Acoustic Metric

On moving, Thanksgiving and the sounds that shape your world

Thanks for reading my newsletter! The breakdown: first a personal essay, some of my recent writing, then some thoughts on the media that I am consuming and finally some vegan food and recipe recommendations. All opinions expressed here are strictly my own. 

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ACOUSTIC METRIC*

Last year I reported a story about a team of German researchers that created a tiny analogue of an expanding, curved universe out of extremely cold potassium atoms. It’s the type of story that I love to write because it involves the kind of physics that held my heart captive for most of my twenties - you use one mildly bizarre system (the atoms) we kind of understand to emulate another (the universe) which is extremely dissimilar and we also only kind of understand it. 

At temperatures close to absolute zero, atoms like potassium do not freeze but rather fully succumb to quantum effects that are imperceptible, or even impossible to see at warmer temperatures. And when the atoms are behaving so thoroughly quantumly, they can be controlled extremely precisely by being hit with lasers and bursts of electromagnetic radiation. If you can push a cloud of potassium to an ultracold temperature you are essentially left with a quantum building block for whatever you may want to emulate, from weird materials to the whole universe, as long as a good enough mathematical model connecting the two exists.

The details of this are, as you may expect, rather gnarly. The math is difficult. The atoms need to sit in a small glass and metal box perfectly devoid of air. You often need several lasers and they all must be perfectly fine tuned. You also typically need many perfectly positioned and aligned lenses, mirrors and crystals that those lasers go through before hitting the atoms. And you need a way to look at what the atoms are doing without destroying their notoriously fragile quantum states, or a way to keep re-doing the experiment over and over because it gets messed up whenever you look. 

Yet, starting in the late 1990s, physicists have become really good at doing exactly this. They have since used ultracold potassium or rubidium or even the more exotic ytterbium to look at physics phenomena that may happen inside of chunks of metal that are hard to look into, or quantum magnets that are impossible to simulate on a computer, or have only been conjectured to happen. I studied ultracold atoms in graduate school, taking a crack at some of that difficult math, because the idea of not just making the quantum world so evident and controllable but using it to further our knowledge of physical reality just simply blew my mind. 

The experiment from my 2022 story about ultracold potassium was much more ambitious than anything I had come in contact with as a researcher. As you may expect, making a tiny analogue universe requires some very specific ingredients.The most important one is something called the metric. It is a neat and compact mathematical expression that summarizes the best way to measure distances in each space and time dimension. Another way to explain the metric is to discuss the shortest way of moving between two points in spacetime. If you live in a spacetime defined by some metrics the fastest way to move between points will be along straight lines like when you run across a soccer field. For other metrics the best choice may be to move along some very specific curve like airplanes when they travel between distant continents. If someone were to teleport you into a completely new universe, you’d want to know at least something about the metric before deciding how to go anywhere within that universe. 

As it turns out, if you’re building an analogue universe from quantum stuff that would look like individual atoms at room temperature, but is much more like many overlapping waves of matter at absolute zero, the way you set the metric is closely related to the speed of sound that can propagate through them. In our actual universe the speed of light, the fastest thing we have ever observed and the one that sets the ultimate cosmic speed limit, always shows up in the equation for the metric. In the ultracold analogue universe, the speed of sound takes its place.

I had a long conversation with one of my editors about how to convey this “acoustic metric” to a general reader who may never have to confront the mathematical formalism that informs researchers to swap light and sound as they construct experiments. We settled on a brief, but descriptive paragraph about it where the adjective “acoustic” never even made an appearance. Instead, I wrote about changing the density and arrangement of the atoms, which are properties that are related to how sound can propagate through them. This was probably the less confusing and more journalistically sound choice. But I still think about this sometimes - if you want to build a tiny universe for yourself, the ways you can fill it with sound really matter.

