When the universe first formed, it consisted mainly of hydrogen atoms. Over time, the hydrogen atoms began to collect together to form large balls of hydrogen gas. The hydrogen atoms continued to attract each other, moving closer together. Eventually, pressure and temperature at the center of the cloud of hydrogen became high enough for nuclear fusion to begin. This formed the first generation of stars in the universe. What caused these early stars to form?

While magnetic forces do exist between charged particles, they are not the primary drivers of star formation. In the early universe, the interaction of hydrogen atoms was dominated by gravitational forces rather than magnetic forces, which are relatively weak in this context and do not facilitate the clumping necessary for star formation.

The momentum from the Big Bang contributed to the initial expansion of the universe but did not directly cause the formation of stars. Instead, this momentum dispersed matter throughout space, while gravitational forces later acted to pull hydrogen atoms together and form stars as the universe cooled and structures began to form.

The expansion of the universe created a vast volume of space, but it also led to cooling, which reduced pressure and allowed matter to coalesce under gravity. Rather than being a source of pressure that could form stars, the expansion facilitated the conditions of density that gravity could exploit to initiate star formation.