I was being serious. But perhaps I wasn't being clear. I'm certain _I_ and probably most everyone on HN could refute a flat-earther (or at least present a coherent case that undoubtable would be ignored). The question I was raising was how many in the "general populace" could do the same.

I probably shouldn't be at this point, but I continue to be amazed by the inability of those I converse with (outside of folks in my tech-circle) to justify or explain basic mechanisms of how the universe functions - especially those that are usually taught at the secondary-school level.