I continue to try to set aside one weekend day or so to go hiking with my DSLR camera, getting recommendations of trails from the Walking Man blog. This works both as exercise, and something to do on the computer that isn’t doomscrolling, as I work through the couple hundred photos I’ll take on a typical hike and find the best ones. These mostly end up in Google Photos albums; the two most recent trips were:

Schoharie Creek Preserve, 6/27/2021

Hand Hollow Conservation Area, 7/4/2021

In the past, I’ve tried to mix this up a bit by visiting built-up areas so I’m not just endlessly taking pictures of trees and birds. I’m probably about due for one of those, but not quite sure where to do it. Maybe I’ll just go stomp around downtown Albany.

Anyway, that’s the last couple of weeks of My Expensive Hobby, now that The Pip isn’t playing baseball all the time.

SteelyKid has gone on a big MCU kick over the last week, working through most of the Avengers movies on streaming. The Pip is less committed to this, but not uninterested, so last night we watched Black Panther for Movie Night. Which on one level is perfectly fine as a visual spectacle (I agreed to watch on that basis, despite having seen it before). On another level, though, the Wakanda of the movie exemplifies everything I dislike about the MCU.

A lot of the problem is just the comic-bookery of it all. At one point, the Pip asked “Is that actual science?” (I think regarding the suit storing kinetic energy) and I replied “Anything in these movies that purports to be science is absolute garbage.” That’s a bit harsh– they have famously brought in the occasional Actual Scientist to consult on this or that bit of technobable– but they’re really bad about having any kind of consistent behavior of… anything. Dropping in the occasional vocabulary word doesn’t change the fact that all MCU technology is functionally magic, able to do anything a hero needs at whatever moment the plot requires it.

They don’t even get science as an institution right, in that everything cool is the work of Super Genius individuals. Shuri is what, 22? And she’s personally responsible for the Black Panther suit, and the magic car-stopping beads, and the giant network of glowing maglev trains that whoosh around under Wakanda City for no clear reason? I know it’s a dramatic convention to put a single face on what in reality would be a massive engineering project involving dozens if not hundreds of people, but it’s a dramatic convention that always sets my eyes to rolling.

There’s also a kind of problem of plot ethics that’s characteristic of the MCU, in that the Deep Issues that it attempts to raise about history and kingship and all the rest are basically resolved by T’Challa being a Good Person. He never seems to be personally conflicted about much of anything, but has an unerring sense of Right that guides him, and the movie basically endorses all his choices. They have the same problem with Steve Rogers in the Captain America thread of the MCU, which I guess makes it natural that by the last couple of movies he’s set up shop in Wakanda.

The biggest source of my dissatisfaction with the MCU in general, which is particularly illustrated by this movie, is a matter of genre positioning. That is, they’ve chosen to make it an alternative history, and that’s a speculative subgenre that almost never fails to rub me the wrong way.

This really starts with the Captain America movies, where they push his origin back to WWII. Which, you know, is fine as a tribute to the original comics, but that early a departure point, featuring a weird Nazi faction running around blasting things with energy bolts, should change… basically everything. And yet, other than some fairly superficial differences, the early 21st century in the MCU looks pretty much like the early 21st century of the people who buy tickets for MCU movies.

Wakanda takes this to an extreme, with the departure point being millennia in the past. And yet, despite having been closed off to outsiders for centuries, and evolving a whole complicated system of magical technology beyond anything known to the rest of the world, everything looks… pretty normal. They’re even taking their cultural cues from the normal world– Shuri flips off T’Challa in one early scene, which is a pretty characteristically American gesture, but… why? Other than, you know, that it got a chuckle from The Pip and the millions of characteristically American kids that they’re trying to sell tickets and merch.

Wakanda ought to be dramatically… different, if it’s been operating entirely independently for centuries. But instead it’s just like the (movie version of) real-world Africa, except rich.

Roll all that together, and I just… can’t. I can’t take it seriously without starting to ask questions about how it all works, questions that don’t have good answers because it’s ultimately all rooted in comic books from fifty years ago. It’s an aesthetic, not a created world with any depth in the places that its presentation makes me want to poke at. And that means that the story doesn’t have any real stakes, so when it comes down to two dudes punching each other in front of a green screen, it’s a great big shrug from me.

And, as with many of my negative reviews of things, I fully recognize that this is mostly a Me Thing. Obviously, millions upon millions of people don’t have these issues with the MCU and, you know, good for them. The whole structure is just fatally flawed for me, though. It doesn’t stop me from watching (obviously), but it does make it next to impossible for me to take it seriously.

We’ve added a regular Movie Night option to our routine with the kids, on Friday and Saturday nights (and the occasional Thursday or Sunday when there’s a long weekend), so I’ve been watching more movies than I have in years. Most of these are re-watches for me, trying to recall things from the 80’s and 90’s that the kids would like– for example, I finally badgered them into watching Die Hard on my birthday a couple of weeks back, and last night we watched Shanghai Noon because The Pip really enjoyed Owen Wilson in Loki. I’m not going to try to reconstruct all of the stuff we’ve watched, but will at least try to comment on the new releases that got into the mix.

