how do scientists explain how a nebula collapses on itself when the laws of physics show that the heat and pressure would cause it to expand

Follows are the solution to this question:

Explanation:

When they look at the issue, in particular, they would be overlooking several things of solar system formation. In normal cases, dust and cloud warming would not trigger the surface to extend because of change throughout the movement of particles.  

This was a dense layer of dark cloud or dust only at the initial phases of a universe. The stubborn event then happened. It event may either be a close-up light explosion or even a various energy form. The above power stream from the independent factor caused the dust storm to expand. That gravity pull of the particles moved all of the substances to a center of a cloud. because as layer compressed. Because as the cloud began to expand, its rotational speeds also decreased to preserve the surface energy. That surplus electricity was transformed into heat and induced the core aspect of a cloud to increase heat.

Its rise in temperatures was fairly large, but again not enough to restrict the collapse. Therefore the failure continued and the sun moved to the center of a whole system. Its excessive energy produced in the process was expended even before the formation of a star to overcome a mutual repugnance of a charged particles and also to fuse them just to shape helium and then the entire period of nuclear fusion began.

that would be called plucking : )

explanation:

''plucking, also referred to as quarrying, is a glacial phenomenon that is responsible for the erosion and transportation of individual pieces of bedrock, especially large "joint blocks". as a glacier moves down a valley, friction causes the basal ice of the glacier to melt and infiltrate joints (cracks) in the bedrock."