Newton and his theory

In 1687 Newton published Philosophiae Naturalis Principia Mathematica. He puts forward a theory of how physical bodies move in space and time. He developed the concept of gravity. 

According to his theory of gravity, stars should attract each other. So they could not remain motionless. Would they not all fall together at some point? He reasoned that this would happen only if there were a finite number of stars distributed over a finite region of space. But he reasoned that, if there were an infinite amount of stars, distributed more or less uniformly over infinite space, this would not happen, because there would not be an central point for them to fall to. 

This argument is an instance of the pitfalls you can encounter in talkin about infinity. It is correct to consider the finite situation, in which the stars all fall in on each other, and then ask how things change if one adds more stars roughly uniformly distributed outside this region. 

According to newton's law, the extra stars would make no difference at all to the original ones on average, so the stars would fall in just as fast. We can add as many stars as we like, but they will still always collapse in on themselves. We now know it is impossible to have an infinite static model of the universe in which gravity is always attractive.