The Mitchells Vs. The Machines: I think this is the clear standout of the new movies we watched. Fast-paced, funny, sweet without tipping over into cloying. We’ve gotten some mileage out of the image-recognition joke (“Dog…pig… dog… pig… burrito… ERROR”).

Soul: I liked this more than the kids, I think, which is not super surprising because it’s pretty heavy. The slapsticky bits with the cat played really well, but some of the other humor went over their heads. A really well-done story, making good use of the animated medium.

Luca: The most recent of the new movies, a perfectly fine piece of work from Pixar. Not near the top of their work, but solid.

In the Heights: Kate and the kids are way into Hamilton which is just Not My Thing; this is more of that. It’s clearly a very well done example of what it is, but what it is is not a thing that I want.

Inside: Bo Burnham’s pandemic special. SteelyKid went through a Burnham phase a while back so I suggested it when it popped up on Netflix. It mostly just made me feel old, because it’s very much working in the visual language of SteelyKid’s generation, which I can only barely follow. SK really loved it, though, and has re-watched it multiple times since, and went down a rabbit hole of analysis videos about it to boot.

Update: I knew as I was writing this that I was forgetting something; specifically, that was Raya and the Last Dragon, which we watched when it was released to streaming. This was a pretty good Disney movie; not top-tier, but well done and enjoyable.

In addition to the semi-regular Movie Nights, I got a stationary bike back in December, and we purchased a much larger TV for the living room, moving our old plasma screen downstairs, so I’ve watched a bunch of episodic content on days when the weather was too crappy to exercise outdoors. These include (but are not limited to):

Shadow and Bone: Kate and I actually watched the first couple episodes together, but she wasn’t that into it, so I finished it while biking to nowhere. Netflix clearly put a ton of money into making it look great, and it’s the right level of florid melodrama to serve well as a diversion while exercising.

The Irregulars: A step below Shadow and Bone in the production quality department, but very much in the same melodramatic vein. Everybody involved is very pretty, though maybe implausibly diverse for Victorian London.

The Mandalorian: I watched these more or less as they came out, a rare case where I was actually sort of up-to-date on pop culture trends. It was good fun, though I would’ve been happier if it had avoided connecting to the main Star Wars movie plotline, and just stayed on the fringes of the galaxy.

The Umbrella Academy: I watched the first season right when it dropped, and it was fun; SteelyKid independently discovered it around the start of the second season. It’s pretty ridiculous, but a lot of fun, particularly Five’s contempt for the others, and the bit where Klaus tries to tell the frog and scorpion fable is awesome.

Age of Samurai: A history series about the unification of Japan at the end of the 1500s (Oda Nobunaga, Toyotomi Hideyoshi, and Tokugawa Ieyasu), with a mix of talking-head segments and lurid re-enactments. This stuff is great for exercise-bike watching.

The Lost Pirate Kingdom: Same idea as the previous, but about the golden age of piracy in the Caribbean in the early 1700s. Again, terrific to watch while pedaling a stationary bike.

As alluded to above, the kids and I are watching Loki, which has been enjoyable to this point. It’s maybe halfway through the season, though, so not really possible to evaluate as a whole.

Some other things I’ve tried and not finished:

Cobra Kai: I’ve watched most of the first season, and enjoy it when it’s on, but there’s kind of a high level of anxiety around the plot as it’s building up, and I often just don’t want to deal with that. Which is why I’ve leaned a bit more toward florid melodrama, where the stakes are more ridiculous.

Jupiter’s Legacy: I watched one episode, and it is Trying So Very Hard to be Grim and Serious and everyone in it is ostentatiously Troubled and just, no thanks.

Invincible: This was better than Jupiter’s Legacy, but the shocking twist at the end of the first episode was, well, shocking, and I’m not sure I want to watch more.

I’m probably forgetting some stuff, but this is enough of a list to make a point of some sort…

With A Brief History of Timekeeping moving into the production pipeline and the end of my directorship at work, I have the opportunity to reorganize a bit of my time, and I’ve been trying to get back into writing more. This includes trying to do more blog posts about more serious topics, which means I need to think of topics for those posts.

Yesterday, I had a great idea for a post about higher education and politics. I think that was it, anyway. Maybe it was just one of those and not the other? I don’t know any more, because in addition to having a blog, I have a dog, and I thought of the idea just as it was time for him to get his morning walk. And during the course of the walk, I completely lost whatever my great idea was.

The reason for this is podcasts. I started listening to a bunch of podcasts several years ago as something to do while sitting in one or the other of the kids’ bedrooms waiting for them to fall asleep, but that quickly expanded to be a thing that I do while walking the dog, and while running errands in the car. And on the whole, I think it’s been a positive development– I’ve found some smart and funny commentators on current events and pop culture, so I’ve gotten some good laughs and a bit of edification out of the deal.

One negative feature, though, is that I’m rarely without somebody else’s voice in my ear. That’s fine when the goal is either information transfer or pleasant diversion, but it’s actually terrible for thinking. There’s a reason why I don’t listen to podcasts while writing or doing class prep, after all– if I pay enough attention to the podcast to understand what they’re saying, I don’t have enough spare processing capacity to do the actual task at hand.

