Point of no return

The point of no return (PNR or PONR) is the point beyond which one must continue on one's current course of action because turning back is dangerous, physically impossible or difficult, or prohibitively expensive. The point of no return can be a calculated point during a continuous action (such as in aviation). A particular irreversible action (such as setting off an explosion or signing a contract) can be a point of no return. The point of no return (PNR or PONR) is the point beyond which one must continue on one's current course of action because turning back is dangerous, physically impossible or difficult, or prohibitively expensive. The point of no return can be a calculated point during a continuous action (such as in aviation). A particular irreversible action (such as setting off an explosion or signing a contract) can be a point of no return. The phrase 'point of no return' originated as a technical term in air navigation to refer to the point on a flight at which a plane is no longer capable of returning to the airfield from which it took off.(V1 speed) It can also mean the instance in which an aircraft taxis down a runway, gaining a certain speed, and must become airborne in lieu of a crash or explosion on the runway—for example, Charles Lindbergh's takeoff in The Spirit of St. Louis in 1927 in which there was uncertainty about the plane's ability to take off from a 5,000 foot mud soaked runway while fully loaded with aviation fuel. The first major metaphorical use of the term in popular culture was in the 1947 novel Point of No Return by John P. Marquand. It inspired a 1951 Broadway play of the same name by Paul Osborn. The novel and play concern a pivotal period in the life of a New York City banker. In the course of the story, the character faces two 'point of no return' realities: first, that his quest for a big promotion will mean either triumph or a dead end to his career, and second, that he can never go back to the small-town life he abandoned as a young man. Another “point of no return” is when crossing the event horizon of a black hole. This is the point when not even light can escape the black hole’s gravity.