***

During his first year of graduate school a friend convinced my husband to buy two tall, black speakers and install them in his small and perennially dark central Illinois apartment. I inherited these speakers a few years later when our academic paths took us to different universities. By that time, the speakers’ origin story had grown more dramatic. Instead of being speakers that a friend advocated for even though they were pricey for a graduate student’s budget, they were speakers that once got the police to come knock on my future husband’s door. He had played a Metallica record, a good vinyl find for our university's town, and the speakers worked so well that some curmudgeon down the hall dialed up local law enforcement. I guess they just really had no appreciation for Cliff Burton’s galloping bass lines on Ride the Lightning.

We moved to New York at a particularly difficult time and for the first few months lived mostly out of our suitcases with our other belongings, largely books and a few pots and pans, hidden away in our respective out-of-state apartments. I bought essentially no furniture in graduate school so when it was time to pack up everything I had amassed in those six years and mail it across half the country, the speakers really stood out. We found their original boxes in the back of my closet, taped them shut with multiple layers of tape and tacitly agreed that we would not blame each other if they did not make it to Brooklyn in one piece. Surprisingly, whatever journey the postal service put them on only destroyed the boxes and we could soon play records in our new apartment, sometimes even at a loud volume.

The two of us had always shared a pretty erratic record-buying strategy so it is hard to determine exactly what sounds shaped the microscom we had built for ourselves in that apartment. When I lived in Illinois I’d buy second hand Sleep records but also vinyls upon vinyls of Ventures covering movie soundtracks or other artists’ classics. Online, I’d order Cult of Luna and Lucy Dacus records the second they’d become available. And if I could afford it, I’d always buy vinyl at a live show, to support the artist in a way that felt less performative, and more financially meaningful, than wearing a t-shirt. My husband’s collection ranged even more widely, from Lighting Bolt and Deconstruction Unit to regional folk music, Indian ragas and some good old fashioned country. We never fought over the record player, you just could not pull a few random records and hope that they’d make sense if played in sequence, Weyes Blood following the Ramones following Lorretta Lynn following Windhand.

A few weeks ago we moved to a bigger apartment in a different part of town, this very varied record collection moved with us, but the speakers did not. They had finally met their fate sometime this past summer, going out with a demonic shriek that may have been caused by faulty re-wiring, or just bad luck. In our new living room, the record player is sitting in a spot we immediately designated for it, perched on a short bench, but still in its box as we have no way to fill the room with its sound. We’ve been playing podcasts on a small smart speaker that some subscription service sent after we begrudgingly renewed it yet again, but there has been very little music in our new space. Less than a month after we spent the first night there, I guess it s all still trying to find its final shape.

***

What got me thinking about the acoustic metric and that specific ultracold atoms experiment was not another piece of scientific research, but rather hearing several artists answer the question of “What is the sound of where you come from?” on the podcast Object of Sound. The metaphor is almost too neat, but because I grew up with so much sound, and music and the radio were so influential on my identity as a young person, I cannot resist reaching for it.

If where I come from is the one particular part of the Croatian coast where I grew up, then it sounds like the woodwind instrument sopila and the Istrian scale, but also like the 1980s Yugoslavian punk and the crunchy heavy metal bands of my high school years. If where I come from is my parents home, then it sounds like Iron Maiden, AC/DC, my dad’s never-ending compilation of slow songs and Radio Rijeka. 

In the past, I sometimes tried to tell people that I am from Chicago where I went to college, but I lived in uncomfortable apartments with uncomfortable people there so it is hard to remember the sounds clearly. I do remember accidentally locking myself in the bathroom while on a date with a girl at a DIY punk show, music blaring on the other side of the bathroom door, making my brief moment of panic that much more dramatic. I also remember seeing Lamb of God and Black Label Society and Cult of Luna with reluctant half-friends and acquaintances because I was dating a man who hated concerts, but the music felt so good in my body that I could not will myself to stay home.

And this is the thing about sound, it is not necessarily tangible, but it is physical and embodied. It is quite literally a vibration and as such it needs a medium, it needs molecules that can bounce and shake and transfer energy to one another, or otherwise everything stays silent. When you feel the loud bass in the bottom of your stomach, that is just a more obvious instance of sound’s default interactions with us as physical objects.

