For decades, scientists have searched for a fifth fundamental force of nature that can explain mysterious aspects of the universe such as dark energy and dark matter. These are pieces of our cosmos that simply can't be accounted for by the four fundamental forces we know of: gravity and electromagnetism as well as the strong and weak nuclear forces.
In addition, while the hunt for this force has been ongoing, researchers have also been desperately hunting for a theory of quantum gravity. That's because quantum gravity can unite the best description we have of the universe on large scales — Albert Einstein's theory of general relativity — and the physics of the subatomic, aka quantum mechanics. Both theories emerged at the start of the 20th century and have been experimentally confirmed time and time again, yet they steadfastly refuse to overlap in a single unified theory.
