Geologists initially believed that the Earth’s continental crust only began forming in a geologic eon known as the Archean, about 2.5 to 4 billion years ago. This estimate was deduced by dating crustal rocks and looking at signatures of mantle depletion. Evidence of mantle depletion is indicative of crust formation, and no signs of such depletion appeared until about 3.8 billion years ago. Thus, this timeframe was the accepted approximate for initial continental crust growth. Yale researchers now argue that for this theory to be true, different parts of the mantle had to have mixed instantaneously, which they say is unlikely. 

“Our study finds that the evidence of depleted mantle in the basalts can be delayed due to finite time mixing effect — much like it takes time to mix cookie dough in order to make a cookie, it takes time for it to be completely mixed,” said Meng Guo GRD ’24, first author of the paper and a student in the Department of Earth and Planetary Sciences.

Earth’s crust was formed by crystallization of the inner layer known as the mantle. The mantle is mostly solid but can flow over large timescales — leading to tectonic plates — and partially melt due to localized high temperatures, low pressures or addition of volatile materials like water, which leads to volcanic eruption and crust formation. This happens because melted rocks rise to the surface and cool to produce the solid, brittle crust. Consequently, the mantle loses elements and its composition is altered. This is called mantle depletion. 

The layers of the newly solidified crust retain the composition of elements of the mantle they crystallized from. WIth this, the composition of the mantle at a certain point in time can be deduced by studying the composition of rocks in the crust from that period, which is called a mantle signature. Since the mantle’s elemental composition becomes more depleted as more crust is produced, crust from different time periods will yield different mantle signatures.

“Many scientists say that if there was continental crust before 3.8 billion years ago, we should see it, but we don’t, so it didn’t exist,” said Jun Korenaga, professor of Earth and planetary sciences and co-author of the paper. “This argument is a little flawed because it takes time for the signature of mantle depletion to appear.”

Korenaga explains that once a part of the mantle melts to form crust, that section cannot immediately remelt and form more crust. This is because the residue left behind by the melting is fairly refractory, meaning that it is resistant to change by temperature or pressure. It needs to mix with the surrounding mantle, a process that takes hundreds of millions of years, before it can melt again and form a new signature. The new signature is the one that would contain evidence of mantle depletion. 

“By incorporating this effect, we were able to demonstrate that even though the first evidence of a depleted mantle was seen only 3.8 billion years ago, the real continental crust was formed about 0.7 billion years earlier,” Guo said.

The study indicates that by the start of the Archean Eon, over 50 percent of the crust had already formed. 

Mark Harrison, distinguished professor of geochemistry in the Earth, planetary & space sciences at the University of California, Los Angeles, said that the study corroborated evidence of early crust formation that existed previously. For example, minerals called zircons have been found that can be dated back to around 4.4 billion years ago. These zircons have characteristics that indicate that they were part of continental crust and did not erupt out of volcanoes. 

“I see Jun as a human hand grenade,” Harrison said. “He has inserted himself into a very hard debate and shown that we don’t know as much as we thought we did. A significant fraction of our community had decided that they knew how the Earth has evolved. That meant that young people would be discouraged from investigating a question that they thought was already answered. That’s where this paper comes in. It will hopefully help us rethink the current paradigm and keep looking for a better one.”

The study was published in the ninth volume of the journal Science Advances. 

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The galaxy, UGC 4211, was formed by the merger of two different galaxies, each of which had a supermassive black hole —  black holes with masses hundreds to billions of times greater than that of our Sun — at its center. The two black holes then gravitated inwards and are now 750 light years away from each other, which is the closest separation of two supermassive black holes that we have conclusive evidence for. The black holes are also “active,” which means that they are currently feeding on the surrounding stellar material and growing. Such active supermassive black holes at the centers of galaxies are called active galactic nuclei, or AGN. 

“We know that over the billions of years that the universe has been evolving, galaxies have merged and continue to merge,” Meg Urry, an author of the paper, a professor of physics and astronomy and the director of the Yale Center for Astronomy and Astrophysics, said. “And, we also know that most galaxies, at least above a certain mass, have a supermassive black hole at their center. So, one of the questions that is not really solved yet is what happens to the two black holes in two galaxies when they merge?”