In Monolithic Undertow: In Search of Sonic Oblivion, Harry Sword opens his discussion of the drone, not as a genre of music as much as an entity that exists in the realm of sounds, by visiting prehistoric sites where the bouncing of chanting and droning noises may have had a hypnotic effect on the people that gathered there. He invokes the idea of entering an altered state by letting a sound envelop you and loosely grounds it in both acoustic studies of these places and effects of noise on the human brain that have been measured in the lab. 

That evidence did not strike me as fully conclusive, but based on my experience of seeing bands like Earth or listening to Cult of Luna’s Vertikal over and over and over at full volume when it first came out, his thought seems plausible. In a later chapter, Sword discusses Sunn O))), a band notorious for a in incredibly loud and monotonous drone sound, and describes their live performances as “physical music, air moving through the room, cavities rattling.” 

When I read this, I knew what it felt like, but it also made me think of how researchers have described sound-based levitation to me in the past, or how often a physics experiment involves trapping an oscillating, vibrating field in some special cavity. This all suggests to me that the sounds of where you are from can be a physical scaffolding for how you experienced the world there as much as walls or windows are.

***

Because I am an immigrant, moving has always been an important part of my story. And because I had for a long time thought that my future held an academic career, moving often and to unpredictable places long seemed like something that would continue to be a staple of how me and my loved ones live. I’ve written about the idea of home and belonging to a place or maybe letting a place define you repeatedly in these letters. Though the last few years have seen me settle not guiltlessly but with lots of comfort into claiming New York for myself having to move again, from one borough to another still rattled me. 

We tried to do it somewhat more responsibly and with less of a sense of adolescent chaos this time around. We hired movers instead of calling in favors from friends and family and we rented sturdy plastic packing bins instead of creating tons of waste with broken up cardboard boxes. Moving during graduate school often involved not just friends but also buses and walking large items over from one place to another by foot. One year I got into a good amount of trouble for stashing boxes in my research office while I had to go back to Croatia to avoid having nowhere to stay in-between leases in August. Moving in with my husband was first a function of lockdown then a process fully overshadowed by a lull in the ongoing COVID-19 crisis. Neither of us had ever really had a calm, well planned, adult moving experience.

Despite our best efforts and day one of the move going exceedingly well, on day two it was still the two of us in the back of a rideshare hugging a bucket of cleaning supplies, our ancient hand-me-down TV riding behind us tentatively held by a seatbelt. I felt childish and helpless that day, especially as we had already made a few trips by bus, on top of both working a full day in offices that were about to require a longer daily commute. I had felt the same way while we were searching and applying for apartments - helpless and small in the face of greed and macro-scale economic circumstance that had rendered our advanced degrees and stable employment insufficient for what at times felt like qualifying for basic comforts. 

Writing this now, a few weeks later and after we settled into the comforts of a much bigger apartment that also manages to cost us less, I am somewhat embarrassed at how indignant I was when I first realized that the last rent increase in our old, hip, heavily gentrified neighborhood would be the one that drives us out. Why did I think we were owed that level of convenience and ease anyway? It was hard to let go of the remarkably accessible farmer’s market, outdoor track and the bagel store with the good vegan cream cheese where everyone knew us. 

I had that conflicting feeling that is a hallmark of trying to be ethical within a system of living that eschews ethics from the jump - I wanted the nice comfy things while also recognizing that they are a huge privilege and that there is no virtue in wanting to live in a more affluent place. What was happening to me was the most mild version of what had happened to people that lived in our old neighborhood before it was hip and expensive enough to be desirable to people like me. Yet, living in a place like New York lends itself to a kind of self-mythologizing that requires place to play as much of a role as people and I had let myself forget that the place can also be relentless, brutal, and not for dreamers who went to graduate school instead of making money or without the fallback of generational wealth.