And that’s what happened yesterday. I had an idea for a blog post that I thought was really promising, but when I set out with the dog, I spent the next half-hour listening to somebody else’s thoughts. Which left no real room for… whatever it was I had wanted to write about. This isn’t to say that the podcast in question was Bad, mind– I enjoyed it quite a bit, and it had some useful analysis of current events. But paying attention to that distracted me from my own idea, to the point where I completely forgot whatever the idea was, and ended up writing a thing about sports and academics instead, that wasn’t at all what I was thinking of earlier.

(This is not that unusual an occurrence, by the way, which is why I’m not more upset. I regularly think of great ideas while in the process of doing other things and totally lose them by the time I get to a place where I could even write down what the idea was. They usually come back around sooner or later.)

Anyway, in thinking about what to write this morning, it occurred to me that this is almost certainly a contributing factor to the decline in my blog writing over the last few years. I used to do a lot of pre-writing while walking the dog– turning the general idea over, thinking of some choice sentences, etc.– but podcasts make that much more difficult, in the same way that they make writing and class prep difficult. If I’m paying enough attention to the podcast to follow what they’re saying, I’m not thinking through my own stuff.

It’s a little interesting to consider why podcasts specifically are a problem, especially given that back when I blogged a lot more, I also read a lot more of other people’s blogs. I think it’s two things: first, I read much faster than most people speak, so I could power through a lot of blog posts in the time it takes for one podcast. (Also, let’s be honest, here, a lot of blog writing doesn’t exactly demand (or necessarily reward) close reading…) More important, though, is when it happens– I wasn’t reading blog posts while walking the dog, after all. Podcast listening taken over in time when I otherwise had nothing else to do but think my own thoughts, and filled it in with listening to other people’s thoughts. And that’s bound to have a detrimental effect on my ability to, you know, write actually interesting stuff.

Does that mean I’m going to cut podcasts out of my media diet? Probably not, because I’ve become very attached to some of them. And there are long-ish stretches of time still when I’m not capable of much great thinking– The Pip still wants an adult in his room as he goes to sleep, for example, and my brain is basically cheese at that point in the evening already. Having realized this, though, I’m probably going to switch to listening to music instead during the morning dog walk, particularly when I’ve got (or need to get) an idea for something to write.

During the recently concluded Weird Pandemic Year, it seemed like there was an uptick in the number of student-organized events on campus, mostly over Zoom, presumably in an effort to stave off boredom. One of these was a panel, organized by some students from the women’s basketball team, asking faculty and staff who had played sports in college to talk about the benefits of that for their careers.

This probably sounds like a weird idea to many faculty, because they feel athletics detract from academics (to the point where a lot of them are reflexively anti-sports). It initially seemed an unlikely topic to me, as well, because academia isn’t all that overtly sporty– career benefits from playing sports seems like more a Thing in the business world, where my finance-industry friends from college cut deals on the golf course, and so on. On thinking about it a bit more, though, before and during the discussion, I think there are some really positive features that are at least in part traceable to my past playing sports.

On the more trivial end, there are things like an attention to rules and structure that come from playing sports. I’m usually good about hitting deadlines for things, in large part because I played basketball back in the day for coaches from the “When I say practice starts at 5, that means you have to be done with the 15-minute pre-practice warm-up routine by 5:00” school. That really fixed the idea of needing to be ahead of the official schedule in my head, and it’s stayed there all these years (which is sometimes socially awkward…) Similarly, I generally like having athletes in class, because for the most part, when I tell them that a certain thing is due on a certain date, they will produce (a version of) that thing by that date. They might have as much time to devote to it as some other students, or assign it as high a priority, but they’re much less likely to beg for extensions or otherwise view the rules as fully negotiable.

Similarly, there’s a tolerance for a certain degree of adversity that comes from having to fight through getting good at a sport that comes in handy. For one thing, nothing Reviewer 3 says is ever going to upset me as much as stuff I’ve had yelled at me in basketball practice. And there’s a bit of the “Confusion Is the Sweat of Learning” attitude (tm-Rhett Allain) in there, too: I know what it’s like to suck at something and then become good, and recognize that the process involves a lot of false starts and mis-steps along the way. Again, this is a trait that I appreciate when I have athletes in class, who often are a bit more chill about not getting something right off than students for whom school has always come very naturally, who can get upset when they hit harder material that they don’t grasp right away.

(There are, of course, athletes for whom sports come very naturally, who struggle when they hit a higher level of competition, and don’t deal well with that. They’ve mostly washed out by the time they would get to us, though; we’re much more likely to see students hitting the academic version of that problem for the first time.)

The biggest thing that’s served me well, though, that comes out of playing sports for many years, is a kind of competitive attitude that’s a good antidote to impostor syndrome. In order to get good at sports, you have to challenge yourself by playing against people who are better than you are. And that necessarily means you will occasionally find yourself taking the field against somebody who at first glance it seems like you have no business competing with. The secret to success is finding a way to compete anyway, to raise your game to something more like their level.