According to Urry, the plausible theory is that after the galaxy merger, the two black holes slowly sink to the center, form a binary — which are a pair of gravitationally-bound stellar objects in orbit around a common center of mass — and then eventually merge, emitting enormous amounts of gravitational waves in the process. Initially, the black holes sink due to friction with galactic gas and dust. Once the black holes get close to the center, however, the density of galactic material decreases and the pull of friction becomes negligible. If they get really close, they can lose energy and merge by emitting gravitational waves but it remains unclear how the black holes make the leap between friction and gravitational waves.

Such a merger takes millions of years to happen — the two black holes from this study are not expected to merge for at least another 200 million years. Based on this information, we should expect to see more instances of black holes orbiting each other. However, Urry said that such observations have been surprisingly few, which makes this discovery particularly significant.

Michael Koss, an astrophysicist at Eureka Scientific and the principal investigator of this research project, said that the discovery was a culmination of a ten-year endeavor to find AGNs in merged galaxies.

“The weird thing about doing astronomy is that you get a time machine but you only get to see one moment,” Koss said. “The entire timescale of these mergers is over a billion years. We don’t get to watch it play out for a particular system. So, either we can look at a bunch of systems or we can run simulations. And, when I was postdoc in Hawaii, there were these ideas based on simulations of galaxies that as two galaxies come close together, their black holes grow very quickly — become AGNs. So, if those simulations are true, then we should look for AGNs in mergers.”

Thus, Koss began looking for AGNs in galaxies that appeared to have been in mergers, and his team’s finding now provides observational evidence for the simulations.

For this study, Yale supplied telescope time at the Keck Observatory in Hawaii. First, Urry describes, the team used the near-infrared imager NIRC2 to survey the centers of galaxies that looked “disturbed,” which is an indicator of a merger. A large fraction of the observed galaxies had dual sources in the center — an exciting finding since the sources could potentially be two active black holes, but the results were not definitive. Thus, the team followed the survey with near-infrared spectrograph OSIRIS to confirm that in this particular galaxy, the sources were indeed a pair of gravitationally-bound active black holes.

OSIRIS proved two things: first, that the two sources had the same red-shift and thus are at the same distance from us; and second, that the two sources are not the same object distorted by gravitational lensing — the bending of light around mass — since the spectra of the two sources were not identical.  In this case, distortion from gravitational lensing could be caused by any cloud of gas and dust between the observing point and the source.

Keck was not the only telescope used for the research, however. The Very Large Telescope, the Atacama Large Millimeter/submillimeter Array and the Hubble Space Telescope all observed the same black hole pair in multiple wavelengths, which means that, unlike past discoveries, this one is highly unlikely to be a false positive.

Locating a supermassive black hole pair in such a close proximity suggests that pairs like this could be quite common in the universe, giving hope that the merging of two supermassive black holes in other systems could be observed and that scientists could detect the gravitational waves emitted from these events.

Since 2015, when the Laser Interferometer Gravitational Wave Observatory detected the first gravitational wave, many such detections have been made but they have all been gravitational waves from mergers of either stellar mass black holes — which are much smaller than their supermassive counterparts — or other astronomical objects, like neutron stars. Chiara M. F. Mingarelli, assistant professor at the University of Connecticut and gravitational-wave astrophysicist, explains that this is because detectors like LIGO can only pick up high-frequency gravitational waves but not the low-frequency ones that would be released when two supermassive black holes collide. These low frequency waves would give rise to a gravitational wave background.

Mingarelli’s current project involves trying to detect this background. Thus, she finds the dual black hole discovery particularly interesting because it has significant implications for the rate of supermassive black hole mergers and the intensity of gravitational wave background.

“This black hole pair is so nearby that either we got really lucky and found it because we are extremely lucky, or we found it because there are lots of them,” Mingarelli said. “We won’t know until we make more such observations, but this particular galaxy could be crucial to understanding the population statistics of black hole mergers and the gravitational wave background.”

The paper was published in Volume 942 of the Astrophysical Journal Letters.

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In December, Yale GALA — the Lesbian, Gay, Bisexual and Transgender Alumni Assocation — will host two events: a book-club meeting and an intercollegiate holiday party. In addition, they are promoting a film festival hosted by Yale in Hollywood, another alumni organization for students and alumni in or interested in entertainment.

