I was just outside and admired the waxing gibbous Moon in the evening sky. (Some of you will be able to ascertain my approximate longitude from this information and the time stamp of this post; Flat-earthers will not.)
If anyone of even moderate intelligence carefully observes the Moon through all its phases for a mere 28 days they will come to understand that it is a sphere, not a flat circular disk.
This is easy to see with your own eyes. Easy. To. See.
No special equipment is needed, just your brain and at least a moderately good working-memory that can recall things from day-to-day for a month and the same familiarity with basic geometric shapes that the average three year-old has.
It helps if you understand how light and shadows work, but again the average child of five or six knows enough about this to get it if it’s explained to them.
- FACT: For those few individuals who may not know, the origin of the word “month” is from the Moon and its cycle, a phenomenon which has been understood since prehistoric times.