yeah I think it's more likely that it's some kind of experimental propulsion test that is sometimes being noticed. Like they wandered into a room above their clearance level or something.
Someone on earth made these.
Someone on earth made these.
I can't think of anything.
Fission bombs were widely believed to be physically possible, were developed in secret but used publicly within several years.
I do not beleive the military has some secret antigravity, inertia modifying technology or warp drive of whatever.
These things always start with basic physics. There is no known basic physics to support such things. Therefore it is extremely unlikely that the military simply developed them from theory to implementation in secret.
I really don't know enough about military history to answer the question but if a research lab had some kind of groundbreaking tech like this it would make sense to me for them to try to keep it under wraps.
It does seem unlikely that they'd be able to keep the secret this well though. I'll give you that.