In physics, many problems were known at their time to be very challenging, for example the notion of heat, or how to understand the ideal gaz law, or the phase transition criticial behaviors, etc. And they were then solved. I'm wondering if people have studied if there are common trends in these problems : what makes some scientific questions difficult but interesting, and what are the various strategies which were used to solve them, especially in the fields of physics. Any advice for bibliographic references about this ? Thanks !