Transistors, the building blocks of modern electronics, are typically made of silicon. Because it’s a semiconductor, this material can control the flow of electricity in a circuit. But silicon has fundamental physical limits that restrict how compact and energy-efficient a transistor can be.

MIT researchers have now replaced silicon with a magnetic semiconductor, creating a magnetic transistor that could enable smaller, faster, and more energy-efficient circuits. The material’s magnetism strongly influences its electronic behavior, leading to more efficient control of the flow of electricity. 

The team used a novel magnetic material and an optimization process that reduces the material’s defects, which boosts the transistor’s performance.

The material’s unique magnetic properties also allow for transistors with built-in memory, which would simplify circuit design and unlock new applications for high-performance electronics.

“People have known about magnets for thousands of years, but there are very limited ways to incorporate magnetism into electronics. We have shown a new way to efficiently utilize magnetism that opens up a lot of possibilities for future applications and research,” says Chung-Tao Chou, an MIT graduate student in the departments of Electrical Engineering and Computer Science (EECS) and Physics, and co-lead author of a paper on this advance.

Chou is joined on the paper by co-lead author Eugene Park, a graduate student in the Department of Materials Science and Engineering (DMSE); Julian Klein, a DMSE research scientist; Josep Ingla-Aynes, a postdoc in the MIT Plasma Science and Fusion Center; Jagadeesh S. Moodera, a senior research scientist in the Department of Physics; and senior authors Frances Ross, TDK Professor in DMSE; and Luqiao Liu, an associate professor in EECS, and a member of the Research Laboratory of Electronics; as well as others at the University of Chemistry and Technology in Prague. The paper appears today in Physical Review Letters.

Overcoming the limits

In an electronic device, silicon semiconductor transistors act like tiny light switches that turn a circuit on and off, or amplify weak signals in a communication system. They do this using a small input voltage.

But a fundamental physical limit of silicon semiconductors prevents a transistor from operating below a certain voltage, which hinders its energy efficiency.

To make more efficient electronics, researchers have spent decades working toward magnetic transistors that utilize electron spin to control the flow of electricity. Electron spin is a fundamental property that enables electrons to behave like tiny magnets.

So far, scientists have mostly been limited to using certain magnetic materials. These lack the favorable electronic properties of semiconductors, constraining device performance.

“In this work, we combine magnetism and semiconductor physics to realize useful spintronic devices,” Liu says.

The researchers replace the silicon in the surface layer of a transistor with chromium sulfur bromide, a two-dimensional material that acts as a magnetic semiconductor.

Due to the material’s structure, researchers can switch between two magnetic states very cleanly. This makes it ideal for use in a transistor that smoothly switches between “on” and “off.”

“One of the biggest challenges we faced was finding the right material. We tried many other materials that didn’t work,” Chou says.

They discovered that changing these magnetic states modifies the material’s electronic properties, enabling low-energy operation. And unlike many other 2D materials, chromium sulfur bromide remains stable in air.

To make a transistor, the researchers pattern electrodes onto a silicon substrate, then carefully align and transfer the 2D material on top. They use tape to pick up a tiny piece of material, only a few tens of nanometers thick, and place it onto the substrate.

“A lot of researchers will use solvents or glue to do the transfer, but transistors require a very clean surface. We eliminate all those risks by simplifying this step,” Chou says.

Leveraging magnetism

This lack of contamination enables their device to outperform existing magnetic transistors. Most others can only create a weak magnetic effect, changing the flow of current by a few percent or less. Their new transistor can switch or amplify the electric current by a factor of 10.

They use an external magnetic field to change the magnetic state of the material, switching the transistor using significantly less energy than would usually be required.

The material also allows them to control the magnetic states with electric current. This is important because engineers cannot apply magnetic fields to individual transistors in an electronic device. They need to control each one electrically.

The material’s magnetic properties could also enable transistors with built-in memory, simplifying the design of logic or memory circuits.

A typical memory device has a magnetic cell to store information and a transistor to read it out. Their method can combine both into one magnetic transistor.

“Now, not only are transistors turning on and off, they are also remembering information. And because we can switch the transistor with greater magnitude, the signal is much stronger so we can read out the information faster, and in a much more reliable way,” Liu says.

Building on this demonstration, the researchers plan to further study the use of electrical current to control the device. They are also working to make their method scalable so they can fabricate arrays of transistors.

