ABSTRACT
This chapter discusses the fundamentals of the gravitational contraction of a self-gravitating cloud. This is because gravitational physics has many physical laws similar to those in plasma physics, due to the similarity between the gravitational force and the Coulomb force. The most energetic phenomena observed in the universe probably originates from the gravitational energy release in the gravitational contraction of the self-gravitating cloud or in the accretion of mass by massive objects. The chapter examines the mechanism to extract energy, mass, momentum, and magnetic flux from the gravitationally contracting cloud. It discusses fundamental points about the effect of rotation and magnetic field on the gravitational contraction of clouds. The chapter explores the growth of magnetic shearing instabilities and the Parker instabilities for a disk with purely toroidal magnetic field. It discusses the stability of non-magnetized rotating flow, and heuristically derives the Rayleigh's Criterion.