***

Throughout the process of applying to rent our new apartment, the issue of noise kept coming up. The owner of our building, now our downstairs neighbor, seemed terribly worried about how much noise we’d make the first few times we met and toured the place. We promised that we are not loud people, that when we stay up late it is only to quietly sit at our computers, that we use headphones a lot, and that I will only rarely take interviews for work from the little home office that I am now lucky to have. I said I’d only have a party for my birthday and that our friends are not loud people either. None of this is really a lie, yet it felt odd to say it out loud given how much my husband and I, as well as me and some of my best friends, have always bonded over having grown up in households where people didn’t know how to communicate any feeling whatsoever without yelling. 

Family members and friends who have stopped by to check out how much space we have now have all remarked on how our new street itself also seems more residential and neighborhood-y and calm.This is true too as it is not around the corner from a busy bar that also occasionally masquerades as a dance club, or a grocery store that stays open late enough for anyone with chemically-induced munchies to stop by, or on the way back from a popular concert venue, and on the way to another famously messy one. Our new neighbors do all seem to be quiet family folks, none of them investing hours into yelling on the street on warm weekend nights or letting the sounds of their video game rage seep through our walls.

Without the big speakers, we have been mostly quiet too. A rattle of a chair or a squeak of the bed here and there, and the bangs of the inevitable moments of clumsiness that send a pot or a can of beans crashing into the floor but not that much more. It felt odd to try and convince someone that we were quiet people, and now it feels odd to both strive for it and not be all that unsuccessful. It is true that we never had big parties or caused that much trouble before, but we both came up through respective crunchy heavy metal scenes, grew up with a punk sensibility and still hold on to a bit of resentment about what used to be called selling out. 

On one mid-November Friday, however, we did host my best friend and their partner for a very small Friendsgiving. Even though it was a dinner for four only, there was very little room left on the island in our new kitchen once we started piling on all the vegan dishes we had made during lunch breaks and after work that day. Plates got piled high and we all had seconds and then dessert after a small break to catch our breaths. At the end of the night, while distributing leftovers into repurposed deli containers, I found myself sneaking just a few more forkfuls of a vegan pasta dish inspired by mac’n’cheese while the rest of our small party laughed in the living room. It all felt so comfortable and homey, even as I knew my stomach would rage at me later.

***

Thanksgiving is inherently a fraught holiday because of its violent colonial history and because it is the kind of family affair that makes spending time with people, like family members, who hold harmful beliefs seem like a virtuous necessity. For me personally, the cartoonish emphasis on the turkey at the center of the table - the reminder that the way we celebrate is to kill an animal and then glamourise its carcass without ever engaging with the fact that it had to die - also makes it difficult to participate in seasonal cheer, no matter how good I’ve gotten at making various sides vegan. 

I am suspicious of the idea that you can just reclaim a holiday and erase its history and traditions. I have also long worried that the idea of chosen family is only useful to those of us who can afford to cultivate one and do not depend on financial and other support from our biological kin. But it is hard to be skeptical and cynical when you are eating well and your heart is warm and someone you love is making a joke that makes you feel fifteen years younger in the best possible way. 

In the aftermath of the whole thing, one that mostly involved Alka Seltzer tablets and solving the maximally efficient packing of the dishwasher problem, I thought about that experiment with ultracold atoms again. I had chosen to pitch this particular experiment and to advocate that it belongs in the news section of the science magazine I write for in part because of the remarkable amounts of experimental control the researchers seemed to have over their system. The idea of the acoustic metric has been around for a while and some physicists have even created acoustic black holes, spots that sound cannot ever escape, but this experiment could also make its ultracold microverse adopt curvature and expand. The system had so many new “control knobs” the researchers told me when I interviewed them. “You have to dial in your questions,” they said.

Facing the age old dilemma of whether you put a fork tines-down or tines-up into the dishwasher, I thought to myself that it was so corny to jump from such fundamental science to something as saccharine as “maybe the sound of friends can reshape my new microcosm too.” But what is the value in resisting sweetness, where is the virtue in trying to hold back, when human lives matter so little these days and outside of our own bubbles most of what is offered to us is complicity in destruction and murder? It has been hard to follow the news this past month or so and not wonder whether all that future holds is a choice between ignoring suffering or letting helplessness in the face of it fully consume you. Learned self-loathing over a little cringe is a useless response to being reminded that we can still care for each other unabashedly.