This research was supported, in part, by the Semiconductor Research Corporation, the U.S. Defense Advanced Research Projects Agency (DARPA), the U.S. National Science Foundation (NSF), the U.S. Department of Energy, the U.S. Army Research Office, and the Czech Ministry of Education, Youth, and Sports. The work was partially carried out at the MIT.nano facilities.

The UK’s AI Security Institute evaluated GPT-5.5’s ability to find security vulnerabilities, and found that it is comparable to Claude Mythos. Note that the OpenAI model is generally available.

Here is the Institute’s evaluation of Mythos.

And here is an analysis of a smaller, cheaper model. It requires more scaffolding from the prompter, but it is also just as good.

The two countries are headed in different directions on energy.

The question is when, not if, U.S. and European auto markets will open up to Chinese EV investment.

Karen Evans, who had led the agency since December, is the latest official to be removed from FEMA.

The nation's government said such cases create "uncertainty" for business. The effort mirrors those of Republicans in the U.S.

EPA and the State Department say the lawsuit is undermining federal authority. DOJ has lost similar cases against states.

Atoco's shipping-container-sized machine will produce up to 1,057 gallons of water daily and can be installed at data centers, hospitals and other critical infrastructure.

This year’s early season wildfires have overwhelmed fire crews in Argentina, Chile and Japan, while fueling historic blazes in the U.S. and Southeast Asia.

The move sets up a fight with the United States, which opposes carbon pricing.

Mozambique, South Africa and Zimbabwe experienced unusually heavy rains in recent months, with the region's worst flooding in years.

MIT engineers have developed a new way to amplify the T-cell response to mRNA vaccines — an advance that could lead to much more powerful cancer vaccines and stronger protection against infectious diseases.

Most vaccines generate both antibodies and T cells that can target the vaccine antigen by activating antigen-presenting cells, such as dendritic cells. In this study, the researchers boosted the T-cell response with a new type of vaccine adjuvant (a material that can help stimulate the immune system). The new adjuvant consists of mRNA molecules encoding genes that turn on immune signaling pathways and promote a supercharged T-cell response. 

In studies in mice, this mRNA-encoded adjuvant enabled the immune system to completely eradicate most tumors, either on its own or delivered along with a tumor antigen. The adjuvant also boosted the T-cell response to vaccines against influenza and Covid-19.

“When these adjuvant mRNAs are included in the vaccines, the number of antigen-targeted T cells is substantially increased. These T cells play an important role in the immune response, assisting in the clearance of virally infected cells or, in the case of cancer, killing cancerous cells,” says Daniel Anderson, a professor in MIT’s Department of Chemical Engineering and a member of MIT’s Koch Institute for Integrative Cancer Research and Institute for Medical Engineering and Science.

Anderson and Christopher Garris, an assistant professor at Harvard Medical School and Massachusetts General Hospital, are the senior authors of the study, which appears today in Nature Biotechnology. The paper’s lead authors are Akash Gupta, a former Koch Institute research scientist who is now an assistant professor at the University of Houston; Kaelan Reed, an MIT graduate student; and Riddha Das, a research fellow at Harvard Medical School and MGH. Robert Langer, the David H. Koch Institute Professor at MIT, and Ralph Weissleder, a professor of radiology and systems biology at MGH and Harvard Medical School, are also authors.

More powerful vaccines

Vaccines that stimulate the body’s immune system to attack tumors have shown promise in clinical trials, and a handful have been FDA-approved for certain cancers. In some patients, these vaccines stimulate a strong response, but in others, a weak response fails to kill the cancerous cells.

The MIT-MGH team wanted to find a way to make those immune responses more powerful. One way to do that is to deliver immune-stimulating molecules called cytokines along with a vaccine. However, cytokines can overstimulate the immune system, leading to potentially severe side effects.

As an alternative approach, the researchers decided to deliver mRNA strands encoding two genes, IRF8 and NIK, which are involved in antigen presentation and can switch immune cells into a more active state.

NIK is an enzyme that activates a signaling pathway involved in immunity and inflammation, while IRF8 is a transcription factor that helps program dendritic cells, particularly a subset called cDC1, which are especially effective at activating T cells. These antigen-presenting cells can digest foreign antigens and present them to T cells, stimulating the T cells to mount an immune response against the antigen.

“We see that the dendritic cells start shifting toward a more cDC1 phenotype, which is the most important dendritic cell phenotype and can generate a stronger T-cell response,” Gupta says. 

