How does Replaceability applies to overcrowded academic areas that have an oversupply of PhDs slaving away in postdocs never to find a permanent job? This glut of PhDs must mean the actual impact of me joining a field like Particle Physics would be very low. Is that correct?
How is that different to one of the recommended career paths by 80000 Hours, Biomedical Research, which is also competitive, but is marked as high impact?
For context, I must mention that Biomedical Research seem to tackle more 'solvable' problems while Theoretical Physics has been mostly stagnated since the standard model (little progress has been made in several decades). For example, a few scientists predicted the Higgs boson within a short time of each other, Higgs was merely the first to do so. It should also be added that Biomedical Research positions exist in Big Pharma, while Theoretical Physics is limited to academia.
I have read many articles about replaceability. In special, the 80000 Hours 3-part series "How many lives does a doctor save?" about the impact of new doctors, as well as the Rational Altruist blog on Replaceability (https://rationalaltruist.com/2013/01/22/replaceability/). But I still have this question.
I believe the answer may be in the post "What does economics tell us about replaceability?" (https://80000hours.org/2014/07/what-does-economics-tell-us-about-replaceability/) but I am no economist and most of it flew over my head. I guess I need someone to dumb it down a little for me.
Thanks
To synthesize your point, you believe that replaceability and economics of scale ensure that individual impact in Theoretical Physics is small, unless you are able to be revolutionary, like Einstein?
I don't have access to the first paper you linked, though I can get an idea of what it debates by reading the abstract. The projects in science have been getting bigger, and that is specially true in Physics. A multi-billion dollar project, the Large Hadron Collider (LHC), was needed to test the Higgs Boson. Now, some Physicists want an even bigger one. Papers have tens, sometimes hundreds of co-authors because that's the number of people involved in the operation of the LHC (and also because everybody wants to have publications so that they can get an academic job).
I have heard a few physicists, disillusioned with the realities of the academic job market, say that you can't act like an early 20th century physicist anymore. This was the time of Einstein, and Bohr, and Rutherford. Nowadays, it's impossible for a lone physicist working in a patent office in Switzerland to look out the window and have a revolutionary insight that will change Physics forever, like Einstein did. The low-hanging fruits are taken.
Besides, one could argue that the sacrifices needed make it a terrible career path in the personal level (years of postdocs, cutthroat competition, small chance of academic job without any choice of where to live). As 80000 Hours argues in https://80000hours.org/articles/personal-fit/ "the path would ideally be reasonably enjoyable and fit with the rest of your life (e.g. if you want a family, you may want a job without extreme working hours)". I don't think the academic job market allows for such considerations, specially in Theoretical Physics.
Other, more applied fields of Physics, of course, are somewhat different, such as Solid State Physics. Albeit still competitive, their job outlooks are better.