The Road to Quantum Gravity
Demystifying the holy grail of physics
For better or for worse, the problematic of quantum gravity has preoccupied the field for over half a century. Although the weakest force, gravity seems to play a special role in the structure of reality. The same dynamics that cause you to drop your phone keeps the planets orbiting the Sun and describe the expansion of the universe.
The study of relativity revealed that this mysterious motion is simply the natural motion of entities within a curved spacetime. Harmonizing gravity with the other groundbreaking physics revelation of our time—quantum mechanics—has proved a bit more challenging to decipher.
It is still debatable whether such a pursuit is the most optimal use of our collective brain power given the experimental difficulty of confirming quantum gravitational theories.
The physicist Jonathan Oppenheim at University College London has even proclaimed the era of postquantum gravity.1 This speculative framework suggests that gravity is so difficult to quantize because it is subject to random stochastic fluctuations, but remains, in essence, a classical object.
Nonetheless, the allure of following in the footsteps of Isaac Newton and Albert Einstein is, for many, too enticing to resist. It is possible that gravity alone of the four fundamental forces is not quantum, but that would indeed be strange. At bottom, nature is quantum mechanical; classical physics is an approximation of quantum physics at large scales or at temperatures where quantum corrections are vanishingly small. There should therefore be extreme conditions where standard general relativity isn’t enough to accurately describe the behavior of the gravitational field.
