with a shorter overall telescope tube length (with the corrector extending the focal length in a "telephoto" type layout) combined with a less costly spherical mirror. Commercially produced versions of this design have been noted to be optically compromised due to the difficulty of producing a correctly shaped sub-aperture corrector in a telescope targeted at the inexpensive end of the telescope market. Newtonian telescope The Newtonian telescope, also called the Newtonian reflector or just the Newtonian, is a type of reflecting telescope invented by the English scientist Sir
Galilean transformation and a "uniform motion" of spacetime. Let represent a point in three-dimensional space, and a point in one-dimensional time. A general point in spacetime is given by an ordered pair . A uniform motion, with velocity , is given by where . A translation is given by where and . A rotation is given by where is an orthogonal transformation. As a Lie group, the Galilean transformations span 10 dimensions, i.e., comprise 10 generators. Two Galilean transformations compose to form a third Galilean transformation, . The set of all Galilean transformations on space forms a group with composition as the