(When The Pip was worried about his baseball playoff games, I told him a story about the coach of some famous underdog team (I remember hearing it as Jim Valvano of NC State, though couldn’t confirm that on Google) who was asked “Do you really think your team has a chance to beat [Favorite]?” and replied “I think we’re the only ones with a chance to beat them, because we’re the only ones playing.” That’s the right attitude to take into any competition.)

That refusal to be cowed is incredibly useful in all kinds of non-athletic contexts, too. I’ve had a lot of occasions where I’ve found myself on a list of panelists or invitees to some event and thought “What are they thinking putting me in with these people?” One of the ways I get through that is to draw on the same stupid competitiveness that makes me take the court and match up against guys 20 years my junior who are better athletes than I ever was. If that’s what I’ve got to do to be in the game, well, I’m going to do my damnedest to find a way to be better than I’ve been before.

Now, I’m not saying that sports is the only way to get these kinds of results– in particular, I suspect you could get a lot of it from music, as well, particularly if you’re in a system where section chairs and the like are competitive. I think it’s a good demonstration, though, that even things that too many of my colleagues would say are in direct opposition to academic success are, in fact, complementary to it. You can pick up skills and character traits through extracurricular activities that turn out to be extremely helpful in a professional context, even when the two areas seem to have nothing whatsoever in common. In many cases, this can more than justify the apparent loss of time to practices and competitions.

So, as I said, it was an illuminating discussion, and I’m glad the students put it together and I agreed to do it. It was also interesting to trip over the fact that even I have internalized the idea that sports and academics are completely separate, if not in tension. It’s also a necessary reminder of a thing I say a lot to other faculty about student life stuff: that it’s important to think carefully and honestly about what positive features students are actually getting out of the the things that they do. Especially when those activities don’t seem directly connected to our overall mission, or when they’re not necessarily things that we’d choose to do in their position.

It’s been exactly seven months since I last updated my progress on A Brief History of Timekeeping, with a report that I had submitted the complete manuscript last December. I have since gotten two rounds of editorial comments on it, and made corresponding revisions, and I sent my editor the (hopefully) (mostly) final versions of the figures yesterday, so it now moves off to the production team at BenBella; in a couple of weeks, I’ll get the joy of going over the copyedits…

In celebration of that, here’s the new and improved table of contents:

• Introduction: A Clock Is a Thing That Ticks
• Chapter 1: Sunrise
• Chapter 2: The Sun, the Moon, and the Stars
• Chapter 3: “Give Us Our Eleven Days!”
• Chapter 4: The Apocalypse That Wasn’t
• Chapter 5: Drips and Drops
• Chapter 6: Ticks and Tocks
• Chapter 7: Heavenly Wanderers
• Chapter 8: Celestial Clockwork
• Chapter 9: To the Moon . . .
• Chapter 10: Watch This
• Chapter 11: Does Anybody Really Know What Time It Is?
• Chapter 12: The Measure of Spacetime
• Chapter 13: Quantum Clocks
• Chapter 14: Time and Gravity
• Chapter 15: Time Enough for Everyone
• Chapter 16: The Future of Time

And, up at the top, you see the US cover (there’s a UK cover as well, though I’m not sure that one’s officially released yet). It also has a release date (January 25, 2022), and can be pre-ordered at Amazon and B&N if you are the sort of wonderful person who likes to do that kind of thing (insert boilerplate here about how pre-ordering books is a tremendously good and important thing to do for your favorite authors, and greatly increases the book’s chances of success).

Finishing this one was a bit of a slog, what with the entire world deciding to go batshit crazy when I was four chapters into the first draft. I’m proud of the final product, though, and look forward to it being released to the wider world at last.

Another day, another handful of Forbes pieces moved here for ad-free archiving. This is a sampling of pieces explaining physics stories that made news for one reason or another (two are about Nobel prizes, three not).

How [2016]’s Nobel Laureates In Physics Changed The Game

The ALPHA Experiment Records Another First In Measuring Antihydrogen

Nobel Prize In Physics 2018: How To Make Ultra-Intense Ultra-Short Laser Pulses

How Does The ‘Shape’ Of An Electron Limit Particle Physics?

Three Hundred And Fifty Years Of Testing Gravity With Clocks: Einstein, Popper, And Jean Richer At The Tokyo Skytree

I used to do more of this kind of thing, but they’re kind of a lot of work often for little reward (in terms of reader engagement), so I tend to do them only when I’m 1) not very busy, and 2) it connects to my other interests in some way that makes it rewarding to write in spite of the low traffic. You can see that in the above, where a couple of these are very explicitly filling in gaps in other coverage of the same stories.

This post is part of a series of posts originally written for my blog at Forbes.com that I’m copying to my personal site, so I have a (more) stable (-ish) archive of them. This is just the text of the original post, from October 2018, with only one of the images that originally appeared with it, because that’s essential to the explanation.

Big news in the study of tiny things dropped last week while I was traveling to Washington DC for a meeting: the ACME Collaboration has a new paper in Nature reporting the latest results of their search for a permanent electric dipole moment of the electron. This is huge because it suggest that the new particles predicted by theories of physics beyond the Standard Model should have masses greater than could be directly detected at the Large Hadron Collider.

