We already know gravity,but now also evidence for fifth force of nature.

Scientists say they have evidence for a new force of nature. We currently know four forces of nature, but a fifth may be added. If that is indeed the case, it could be the start of a physics revolution.
The current four forces of nature together explain how the world and the universe work. 
For example, they tell us why the sun shines and why everything on earth falls down.
By hitting atoms against each other, so-called subatomic particles are created. Such a particle is also called a muon. Scientists have now discovered that the behavior of the muons does not fit current theories.

They think an unknown force of nature influences the muons. "We think there could be another force, something we're not aware of right now. It's something else, which we call the 'fifth force'," says one of the scientists.
According to the researchers, there is "strong evidence" for a new force of nature, but not yet conclusive evidence.

If the fifth force of nature is confirmed, it would be one of the greatest scientific breakthroughs ever. It would change science in a way that Einstein's theory of relativity did.