I graduated from the U of Chicago with a B.A. in Physics in '94. I didn't study physics because I was particularly interested in becoming a Physicists, but rather because of philosophical questions I had regarding the nature of the Universe. In particular I wanted to be able to "wrap my head around" the concepts of Relativity and Quantum Mechanics. When I graduated I had no better understanding of those topics than when I started.
Back in 2013, as a result of an article about the Planck Cosmology Probe I realized that my understanding of the phrase "expansion of the universe" was entirely wrong. I subsequently found an excellent article on the "metric expansion of space" in Wikipedia; it was instrumental in making me understand what the phrase actually meant.
Once I understood what it actually meant, it was at first extremely difficult to see how it could be true. But, then an idea occurred to me about a possible mechanism that would allow for such an expansion to occur. Armed with that idea, suddenly large sections of relativity and quantum started to make sense for the first time; things started to snap into place.
For what it's worth, I have created a Mac / iPad / iPhone app that explains and qualitatively models many aspects of the concept which is really quite simple and straightforward:
A PDF made up of all the text included in the app can be found here:
An extremely concise description of the entire idea can be found here:
