> The notion that north should always be up and east at the right was established by the Egyptian astronomer Ptolemy (90-168 AD). "Perhaps this was because the better-known places in his world were in the northern hemisphere, and on a flat map these were most convenient for study if they were in the upper right-hand corner," historian Daniel Boorstin opines. Mapmakers haven't always followed Ptolemy; during the Middle Ages, Boorstin notes, maps often had east on top--whence the expression "to orient."

Strange. “Upper Egypt” is the southern part of Egypt and “Lower Egypt” is the northern part. The source of the Nile (to the south of Egypt) was the key reference point to ancient Egyptians.

I searched, and Ptolemy was a Greek who lived in Egypt, not an ethnic Egyptian.

The first time I realized the Nile flowed from South to North, I thought someone was pranking me. It just felt fundamentally wrong. That’s probably because when you look at a globe, the Nile seems like it should be dripping downward…

But the Mediterranean is right there. Did you think the Mediterranean drains into some sinkhole in the middle of Africa?

Well I was about eleven years old, so I’m not sure I’d even heard of the Mediterranean by then.

Upper is literally higher up with respect to distance from the Earth’s centre of gravity.

When I was 8 or 9 in school we studied Egypt and I had to know and no one could answer. Might have been one of the first things I used Google for.

Isn't Earth's center of gravity at it's core? Isn't all of the Earth's surface "upper" to it's center of gravity?

Altitude, way rivers flow