The nebular hypothesis of the formation of the solar system assumes that the material that became the solar system began as a large spherical cloud of gas and dust, rotating slowly. As the solar system formed, most of this material was transformed into a compact, flattened disk, rotating more rapidly. What is the explanation for this change in shape and rate of rotation?

Then What process heated the early solar nebula as it slowly condensed toward a central protosun? I. e. why was the temperature rising in the center of the contracting nebula?

a) conservation of the angular momentum

b) As a consequence of the interaction between particles.

Explanation:

A star is formed in a molecular cloud of gas and dust, mainly composed of hydrogen and helium. The Nebular Theory establishes, for the formation of the solar system, that the cloud starts to collapse under its own gravity when it receives a shock wave from a near event, for example, a supernova explosion. That results in the cloud breaking in small pieces, and those pieces constitute a possible future star.

Then it begins to accrete and rotate as a consequence of the angular momentum. In the center of that disk when it reaches the necessary temperature and pressure a protostar will born.

However, as the solar nebular condenses in the center due to its own gravity, the density increases, allowing more collisions between the particles that are in the nebula (atoms, free protons, etc), so the pressure rises and the temperature increases.          

sleep paralysis is a parasomnia, events associated with sleep.

sleep paralysis happens when you are in the middle of waking up or falling asleep. it is the feeling of being conscious but unable to move. it definitely involves hallucinations.

i had a friend that had sleep paralysis and he told me a story one time where he was laying in bed and he couldn't move his body no matter how hard he tried and there was someone standing in the corner of his room coming towards him. he couldn't move and you can't "wake up" because you are already conscious. sometimes sleep paralysis can be triggered by frequent waking up during the night based off of multiple trips to the bathroom, or if you had ever been abused, sleep paralysis can start happening from things like that.

a.) travels faster in solids because the particles are closer together.

air is a gas water is a liquid