According to the landing page "If every cell on the game field was as small as a speck of dust it would take 17 billion years at the speed of light to travel the width of the board." 17 billion light years is 1.608×10^26 metres, while the size of dust specks varies but is roughly around 10^-6 metres. That's a big field.
That said, I don't think the concept of "the entire map" makes sense. I expect it's functionally infinite, probably capable of scrolling to 2^32 or 2^64 cells, only allocating new regions in the database as people scroll there and start working. On that scale, you probably wouldn't see any activity at all.