Central Galactic Plane

The Earth experiences 'seasons.'
Given geographical location one could have 3 months of Winter, 3 months of Spring, 3 months of Summer, and 3 months of Fall.
If you could translate that on a celestial scale, our Earth experiences a 'season' roughly every 6,500-8,000 years. Such as great floods, your ice ages, etc.

Our solar system is within an 'arm' of our Galaxy. That arm slowly floats up and down as it spins, crossing the central galactic plane.

There is matter that 'floats' with us and there is matter that floats within the cgp. The closer we get to the cgp, the more frequent 'foreign objects' as we tresspass upon their orbital domain.

The closer we get you will notice disturbance upon all planets.

And as much when you go south of the equator your toilet flows in the opposite direction, thus is the natural phenomena of 'flip.'

That is the easiest way I could have said so all could understand.