Last night I went to a showing of Chasing Einstein, a new documentary about the search for dark matter. It’s quite well done, and if you’re near New York, Berkeley or LA, you might want to take the opportunity to go see it in a theater.
The film starts out with a segment on LIGO, talking to Barry Barish and Rainer Weiss. Later on there are scenes from their Nobel celebration ceremony at Caltech and the award ceremony in Stockholm. There are no claims made that LIGO’s results are related to dark matter. Rather, this material functions as a counterpoint to the dark matter material, contrasting a great success story to the rather frustrating lack of success that physicists have had with dark matter.
Attention then turns to Elena Aprile and the Xenon1T experiment. Aprile is in the physics department at Columbia, and attended the screening I was at. I think she’s the great heroine of this film, although a bit of a tragic one. She and her collaborators have done a fantastic job of getting a series of highly sensitive detectors to work. If a WIMP particle responsible for dark matter had existed in the region advertised by many theories, they would have found it and followed the LIGO people to Stockholm. Instead they put a strong limit on the possible properties of such a conjectured particle. The film includes a heart-breaking scene when they unblind their data, quickly realizing that their years of effort haven’t been rewarded with the discovery that they had been hoping for. Aprile has a realistic take on the prospects for future experiments of this kind: they can be make somewhat more sensitive, but it’s hard to be optimistic that the remaining accessible parameter space contains a new particle.
Attention then turns to Erik Verlinde and his “Emergent Gravity” explanation for the dark matter phenomenon. I’ve never found the motivation for this compelling, so haven’t followed his work carefully. For someone who has, see Sabine Hossenfelder’s blog where she has written on the topic quite a few times (and has her own version of a model here). Grad student Margot Brouwer worked on this attempt to experimentally test Verlinde’s ideas, and she is also featured in the film. My understanding is that the positive results her group found are matched by other more negative results, see here.
Tech entrepreneur Cree Edwards appears at various points in the film, and I’m guessing that he’s the one who brought together the physicists and filmmakers to make the film (and probably financed it). He has an amateur’s interest in fundamental physics, and his questioning of the physicists reminds one of how people’s fascination with the subject is often deeply connected to their desire to make sense of the world, hoping to find explanations of the great puzzles of human existence. I fear he’s not likely to find much of what he’s looking for in physics, but glad to see that his questioning led to an excellent film.
Finally, the film contains scenes of observing a solar eclipse, an added attraction.