The researchers packaged the mRNA in lipid nanoparticles similar to those used to deliver mRNA Covid vaccines, but with a different chemical composition that promotes their delivery to the spleen after being injected intravenously. 

Inside the spleen, the particles encounter antigen-presenting cells, including dendritic cells. Within 24 hours, these cells begin expressing IRF8 and NIK, and both of these pathways help drive dendritic cells to mature and become activated so that they can prime an anti-tumor response. 

Over a few days to a week, the T-cell population expands. These T cells, along with other immune cells such as natural killer (NK) cells, can then recognize and attack tumors.

“Most cancer immunotherapies rely on external signals to activate immune cells. We take a different approach — reprogramming immune cells from within by targeting their internal signaling machinery, enabling a more potent and durable anti-tumor response,” Das says. 

Stronger T cells

The researchers tested the immune-remodeling mRNAs in several mouse models of cancer, including an aggressive bladder cancer, colon carcinoma, melanoma, and metastatic lung cancer. In nearly all of these mice, the injected mRNA stimulated a strong T-cell response that significantly slowed tumor growth and in many cases completely eradicated the tumors. This happened even when the mice were not given a vaccine against a specific cancer antigen. When they were, the response was even stronger.

“We showed that you can get an anti-cancer response with these adjuvants without including the antigen, just by activating the immune system. However, cancer-specific antigens with the adjuvants in a vaccine further improved the responses,” Anderson says.

The mRNA adjuvant also enhanced the immune response to immunotherapy drugs called checkpoint blockade inhibitors. These drugs, which work by lifting a brake that tumor cells put on T cells, are FDA-approved to treat several kinds of cancer. These drugs don’t work for all patients, but combining them with the mRNA vaccine adjuvant could offer a way to make them more effective, the researchers say.

“The microenvironment of solid tumors is often hostile to T cells and represents a major barrier to effective immunotherapy. We find that immune remodeling with these adjuvants creates a T cell–permissive environment and promotes tumor rejection,” Garris says.

The researchers also explored whether their new adjuvant could boost the immune response to vaccination against viral infection. When they delivered the mRNA particles along with Covid or flu vaccines, they found that the vaccine generated a 10-to-15-fold stronger T cell response in the mice.

The researchers now plan to test this approach in additional animal models, in hopes of developing it for use in both cancer and infectious diseases. 

“While there are differences between the mouse systems that we’ve worked in and humans, we are optimistic that these adjuvants will work in humans and could improve a range of different vaccines,” Anderson says.

The research was funded by Sanofi, the National Institutes of Health, the Marble Center for Cancer Nanomedicine, and the Koch Institute Support (core) Grant from the National Cancer Institute.

Nature Climate Change, Published online: 13 May 2026; doi:10.1038/s41558-026-02631-y

Assessments of coastal ecosystem resilience typically consider the impacts of annual mean sea-level rise, while increases in the seasonal sea-level cycle could also affect intertidal ecosystems. The authors show how such increases can threaten intertidal zones through altering the frequency and duration of inundation and emergence events.

Nature Climate Change, Published online: 13 May 2026; doi:10.1038/s41558-026-02630-z

Climate-friendly intentions do not always translate into action. This Review synthesizes evidence on the intrapersonal, social and structural mechanisms underlying this gap and outlines interventions that offer actionable strategies to close it.

Nature Climate Change, Published online: 13 May 2026; doi:10.1038/s41558-026-02639-4

The carbon sink of tropical forests is in part constrained by biomass turnover. This study assesses aboveground biomass turnover in the Amazon and finds that convective storms are the main driver of spatial variation in turnover and future climate impacts will lead to accelerated biomass turnover.

Last week, Instagram ended its opt-in, and therefore rarely used, end-to-end encryption feature. Years after publicly promising to provide the privacy protections of end-to-end encryption across its platforms by default, it instead gave up on that technical challenge. Now, we've all lost an option for safer conversations on one of the biggest social media platforms in the world.

In an announcement in 2023, Meta bragged about how it had successfully encrypted Messenger, and teased that Instagram was in progress. Even before then, they’d talked about how important encryption was in Messenger and Instagram in a white paper published in 2022, stating: 

We want people to have a trusted private space that’s safe and secure, which is why we’re taking our time to thoughtfully build and implement e2ee by default across Messenger and Instagram DMs.