A lot of people wrote stories about this last week– the collection of links I retweeted from airports includes an NSF press release, a Science News article, and a a post from fellow Forbes blogger Brian Koberlein. Those will give you the basic outline of what’s being reported; in this post, I want to dig a little deeper into the physics at work.

Most of the coverage of this adopts the framing of talking about this as measuring the “shape” of the electron, something that’s been standard for news releases since at least 2011 when I wrote a ScienceBlogs post about an experiment from Ed Hinds’s lab. This provides a nifty visual analogy– most of the press stories quote Dave DeMille of Yale comparing this to shifting a two-nanometer-thick slice from the south pole to the north pole of a perfect sphere the size of the Earth. (Note to the planetary science crowd: Yes, we know that the Earth is not a perfect sphere, but bulges out at the equator by far more than that.) What’s less clear from a lot of these stories, though, is what this has to do with particle physics. For that matter, what does it even mean to talk about the electron having a shape?

As physicists constantly have to emphasize when talking about electron spin, the electron is not literally a tiny ball of charge. In fact, to the best of our knowledge, the “bare” electron is a featureless point. If you could turn off all of its interactions with the rest of the universe, an electron would be infinitesimally tiny and basically uninteresting.

Happily, electrons do interact with the rest of the universe, which is what allows us to measure their properties. Because the universe is quantum, though, those interactions mean that we never get to see a “bare” electron: instead, we see some combination of the “bare” electron and its interaction with the rest of the universe. These interactions change the energy of the electron, and we can use the light absorbed and emitted by an electron to determine its energy to very high precision. We can then look at how that energy changes when we apply other kinds of fields.

The most significant type of interaction is simply between the charge of the electron and an applied electric field (say, from another charged particle nearby). This creates a very large energy shift that makes the electron “want” to get closer to positive charges and farther away from negative charges. This “electric monopole” interaction absolutely dwarfs any other interaction you might be interested in.

The next most significant interaction is a “magnetic dipole” interaction between an applied magnetic field and the intrinsic spin of the electron. This is a tiny shift, but you can see its effects because it’s not symmetric: a magnetic field in one direction will increase the electron’s energy by a tiny amount, and a field in the opposite direction will decrease it by the same amount. If you do something to trap an electron in place, most of its energy comes from the electric monopole interaction with whatever’s trapping it, but if you switch a magnetic field back and forth between two directions, you’ll see a tiny difference between the two states that you can measure using spectroscopy. This shift is something like a millionth of the energy of a typical electronic state in an atom or molecule, but measuring energy differences at that level is pretty routine for atomic physicists.

What ACME is looking for (along with a bunch of other experiments) is an “electric dipole” interaction, which has a mix of the characteristics of the other two. Like the electric monopole interaction, it’s an energy shift caused by an applied electric field, and like the magnetic dipole interaction, it depends on the direction of the applied field, shifting up for one direction and down for the other. Again, this is absolutely minuscule compared to the energy from the monopole interaction, but if you use the monopole interaction to stick an electron to an atom or molecule so it can’t simply move in the direction of the electric field, you can hope to pick this up as a shift in the energy of the electron that changes direction when you change the direction of the field.

The strength of this electric dipole interaction is measured by a thing called an “electric dipole moment,” and in classical electromagnetism, you calculate these all the time for macroscopic distributions of charge. A perfect sphere of charge would have zero dipole moment– no matter what direction you apply the field in, you get the same total energy. Any “lopsided” distribution will have a non-zero dipole moment, which is what leads to the “shape of the electron” characterization of this experiment: a sphere of charge with a tiny “bump” on one pole and a corresponding dent on the other will give you an electric dipole moment, and then you can use the charge and the radius to calculate how big a “bump” you would need to generate a particular value of the electric dipole moment.

But what does any of this have to do with particle physics? Well, again, we never truly see a “bare” electron, only the combination of the electron and its interactions with the rest of the universe. Those interactions include not only the fields applied in the course of an experiment, but also the inescapable vacuum electromagnetic field. Quantum physics tells us that you can never have nothing at all– there’s always zero-point energy around, and the electron interacts with these zero-point fields. In the Feynman picture of these things, that interaction takes the form of a cloud of “virtual particles” surrounding the electrons, and mediating its interactions with those applied fields.

These “virtual particles” are what make precision spectroscopy one of the well-established methods for searching for exotic physics. The interaction between the electron and the virtual particles leads to a shift in the electron’s energy, and in keeping with the “everything not forbidden is mandatory” nature of quantum physics, those virtual particles include absolutely everything, up to (in principle) bunnies made of cheese.

That might seem like a recipe for madness, but happily, the size of the shift caused by the appearance of a particular type of virtual particle decreases as the mass of that particle increases, and the number of virtual particles involved. When theorists try to predict the energy of an electron in some experiment, they don’t have to calculate the effect of every conceivable particle in huge numbers, just those particles whose mass is small enough for small numbers of them to cause a shift in energy large enough to be detected by the experiment. Or, to turn things around, when experimentalists measure some shift in the energy of an electron in some experiment, they can work backwards and determine the mass of the virtual particles that caused it.

