The company tacitly admits that browser notifications, as designed, might have been a bad idea, saying that its own data shows users receive a high volume of notifications but rarely interact with them.
Read more This is today’s edition of The Download, our weekday newsletter that provides a daily dose of what’s going on in the world of technology.
How do our bodies remember?
“Like riding a bike” is shorthand for the remarkable way that our bodies remember how to move. Most of the time when we talk about muscle memory, we’re not talking about the muscles themselves but about the memory of a coordinated movement pattern that lives in the motor neurons, which control our muscles.
Yet in recent years, scientists have discovered that our muscles themselves have a memory for movement and exercise. And the more we move, as with riding a bike or other kinds of exercise, the more those cells begin to make a memory of that exercise. Read the full story.
—Bonnie Tsui
This piece is part of MIT Technology Review Explains: our series untangling the complex, messy world of technology to help you understand what’s coming next. You can read more from the series here.
This story is also from our forthcoming print issue, which is all about the body. If you haven’t already, subscribe now to receive future issues once they land. Plus, you’ll also receive a free digital report on nuclear power.
2025 climate tech companies to watch: Traton and its electric trucks
Every day, trucks carry many millions of tons of cargo down roads and highways around the world. Nearly all run on diesel and make up one of the largest commercial sources of carbon emissions.
Traton, a subsidiary of Volkswagen, is producing zero-emission trucks that could help clean up this sector, while also investing in a Europe-wide advanced charging network so other manufacturers can more easily follow suit. Read the full story.
—Amy Nordrum
Traton is one of our 10 climate tech companies to watch—our annual list of some of the most promising climate tech firms on the planet. Check out the rest of the list here.
This test could reveal the health of your immune system
We know surprisingly little about our immune health. The vast array of cells, proteins, and biomolecules that works to defend us from disease is mind-bogglingly complicated. Immunologists are still getting to grips with how it all works.
Now, a new test is being developed to measure immune health, one that even gives you a score. But that’s a difficult thing to do, for several reasons. Read the full story.
—Jessica Hamzelou
This article first appeared in The Checkup, MIT Technology Review’s weekly biotech newsletter. To receive it in your inbox every Thursday, sign up here.
The must-reads
I’ve combed the internet to find you today’s most fun/important/scary/fascinating stories about technology.
1 China is cracking down on imports of Nvidia’s AI chips
Customs officers are combing shipments looking for the company’s China-specific chips. (FT $)
+ US officials are investigating a firm that’s suspected of helping China sidestep export restrictions. (NYT $)
2 Tesla’s ‘full self-driving’ feature is under investigation
After multiple reports of vehicles using it ran red lights. (WP $)
+ The company is slashing its prices to compete with Chinese giant BYD. (Rest of World)
+ Elon Musk will still receive billions, even if he fails to achieve his ambitions goals. (Reuters)
3 A data hoarder has created a searchable database of Epstein files
Making it simple to find mentions of specific people and locations. (404 Media)
4 OpenAI says GPT-5 is its least-biased model yet
Even when proceeding with “challenging, emotionally charged prompts.” (Axios)
5 The developers behind ICE-tracking apps aren’t giving up
They’re fighting Apple’s decision to remove their creations from its app store. (Wired $)
+ Another effort to track ICE raids was just taken offline. (MIT Technology Review)
6 The world’s biodiversity crisis is worsening
More than half of all bird species are in decline. (The Guardian)
+ The short, strange history of gene de-extinction. (MIT Technology Review)
7 YouTube is extending an olive branch to banned creators
It’s overturned a lifetime ban policy to give the people behind previously-banned channels a second chance. (CNBC)
+ But users kicked off for copyright infringement or extremism aren’t eligible. (Bloomberg $)
8 This startup wants to bring self-flying planes to our skies
Starting with military cargo flights. (WSJ $)
9 Your plumber might be using ChatGPT
They’re increasingly using the chatbot to troubleshoot on the ground. (CNN)
10 Do robots really need hands?
Maybe not, but that’s not standing in the way of researchers trying to recreate them. (Fast Company $)
+ Will we ever trust robots? (MIT Technology Review)
Quote of the day
“Social media is a complete dumpster.”
—Hany Farid, a professor of computer science at the University of California, Berkeley, describes the proliferation of AI slop videos infiltrating digital platforms to the New York Times.
One more thing
Who gets to decide who receives experimental medical treatments?
There has been a trend toward lowering the bar for new medicines, and it is becoming easier for people to access treatments that might not help them—and could even harm them. Anecdotes appear to be overpowering evidence in decisions on drug approval. As a result, we’re ending up with some drugs that don’t work.
We urgently need to question how these decisions are made. Who should have access to experimental therapies? And who should get to decide? Such questions are especially pressing considering how quickly biotechnology is advancing. We’re not just improving on existing classes of treatments—we’re creating entirely new ones. Read the full story.
—Jessica Hamzelou
We can still have nice things
A place for comfort, fun and distraction to brighten up your day. (Got any ideas? Drop me a line or skeet ’em at me.)
+ I love this crowd-sourced compendium of every known Wilhelm scream in all sorts of media.
+ Happy birthday to pocket rocket Bruno Mars, who turned 40 this week.
+ Here’s how to visit an interstellar interloper.
+ Bumi the penguin is having the absolute time of their life with this bubble machine 
MIT Technology Review Explains: Let our writers untangle the complex, messy world of technology to help you understand what’s coming next. You can read more from the series here.
“Like riding a bike” is shorthand for the remarkable way that our bodies remember how to move. Most of the time when we talk about muscle memory, we’re not talking about the muscles themselves but about the memory of a coordinated movement pattern that lives in the motor neurons, which control our muscles.
