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Weed_O_Whirler t1_j4w346h wrote

First, some terms. There is "true north" and "magnetic north." True north is perpendicular to east. Magnetic north is close to perpendicular to east, but not quite.

True north is defined as the point that Earth's rotation axis points through. To visualize, look at this globe. The "true north" pole is where the pole sticks through the globe, the place the Earth is rotating about. This is what is perpendicular to east. Which, when you think about it as a rotation, makes sense. As the Earth rotates, the Sun is going to appear to rise in the direction the Earth is spinning. This globe photo may help illustrate that if it's not clear as of why.

Now, magnetic north is based on the magnetic field of the Earth, and it is close to truth north, but the true north pole is about 1200 miles away from the magnetic north pole. In the latitude bands most people live in, that distance doesn't matter much- if you point true north of magnetic north, you're basically pointing in the same direction- but as you move really far north (or really far south), that distance matters more.

So, is it a coincidence that magnetic north and true north are close to aligned? No, it's also due to rotation. The Earth's magnetic field is caused by spinning liquid metal in the outer core, and that core's direction of spin is highly influenced by the direction of the Earth's rotation. So, most of the the time, the Earth's magnetic field is close to aligned with the Earth's rotation axis. Since the Earth's magnetic North pole was discovered, it has moved by 600 miles. The Earth's magnetic field will also flip-flop at some point in the future (Magnetic north pole will go to the geographic south pole) and has flip-flopped in the past. During this flip-flopping time, the magnetic north pole will have to wander all the way down the globe, and thus magnetic north and true north will be no where close to each other (and at some point, magnetic north will lie due east!). But most of the time, the Earth's magnetic field stays relatively aligned to the Earth's rotation.

(This is sort of going down a rabbit hole, but you can watch this video about why Canada labels their runways using true north, while most of the rest of the world uses magnetic north, but it comes down to how those little variations in where magnetic north is don't impact much, unless you're really far north or south)

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CrustalTrudger t1_j4w5c3v wrote

To add an extra level to the rabbit hole, there are actually three norths. True north, magnetic dip north, and geomagnetic north. True north has been covered, but magnetic dip north is the location where the magnetic field is oriented vertically (so if you had a magnetic inclinometer, where it would point vertically) whereas geomagnetic north is the intersection of the surface of the Earth with the best fit dipole field. In detail, if the Earth's magnetic field was a true dipole (like a bar magnet) then the north and south dip poles (1) would be antipodal with respect to each other and (2) they would be equivalent to the geomagnetic poles (which are by definition antipodal), but neither of those tend to be true as the location of the dip poles migrate as part of secular variation.

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dukesdj t1_j4w8w7y wrote

> magnetic dip north is the location where the magnetic field is oriented vertically

Presumably in general magnetic dip poles do not strictly need to some as a single pair and could come in any number of pairs? I am essentially thinking along the lines that there is no strict mechanism to enforce that only two such locations would exist in a general astrophysical dynamo (for example there are many locations with locally vertical field at the surface of the Sun).

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CrustalTrudger t1_j4w9a5g wrote

I would assume so, but as far as I know on Earth, we tend to find two distinct dip poles roughly equivalent to a north and south pole (i.e., one with a +90 inclination and one with a -90 inclination). You might expect that during a geomagnetic reversal (which is often described as a weakening/temporary collapse of the dipole component and thus a relative strengthening of the higher order field components) you could have more than one pair of dip poles, maybe?

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jpbarber414 t1_j4wag1t wrote

One thing I would like to add, the ☀️ sun moves along the ecliptic plane which changes depending on the time of year.

The ecliptic plane is defined as the imaginary plane containing the Earth's orbit around the sun. In the course of a year, the sun's apparent path through the sky lies in this plane. The planetary bodies of our solar system all tend to lie near this plane, since they were formed from the sun's spinning, flattened, proto-planetary disk.

The sun never truly "rises" in the East nor sets in the West.

https://www.nasa.gov/multimedia/imagegallery/image_feature_635.html

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WazWaz t1_j4xiitc wrote

Never? I'm pretty sure maths says it does it exactly twice per year, with the rise and set happenning at the same moment, at two specific points on opposite sides of the planet.

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