The nuclear missiles on our subs are aligned in the tubes using Earth's Spin and local variations in gravity.
They're programmed in flight to take the Earth's rotation and shape into consideration for aiming.
They also take a star-shot in flight, navigating by stellar locations, with Earth's rotation taken into account.
Sure, all of this could be a con. It's possible. But think of how goddamned huge the conspiracy would have to be.
Anyone that writes the missile software, for all the applications, needs to know the truth and take that into account for their part. Anyone that writes ANY missile software, Navy or Air Force, has to be in on this.
All the rockets and satellites, all the shuttle operations, all a big conspiracy, and no one is talking.
Every transport that has computer navigation, all the people that support that navigation are in on the conspiracy and not talking.
You cannot get the education to get a job at NASA, or General Dynamics, or Lockheed, or Martin Marietta, or Electric Boat, or Boeing, unless and until you agree to support the conspiracy. I mean, god forbid some flunky or newbie accidentally stumble across an I the conspirators forgot to dot, or a t that wasn't crossed, and the problem blows up on social media.
Every astronomer, same conspiracy, still keeping quiet.
Every efficiency expert that came up with the great-circle flight plans so that airlines could save fuel has to know that REALLY, they're wasting fuel for this big anti-biblical conspiracy, and not a single one has tried to suggest it would be better for all their souls to come clean...
Hell, they can't even allow those rich doctors who get a plane to get their pilot's license unless they promise not to mention that they see a flat Earth once they get high enough...
There would almost have to be more people in on this secret than outside of it. So not a conspiracy as much as a status-quoracy. And what would the point of that be?
