What is quantum gravity?

Artist's illustration of the quantum world. Two spherical shapes are connected by a series of blue sparks/strings, they are subsequently surrounded by glowing orange and red streaks of light, the scene is very abstract.

Quantum gravity is an attempt to unite the incompatible worlds of quantum mechanics and gravity. It does so by modifying one or both theories to reconcile the models.

Our understanding of physics is far from complete. On small scales, we have the theory of quantum mechanics. A paradigm of quantum mechanics is the Standard Model, which explains many of the smallest particles and how they behave. On large scales, the main force governing objects is gravity, described by general relativity. But when trying to reconcile these two models together, scientists have fallen short; quantum mechanics and general relativity are not compatible with each other.