For the past century there have been two unreconciled main branches of Physics: General Relativity and Quantum Mechanics. Albert Einstein had a significant role in each. He spent much of his life trying to reconcile them. In recent years a variety of approaches have been put forward, such as string theory — none fully successful. Recently I have been following the work of Stephen Wolfram who announced his open-source project to find the fundamental theorem of physics. I think he is on a fruitful path.
In many of my posts in this category I will ponder pieces of his work.