“The LGBTQ+ community, we live within a larger society that is not always welcoming so the idea of being able to share experiences with kindred spirits is a very important goal,” said Bob Barnett DRA ’89, the organization’s secretary and newsletter editor.

Starting on the very first day of the month, the Yale in Hollywood Fest is a three-day online film festival that will showcase features and shorts that include one or more Yale-affiliated people in their production. The festival will be streamed worldwide. The Yale GALA Book Club Reading is yet another online event and is one that is hosted on the third Thursday of every month. 

This time, members are reading Michael Ausiello’s memoir “Spoiler Alert: The Hero Dies: A Memoir of Love, Loss, and Other Four-Letter Words,” the heartbreaking but humorous story of his relationship with his boyfriend, who was later fatally diagnosed with cancer. 

Finally, there is The Holidays Party in NYC on Dec. 28 — co-hosted with LGBTQ+ organizations from Princeton, Columbia, Stanford, UPenn, Harvard and Cornell — which is open to LGBTQ+ students, staff and alumni from any university.

According to co-president of Yale GALA Mickey Dobbs ’92, LGBTQ+ alumni get-togethers were the organization’s original focus in the early 1980s. In later decades, when students became more vocal about LGBTQ+ issues on campus, the alumni wanted to participate, and Yale GALA’s connection to campus increased. Since then the goal has been to not only serve LGBTQ+ alumni but also work with students on campus issues.

In addition to hosting social events, Yale GALA sponsors two prizes each year. The first one, called the GALA Senior Essay Prize, is awarded for a senior project related to lesbian, gay, bisexual and transgender studies in conjunction with the LGBT Studies program at Yale. 

Recently, the association started awarding the Camila María Concepción ’14 Yale GALA Prize to any student who made significant contributions to the trans, non-binary and gender-nonconforming communities in their undergraduate years. It is awarded in memory of Camila María Concepción, a trans writer and activist who not only worked for the GALA in her time at Yale but also later continued to promote trans visibility in the media.

Over the years, the organization has become more inclusive, changing its name from Yale Gay and Lesbian Alumni to Yale GALA Lesbian, Gay, Bisexual and Transgender Alumni Association and actively trying to encourage more people of colour and more women to take part in its programming. In addition, it has become more and more involved with LGBTQ+ organizations at other universities.

“Campus has changed a lot since we started,” Barnett said. “We went from a Yale where being gay was inconceivable. It was seen as a disease and a crime. Older alumni bring that awareness versus the younger generation who are more politically astute but believe that we own our rights and anything that compromises that is unacceptable.”

This diversity means that Yale GALA is trying to meet the desires of people with very different experiences. Thus, the surveys and the listening sessions are a way to determine what the alumni would actually like to see the organization doing — what kinds of events and activities would make them feel most engaged with the community. 

GALA is also trying to include graduating students in these programs, notably there is a brainstorming workshop on Dec. 11 for incoming alumni to share their ideas.

These programs are conducted in conjunction with Innerlytics, a consulting firm that uses data analysis to understand bias and to then use that information to help organizations become more equitable. It was founded by Yale alum Jordon Rose, who graduated just this year from Yale School of Management, and now volunteers for the GALA.

The information gathered will then be used to plan for the future.

“It will directly shape the next five years of the organization,” Rose said. “The surveys are to see who’s out there. What do you want? What are your needs? Do you want more big events with a lot of people or more intimate ones? These are the questions that the surveys are asking. The 15-minute listening sessions are a follow-up. On a surface level, they are moments for people to give suggestions and to vent. If you look a little deeper, the listening sessions are an avenue to understand how disenfranchised community members can be more active.”

Rose told the News that although Yale GALA has significantly changed over the years, it still consists of a disproportionately large number of people who are white and male. So, Rose said, one aim of the listening sessions is to find a way to invite more people of color, more women, more gender-diverse people to volunteer and become active in the organization.

Dobbs mentioned the COVID-19 pandemic as a turning point since it meant that they had to move from in-person to online events for a while, which meant that more people could join from all over the world. Now, as they return to hosting in-person events, they are trying to figure out how they can keep reaching people from different locations.

While the surveys and listening sessions are the biggest thing they are doing right now, there is one event planned for April next year: the student-alumni dinner, organized jointly with the Office of LGBTQ+ Resources on Yale campus. 

