in the ballpark

An early source is the 1945 book Memoirs of a Shy Photographer by Kenneth Patchen: 1945, Kenneth Patchen, Memoirs Of a Shy Photographer, New Directions: "You're out in left field." "And you're out of the ballpark!" In context, the first speaker is suggesting the listener's perspective is fringe; which may also be the origin of the idiom "out in left field." The response keeps the baseball metaphor, and suggests the first speaker is even further fringe than themselves. In 1950, a scientific paper related to the US atomic program and/or ballistic missile development decides on a range the area of a standard baseball park as an "on target" area for a desired missile landing. Thus, a missile that lands "in the ballpark" was considered sufficiently accurate (for nuclear weapons at least). Later, in the 1960s, the term "ballpark" would be repurposed for the name of the desired landing zone for de-orbiting satellites.