And as that physicist tried to tell me, the questions you ask, and how you go about testing their answers in the real physical world matters. For years, watching one global crisis turn into another and yet another and yet another, I have been asking myself about what kind of future is possible for me and everyone else. I was born during a war and the trauma of it is in my bones, maybe in my genes too. Maybe this is why so much of my writing ends up here - putting stock into imagination and kindness and our ability to live for the future we want to see rather than just pushing through a painful present weighed down by a painful past. 

How much can one homemade vegan meal for four people that comfortably live in New York City on the eve of a difficult holiday during a difficult time really do? Probably not very much in the grand scheme of things, but when I really dial into my questions about what I want going forward, and what I think we can all do, the sound of all of my friends and loved ones is what comes through most powerfully. It’s what I feel rattle in the bottom of my stomach the most, somewhere between the feeling of a really good heavy metal show, a really inspired marching drum at a rally, and the inception of a deep belly laugh. I guess beyond all, I still believe that if we care for each other, we can lend our voices to shaping a better universe than the one we find ourselves in right now.

If you are based in the United States and have not contacted your representatives about stopping the violence in Gaza yet, please consider doing so.

Best,

Karmela 

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ABOUT ME LATELY

WRITING

The most personally exciting thing I have written this past month must be the first installment of my new monthly vegan baking column for New Scientist. I wrote about what eggs do in cakes and how to replace them as informed by their chemistry, then shared a recipe for an easy chocolate cake that also happens to be the basis of all chocolate cakes that I have made in the past few years. I am really grateful for the chance to connect a hobby that I love with the job that helps me pay rent.

Right before Thanksgiving I attended the American Physical Society Meeting of the Division of Fluid Dynamics and my favorite story to come out of those three days of reporting so far has been this one about shrimp using hairy appendages to swim. The graduate student who presented this research opened with an incredible quote that then became the natural lede for the story so big shouts out to her and her great energy even before 9 am on the very first day of the conference.

And then there is one of my forever-favorite topics: ultracold atoms in space. I was delighted to have another excuse (the first was in 2021 when I reported this Scientific American piece) to speak with a researcher that works with teams that have been sending ultracold atoms into orbit on both small rockets and the International Space Station. This time there was the added excitement of my story being about how these systems are almost ready to be used as incredibly precise tests for Einstein's ideas about gravity. 

READING

I have been utterly consumed with Chanda Prescod-Weinstein’s Disordered Cosmos: A Journey into Dark Matter, Spacetime, and Dreams Deferred. I’ve read parts of this book before, and I have taught excerpts from it while I was a high school teacher, but my new hour-long commute to work has given me an excuse to read it from start to finish again and it really has been so engrossing. Prescod-Weinstein, who I have admired for her advocacy and writing on top of being a brilliant physicist, effortlessly makes the reader feel included in, invigorated by and reminded that they have a real stake in the ongoing story of science. 

She grapples with both her love of knowledge and discovery and the harms that science as a profession and an institution has done to her and others in a way that is compelling and heartbreaking at once. I would lie if I did not say that I see some faint echoes of myself in some of her writing and those have also been both beautiful and painful. This is not yet another book trying to convince you that physics is cool and it very clearly underscores that it is an absolute reflection of privilege to think that doing science is about a sense of curiosity only. But it is also not a book that wallows or a book that does not offer any hope. 

Precod-Weinstein is a strong writer, her style is propulsive and accessible, and her points are clear and firm. I respect her steadfast honesty and strength of belief very much. In some ways Disordered Cosmos is a celebration of the wonders of the universe as seen through an incredibly sharp narrator who does not want to ignore the realities of the world we built inside of it, but it is also a stirring call for all of us, scientists or not, to do better overall.

LISTENING

On the instrumental, experimental, slightly psychedelic side of things I have enjoyed On Patrol by Sun Araw. All the drums on this record are really hypnotic and there is a little drone here and there, all making a good mix for that midafternoon slump when the day is not over yet, but your brain suddenly resists any efforts to put it to work. 

