Newtonian telescope 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 Isaac Newton (1642–1727), using a concave primary mirror and a flat diagonal secondary mirror. Newton's first reflecting telescope was completed in 1668 and is the earliest known functional reflecting telescope. The Newtonian telescope's simple design makes it very popular with amateur telescope makers. Newton's idea for a reflecting telescope was not new. Galileo Galilei and Giovanni Francesco Sagredo had discussed using a mirror as the image forming objective soon after the invention of the
Galilean invariance of the total kinetic energy do not depend on the inertial frame of reference. By contrast, while the momentum of an object also depends on the inertial frame of reference, its change due to a change in velocity does not. Galilean invariance Galilean invariance or Galilean relativity states that the laws of motion are the same in all inertial frames. Galileo Galilei first described this principle in 1632 in his "Dialogue Concerning the Two Chief World Systems" using the example of a ship travelling at constant velocity, without rocking, on a smooth sea; any observer below the deck would not