In the case of the new ACME results, what they have is actually a lack of a shift: they apply a variety of electric and magnetic fields to a sample of cold thorium monoxide molecules, and look for an energy shift that changes with the direction of the electric field in the way they would expect if the electron has an electric dipole moment. They don’t see a shift that’s bigger than the uncertainty in their experimental measurements, which lets them put a hard upper limit on the size of any possible electric dipole moment of the electron: it has to be smaller than 0.000000000000000000000000000011 e-cm (one e-cm being the dipole moment you would get from an electron and a positron separated by one centimeter).

That hard upper limit for the electron’s electric dipole moment leads to a hard lower limit for the mass of any hypothetical particle with the right characteristics to cause an electric dipole moment. If you assume that the dipole moment would be created by “one-loop” Feynman diagrams, the simplest type shown in the figure above, the minimum mass for these particles would be about 30 TeV, or a bit more than double the maximum energy available at the Large Hadron Collider. If you allow for the possibility that the “one-loop” contribution is zero (something that’s not too difficult to arrange theoretically, but kind of inelegant), and it’s “two-loop” contributions that matter, the lower mass limit drops down to around 3 TeV, which is still pretty huge.

This is, obviously, a pretty stringent constraint on possible theories. Some years back, I wrote an article for Physics World that included a graph of predictions for various exotic theories, and this result takes a big bite out of that chart– they’re at the 10^-29e-cm level now. There’s still some wiggle room for theorists, but this is yet another strong piece of evidence that whatever beyond-the-Standard-Model physics is out there is something very different than the simplest models that particle theorists find aesthetically appealing.

This post is part of a series of posts originally written for my blog at Forbes.com that I’m copying to my personal site, so I have a (more) stable (-ish) archive of them. This is just the text of the original post, from October2016, without the images that appeared with it, which were from the publicity materials sent out by the Nobel Foundation.

Most years, when I write about the Nobel Prize in Physics, I can feel free to pitch it a little on the high side, because there are large numbers of media reports giving a more basic version of the story. This year, as I grumbled on Twitter a while ago, that hasn’t been a great assumption. Between the U.S. Presidential election sucking up media attention and the kind of esoteric nature of the prize, the coverage has been… sparse. Even outlets that are generally really good, like the New York Times, offer only brief and sketchy descriptions. (Philip Ball’s piece for Prospect in the UK is a rare exception.) And some of the less-good outlets offer, well, lazy and dismissive pieces that devote more words to jokes about baked goods than explaining the physics. As a result, my piece from last Tuesday is standing more alone than I expected it to, and as a result is less illuminating than it ought to be.

This is genuinely important physics, though, and deserves better than the duck-and-run treatment it’s mostly gotten, so I’ll circle back and try to explain the general nature of the Nobel-winning work in a broader context, without so much specific and detailed physics content. The work that Haldane, Kosterlitz and Thouless won for has genuinely transformed the way people think about condensed matter physics, and as such is richly deserving of the wider recognition that’s supposed to come with the Nobel. Explaining how and why goes all the way back to the question of mindsets and approaches that I’ve blogged about before.

The fundamental reason why Haldane, Kosterlitz and Thouless needed to do what they did is that they’re working in a subfield where the simple and straightforwardly reductionist approach that characterizes physics seems to run into trouble. As I’ve said before, physics largely works by abstracting away messy details to get down to simple universal behavior. In the introductory mechanics course I’m teaching this term, for example, we start by treating complicated macroscopic objects — baseballs, people, cars — as featureless points, and ignore things like air resistance and friction when considering simple motion. Later on, we’ll add those complicating factors back in, but taking them away lets us explore the basic underlying laws.

This works great for a wide range of physics subfields — from huge astrophysical objects down to subatomic particles — but there are areas that are unavoidably complex. One of the biggest of these is the subfield of “condensed matter,” which tries to study the properties of vast assemblages of atoms making up solid or liquid systems. In condensed-matter systems you’re worried about the collective behavior of many more particles than you have any hope of counting. As Phillip Anderson pointed out in a famous paper from 1972, these collective behaviors aren’t necessarily obvious, even when the underlying rules governing the interactions between particles are simple and well-understood. More is different, in Anderson’s phrase, but more importantly, more is difficult.

There are still reductionist things you can do to try to understand these systems, and strip out some of the complexity– you imagine perfect crystals free of dirt and defects, extending infinitely far in all directions, and weak interactions between individual particles. And you can talk about condensed-matter systems in terms of collective properties that are a little more abstract than the individual motions of the particles making the system up. These methods get you a handful of problems you can solve with pencil and paper, and give a conceptual framework for thinking about this stuff, that you can use to draw some very general conclusions about what sort of collective states are possible.

As with most of physics, though, you exhaust the pencil-and-paper problems pretty quickly. Once you start adding complicating factors back in — defects in the lattice, strong inter-particle interactions, boundaries to the system — things get very messy, very quickly. And unlike basic classical mechanics where you can think about the motion of just a few objects, it’s extraordinarily difficult to simulate these systems in a direct way, because the collective behavior you’re after demands many more particles than you can readily keep track of.

