Sabine Hossenfelder: Backreaction: The Superdetermined Workshop finally took place

In case you’re still following this blog, I think I owe you an apology for the silence. I keep thinking I’ll get back to posting more than the video scripts but there just isn’t enough time in the day. 

Still, I’m just back from Bonn, where our workshop on Superdeterminism and Retrocausality finally took place. And since I told you how this story started three years ago I thought I’d tell you today how it went.

Superdeterminism and Retrocausality are approaches to physics beyond quantum mechanics, at least that’s how I think about it – and that already brings us to the problem: we don’t have an agreed-upon definition for these terms. Everyone is using them in a slightly way and it’s causing a lot of confusion. 

So one of the purposes of the workshop was to see if we can bring clarity into the nomenclature. The other reason was to bring in experimentalists, so that the more math-minded among us could get a sense of what tests are technologically feasible.

I did the same thing 15 years ago with the phenomenology of quantum gravity, on which I organized a series of conferences (if you’ve followed this blog for a really long time you’ll remember). This worked out beautifully – the field of quantum gravity phenomenology is in much better condition today than it was 20 years ago.

It isn’t only that I think we’ll quite possibly see experimental confirmation (or falsification!) of quantum gravity in the next decade or two, because I thought that’d be possible all along. Much more important is that the realization that it’s possible to test quantum gravity (without building a Milky-Way sized particle collider) is slowly sinking into the minds of the community, so something is actually happening.

But, characteristically, the moment things started moving I lost interest in the whole quantum gravity thing and moved on to attack the measurement problem in quantum mechanics. I have a lot of weaknesses, but lack of ambition isn’t one of them. The workshop was originally scheduled to take place in Cambridge in May 2020. We picked Cambridge because my one co-organizer, Huw Price, was located there, the other one, Tim Palmer, is in Oxford, and both places collect a decent number of quantum foundations people. We had the room reserved, had the catering sorted out, and had begun to book hotels. Then COVID happened and we had to cancel everything at the last minute. We tentatively postponed the meeting to late 2020, but that didn’t come into being either.

Huw went to Australia, and by the time the pandemic was tapering out, he’d moved on to Bonn. We moved the workshop with him to Bonn, more specifically to a place called the International Center for Philosophy. Then we started all over again.

We didn't want to turn the workshop into an online event because that would have defeated the purpose. We wanted the people working on superdeterminism and retrocausality to have a chance to get to know each other. Our sponsor, the Franklin Fetzer Fund, was very supportive even though we had to postpone the workshop twice.

Of course the pandemic isn’t quite over and several people still have travel troubles. In particular, it turned out there’s a nest of retrocausalists in Australia and they were more or less stuck there. Traveling from China is also difficult at the moment. And we had a participant affiliated with a Russian university who had difficulties traveling for yet another reason. The world is in many ways a different place now than it was 2 years ago. One positive thing that’s come out of the pandemic though is that it’s become much easier to set up zoom links and live streams and people are more used to it. So while we didn’t have remote talks, we did have people participating from overseas, from Australia, China, and Canada. It worked reasonably well, leaving aside the usually hiccups, that they partly couldn’t see or hear, the zoom event expired when it shouldn’t have, etc. I have organized a lot of workshops and conferences and I have attended even more of them. This meeting was special in a way I didn’t anticipate. Many of the people who are working on superdeterminism and retrocausality have for decades been met with a mix of incredulity, ridicule, and insults. In fact, you might have seen this play out with your own eyes in the comment sections of this and other blogs. For many of us, me included, this was the first time we had an audience who took our work seriously. All of this talk about superdeterminism and new physics beyond quantum mechanics may turn out to be complete rubbish of course. But at least at present I think it’s the most promising route to make progress in the foundations of physics. The reason is quite simple: If it’s right, then new physics should appear in a parameter range that we can experimentally access from two sides, by making measuring devices smaller, and by bringing larger objects into quantum states. And by extrapolating the current technological developments, we'll get there soon enough anyway. The challenge is now to figure out what to look for when the data come in.

The talks were recorded. When they appear online, I will post a link. We want to produce a white paper that lays out the terminology that we can refer to in the future. I am working on a new paper in which I try to explain why I think that either superdeterminism or retrocausality is correct. This isn't the end of the story, it's just the beginning. Stay informed.