The Puzzle of Quantum Gravity

This whole article is way over my head, but the story is an intriguing one (via Mark Thoma):

What is the hottest problem in fundamental physics today? Physics aficionados most probably would answer: quantum gravity. Of all the fundamental forces of nature, only gravity still stands outside the rubric of the quantum theory. The difficulty of quantizing gravity has led to radical theories such as string theory, with its bold predictions of higher space dimensions and parallel universes. It's unclear if these theories are "crazy enough to have a chance of being correct," as Niels Bohr used to say. And too few people know the dramatic early history of this field.

In fact, the field of quantum gravity was born in 1916, even before physicists had properly explained the other fundamental forces, electromagnetism and the nuclear forces. Twenty years later, a young Russian physicist by the name of Matvei Bronstein realized that gravity would be the hardest force of all to quantize. But before he could do something about that, he was swept up in Stalin’s Great Terror and executed at the age of 30.

I don't really follow quantum theory, but it is interesting to listen to explanations of the multitude of dimensions in string theory.  None of it makes sense to me, but it is interesting.  The story of a brilliant physicist who gets swept up in a purge and executed leaves a lot of room to wonder, what if?