This leads to a situation where the very simplified models physicists can usefully work with in a fairly direct way — in the case of Kosterlitz and Thouless a two-dimensional fluid, or in the case of Haldane, a one-dimensional string of quantum magnets — don’t obviously capture the complete reality. In particular, the Berezinskii-Kosterlitz-Thouless system I wrote about the other day is one where the simplest theoretical models say that superfluid behavior — where particles flow without resistance — shouldn’t be possible in a two-dimensional system, while some experiments seemed to show a low-temperature transition to exactly that sort of behavior. So there must be more going on than can be captured with the tools that were readily available in the late 1960’s and early 1970’s.

What Kosterlitz and Thouless (and Berezinskii independently) did was to bring in another high-level way of looking at collective behavior that simplifies the problems, namely looking at the topology of the system. You can sort of see how this works in the two-dimensional superfluid problem: if you imagine looking down on a sheet of fluid, a superfluid flow just looks like all the particles moving in the same direction at the same speed, say, from left to right across the screen of whatever you’re using to read this. Breaking that up requires particles to move in other directions — toward the top or bottom of the screen, and even back from right to left — otherwise, they’d still be part of the superfluid flow. This diversion necessarily introduces some circular motion, little eddies in the flow where it looks like the fluid is spinning clockwise or counter-clockwise. And the amount and rate of flow possible in these “vortices” is governed by straightforward quantum-mechanical rules, meaning that each has an energy and an entropy associated with it.

The Nobel-worthy realization here is that these “vortices” in the flow change the topology of the system — each individual vortex looks a bit like a whirlpool with a hole punched through the center. And topology is all about classifying sheets by the numbers of holes punched through them. When you bring the math of topology to bear on the problem of vortices in a two-dimensional fluid, you find that there are conditions where these vortices tend to pair up — loosely, one spinning clockwise and the other counter-clockwise — in a way that cancels out their disruption of the flow so you still basically have a superfluid. Put a bit more energy into the system, though — by raising the temperature — and these vortices split up, destroying the superfluid flow. There’s a sharp transition between the basically-superfluid phase and the not-superfluid phase, and that behavior emerges very naturally from the topological picture (you’re basically going from a sheet with no holes in it to a sheet with holes in, which is necessarily a sudden jump), while it’s extremely difficult to understand from trying to look at the microscopic motion of individual particles.

That’s the transformative aspect of this work: describing systems containing enormous numbers of atoms in terms of their topology offers a whole new way of looking at problems that can’t readily be solved using a lower-level description. In a sense, it’s re-enabling reductionism: you can’t easily understand what’s going on in condensed matter by breaking things down to the level of individual particles, but if you think about a higher-level description, you can classify systems very simply in terms of topology, and this lets you solve problems that you couldn’t hope to work out with other methods.

So, this is one of those Nobel Prizes where the achievement is not so much the specific technical problem that was solved — like the prize for blue LED’s in 2014 — but the introduction of a new tool that broadens the scope of problems that physicists can attack. To attempt an analogy for non-scientists, bringing topology into condensed matter is a bit like introducing the “Intentional Fallacy” to the study of literature — it allows you to ask and answer questions that you couldn’t even consider asking under previous methods. It’s not just an excuse to bring baked goods to a press conference, it’s a game-changing innovation in physics, and for that richly deserves the acclaim that comes with a Nobel Prize.

This post is part of a series of posts originally written for my blog at Forbes.com that I’m copying to my personal site, so I have a (more) stable (-ish) archive of them. This is the text of the original post, from August 2017, with only one of the images that appeared with it, which is necessary for the explanation.

A bit more than eight months ago, I blogged about an experiment from the ALPHA collaboration at CERN, about an experiment where they did some rudimentary spectroscopy of antihydrogen. Not even a year later, they’re back, with another paper on antimatter spectroscopy, which is cool enough to need another blog post. This time around, they’re measuring the “hyperfine splitting” in antihydrogen (here’s a news story from Physics World), and explaining why this is a particularly valuable thing to study requires a bit of background about how atoms are put together.

These days, everybody learns in grade school that an atom looks a bit like a little solar system, with a positively charged nucleus orbited by negatively charged electrons. Hydrogen is the simplest atom of all, with a nucleus containing a single proton, orbited by a single electron. This picture isn’t quite right, of course, but it’s a good lie-to-children — that is, a simplified conceptual picture you can use at the start to get a handle on things that are a more complicated than the simple version.

One of the biggest ways this “solar system” picture is wrong is that the orbits of the electron are nothing like those of a planet in the actual Solar System. A planet is very much a classical sort of object, so you could speed it up or slow it down by a tiny amount, and it would happily continue orbiting, just a tiny bit closer or farther away from the Sun. An electron in an atom, on the other hand, is very much a quantum-mechanical object, and can only exist in orbits that have very particular energies. You can’t make an arbitrary change in the energy of an electron, you can only change it by certain very specific amounts, and when you do, the energy added or subtracted has to come from or be carried away by a photon of light.

The simplest such model was worked out by Niels Bohr in 1913, and does a nice job of getting the electron energies in hydrogen from just thinking about the electrostatic attraction between the electron and the proton. With the development of quantum mechanics in the 1920s, we got a better handle on what, exactly, the energies of the electron in hydrogen ought to be, and more importantly what effects were being left out that change those energies.

