A new physics paper takes a step toward creating a long-sought "theory of everything" by uniting gravity with the quantum world. However, the new theory remains far from being proven observationally.

The ball rolls across the floor because it was kicked, just as Earth orbits the sun because it is tugged by gravity. The connection between cause and effect is fundamental to how we understand the ...

String theory began over 50 years ago as a way to understand the strong nuclear force. Since then, it’s grown to become a theory of everything, capable of explaining the nature of every particle, ...