So where did the reversal come from? In a statement, Meta claimed that, “Very few people were opting in to end-to-end encrypted messaging in DMs.” This isn’t all that surprising, as turning it on was an optional four-step process that few people knew about. Defaults matter, and Meta’s choice to blame people for failing to opt into this feature is proof of how much. In that same statement, the company pointed people to WhatsApp for access to encrypted messaging. Yet if Meta truly wanted people to have a trusted private space to communicate, it would meet them everywhere they are: on WhatsApp, on Messenger, and on Instagram.

But at least Meta was straightforward about the fact that it will not continue to support or work on this feature. That's rare. Most tech company promises aren’t broken explicitly, they just remain undelivered long enough to be forgotten. 

This is particularly disappointing as other companies take even bigger swings, like Google and Apple working together to implement end-to-end encryption over Rich Communication Services (RCS), and Signal’s continued work to make its app simpler and easier to use for everyone.

Meta abandoning this principle is disheartening, especially as we are still waiting for other promised features from the company, like end-to-end encryption in Facebook Messenger group messages. Instead of blaming users for not using these sorts of features and then abandoning the promise of delivery, Meta—and other tech companies—should start by enabling strong privacy protective features by default.

On April 28, 2025, the power grid serving continental Spain and Portugal went down, causing gridlock in cities, cutting communications networks, and stranding people on trains, in airports, and in elevators all across the Iberian peninsula and briefly in a small area in southwest France close to the Spanish border. The unprecedented, massive blackout lasted as long as 12 hours in some areas, including in the capital city, Madrid. Not surprisingly, placing blame for the outage was rapid. Quick reactions pointed to cyberattack, sabotage, and natural phenomena such as solar flares. 

But such theories were quickly laid to rest, and a panel of experts was formed to determine exactly what caused the blackout. After a year following the outage — and after much analysis by many experts — there isn’t a simple answer: In short, no one technology was to blame. While solar and wind generation was high, experts agree that the renewables weren’t at fault. 

In this Q&A, Pablo Duenas-Martinez, a research scientist at the MIT Energy Initiative and an assistant professor at Universidad Pontificia Comillas in Madrid, provides an update.

Q: How does a proper, well-functioning power grid behave, and what does the system operator do to help?

A: There are two components to the flows on a power grid. One is “active power” — the part that lights up our light bulbs and runs our engines. With active power, the demand on the grid must always equal supply. The other component is “reactive power,” the part we can’t see but controls the voltage at which the power is delivered so it suits our devices. If voltage is too low, lights will flicker. If voltage is too high, devices may not only fail to work, but be damaged beyond repair.

The operator of the transmission system — the TSO — must control both components, and that can be tricky. Active power supply and demand are largely coordinated through markets. But controlling reactive power is harder. The main way the TSO can control it is to call on operators of conventional power generators, so generators burning natural gas, or coal, or nuclear plants. Those systems can be adjusted to either absorb or inject reactive power as needed to control voltage on the power grid — indeed, they are typically required by law to provide “reactive power control.”

In contrast, solar and wind generators always absorb reactive power. The large solar and wind sources can provide reactive power control when it’s needed, but doing so is costly for them — and in Spain, unlike in most countries, it’s not mandated by law, so they typically don’t do it. Meanwhile, there are many small solar systems — imagine lots of rooftop solar installations and small solar farms. Those small systems are directly connected to the distribution system. As a result, they’re not controlled by the TSO; the TSO may not even know whether they’ve shut down or are still running and absorbing reactive power.

Sometimes, fluctuations in voltage called “oscillations” can happen on a power grid: for example, when a transmission line or a generator is connected or disconnected. Oscillations can increase and decrease the voltage rapidly, and if voltage gets too high, generators and user devices can start “tripping” — that is, automatically disconnecting to prevent being damaged. Operators have standard protocols to follow to bring oscillations under control.

Q: So what happened on April 28 of last year?

A: The Spanish grid is loosely connected to the French grid and in practice is merged with the grid serving Portugal. Within Spain, we have many large solar and wind farms and lots of small installations of solar systems, many located in the southwestern area of the country. On April 28 — as on most spring days, when demand is low — about two-thirds of the power on the grid came from renewable sources. The rest came from a mix of nuclear and natural gas plants.

