“Ground Zero” is any place that is at point-blank range – they both mean the same thing. Zero-point-blank meters from the point of impact. The recent usage of the term refers to the impact points for September 11; the usage is flawed in the case of the towers, since the aircraft hit several meters above the area we now call “ground zero.” It’s where the crater is, so it’s as good a spot as any.
The “letter” notation for D-Day (Dee Plus Seven is a week after the landing, Aitch plus six is six hours after the landing) has been carried over and is what gives us “T” time to this day in military and space operations. You’ve doubtless heard “Tee minus ten, nine, eight…” in rocket countdowns; what is less well known is that we also still count “Tee-plus” in seconds (and also in minutes, hours, and days on long missions).
Can anyone confirm or deny this? I had understood (probably from somewhere on this board) that “point blank range” does not, contrary to popular belief, mean “zero range”, but that it refers to the distance for which a gun’s sights are calibrated. After all, a bullet will drop slightly in flight, so you want your sights to aim a little bit low to account for this. But the sights define a line, while the bullet’s path is (approximately) a parabola, so they’ll only intersect at a point. That point being “point blank”.
Ground zero is the term used for the epicenter of any expolsion, not just the Japan nukes. It is a bit of black humor by the Pentagon workers who didn’t have much confidence in their survivability during nuclear war. The bullseye was commonly thought to be painted right in the courtyard on the Soviet maps.
