.
Gravity, velocity, and centrifugal force are major factors keeping airplanes
up in the sky, and satellites out there orbiting the Earth. Those three factors
are also major during Moon landings and recovering LEMs. Those factors will
be very major whenever somebody gets around to landing people on Mars.
* Probably the flatters with the weakest legs to stand on are the conspiracy
theorists alleging that the USA, Russia, China, SpaceX, Google Earth, and
the European Space Agency, plus all the imaging teams, all the astronauts,
all the cartographers, and all the folks involved in designing satellite
communications and the GPS system, have colluded to fool the world into
believing the Earth is spherical.
_