Eli5: what does it mean when someone talks about the poles reversing?


I hear people talking about the earths magnetic poles reversing but how exactly could/would that happen?

In: 27

It’s happened before. We know. Layers of rock containing materials with magnetic properties hold information about the earth’s magnetic poles when that layer of rock was placed. We’ve seen north and south magnets swap sides over time.

Earth’s molten core is made of mostly iron, which is magnetic. With the way the earth spins, it’s caused the north/south of said magnet to align itself about with the axis of rotation of said earth. However it’s also still a liquid and as such unstable. From the previous historical records we know that which end is north and south can, and occasionally do, swap.

Nobody can be 100% sure, but based on past results, and variation in the poles measured over time, we feel like we might be due for another event sooner than expected.

The earth has a big magnetic forcefield around it, this forcefield can decay because our planet has lots of magnetic liquid metals around the core, we wobble and spin so it moves around.

If it decays enough, north and south can flip entirely, exposing us to all sorts of nasty space energy

The north and south pole switch. The insides of earth has massive convection currents made of metals with a iron-ish core which makes earth like a big magnet. The magnetic field for solid magnets dont really change because its not a moving liquid.

The earth poles switch about every 250,000 years and were “overdue” but its actually difficult to determine. Most of the time when it flips it takes a long time and has very little impact on life but we have evidence that a few times the fields weakened during this process to cause a substantial impact on the environment.

Either way we know it will effect some stuff like navigation systems and satellites which will cause a few issues but more than likely not to the degree the doomsdayers are saying.

If its the bad one..radiation levels increase causing cancer along with failure to power grids, communications like cell phones will fail and this will also throw of migratory patterns for many animals and insects which will cause ecological disasters including crops to not get pollinated and stuff like that but….like I said, that is statistically very unlikely.

Inside of the Earth there is semi-molten rock, iron in particular. This causes magnetism, similar to how electricity flowing through a circular coil does. What matters most is the direction: if the flow changes from clockwise to counter-clockwise, the polarity reverses.

For reasons not yet fully understood reasons, this flow is unstable and changes over time. Luckily, time here means hundreds of thousands of years because everything is so heavy and slow to change.

The actual change is not a sudden switch of polarity. Right now, the poles are already moving around quite a bit. A hundred years ago, it moved at ~10 kilometers a year, it since then accelerated to over 50. The reversing will most likely come with poles moving around even faster, and them temporarily getting weaker, too. It might even happen that there will be more than two poles for some time.

Maybe it is best to look at the largest weather patterns, abusing **our atmosphere as a crude simulation for magnetic reversal**:

Take a look at how the wind high over Antarctica changed within the year 2022:

– [Winter](https://earth.nullschool.net/#2022/01/01/1200Z/wind/isobaric/10hPa/orthographic=-320.77,-90.00): A weak counter-clockwise current.
– [Summer](https://earth.nullschool.net/#2022/07/01/1200Z/wind/isobaric/10hPa/orthographic=-320.77,-90.00): An enormous clockwise current.

So how can one turn into the other? Lets take a look at the first of every month to see how it changes:

– [January 2022](https://earth.nullschool.net/#2022/01/01/1200Z/wind/isobaric/10hPa/orthographic=-320.77,-90.00): the winter counter-clockwise cycle.
– [February](https://earth.nullschool.net/#2022/02/01/1200Z/wind/isobaric/10hPa/orthographic=-320.77,-90.00): the cycle moved outwards, now there is meandering at the center.
– [March](https://earth.nullschool.net/#2022/03/01/1200Z/wind/isobaric/10hPa/orthographic=-320.77,-90.00): more meandering, but we notice that it generally moves clockwise.
– [April](https://earth.nullschool.net/#2022/04/01/1200Z/wind/isobaric/10hPa/orthographic=-320.77,-90.00): now we have a full clockwise current inside the counter-clockwise one.
– [May](https://earth.nullschool.net/#2022/05/01/1200Z/wind/isobaric/10hPa/orthographic=-320.77,-90.00): the summer cycle dominates the South pole.
– [June](https://earth.nullschool.net/#2022/06/01/1200Z/wind/isobaric/10hPa/orthographic=-320.77,-90.00): the summer cycle dominates the South pole.
– [July](https://earth.nullschool.net/#2022/07/01/1200Z/wind/isobaric/10hPa/orthographic=-320.77,-90.00): the summer cycle dominates the South pole, but it wobbles.
– [August](https://earth.nullschool.net/#2022/08/01/1200Z/wind/isobaric/10hPa/orthographic=-320.77,-90.00): the summer cycle dominates the South pole. The wobbling continues; it compares to the poles moving around as they do right now. It indicates the coming change.
– [September](https://earth.nullschool.net/#2022/09/01/1200Z/wind/isobaric/10hPa/orthographic=-320.77,-90.00): the strong summer cycle is now quenched between two smaller clockwise ones.
– [October](https://earth.nullschool.net/#2022/10/01/1200Z/wind/isobaric/10hPa/orthographic=-320.77,-90.00): the two small ones died off again, but the main one shrunk.
– [November](https://earth.nullschool.net/#2022/11/01/1200Z/wind/isobaric/10hPa/orthographic=-320.77,-90.00): the two quenching ones are back with a vengeance. The magnetic equivalent of those are the aforementioned additional poles that might temporarily pop up.
– [December](https://earth.nullschool.net/#2022/12/01/1200Z/wind/isobaric/10hPa/orthographic=-320.77,-90.00): The large one was pushed off and weakened, and one of the smaller ones invaded its territory. In effect, there are now two similarly strong cycles with opposite direction, fighting for the South pole. This creates an S-pattern.
– [January 2023](https://earth.nullschool.net/#2023/01/01/1200Z/wind/isobaric/10hPa/orthographic=-320.77,-90.00): The yearly cycle of cycles begins anew.

Feel free to play around with it, there is a panel with many options at the bottom left. In particular, finer dates, the more chaotic North pole due to the complex landmasses, and other heights will be interesting!

The core of the earth, with iron/nickel solid inside a ring of iron-nickel liquid, sees convection (circulating movement) of the liquid, which also spins the solid, and this generates a magnetic field.

Exactly how powerful, and in what direction it is oriented, depends on the way the iron liquid is moving around, and that is somewhat chaotic. It is partly influenced by the way the earth rotates, so it tends to orient roughly the same way (which is why we have a north and south magnetic pole that is roughly the same as the true rotational axis poles), but it is also strongly influenced by heat transfer requirements, which affects the rate and strength of convection currents in the liquid. Sort of like how a pot of boiling water can get somewhat chaotic.

Now, for reasons we do not quite exactly understand in detail, every so often (hundreds of thousands of years or thereabouts) the field flips inside out/upside down (the north magnet side moves to the south rotational pole, and the south magnet end moves to the north rotational pole. Not exactly clear how this works and how fast it goes.

But that is what people usually mean when they talk about pole reversal. Some people seem to think, very incorrectly, that it is the rotational poles that switch somehow. The spinning of the entire earth does not change, though, so no such “reversal” happens. Only the direction a compass points will flip direction. Sun will rise the same place and at the same time as it always does, moon will go through its phases the same way. Magnets will be “backwards” though.