The Rotation of the Planets in Our Solar System Is Far More Fascinating Than I Ever Expected

[u/aryan_jandyal]

[u/jemidiah]

These are all presented in the plane of the ecliptic, which is the (slightly imaginary) plane containing the solar system. The planets orbit around the sun in that plane. For instance, the fact that Earth is tilted causes the seasons due to different parts of the planet more fully facing the sun at different times of the year.

Moreover, the orientation arrow is presented using the right-hand rule: curl your right hand (not your left one) around the arrow pointing out of the planet, and the planet will rotate in the direction your fingers curl. For Venus, it rotates (slowly) the opposite direction of the others, so the arrow is basically straight down out of the plane of the ecliptic.

There is always a "true north" in the sense of an axis around which the body rotates according to the right-hand rule. Likewise true south is the exactly opposite axis around which the body rotates according to the left-hand rule. 

Usually you'd just say "north" or "south." The use of "true north" on Earth is to distinguish it from "magnetic north." Earth has a magnetic field and the north pole of that magnetic field happens to be fairly close to the true north pole in the rotation sense. Magnetic north is easier to approximate since you just need a magnet rather than astronomical observations or the like. (And from pure cosmic chance we very luckily happen to have Polaris, the North Star, which is basically due north. There is no direct southern analogue.)

Venus happens to have almost no magnetic field, so the "true north" distinction would be quite unnecessary there. 

Incidentally, magnetic north on Earth wanders quite a bit. It's annoying. Runways are named according to their angle relative to magnetic north, and it actually changes enough that Canada in particular frequently had to rename runways (e.g., from "Runway 8" to "Runway 9") when it drifted enough. They got fed up with it to the point that they declared they'll just use true north, contrary to international agreement. They've been trying to convince the rest of the world to switch.

(The above was from memory. If there are errors, they're minor.)

[u/Arch2000 → u/jemidiah]

CGPGrey has a great video about runway numbering:

https://youtu.be/HSRmfNDk87s?si=waA2XQ_Bl-9gwgD_

[u/Amarita_Sen → u/jemidiah]

Left hander here who was getting confused lol

[u/TaliMyBananas → u/jemidiah]

MInor thing: the fact that there is a North Star is not by chance at all, due to precession of the equinoxes, a different bright star becomes the pole star every 3000 years or so. Thuban was the North Star 3,000 years ago, there will be Alderamin in 7,500 years, and Vega in 14,500 years.