The event was once annual, according to Dobbs, but was discontinued due to a lack of alumni attendance. The association is trying to restart the tradition in 2023 and hopes that the surveys will help them find a way to improve attendance.

The Yale GALA Book Club Reading began mid-2020 and became a regular event at the start of 2021.

Correction, Dec. 4: This story was updated to reflect the correct host of the film festival. 

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Manafzadeh’s abstract and presentation focused on the research on joint poses and functions that she did as part of her dissertation at Brown University — work that she is continuing at Yale. The goal of her research is to figure out how joints and their functions have evolved over time and to construct the evolutionary history of vertebrate motion from that information.

“She’s very clearly among the absolute top people in the field at her career stage,” said Bhart-Anjan Bhullar, an associate professor of Earth & Planetary Sciences at Yale. “Her research is unique, it’s productive, and it’s advanced — I think she’s decades ahead of other people trying to do similar work.”

The award was based on an abstract that Manafzadeh submitted to the SVP and her oral presentation during the annual SVP meeting, which was held in Toronto between Nov. 2 and 5. 

Manafzadeh’s project focused on figuring out how joints worked in extinct animals. According to Manafzadeh, the difficulty with studying joints of extinct animals is that when an animal fossilizes, most of the time only its bones are left while the soft tissues like ligaments — which connect one bone to another — and cartilage — which cover the end of bones and reduces the friction between them — decay. 

It has therefore been a challenge for scientists to deduce how an animal moved and walked while alive based only upon the dry bones that remain. For a long time, the way paleontologists did this was by simply picking up the fossil bones, moving them around with their hands and working out which joint poses looked right.

“Armita came to my lab interested in understanding more about how joints work in the vertebrate skeleton,” Stephen Gatesy, Manafzadeh’s dissertation advisor at Brown, said. “Trying to reconstruct an extinct animal’s joint mobility is central to how paleontologists interpret fossil evidence. Did Australopithicus afarencis (“Lucy”) walk like a modern human? Could Archaeopteryx perform flapping flight or only glide?  How fast could T. rex run, or was it restricted to a slow walk?  Bringing dead remains to life literally requires reanimation, and joints offer some of the best information about movement we have.” 

At Brown, Manafzadeh took a similar approach but with data-driven computer simulations so that the results are quantitative and mathematically rigorous. First, she took CT scans of birds to produce 3D models of their bones. The models were then run through a computer animation software to quantify how the bones fit together based on their shapes. 

Manafzadeh then studied several species of live birds to see if the model predicted the joint poses correctly in each case, producing a mathematically rigorous method for predicting joint poses from only their constituent bones, which could be used to deduce how the joints, and therefore the live animal, moves. 

The same method can then be applied to extinct animals to figure out how they moved when they were alive. 

“Our entire understanding of how vertebrates’ motion has evolved over deep time, even how our own locomotion came to be, relies on the reconstruction of the locomotion of specific animals in the fossil record,” Manafzadeh said. “And, so, to have a method to reconstruct the locomotion of those extinct animals lets us piece together that picture of evolutionary history.” 

Since joining Yale Institute for Biospheric Studies this summer to work in Bhullar’s lab, Manafzadeh has been using the same technique to study the fossil of the dinosaur Deinonychus, whose bones currently reside at the Class of 1954 Environmental Sciences Center. 

The dinosaur was discovered and named by Yale Professor John Ostrom in 1969 and helped advance the field’s understanding of the relationship between present-day birds and extinct dinosaurs. 

The name Deinonychus means “terrible claw,” owing to the large claw on the second toes of its hind legs. For decades, scientists have mulled over what the claw was for, theorized to have been used for hunting down prey, and how the animal moved with it. Manafzadeh is trying to use simulation to figure out exactly that. 

Bhullar says that he was not surprised that she received the Romer Prize.

“This award, it’s a pretty big deal in the field of vertebrate paleontology,” Bhullar said. “The way paleontologists view it is that it is given to someone who will someday lead the field, and I have to admit, I thought there was a good chance that she’d get it.

Gatesy shared Bhullar’s sentiment.

“She cares about pushing our field forward, she cares about fairness, and she cares about helping others,” Gatesy said. “She already has an international reputation, and I see her going far.”

The Deinonychus skeleton that Manafzadeh studied hangs by the stairwell in the Class of 1954 Environmental Sciences Center at 21 Sachem St.