Inexplicably I started thinking about Q Lazzarus’s Goodbye Horses a few days ago and the playlist that Spotify served me after I gave it a few spins, including Sonic Youth, Boy Harsher, and New Order, was a real hit.

I have also been revisiting some records I loved in college and Opeth’s Blackwater Park and Ghost Reveries are still as good as I remember. I liked some of the band’s later work that veered more towards progressive rock too, but this older combination of epic storytelling, gothic imagery, beautiful melodies and harsh forays into black metal at its best is really what always makes this music intoxicating.

WATCHING

We watched David Fincher’s The Killer on a particularly sleepy night and it left me somewhat underwhelmed. There is a great episode of The Big Picture that breaks down the movie and its mannerisms better than I can, and I do recommend listening to it, but all of the great details the hosts point out as clear signs of satire and self-mockery were just not that clear to me. The film looks amazing, its cast is amazing, its nods to harms of late stage capitalism (much of the main character’s crime is enabled by access to WeWork, Equinox and Amazon Prime) are clever, and after some thought I softened a bit on the heaviness and absurdity of its relentless first person narration. I probably need to watch this film again, but given how compelling the first season of Mindhunter was and how I actually quite liked Mank I did expect a little more.

On a friend’s urging we saw Five Nights at Freddy’s in a pretty empty Brooklyn movie theater. Though this movie is almost certainly not good and I also just don’t have the pre-existing relationship with the franchise that would make it meaningful to me anyway, we had a pretty fun time. The whole thing looked better than I expected, the acting was fairly decent and I did not mind the mildly nonsensical plot as much as I wanted it to be scarier. What I enjoyed the most was my friend catching us up on all the lore around the game the film was based on and the way it has long existed on the Internet. I don’t have to think a piece of fiction is incredible art to understand that if something is your Internet thing then it will always scratch a particularly exhilarating itch.

On the TV front, we have been slowly picking up where we left off with Slow Horses and Invincible, two very different shows that recently entered their second season. Slow Horses was never a revolutionarily good or intellectually mind-blowing show, but well-made, old-school spy content is just inherently satisfying, sort of like eating your PB&J on spongy white bread. So far it has remained exactly that, delivering on all the familiar beats without ever becoming too predictable.

I’ve had a harder time getting back into Invincible even though the first three episodes of the new season did offer some clever plot twists and interesting character moments. I may be too impatient to see what the throughline for the season will be so the slight monster-of-the-week-ness so far has unreasonably bothered me, but I am not yet fully tired of the show’s often brutal exploration of what it would actually be like to grow up as a superhero.

EATING 

I made a vanilla and strawberry cake filled with a strawberry rose jelly for a friend’s engagement party and I am proud of both how nice it looked and how much the happy couple enjoyed it. My other big cake success was a flourless chocolate cake, almost more of a fudge slice than anything else, that I brought to family Thanksgiving. I dusted it with powdered sugar and topped it with pomegranate arils and chocolate shavings. Digging into its cold, rich texture with each bite punctuated by sweet and sour pops of pomegranate felt like such an indulgence even after an already unrestrained holiday meal.

For my contribution to the savory side of Thanksgiving I made a vegan version of these candied sweet potatoes and a riff on this green bean casserole except that I topped mine with thin shallot slices and panko breadcrumbs instead of the traditional fried onions. My takeaway from both making and eating these was the same as every other year - they are good enough and accessible enough to be made for other occasions too.

Finally, I had a great outdoors meal for one at Zaytinya in Washington, DC while I was traveling for work. Not only were the baba ganoush, olives and falafel all fantastic but the very friendly staff also kept bringing me warm pita bread without me ever having to ask for it which must be what at least one version of heaven is like. The place is somewhat pricey and despite its Mediterranean menu it does operate under the umbrella of a Spanish-American celebrity chef’s restaurant universe, but for a one time treat while away from home and working long hours it did the trick.