> When I was getting my PhD in condensed matter physics I was going to the department colloquium all the time and seeing astrophysics talks about how some people thought the hubble constant was 40 km/s/Mpc and others thought it was 80 km/s/Mpc. With timescape cosmology maybe they were both right.
You're (mis)remembering a different (old) problem and confusing it with a new one. The problem in the 1970s and 1980s was: what is the local expansion rate of the universe? Where "local" mean "within a few hundred megaparsecs". There were two main groups working on the problem: one group tended to find values of around 50 km/s/Mpc and other values of around 100. Gradually they began to converge (in the early 1990s, the low-H0 group getting values of around 60, the high-H0 group values of around 80), until a consensus emerged that it was in the low 70s, which is where we are now.
The "Hubble tension" is a disagreement between what we measure locally (i.e., a value in the low 70s) and what theory (e.g., LCDM) says we should measure locally, if you extrapolate the best-fitting cosmological models -- based on cosmological observations of the CMB, etc. -- down to now (a value in the upper 60s). This has only become a problem very recently, because the error bars on the local measurement and the cosmological predictions are now small enough to suggest (maybe/probably) meaningful disagreement.
> Another longstanding problem in astronomy is that since the 1970s it's been clear we have no idea of how supermassive black holes could have formed in the time we think the universe has existed. With the JWST there are a flood of results that show the first 500 million years of the universe probably lasted a lot more than 500 million years
https://iopscience.iop.org/article/10.3847/2041-8213/ac9b22
That's not a "longstanding" problem, it's a problem from the last 25 years or so. In order for there to be a problem, you have to have what you think are reliable estimates for the age of the universe and evidence for large supermassive black holes very early in the universe. This is something that has emerged only relatively recently.
(Your link, by the way, is to a paper that has nothing to do with black holes.)
> When I was getting my PhD in condensed matter physics I was going to the department colloquium all the time and seeing astrophysics talks about how some people thought the hubble constant was 40 km/s/Mpc and others thought it was 80 km/s/Mpc. With timescape cosmology maybe they were both right.
You're (mis)remembering a different (old) problem and confusing it with a new one. The problem in the 1970s and 1980s was: what is the local expansion rate of the universe? Where "local" mean "within a few hundred megaparsecs". There were two main groups working on the problem: one group tended to find values of around 50 km/s/Mpc and other values of around 100. Gradually they began to converge (in the early 1990s, the low-H0 group getting values of around 60, the high-H0 group values of around 80), until a consensus emerged that it was in the low 70s, which is where we are now.
The "Hubble tension" is a disagreement between what we measure locally (i.e., a value in the low 70s) and what theory (e.g., LCDM) says we should measure locally, if you extrapolate the best-fitting cosmological models -- based on cosmological observations of the CMB, etc. -- down to now (a value in the upper 60s). This has only become a problem very recently, because the error bars on the local measurement and the cosmological predictions are now small enough to suggest (maybe/probably) meaningful disagreement.
> Another longstanding problem in astronomy is that since the 1970s it's been clear we have no idea of how supermassive black holes could have formed in the time we think the universe has existed. With the JWST there are a flood of results that show the first 500 million years of the universe probably lasted a lot more than 500 million years https://iopscience.iop.org/article/10.3847/2041-8213/ac9b22
That's not a "longstanding" problem, it's a problem from the last 25 years or so. In order for there to be a problem, you have to have what you think are reliable estimates for the age of the universe and evidence for large supermassive black holes very early in the universe. This is something that has emerged only relatively recently.
(Your link, by the way, is to a paper that has nothing to do with black holes.)