There are a collection of effects that shift the energy of the electron in an atom that sort of get lumped together as “fine structure,” because they take states that have exactly the same energy in the very simplest analysis and split them apart by a small amount. This means that instead of a single frequency of light that can be absorbed to change the electron energy, you have two very similar (different by less than a percent) frequencies. The most interesting of these effects has to do with the “spin” of the electron, which is an inherent property making the electron behave like a tiny magnet. For certain types of orbits, the electron energy shifts up or down a tiny amount due to an interaction between the spin and the orbit. You can think of it fairly loosely in terms of a current loop: from the electron’s perspective, it’s a magnet at rest being orbited by a proton. That orbiting proton creates a magnetic field, and the electron’s energy goes up or down a tiny bit depending on whether the magnet associated with the electron spin is aligned with the field the proton makes or not.

This isn’t the full story, though, because the proton also has a spin, and behaves like a tiny magnet. Which leads to the “hyperfine” effect (so called because the energy splitting it generates is much smaller than the fine structure, and physicists aren’t good with names). If the electron and proton spins are lined up with each other (both up or both down), the energy goes up a bit as the intrinsic magnetic field of the proton raises the electron’s energy; if they’re pointing in opposite directions, the energy goes down a bit. Among other things, this takes the “ground state” of hydrogen and splits it into two states. This ground-state splitting is incredibly important for astronomy, because the universe is full of clouds of cold hydrogen atoms in the ground state that can move back and forth between these two levels by emitting radio waves with a wavelength of around 21 centimeters. Many radio telescopes are specifically designed to look for this “21-centimeter line” in hydrogen, and we’ve learned an enormous amount about the universe by studying this light.

The paper from the ALPHA team that I discussed back in December was measuring the first kind of these energy effects: they looked at the light needed to drive anti-hydrogen atoms from the ground state to the lowest excited state, and that energy is mostly determined by the simple electrostatic interaction between the electron and proton (or positron and the anti-proton). The energy involved is several million times greater than the hyperfine splitting, and the wavelength of the light in question is several million times shorter than the 21-centimeter line, at 121 nanometers.

The current experiment is measuring that several-million-times-smaller hyperfine splitting, using basically the same principle as the earlier measurement: they collect a bunch of antihydrogen in a magnetic trap, hit them with light of the appropriate frequency, and see how many atoms are left. If the frequency of the light they’re hitting the anti-atoms with matches the transition frequency, the resulting state change causes atoms to fall out of their trap and annihilate with ordinary matter in the walls, which they can detect.

The process is complicated by the fact that their trapped atoms are held in a whopping huge magnetic field, which shifts the energy of the electron orbits. They’re rescued by a quirk of atomic structure, though, which is that in the high-field limit, the states split into two groups of two, giving two transition frequencies that differ by exactly the hyperfine splitting. This lets them do something that looks a lot more like ordinary spectroscopy. In the December paper, they fixed the laser at the frequency for ordinary hydrogen and confirmed that it caused losses of antihydrogen. In this paper, they vary the microwave frequency to find the maximum loss for one of the transitions, then increase the frequency by approximately the hyperfine splitting for hydrogen, and repeat the process to find the maximum for the other. The difference between the two frequencies of maximum loss gives the hyperfine splitting in antihydrogen.

Since hydrogen is the simplest atom, and the only one whose properties can be calculated exactly, this hyperfine splitting has been extensively studied, and measured to impressive precision. The exact frequency of light absorbed or emitted when a hydrogen atom switches ground states is 1,420,405,751.773 Hz, plus or minus about 0.001 Hz. The ALPHA team can’t quite match that phenomenal precision, but it’s a very respectable first effort: 1,420,400,000 Hz plus or minus 500,000 Hz.

So, why is this an interesting measurement? Well, for one thing, the precision to which the hyperfine splitting is known makes it an attractive target. It’s also a whole lot easier to work with microwaves than the vacuum ultraviolet lasers needed for the earlier work, which is part of why the December paper involved a fixed laser frequency. (This is not to say that it’s easy in any objective sense, though — one of the issues they face is that one of the two frequencies they use is much harder to get into their very complicated magnetic trap apparatus than the other, so they have a huge disparity in the intensity of the radiation hitting the trap.)

There are also some physics reasons to think the hyperfine splitting might be a good place to look for differences between hydrogen and anti-hydrogen. The hyperfine interaction is between the spin of the proton and the spin of the electron, which means it’s both very weak (since the magnetic field generated by either is tiny) and very short-range (because it’s a dipole interaction, rather than the direct charge-charge interaction). Much of the shift happens thanks to interactions when the electron is inside the nucleus, and that’s exactly the sort of scenario where you’d expect exotic physics to show up.

They have a long way to go before they get to the sort of precision where anybody might expect differences between matter and antimatter to show up. (In the very simplest models of high-energy physics, there’s absolutely no difference, but those models can’t fully explain why the Big Bang created enough extra matter to make, well, us. So there’s got to be some difference somewhere.) This experiment, maybe even more than the December one, is a promising step in the development of high-precision spectroscopy of anti-matter.