Can’t we just define astronomical “North” as “Towards Polaris”?
Locally anyway. Once you’re a couple of hundred light years away that’ll have enough of a parallax error to be as useless as magnetic north in high latitudes.
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wheresthefish Partly filled with wrong, Thu 18 Mar 2021, 11:06,
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hey, what can I say? I like to know which half of the galaxy I'm pointing towards
also, "north" is not without its issues, either. Is that geodetic north pole, grid north or magnetic north. If it's the geodetic (or true) north pole, is that an instantaneous pole of the current axis or the fixed position defined by the International Terrestrial Reference System, which isn't really fixed as the earth changes shape with plate tectonics and associated major earthquakes and can really only be estimated without precision. If it's the magnetic north pole that compasses point to, that roams arounds with fluctuations in the outer core convection currents, and is it still north when it changes directions as it does every half a millions years or so, or do we relabel the compass?
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cumquat may will not be commenting further on the allegations, Thu 18 Mar 2021, 12:39,
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North is always relative to the direction of rotation, and always follows the right hand rule.
Raise your right thumb. Extend your right index finger. The direction of your finger is the direction of rotation. The direction of your thumb is relative north. This is true for any rotating body.
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brb Learn Ukrainian and prepare for a referendum, Thu 18 Mar 2021, 13:47,
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Oh cool, we're also oppressing the left-handed now are we? About bloody time.
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evil_andy Stick stick stick stick sticky sticky stick stick, Thu 18 Mar 2021, 16:37,
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Fleming's left hand rule also defines north and south, but in in terms of magnetic polarity.
www.bbc.co.uk/bitesize/guides/zc3dxfr/revision/3
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brb Learn Ukrainian and prepare for a referendum, Thu 18 Mar 2021, 17:26,
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i think the point was about precision, rather than general direction
the axis of rotation is not a fixed point, it wobbles as well as follows a processional pattern over the millennia.
North is not "always relative to the direction of rotation, and always follows the right hand rule", this is a backwards application to the term, it's the right hand rule (in this application) because we've arbitrarily called the thumb direction north, not north because of the right hand rule. and it's most definitely not "true of every rotating body". venus rotates in the opposite direction to earth while orbiting the sun on the same plane. an axis of rotating body goes in both direction, which hand rule you want to use depends entirely on which axial direction you want to refer to in relation to the direction of rotation.
North's an arbitrary term first used long before the heliocentric model of the solar system and that the earth rotated on an axis was understood. The chinese and islamic cultures based their navigation and maps around what we call south. Later with the first use of lodestones it was used interchangeably as both the angle perpendicular to the sun in the morning and the direction of the compass, which were close but not identical. Because of this magnetic convention the terms are often applied to magnetic dipoles by laymen, north and south, but physicists are much more likely to use + and -, I'd imagine because of brevity.
My half-joking point was more about having a term that orients people in terms of the galaxy around them, as some ancient cultures who used star navigation did, taking advantage of the the not unconnected phenomenon that the earth rotates in close to the same plane as it orbits the sun, rather than a term that simply references terrestrial orientation. Maybe engender a bit more connection to the milky way and lessen the association with top and bottom caused by the convention
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cumquat may will not be commenting further on the allegations, Thu 18 Mar 2021, 23:25,
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out of curiosity I just looked up the conventions for how we label the poles in venus
interestingly, they match up the same orientation as earth even though they rotate in opposite directions relative to their solar orbits. Our north and their north point towards Polaris (www.windows2universe.org/venus/venus_polar_regions.html) So in Venus they'd use the left hand rule to determine "north", which shows how arbitrary these terms are.
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cumquat may will not be commenting further on the allegations, Thu 18 Mar 2021, 23:40,
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