Ask a Spaceman and RealSpace, and the YouTube series Space In Your Face. Sutter contributed this article to Live Science's Expert Voices: Op-Ed & Insights.

Quantizing gravity — and for the faint of heart, don't worry, we'll define what that means soon enough — can't be that hard, could it? I mean, we've got the other forces —electromagnetism, strong nuclear and weak nuclear — all quantized up like nobody's business. Surely gravity, the feeblest and wimpiest of the forces, would be a piece of cake, a nice little dessert to wrap up our quantum feast. Right? 

Well, let's look at a simple example to get the problems started: electron meets photon. What happens? Specifically, what happens in a fully quantum-physics description of the event? Do they just bounce off each other? Can photons even "bounce"? How is energy or momentum exchanged? Will they fall in love, or hate each other at first glance?