So what exactly does that mean? If I'm driving from Chicago to Milwaukee will my compass say I'm heading South?

Fun fact, the earth Northern Magnetic pole (ie the magnetic pole in the northern hemisphere) is actually the south pole of the magnetic dipole. So your compass actually is already telling you that you're heading south.

But yes, the compass you have today will point south instead of north, but this can be solved by repainting which pole of the compass is red :)

The flip can possibly happen in a lifetime, but it probably takes thousands of years. But we have never observed it so we don’t really know how, but we know that it happens.

https://en.m.wikipedia.org/wiki/Geomagnetic_reversal#Charact...

During the reversal, it is thought that Earth would have multiple magnetic poles (much like Sol). These would gradually move over the planet resulting in effects as benign as auroras over the equator, or as disastrous as telluric currents powerful enough to ruin electrical infrastructure.

> say I'm heading South

After the reversal is complete, yes. During the reversal your compass could well be rendered useless (pointing toward your closest pole); assuming we're right about how the reversal would happen.

I wonder what effect multiple magnetic poles would have had if they had occurred during the Age of Discovery (15th-18th centuries).

I guess with celestial navigation it would've had less effect that one might think, but it certainly wouldn't have made navigation any easier.

Compasses manufactured for the northern hemisphere have extra weight added to the "south" end of the needle because the "north" end is partially being pulled toward the ground as well as the north magnetic pole. So your compass probably just wouldn't work at all.

My car already gets confused in Chicago. Today, I was driving south towards lower Wacker, and my car thought I was driving alongside Navy Pier in the lake... Wasn't until I got clear onto 290 that it regained its senses.

I'd guess it would cause the mass death of animals that use the poles to navigate.

Wikipedia seems to suggest this is unlikely:

> Hypotheses have also advanced toward linking reversals to mass extinctions.[47] Many such arguments were based on an apparent periodicity in the rate of reversals, but more careful analyses show that the reversal record is not periodic.[17] It may be, however, that the ends of superchrons have caused vigorous convection leading to widespread volcanism, and that the subsequent airborne ash caused extinctions.[48] (https://en.wikipedia.org/wiki/Geomagnetic_reversal)