The Milky Way consists of a flat disk of stars, with a diameter of 80K light years and a thickness of six thousand light years. It also possess a spherical halo of stars, with a diameter of almost 100 thousand light years. The total mass is about one hundred thousand million solar masses, but some think a good deal more is in an extended halo. Our solar system is thirty thousand light years fro the central plane of the rotating disk, which moves at (?) 250 km./s. –S. Weinberg, The First 3 .. [can’t read my writing].