Why are there only 4 forces in nature?

The four fundamental forces (gravity, electromagnetic force, weak force, and strong force) are the interactions in physical systems that appear not to be reducible to more basic interactions. read more

The four fundamental forces (gravity, electromagnetic force, weak force, and strong force) are the interactions in physical systems that appear not to be reducible to more basic interactions. This means there are four forces because our current understanding of how the universe works requires four forces - no more and no less. read more

Lastly, the weak force is responsible for radioactive decay, specifically, beta decay where a neutron within the nucleus changes into a proton and an electron, which is ejected from the nucleus. Without these fundamental forces, you and all the other matter in the universe would fall apart and float away. read more

No, and there never will be one. We have no science at all which can answer any meaningful "why" question about the structure of the universe, especially not about why things we do not observe are missing. read more