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Hi friend,
Hello again! It’s been a busy couple of months, with travel and lots of last-minute book things, but also a fun time for science news of direct interest to me personally. This issue of Watch This Spacetime includes updates on a potential dark matter detection, neutrinos in ice, misbehaving dark energy, and, if you scroll down, a book cover reveal – UK edition! |
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-Katie |
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Did we detect dark matter?
You may know that my main area of research is dark matter: some mysterious, invisible stuff that makes up about 85% of the matter in the universe, holds galaxies together, and generally forms the underlying structure upon which all those pretty stars and galaxies are built. We have many, many pieces of evidence for the existence of dark matter (including studies based on how stars move in galaxies, how galaxies cluster together, how matter bends space, and even the abundances of the elements formed in the early universe), so we have good reason to believe it’s there, but we also have good reason to believe it’s made of something that doesn’t interact with light and might not interact in any other way with ordinary matter, aside from via its gravity. Still, we’d love to get to know it better, and there are lots of theories for dark matter that involve it doing some kind of particle physics we can in principle detect, so we (the physics community) have built a number of optimistically named dark matter detectors that we hope will alert us if a dark matter particle interacts inside them.
The big news is that one of those detectors, called LZ (which stands for LUX-ZEPLIN and yes those are both also acronyms), saw an event. On June 16, 2023, one of the nuclei in the detector material was nudged by something unseen. The usual things they would attribute such a movement to, so called “backgrounds” like cosmic rays or neutrons from radioactivity in the detector walls, don't seem to be able to explain it. So, maybe the culprit was a dark matter particle zipping through the detector. But there are reasons not to get too excited yet. First, of course, this was one event. It's hard to say a lot from one event. It was also found at a surprisingly high energy (i.e., it was a pretty strong nudge), and most models for dark matter would produce lower-energy events. Also, there have been a few papers (probably more; I’m not fully up to date at the moment) suggesting that if the dark matter model that could explain this event were true, some weird things should have been seen in astronomical data, and also maybe in other channels in the detector. There’s a nice not-too-technical discussion here.
There have been other intriguing hints and even claimed dark matter detections by other experiments, but so far nothing has panned out (at least, nothing has convinced the rest of the physics community). So we’ll have to wait and see. LZ has a lot more data to analyze, and we should know more soon. |
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Nobel Neutrinos
Just a few days ago, there was another reason to geek out about particles in the news: the Nobel Prize in Physics was awarded to Francis Halzen, a physicist who helped spur on the creation of the world’s coolest (in more ways than one) neutrino detector. The IceCube detector consists of an array of light-detecting devices (called photomultiplier tubes) embedded deep in the ice sheet at the South Pole. When a neutrino flies through the detector, once in a very long while it will interact with an electron or nucleus in the water and cause a charged particle to go screaming through the ice, moving faster than a light beam could. (Light goes slower in ice than in a vacuum, so a particle moving faster than light in that specific context is not illegal or anything.) Breaking the speed-of-light-in-ice means the particle creates a kind of electromagnetic “sonic boom” – an expanding cone of light called Cherenkov radiation. This is the same kind of light responsible for the blue glow that you see in photos of nuclear reactors. Anyway, IceCube being so big – about a cubic kilometer in volume – means that it is very good at seeing neutrino events and it has been especially important for its ability to see neutrinos coming to us from super-energetic astrophysical sources outside our Galaxy. Physicist John Beacom has a nice explainer here, and I wrote a few threads about the neutrinos and the prize on Bluesky, if you’d like to see a bit more about that. |
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A Dynamical Dark Energy Explainer
This isn’t news exactly, but I recently started writing updates for Perimeter Institute’s new researcher-aimed newsletter, which you can sign up for here (I believe that clicking on “Research Opportunities Radar” gets you the right version). You can see the whole newsletter in webpage form here, but if you’re specifically interested in my take on recent developments in dark energy, my 3000-ish-word article on it is here. The next edition, to come out later this month, is scheduled to include an update on quantum error correction. |
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Now onto some book news and UK cover reveal!
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UK Cover Reveal
When you get a book deal with one publisher and then sell foreign rights to other publishers, each one gets to create their own version of the cover, based on things like the publisher’s general vibe and the perceived preferences of the local market. With my first book, the US and UK versions of the cover were different, but both really cool in their own ways. In my last newsletter, I showed you the US cover of my book, which can be seen on Simon and Schuster’s page (or wherever else you shop in the North American market). A couple weeks ago, the UK cover was finalized, and I think it is just as awesome. Here it is! |
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| More Book Info on My Webpage |
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The same in-house designer who did the UK cover for my first book did this one. I like that they sort of work as a set.
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The hexagonal grid pattern looks cool but also nicely echoes a really important particle physics diagram that appears in the book, called “The Eightfold Way” (the Wikipedia discussion of it is pretty good). The importance of symmetry in our understanding and creation of physics theories is a huge theme in the book, so I love that there’s a nod to it in the cover design.
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The star and galaxy images in the grid are from JWST, which, unusually, has a hexagonal diffraction spike pattern (you can read more about how that works here or see a nice NASA infographic here). The original proposed version of the cover used Hubble images, but those have four-pointed diffraction spikes; I asked the designer to switch to JWST to get the hexagonal pattern, because I am just that kind of nerd. Anyway, I think it came out great!
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The other big book update is that we got our third blurb, this one from celebrated quantum gravity physicist and best-selling author Carlo Rovelli! Here it is:
"Katie Mack's writing on physics is always a joy: not just because of the wit, and the charming lightness, but especially because she describes science as it really is, not the sanitized version which is often presented. If you want to know how a great scientist of today really thinks about reality, read this!"
—Carlo Rovelli, author of On the Equality of All Things
This one was particularly exciting for me to receive because Carlo is the first physicist to comment on the book. I’m really glad he liked it! And to return the favor: his book Helgoland, about the development of quantum mechanics and the people behind it, was truly excellent and I definitely recommend it. (I talked with him about it for an online event in 2021; video here.)
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Other Updates |
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I gave my first talk about the book last month, in the CERN auditorium. It was fun to speak there, partly because that’s the auditorium where the Higgs boson discovery announcement was made!
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While I was in Geneva I entered a Swiss watch calibration contest and, to my great surprise, I won! Instagram posts here and here.
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I spoke at the Griffith Observatory, about dark energy, for their All Space Considered show. You can see the video here (my bit starts at about 55:30).
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My pilot buddy Mike has a podcast and he interviewed me for an episode recently; you can check it out to hear more about my aviation side.
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US Pre-Order Links (see my webpage for Canadian links) |
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