The day before the blackout, the TSO confirmed that there were no conventional generators scheduled to run. So, to ensure safe operation the next day, the TSO took steps that included dispatching 12 conventional generators, 10 of them to provide reactive power control. One of the units in the south called him back and said, “I won’t be available. I cannot switch on tomorrow.” The TSO thought he had things under control and continued operations with only nine units available to provide reactive power control.

During the morning on April 28, several small oscillations on the power grid were detected coming from Europe, plus one from Spain. To stabilize the weakened grid, the TSO connected additional transmission lines and took other technical actions.

At 12:19 p.m., a major oscillation was detected on the grid, again coming from Europe. In response, the TSO — again following standard protocol — reduced exports to Portugal, switched the flows to France from alternating current to direct current, and connected five more transmission lines within Spain. While those steps stabilized the voltage, the TSO recognized that there was now limited capacity on the system to control voltage. So, he called on a different conventional generator to begin running. But that unit couldn’t be available for an hour.

Suddenly, as a consequence of the previous actions, the voltage increased dramatically, and generating units began to trip. Within half-a-second, many of the small solar generators — especially prone to damage from high voltages — automatically shut down. Twenty milliseconds later, a big solar plant in southwestern Spain tripped. Because the solar plants were no longer absorbing reactive power, voltage on the system went up even more, and more systems shut down. The grid went into what some have called a death spiral, resulting in a total blackout across the Iberian peninsula and some areas of southern France.

Q: What have we learned from this Iberian blackout, and have changes been implemented to ensure that the same won’t happen again — or happen elsewhere?

A: A resilient power system must prevent, mitigate, respond, and recover. In this case, the first three components clearly failed. Preventive mechanisms were insufficient; they initially mitigated the oscillatory events, but left the system in a weakened state, and the response triggered the death spiral that led to the final blackout.

The good news is that the recovery was quick. The northern and southern sections of the peninsula had power back within a few hours. I live in the suburbs of Madrid, and I had power back just six hours later. My parents live downtown, so that was far more challenging — a big city with a large, complex load. Even so, they had power back in 12 hours — and 12 hours is quick for such a major, widespread blackout.

In the end, experts and analysts have agreed that the blackout was caused by a series of events that were all happening in the same place, at the same time. And the experience did provide a number of valuable learnings:

Lesson 1

The experience clearly demonstrated the importance of having a sufficient number of conventional power plants prepared to provide reactive power control, or to turn on right away when called on. There’s a recommendation calling for a set ratio between conventional generators and renewables on a power grid. Conventional facilities such as nuclear, hydroelectric, and fossil fuel plants rely on heavy metal wheels to generate electricity. Those massive rotating wheels have high inertia, so they’ll keep running and can help stabilize frequency and voltage even when solar and wind plants shut down. Before the blackout, Spain had a sufficient number of “rotating units” to meet the recommended ratio. However, in southern Spain, there was just one such unit — well below the recommended number, given the huge number of small solar units plus several large solar units in the area.

The message here is that you can't just look at the country as a whole. You have to look at regions. Voltage is a local problem that can propagate at the system level. Before the blackout, southern Spain typically had at most three conventional power plants. Now the region usually has six or seven at the ready to help with reactive power control.

Lesson 2

The rules or protocols for controlling reactive power and dealing with oscillations were not well designed. By law, rotating generators must automatically — and without being paid — do a defined amount of reactive power control. But making the needed operational change costs money, and a plant can do less than the required amount and not incur any kind of penalty. However, the TSO doesn’t know in advance how much reactive power control a given plant will actually do. Now that loophole in the law has been reviewed by the regulator.

The main rules have been updated, and now also require large solar and wind power plants — those above 5 megawatts — to provide reactive power control. More importantly, voltage control will be auctioned and remunerated, incentivizing rotating conventional generators and bringing in a new money stream for solar and wind power plants. Those power plants that do not upgrade their installation for voltage control might be disconnected by the TSO if local voltage issues arise.

Lesson 3

Another learning concerns the many small solar power generators and the protections that cause them to trip. The TSO doesn’t know in advance when this may happen because the small solar sources are directly connected to the distribution system, and therefore are under the umbrella of the distribution system operator. So, the learning here is that there should be more communication and coordination between the operator of the transmission system — the TSO — and the operator of the distribution system.

