  To build insight into the atmosphere and ocean, it is useful to apply
qualitative reasoning to predict the geophysical fluid dynamicss of worlds
radically different from our own such as exoplanets, earth in Nuclear Winter,
other solar system worlds, and far future terrestial climates. Here, we look at
atmospheric and oceanic dynamics on a flat earth, that is a disc-shaped planet
rather like Sir Terry Pratchet's fantasy Discworld. Altough this has the
disadvantage that this geometry is a completely imaginary, there is a rich
larray of videos by flat earth proponents whose errors illuminate how concepts
can be misconceived and misapplied by amateurs and freshman science studients.
As such, this case is very useful to geophysics instructors. We show that
weather and ocean flows on a flat, nonrotating earth and a rotating spherical
planet are wildly different. These differences are a crushing debunk of the
flat earh heresy, if one were needed. The "high contrast" of these very
different atmospheres and oceans is valuable in instilling the open-mindedness
that is essential in understanding excoplanets and Nuclear Winter and
Post-Climate-Apocalypse earth.
