Virtually all natural history museums have a diorama displaying fish with strange leg-like fins emerging from the water onto land. This is a critical evolutionary event—gills somehow evolving into lungs and fins evolving into legs—that allegedly occurred many millions of years ago.

Some readers might think the answer to this question is so obvious that maybe we’re offering it as a kind of joke—but it’s no joke. A growing number of people seem to actually believe the earth is flat, a view that a few NBA stars recently voiced.^1,2 Do we know the earth is round, and does it matter?