I’ve reached the point in the semester teaching cosmology where we I’ve gone through the details of what we call the three empirical pillars of the hot big bang: Hubble Expansion Primordial [Big Bang] Nucleosynthesis (BBN) Relic Radiation (aka the Cosmic Microwave Background;
It has been two months since my last post. Sorry for the extended silence, but I do have a real job. It is not coincidental that my last post precedes the start of the semester. It has been the best of semesters, but mostly the worst of semesters. On the positive side, I’m teaching our upper level cosmology course. The students are great, really interested and interactive.
Dark matter remains undetected in the laboratory. This has been true for forever, so I don’t know what drives the timing of the recent spate of articles encouraging us to keep the faith, that dark matter is still a better idea than anything else. This depends on how we define “better.” There is a long-standing debate in the philosophy of science about the relative merits of accommodation and prediction.
I noted last time that in the rush to analyze the first of the JWST data, that “some of these candidate high redshift galaxies will fall by the wayside.” As Maurice Aabe notes in the comments there, this has already happened. I was concerned because of previous work with Jay Franck in which we found that photometric redshifts were simply not adequately precise to identify the clusters and protoclusters we were looking for.
One does not simply form stars from 100% of the available baryons.
I went on a bit of a twitter bender yesterday about the early claims about high mass galaxies at high redshift, which went on long enough I thought I should share it here. For those watching the astro community freak out about bright, high redshift galaxies being detected by JWST, some historical context in an amusing anecdote… The 1998 October conference was titled “After the dark ages, when galaxies were young (the universe at 2 < z <
Just as I was leaving for a week’s vacation, the dark matter search experiment LZ reported its first results. Now that I’m back, I see that I didn’t miss anything. Here is their figure of merit: LZ is a merger of two previous experiments compelled to grow still bigger in the never-ending search for dark matter.
Avi Loeb has a nice recent post Recalculating Academia , in which he discusses some of the issues confronting modern academia. One of the reasons I haven’t written here for a couple of months is despondency over the same problems. If you’re here reading this, you’ll likely be interested in what he has to say. I am not eager to write at length today, but I do want to amplify some of the examples he gives with my own experience.
In previous posts, I briefly described some of the results that provoked a crisis of faith in the mid-1990s. Up until that point, I was an ardent believer in the cold dark matter paradigm. But it no longer made sense as an explanation for galaxy dynamics. It didn’t just not make sense, it seemed strewn with self-contradictions, all of which persist to this day.
The fine-tuning problem encountered by dark matter models that I talked about last time is generic. The knee-jerk reaction of most workers seems to be “let’s build a more sophisticated model.” That’s reasonable – if there is any hope of recovery. The attitude is that dark matter has to be right so something has to work out. This fails to even contemplate the existential challenge that the fine-tuning problem imposes.
OK, basic review is over. Shit’s gonna get real. Here I give a short recounting of the primary reason I came to doubt the dark matter paradigm. This is entirely conventional – my concern about the viability of dark matter is a contradiction within its own context. It had nothing to do with MOND, which I was blissfully ignorant of when I ran head-long into this problem in 1994.
