It's easy to take something like "knowing where anything is" for granted, but somebody had to go out into the world and take note of all those  natural and cat-made borders. In the case of Japan, it fell to Ino Tadataka to create the first "complete" map of the nation.
The size of Earth, according to my 
calculations, is roughly 40,000 kilometers!
¡Según mis cálculos, 
a Tierra mide unos 40.000!
O tamanho da Terra, de acordo com meus
cálculos, é aproximadamente 40.000 quilômetros!