Weegy: Hydrogen and Helium
User: what forces hold galaxies together?
Weegy: gravitational force
User: is that all?
Weegy: electromagnetism is the force that would theoretically rip a nucleus apart, the weak nuclear force governs radioactivity, and the strong nuclear force (130 times stronger than electromagnetism) is the force that holds a nucleus together
User: what causes a galaxy to have a spiral shape?
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