The Rotation of the Milky Way

The solar, like the galaxies are dancing. Why does it do that? It's sort of like on the merry-go-round where your horse goes up and down. The sun is oscillating around the center of the galaxy, over like a 30 million year cycle. So there's also a lot of change in our galactic neighborhood on a million year timescale. I feel like I've never wanted a time machine more than during this conversation.