Ancestors

Toot

Written by Matt McIrvin on 2024-12-08 at 00:27

I was also reminded of this list in my head of places with a reversed compass rose, so that East is counterclockwise of North:

1. The Land of Oz, according to published maps (Wikipedia recounts an anecdote that L. Frank Baum copied a paper map from a projection slide he'd made for the lecture circuit, but accidentally started drawing off the wrong side of the slide, and just ran with it presumably because it's a weird fantasy land)

2. The Moon, at the time of the Apollo missions (because in those days they were still using a coordinate system derived from astronomical East and West, projected up from the Earth onto the sky... but this usage has reversed now)

3. A table of mah jong players (this once puzzled me but it makes sense--"east, south, west, north" is a conventional ordering of compass directions in Chinese, and counterclockwise play is the typical game convention there, so if you want both, East has to be to North's right--it hardly needs to correspond to real geography)

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Descendants

Written by Matt McIrvin on 2024-12-08 at 15:01

Actually the convention for all mapping of solar-system bodies in the pre-space-probe age was to use astronomical definitions of East and West, so the compass was flipped (but since the maps were drawn from telescopic images and the astronomical telescopes in use tended to invert the view, maps by Northern Hemisphere astronomers would often in practice do this by putting East in the normal place but South at the top).

Today, when good data will often come from space probes rather than Earthbound telescopes, that convention's been abandoned and the general convention is to map them all like we do the Earth, with East clockwise from North.

I was going to say that it's relative to the body's rotation, but that's not always true: Venus's (slow) rotation is retrograde, but IAU conventions align its north with solar-system north and take its axial tilt as 3 degrees, not 177 degrees.

Star maps still seemingly have the east-west axis pointing the "wrong" way because they're still looking up instead of down, with directions projected up from the Earth.

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Written by Matt McIrvin on 2024-12-08 at 15:07

But I still find it utterly weird that they were still using the "astronomical" convention for lunar latitude and longitude at a time when astronauts were literally walking on the Moon's surface, as if they'd been transported into a star map. That's why the craters just east of the Apollo 11 landing site were called West Crater and Little West Crater.

I recall there's at least one recording of an astronaut walking around on the Moon joking about how here East is West and West is East.

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Written by Virginicus on 2024-12-08 at 15:45

@mattmcirvin The twain finally met!

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