Archive for Sean Carroll

Beyond Falsifiability: Normal Science in a Multiverse

Posted in The Universe and Stuff with tags , , , , , , on January 17, 2018 by telescoper

There’s a new paper on the arXiv by Sean Carroll called Beyond Falsifiability: Normal Science in a Multiverse. The abstract is:

Cosmological models that invoke a multiverse – a collection of unobservable regions of space where conditions are very different from the region around us – are controversial, on the grounds that unobservable phenomena shouldn’t play a crucial role in legitimate scientific theories. I argue that the way we evaluate multiverse models is precisely the same as the way we evaluate any other models, on the basis of abduction, Bayesian inference, and empirical success. There is no scientifically respectable way to do cosmology without taking into account different possibilities for what the universe might be like outside our horizon. Multiverse theories are utterly conventionally scientific, even if evaluating them can be difficult in practice.

I’ve added a link to `abduction’ lest you think it has something to do with aliens!

I haven’t had time to read all of it yet, but thought I’d share it here because it concerns a topic that surfaces on this blog from time to time. I’m not a fan the multiverse because (in my opinion) most of the arguments trotted out in its favour are based on very muddled thinking. On the other hand, I’ve never taken seriously any of the numerous critiques of the multiverse idea based on the Popperian criterion of falsifiability because (again, in my opinion) that falsifiability has very little to do with the way science operates.

Anyway, Sean’s papers are always interesting to read so do have a look if this topic interests you. And feel free to comment through the box below.

Building Blocks and Blueprints in Cosmology

Posted in The Universe and Stuff with tags , , , on August 1, 2013 by telescoper

Still playing catch-up from my recent travels, so to provide a blog post for today I’ve decided shamelessly to rip off an interesting comment on a blog post by Sean Caroll which picked up on the theme I posted about a few days ago, namely my perception that the current generation of cosmologists seems rather reluctant to question the standard paradigm. Please bear with me if that all sounds a bit incestuous…

Anyway, Peter Edmonds commented in order to draw attention to a series of papers on related matters by Avi Loeb (of Harvard University) which can be found on the arXiv here, here, here and there.
I’d encourage you to read the four interesting papers I’ve linked to above as I think they are extremely thought-provoking. The last of these begins with this paragraph, so you can see why it’s relevant to the aforementioned topic.

Too few theoretical astrophysicists are engaged in tasks that go beyond the refinement of details in a commonly accepted paradigm. It is far more straightforward today to work on these details than to review whether the paradigm itself is valid. While there is much work to be done in the analysis and interpretation of experimental data, the unfortunate by-product of the current state of affairs is that popular, mainstream paradigms within which data is interpreted are rarely challenged. Most cosmologists, for example, lay one brick of phenomenology at a time in support of the standard (inflation+Λ+Cold-Dark-Matter) cosmological model, resembling engineers that follow the blueprint of a global construction project, without pausing to question whether the architecture of the project makes sense when discrepancies between expectations and data are revealed.

To put this another way, a great deal of modern astrophysics and cosmology is rather incremental. I don’t mean that in a derogatory way, just that such research often involves large-scale observational projects that have to proceed slowly and painstakingly. Working at the coal face in large consortia like this makes it difficult to take the time to step back and consider the bigger picture. We ask a lot of early career researchers nowadays when we expect them to cope with detailed analytic work as well as assimilating and synthesizing a coherent view of the overall landscape. Producing a stream of research papers doesn’t in itself make an excellent research. Productivity needs to be balanced by a proper appreciation of which questions are the most important ones to ask, which often requires (and I apologize for using such an awful cliché) thinking outside the box.