# How come gravity generates enough pressure to start a fusion reaction in stars even though it is the weakest force?

Given the fact that gravity is the weakest of all forces, how does a gas cloud manage to collapse on itself under gravity and start a fusion reaction, outweighing the electromagnetic and nuclear forces between atoms? Even if the mass is greater, it would mean that the electromagnetic and nuclear forces between atoms would also be greater. How does gravity overcome these forces?

• @PeterDuniho: Both electromagnetic forces and gravitational forces are effectively infinite range. More precisely, they're both inversely proportional to the square of the distance between the objects. In contrast, the strong & weak nuclear forces are (roughly speaking) proportional to $e^{-r/\lambda}/r^2$, where $\lambda$ is a length on the scale of nuclei; this exponential factor means that the forces fall off much more quickly than for the "long-range" forces of electromagnetism & gravity. – Michael Seifert Jun 26 '20 at 0:40