To spell out my views: there has been a bit of a real slow-down in theoretical physics, because exploring the tree of possible theories without experiment as a pruning mechanism is slower than if you do get to prune. I think the theory slowdown also looks worse to outsiders than it is, because the ongoing progress that does happen is also harder to explain due to increasing mathematical sophistication and a lack of experimental correlates to point to. This makes e.g. string theory very hard to defend to laypeople without saying “sorry, go learn the theory first”.
This is downstream of a more severe slowdown in unexplained empirical results, which results from (imo) pretty general considerations of precision and energy scales, per the modern understanding of renormalization, which suggest that “low-hanging fruit gets picked and it becomes extremely expensive to find new fruit” is a priori pretty much how you should expect experimental physics to work. And indeed this seems to have happened in the mid 20th century, when lots of money got spent on experimental physics and the remaining fruit now hangs very high indeed.
And then there’s the 90s/2000s LHC supersymmetry hype problem, which is a whole nother (related) story.
To spell out my views: there has been a bit of a real slow-down in theoretical physics, because exploring the tree of possible theories without experiment as a pruning mechanism is slower than if you do get to prune. I think the theory slowdown also looks worse to outsiders than it is, because the ongoing progress that does happen is also harder to explain due to increasing mathematical sophistication and a lack of experimental correlates to point to. This makes e.g. string theory very hard to defend to laypeople without saying “sorry, go learn the theory first”.
This is downstream of a more severe slowdown in unexplained empirical results, which results from (imo) pretty general considerations of precision and energy scales, per the modern understanding of renormalization, which suggest that “low-hanging fruit gets picked and it becomes extremely expensive to find new fruit” is a priori pretty much how you should expect experimental physics to work. And indeed this seems to have happened in the mid 20th century, when lots of money got spent on experimental physics and the remaining fruit now hangs very high indeed.
And then there’s the 90s/2000s LHC supersymmetry hype problem, which is a whole nother (related) story.