Lesson 4

In most countries, laws dictate a range of voltage that is approved. In Spain, the upper limit is high — in fact, it’s very near a voltage at which equipment may be damaged. And the Spanish grid tends to hover close to that upper limit, even during normal operation, and that can be a big problem: If there are strong oscillations — as there were leading up to the blackout — voltage can reach that upper limit, and protections on devices will automatically trip. The panel of experts has strongly recommended to lower this upper limit in Spain and align it with the rules in neighboring countries, including Portugal and France. The TSO is still studying the recommended change.

Lesson 5

During normal operation, the TSO controls voltage by activating rotating generators that can provide reactive power control. But as we saw in conditions leading up to the blackout, the TSO doesn’t always have rotating generators available.

Theoretically, TSOs have two more ways to control voltage. They can connect a device called a shunt reactor, which absorbs reactive power — a means of dealing with voltage rise. And they can regulate voltage directly using a “STATCOM,” a special device that provides rapid, dynamic voltage control.

However, neither the shunt reactors nor the STATCOM could help prevent the blackout. The shunt reactors available at that time were operated manually, and collapse of the grid happened so quickly that the TSO didn’t have time to connect them. And at that time, there was a single STATCOM device on the Spanish system. Planning was under way to install three more devices — and that installation is being rapidly completed.

From newspaper articles and off-the-record conversations, I’ve learned that the system has — due to similar external circumstances — been close to blackout again during the past year. But in part due to the learnings and to changes that have been implemented as a result, it didn’t happen again.

The hallowed history of student pranks (often known as hacks) at MIT includes the annual Baker House Piano Drop and the MIT weather balloon at the Harvard-Yale football game in 1982. One hack that has shown remarkable staying power in local lore is the 1958 measurement of the Massachusetts Ave. Bridge in “smoots,” a now accepted unit of meausrement named for the 5-foot, 7-inch Oliver R. Smoot Jr. ’62. Then a first-year pledge at the Lambda Chi Alpha fraternity, Smoot famously laid down hundreds of times across the span one storied night as his peers painted markers across the bridge, totaling 364.4 smoots (plus 1 ear). Nearly 70 years later, the smoot markings remain.

On April 4, an MIT team set out on a similar journey across the Charles River to pull off a new hack, this time measuring the Longfellow Bridge in “kleins.” This new measurement is named after Smoot’s classmate Martin Klein ’62. One klein (4 feet, 9.5 inches) is equal to 0.85820896 smoots. The expedition was undertaken in honor of both Smoot and the 85th birthday of Klein.

Known as the father of commercial side-scan sonar, Martin Klein serves on the MIT Sea Grant Advisory Board and the MIT Museum Collections Committee. He is a life fellow of both the Marine Technology Society and the Explorers Club, an international organization dedicated to the advancement of field exploration and scientific inquiry. His sonar technology has been used worldwide to help locate countless famous shipwrecks, including the Titanic, the World War I ocean liner RMS Lusitania, and the treasure-laden Nuestra Señora de Atocha.

Appropriately, the MIT team used a “side-scan” method to survey the Longfellow Bridge. Reclined on a custom-engineered wooden cart topped with a mission-specific chaise lounge pillow, Klein himself acted as the official observation device — by looking to the sides — as the team pulled him along the bridge. Some of the noted anomalies and discoveries included a Duck Boat passing underneath, a mermaid tail, a kayak paddle, a sleeping goose, and a tenacious survey team.

The initiative was spearheaded by Makenna Reilly, a second-year undergraduate in mechanical engineering, and Andrew Bennett ’85, PhD ’97, MIT Sea Grant education administrator and senior lecturer in the Department of Mechanical Engineering (MechE). Over a dozen surveyors joined the expedition, including alumni, faculty, and staff from MechE, MIT Sea Grant, MIT Edgerton Center, MIT Museum Hart Nautical Collections, Harvard Extension School, and Woods Hole Oceanographic Institution. MIT students also joined the effort, including senior Teagan Sullivan, junior Adrienne Lai, and graduate students Ansel Garcia-Langley, Erin Menezes, Manuel Valencia, and Gerardo Berlanga Molina.

The Longfellow Bridge was determined to be 442 kleins (plus 2 legs) and was celebrated as the “Shortfellow Bridge” in a ceremony following the event. 

One klein = 57.5 inches = 146.05 centimeters = 1.4605 meters = .0009075126 miles = 1.597222 yards = 4.791667 feet = .0007886069 nautical miles = .007260087 furlongs = 0.7986111 fathoms = 172.5 barleycorns = 292,100,000 beard seconds = 647.4421 Ligne = 14.375 horse hands = 4.819655 shaku = .85820896 smoots.

