It seems substantive advancements in physics have been moving at a snails pace for some time now vs the first half of the 20th century. Have there been any paradigm shifting discoveries over the past 30 years?
If you want to include cosmology in physics (because, clearly, there are some fundamental forces at play re: these discoveries), then I’d say we’ve made good advances in identifying physics phenomena, but not at integrating them into any coherent model. To wit, dark matter, dark energy.
It’s fairly inarguable that particle physics hasn’t seen anything approaching a paradigm shift in the last 30 years. There was stuff like gluons/jets or the W and the Z that were hyped as big discoveries at the time, and the Higgs will no doubt be in a year or two’s time. But the bottom line is that the Standard Model has stood up to testing astonishingly well over that period.
Your timescale obviously includes all the string theory “revolutions”. People can no doubt argue over whether they have been “substantive”. Personally, yes they have been, though I’m still unconvinced whether strings themselves play any role in nature.
The observational biggie in the last thirty years however has surely been the realisation that the universe is accelerating. Since nobody can really explain this yet, it’s difficult to claim that this is quite an advance in our understanding of gravity, but it is one hell of a puzzle. And it’s one that nobody anticipated. Undoubtedly the biggest empirical surprise of the period and surely one with profound consequences. Once they’re figured out.
Yep, you could even put it like this: humanity has been unaware of the very existence of most of the Universe’s matter/energy until now.
Depending on the nature of dark matter and dark energy, we may even look back on this period as the opening of a whole new chapter of physics.