Its a reasonable question, but the galaxy is very old, almost as old as the universe itself, about 14 Gyr and some of its stars are as old as the galaxy itself. Others are youngsters, just a few million years old. Sol is 4.6 billion years old, which makes it middle aged. There is little correlation between the stars' rotations, their planes of revolution are totally random, because they were all formed at different times and places, as actual observations have confirmed.

The plane of a solar system is not related to the spin of the galaxy, but to the angular momentum of the specific nebula where it formed, and these are constantly being churned up by nearby supernovae, solar winds, pressure, shock, acoustic and gravity waves moving through the interstellar medium, spiral arms, even collisions with other galaxies and tidal effects from passing galaxies and internal tides from large objects like molecular clouds and clusters.

At our time scale, the galaxy appears sedate and well behaved, but it is actually a churning, boiling, rippling cauldron of forces. Astronomers call it the Grand Design, and it is only now starting to take shape in our understanding.

I cannot tell you how happy I am to have lived in a time where we have just started learning these things, and that I have a little understanding of it myself. The Milky Way isn't just alive, its evolving.

Next time you're at Stanford Bookstore, or at the Library, look through "Galactic Astronomy" by Binney and Merrifield. It's a good recent survey of the field, with strong emphasis on what we know, don't know, and how we know what we know.