Additional participants in the event include:

• Elisabeth (Libby) Meier, assistant curator for the Hart Nautical Collections at the MIT Museum;
• Dana Yoerger, PhD ’82, senior scientist applied ocean physics and engineering at WHOI;
• Professor George Buckley, assistant director of sustainability at Harvard University Extension School and diver of the year of the Boston Sea Rovers;
• Paul K. Matthias, senior program manager of the Ocean Observatories Initiative at the WHOI;
• Jim Bales, associate director of the Edgerton Center at MIT;
• John Freidah of MechE; and
• Joice Himawan ’83.

Dark matter is thought to make up most of the matter in the universe, but the only way it interacts with its surroundings is through gravity. If two colliding black holes spiral through a dense region of dark matter and merge, gravitational waves rippling across space and time could carry an imprint of that dark matter.

Now, physicists may be able to spot such imprints of dark matter in gravitational waves that are detected on Earth. 

Researchers at MIT and in Europe have developed a method that makes predictions for what a gravitational wave should look like if it were produced by black holes that moved through dark matter, rather than empty space. They applied the technique to publicly available gravitational-wave data previously recorded by LIGO-Virgo-KAGRA (LVK), the global network of observatories that detect gravitational waves from black hole mergers and other far-off astrophysical sources.

The researchers looked through the gravitational-wave signals recorded over the LVK’s first three observing runs. From 28 of the clearest signals, the team found that 27 originated from black holes that merged in a vacuum, as physicists expected. But the pattern of one signal, GW190728, showed possible signs of a dark matter imprint. 

The scientists emphasize that they have not detected dark matter. Rather, the new method offers a new way to screen gravitational-wave data for hints of dark matter, which physicists can then follow up and confirm with other techniques. 

“We know that dark matter is around us. It just has to be dense enough for us to see its effects,” says Josu Aurrekoetxea, a postdoc in the MIT Department of Physics. “Black holes provide a mechanism to enhance this density, which we can now search for by analyzing the gravitational waves emitted when they merge.”

Aurrekoetxea and his colleagues report their results in a study appearing today in Physical Review Letters. The study’s co-authors are LVK member Soumen Roy of Université Catholique de Louvain (UCLouvain) in Belgium, Rodrigo Vicente of the University of Amsterdam, Katy Clough of Queen Mary University of London, and Pedro Ferreira of Oxford University. 

A dark pull

Dark matter is an invisible, hypothetical form of matter that, unlike normal everyday matter, has no interactions with the electromagnetic force. Dark matter can pass through light, magnetic fields, and any other form of energy along the electromagnetic spectrum without leaving a trace. The only evidence that dark matter exists is through its apparent interaction with one other force: gravity. 

By observing how gravity bends around distant galaxies, astronomers have surmised that there must be an extra force, outside of the galaxies’ own gravitational pull, to explain the bending fields, or “lensing.” This extra force, physicists suspect, is dark matter, which could account for over 85 percent of the matter in the universe. But exactly what dark matter is is a matter of huge debate, with theories for dark matter particles that range widely in particle size and properties. 

One class of proposed dark matter consists of “light scalar” particles, whose masses are many orders of magnitude lighter than an electron. Theorists predict that such dark matter should behave not just as particles, but also as coordinated waves when moving near black holes.

When waves of dark matter come in contact with a rapidly spinning black hole, physicists predict that the black hole's rotational energy can be transferred to the dark matter, amplifying it. This phenomenon, known as superradiance, would whip up the waves to extremely high densities of dark matter, akin to churning cream into butter.

At high enough densities, light scalar dark matter, which is invisible by all other accounts, should leave an imprint on the gravitational waves that reverberate from the colliding black holes. 

But exactly what would that imprint look like? And could such an imprint be detectable in gravitational waves that arrive on Earth, from black holes that merged many millions of light years away? 

For answers to those questions, Aurrekoetxea and his colleagues developed a model to predict the gravitational waveform, or the pattern of gravitational waves that two black holes would produce, if they collided in an environment of dark matter, versus in a vacuum (empty space, with no dark matter). 

