Thanks to u/Quantum for the topic:
The theory is that as our solar system moves around the center of our galaxy, it travels through a magnetic field that reverses the polarity of solar system roughly every 12,000 years. This may cause the sun to micro nova and the earth to rotate 90 degrees.
The Earth Disaster Documentary
and thanks to those that voted!
previous round table discussions
Consider the Precession of the Equinoxes and Milankovitch Cycles. Add an occasional asteroid impact and a few 'prehistoric' nuclear winters and there you go.
I think the solar system passing through magnetic fields every 12000 years is an unreasonable hypothesis. What is the source? Would have to be the galactic center. But then, why is our local black hole a 19,000-pole stepping motor? Why and how 19,000 poles? How can a uniform mass of infinite density produce such a complex and arbitrary field? I can't believe the hypothesis.
As for Earth rotating 90°, I am not as sure either way. I can imagine a polarity switch flipping the inner planetary core, stirring up the mantle, and shifting the crust a bit. Probably highly volcanic. Probably hasn't happened before. Why? Because the earth isn't spherical, it's squished down some. More distance East/West than North/South. Rotating 90° would apply the squishing force perpendicular to the previous squish. Earth would be rounder if it ever turned by so much. Then again, a 180° flip might have been possible...
The explanation I’ve heard that makes the most sense is the sine-wave motion our solar system makes with the galactic plane. Every 12,000 years we pass from one side of the plane to the other. Likewise, at 6000 and 18000 years our motion changes direction, which could account for the importance of the “transition eras” in between catastrophes
That's reasonable.