Hi /sci !!

Wood worker here. I frequent /diy, /pol, /gif, /x, and/g. I recently need to flatten a plane, and could not find my certified flat granite.

So I got to thinking, what is "flat". What defines it, and how do we measure it? Can I make a flat surface? What came first? Flat tools or flat surfaces?

I'll try /diy next. Thread game idea incoming too.