An imprint’s prediction

For their new study, the team performed detailed numerical simulations to predict the gravitational wave that would be produced given various properties of two colliding black holes — a system known as a “black hole binary.” They considered black hole binaries across a range of scenarios and properties, for example, varying the size and mass of each black hole, the environment of dark matter that the black holes might pass through, and the density of the dark matter that the black holes would spin up. 

They designed the model to predict what a gravitational wave from a black hole binary would look like if it carried an imprint of dark matter, and furthermore, what that wave would look like if it traveled a given distance across space and time, to eventually arrive at a detector on Earth.

With their model, they looked to see whether any gravitational-wave signals that have been detected on Earth match their predicted patterns of dark matter imprints. To do so, they applied the model to publicly-available data recorded by LVK over the observatories’ first three observing runs. The observatories have picked up hundreds of gravitational-wave signals during this period. For their purposes, the researchers focused on the clearest signals, comprising gravitational waves from 28 separate events. 

For each event, the team compared the pattern of the actual gravitational wave against their model of what the signal would look like if it were generated by the same event in an environment of dark matter. They also compared the gravitational wave to the more expected scenario in which the signal was produced in a vacuum. 

Of the 28 clearest signals that they analyzed, 27 were solidly within the predictions for having been produced in a vacuum. However, the pattern of one event, GW190728, showed a “preference,” or an agreement with the team’s dark matter model. In other words, the signal may carry an imprint of dark matter. 

GW190728 is a gravitational wave that is named after the date that it was detected — on July 28, 2019. Scientists previously determined that the gravitational wave originated from a black hole binary with a total mass of about 20 times the mass of the sun. With their model, the team showed that such a system could have merged through a dense cloud of dark matter and produced a similar gravitational wave to GW190728. 

“The statistical significance of this is not high enough to claim a detection of dark matter, and further checks should be performed by independent groups,” Aurrekoetxea says. “What we think is important to highlight is that without waveform models like ours, we could be detecting black hole mergers in dark matter environments, but systematically classifying them as having occurred in vacuum.”

“We now have the potential to discover dark matter around black holes as the LVK detectors keep collecting data in the coming years,” says co-author Soumen Roy, who led the data analysis part of the work. “It is an exciting time to search for new physics using gravitational waves.”

“Using black holes to look for dark matter would be fantastic,” adds co-author Rodrigo Vicente, who developed the analytical model of the signal. “We would be able to probe dark matter at scales much smaller than ever before.”

This work was supported, in part, by the U.S. National Science Foundation and MIT’s Center for Theoretical Physics — a Leinweber Institute.

This week, Apple released iOS 26.5, an update that supports end-to-end encryption for Rich Communication Services (RCS), meaning conversations between Android and iPhone will soon be encrypted in the default chat apps. This has been a long time coming, and is a welcome delivery on a promise both Google and Apple made.

With this update, conversations that take place between Apple’s Messages app and Google Messages on Android will be end-to-end encrypted by default, as long as the carrier supports both RCS and encrypted messages (you can find a list of carriers here). RCS messages are a replacement for SMS, and in 2024 Apple started supporting it, making for a marked improvement in the quality of images and other media shared between Android and iPhones. 

Now, those conversations can also benefit from the increased privacy and security that end-to-end encryption offers, making it so neither Google, Apple, nor the cellular carriers have access to the contents of messages. This feature comes courtesy of both Apple and Google supporting the GSMA RCS Universal Profile 3.0, which implements the Messaging Layer Security protocol for encryption. Metadata will likely still be collected and stored for these conversations, making alternatives like Signal still a better option for many conversations. Likewise, if you back up those conversations to the cloud, they may be stored unencrypted unless you enable Advanced Data Protection on iOS (Google Messages end-to-end encrypts the text of messages in backups, but not the media, so we’d like to see a similar offering as ADP on Android). Still, this is a significant step forward for the privacy of millions of conversations worldwide.

End-to-end encrypted RCS messaging is still marked as beta on Apple devices, likely because the rollout is dependent on carriers as well as the Android phone running the most recent version of Google Messages. 

It might take some time before you get this feature in your chats and until you do, remember that the conversations are not protected with end-to-end encryption. But once everyone in the conversation is on the right software version and the carrier support is implemented, you will see a lock icon and the text, “Encrypted” at the top of the conversation for any chats you have over RCS, as seen here:

We applaud Apple and Google for getting this across the finish line and Encrypting It Already! More companies should take these sorts of difficult but necessary steps to protect the privacy of our conversations and our data.