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Researchers from the University of California, Berkeley, including Charles Brown II, an assistant professor of physics planning to join Yale faculty in January 2023, found a new and more direct method to examine singularities in the band structure of materials. This method has the potential to enhance our understanding of the properties of the materials themselves. 

The research, published in Science, employed quantum simulation to derive the results in this quantum simulation. They used lasers to imitate a crystal lattice and ultra-cold atoms of rubidium-87 to imitate the electrons in the lattice. Then, they accelerated the rubidium atoms into a singularity in the energy band structure — where two energy bands meet — and turned them at an angle before accelerating them away. This changed the proportion of atoms in different energy bands depending on the turning angle. 

“We’re using a simpler system over which we have a lot of control to emulate condensed matter systems, like real physical crystals, for example, graphene,” Brown said. “Using systems like the ones I work on, where you make an artificial crystal out of light … by studying how atoms hop around that artificial crystal, you can, in many ways, exactly emulate how electrons hop around in solid piece of graphene, and so you can also emulate the interesting physical properties of this material.” 

From the resulting proportion, researchers can work out some interesting properties of the band structure of the material, which can later be related to topics like superconductivity and quantum magnetism. 

Vladyslav Kozii, a member of the study’s theory team and assistant professor at Carnegie Mellon University, clarified that this emulation is possible because the equations of motion that govern the atoms in this optical lattice are the same as the ones that govern electrons in a crystal lattice. 

This experimental set-up was used to study the singularities in the band structure of the lattice. Band structure depicts the ranges of energies that particles can and cannot occupy in a lattice, and singularities are points where two energy bands touch — where they are at the same energy level.

“The concept we were playing with is that you figure out the geometry of the space you’re in, … whether there’s hills or valleys, by walking through the space,” said Dan Stamper-Kurn, the principal investigator of the experimental group, “That was the idea of this experiment — that by transporting the atoms through the lattice, we can figure out the geometry of the space it was transported through.” 

In this study, the team accelerated the rubidium atoms into such singularities in the optical lattice. Aleksandr Avdoshkin, a graduate student in the theory team, explained that instead of moving the atoms, it was easier to move the optical lattice itself so that the atoms moved relative to the lattice. 

Once the atom was in the singularity, the lattice was turned. The atoms were accelerated away, but now the proportion of atoms in each energy band had changed. At the singularity the bands have the same energy, and when moving through that point, some atoms transferred from lower to higher energy, for example. Then, the proportion of atoms in each band was measured. The researchers observed that the proportion depended solely on the turning angle, and making one full rotation resulted in the proportion making oscillations as well, with the number of oscillations per rotation depending on the type of singularity the atoms were passing through. 

Shao-Wen Chang, a graduate student in the experimental team, described that there are two types of singularities, linear and quadratic, differentiated by the rate at which the energy difference between the two bands grows with distance from the singularity. 

At a linear singularity, the proportion of atoms in each band underwent one full oscillation for each 360 degree rotation of the angle, while at a quadratic singularity, it underwent two full oscillations for each rotation, as seen in the part C’s of the diagrams below. This information can be used by scientists to determine some important properties of the material. 

According to Brown, the linear band-touching points (singularities), called Dirac points, had been studied extensively prior to this experiment. However, the quadratic ones had not been, which was partly because it was difficult to probe them using earlier methods. Thus, one important aspect of this study is that scientists could examine those points directly.

“There are all these exotic physics effects theorized to be associated with quadratic band-touching points, different topological effects, maybe even superconductivity and exotic quantum magnetism,” said Brown. “But, in my field, there hadn’t been a good technique to study them until now. But we knew we needed to study them because quadratic band-touching points appear in raw materials so understanding them better helps us understand how many interacting particles subject to quantum mechanics work.”

The cold-atom quantum simulation approach allows a way to probe the singularities simply and directly by changing the setup of the lasers, which Kozii said, isn’t something you can do with actual solid-state systems at all. 

The researchers all stressed that their work developed a new tool that can help understand singularities in band structure, which give rise to a lot of the materials’ properties and can be important to atomic physics and material science.

“You can do manipulations with physical systems which could not be imagined a few years ago — I think that’s really cool,” Kozii said.

This study was published in Volume 377, Issue 6612 of Science.

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