Why are maps always north-up?

Open any world map and north is always up, south always down.

But Earth is a ball floating in space. It has no "up" at all.

Take a guess first: did the planet decide that north goes on top, or did the mapmakers?

1. A ball has no up. Paper does.

Earth has no "up" in space. North-up is simply the direction we chose when we flattened the ball onto a sheet.

Any direction would work — as long as everyone agrees on the same one.

2. Ptolemy set the rule

In the 2nd century, Ptolemy drew his grid of latitude and longitude and wrote it down: north at the top, east on the right.

The map was so useful that people copied it for eighteen hundred years. Wikipedia calls it an "almost universal convention".

3. Other directions have been "up"

Many medieval European maps put east at the top — the word "orient" literally means "facing the sunrise".

Qin-era Chinese maps put north up, but some Han-era maps put south up. Many old Islamic maps placed south at the top too.

Guess with me

1. Guess: if every printer on Earth put south on top tomorrow, would the map feel "wrong", or just "unfamiliar"?
2. Try: rotate your phone map 180° and find a street you know well. Can you still read it?
3. Ask: some Australians print south-up world maps on purpose. What do you think they want to remind us of?