Question

The milky way galaxy is a huge, flattened cloud of spiral arms radiating out from the center. Why does it hae this shape?

Answer 1

A galaxy is the end stage in the evolution of the universe
It was initiated by the force of gravity but later another force took over.
The outer arms are satellite systems and are governed by the law of gravity.
As the star systems migrate towards the galactic center they merge into a neutron density matter and the annihilation of this matter drives the galaxies collapse.
As the galaxy formed,it spun into a flattened disc,but as the stars merged the galaxy began to collapse at an accelerated rate and the action of the of the collapse caused the arms to rotate in step with the galactic center.
An observer looking at the galaxy with a spectroscope would see a red shift ans may interpret it as an accelerating recessional velocity.
It the observer could view the galaxy from the other side he would see the same red shift,he would then know that the galaxy was in a state of collapse and not receding.