Yet in recent years, scientists have discovered that our muscles themselves have a memory for movement and exercise.
When we move a muscle, the movement may appear to begin and end, but all these little changes are actually continuing to happen inside our muscle cells. And the more we move, as with riding a bike or other kinds of exercise, the more those cells begin to make a memory of that exercise.
When we move a muscle, the movement may appear to begin and end, but all these little changes are actually continuing to happen inside our muscle cells.
We all know from experience that a muscle gets bigger and stronger with repeated work. As the pioneering muscle scientist Adam Sharples—a professor at the Norwegian School of Sport Sciences in Oslo and a former professional rugby player in the UK—explained to me, skeletal muscle cells are unique in the human body: They’re long and skinny, like fibers, and have multiple nuclei. The fibers grow larger not by dividing but by recruiting muscle satellite cells—stem cells specific to muscle that are dormant until activated in response to stress or injury—to contribute their own nuclei and support muscle growth and regeneration. Those nuclei often stick around for a while in the muscle fibers, even after periods of inactivity, and there is evidence that they may help accelerate the return to growth once you start training again.
Sharples’s research focuses on what’s called epigenetic muscle memory. “Epigenetic” refers to changes in gene expression that are caused by behavior and environment—the genes themselves don’t change, but the way they work does. In general, exercise switches on genes that help make muscles grow more easily. When you lift weights, for example, small molecules called methyl groups detach from the outside of certain genes, making them more likely to turn on and produce proteins that affect muscle growth (also known as hypertrophy). Those changes persist; if you start lifting weights again, you’ll add muscle mass more quickly than before.
In 2018, Sharples’s muscle lab was the first to show that human skeletal muscle has an epigenetic memory of muscle growth after exercise: Muscle cells are primed to respond more rapidly to exercise in the future, even after a monthslong (and maybe even yearslong) pause. In other words: Your muscles remember how to do it.
Subsequent studies from Sharples and others have replicated similar findings in mice and older humans, offering further supporting evidence of epigenetic muscle memory across species and into later life. Even aging muscles have the capacity to remember when you work out.
At the same time, Sharples points to intriguing new evidence that muscles also remember periods of atrophy—and that young and old muscles remember this differently. While young human muscle seems to have what he calls a “positive” memory of wasting—“in that it recovers well after a first period of atrophy and doesn’t experience greater loss in a repeated atrophy period,” he explains—aged muscle in rats seems to have a more pronounced “negative” memory of atrophy, in which it appears “more susceptible to greater loss and a more exaggerated molecular response when muscle wasting is repeated.” Basically, young muscle tends to bounce back from periods of muscle loss—“ignoring” it, in a sense—while older muscle is more sensitive to it and might be more susceptible to further loss in the future.
Illness can also lead to this kind of “negative” muscle memory; in a study of breast cancer survivors more than a decade after diagnosis and treatment, participants showed an epigenetic muscle profile of people much older than their chronological age. But get this: After five months of aerobic exercise training, participants were able to reset the epigenetic profile of their muscle back toward that of muscle seen in an age-matched control group of healthy women.
What this shows is that “positive” muscle memories can help counteract “negative” ones. The takeaway? Your muscles have their own kind of intelligence. The more you use them, the more they can harness it to become a lasting beneficial resource for your body in the future.
Bonnie Tsui is the author of On Muscle: The Stuff That Moves Us and Why It Matters (Algonquin Books, 2025).
Attentive readers might have noticed my absence over the last couple of weeks. I’ve been trying to recover from a bout of illness.
It got me thinking about the immune system, and how little I know about my own immune health. The vast array of cells, proteins, and biomolecules that works to defend us from disease is mind-bogglingly complicated. Immunologists are still getting to grips with how it all works.
Those of us who aren’t immunologists are even more in the dark. I had my flu jab last week and have no idea how my immune system responded. Will it protect me from the flu virus this winter? Is it “stressed” from whatever other bugs it has encountered in the last few months? And since my husband had his shot at the same time, I can’t help wondering how our responses will compare.
So I was intrigued to hear about a new test that is being developed to measure immune health. One that even gives you a score.
Writer David Ewing Duncan hoped that the test would reveal more about his health than any other he’d ever taken. He described the experience in a piece published jointly by MIT Technology Review and Aventine.
The test David took was developed by John Tsang at Yale University and his colleagues. The team wanted to work out a way of measuring how healthy a person’s immune system might be.
It’s a difficult thing to do, for several reasons. First, there’s the definition of “healthy.” I find it’s a loose concept that becomes more complicated the more you think about it. Yes, we all have a general sense of what it means to be in good health. But is it just the absence of disease? Is it about resilience? Does it have something to do with withstanding the impact of aging?
Tsang and his colleagues wanted to measure “deviation from health.” They looked at blood samples from 228 people who had immune diseases that were caused by single-gene mutations, as well as 42 other people who were free from disease. All those individuals could be considered along a health spectrum.
Another major challenge lies in trying to capture the complexity of the immune system, which involves hundreds of proteins and cells interacting in various ways. (Side note: Last year, MIT Technology Review recognized Ang Cui at Harvard University as one of our Innovators under 35 for her attempts to make sense of it all using machine learning. She created the Immune Dictionary to describe how hundreds of proteins affect immune cells—something she likens to a “periodic table” for the immune system.)
Tsang and his colleagues tackled this by running a series of tests on those blood samples. The vast scope of these tests is what sets them apart from the blood tests you might get during a visit to the doctor. The team looked at how genes were expressed by cells in the blood. They measured a range of immune cells and more than 1,300 proteins.
The team members used machine learning to find correlations between these measurements and health, allowing them to create an immune health score for each of the volunteers. They call it the immune health metric, or IHM.
When they used this approach to find the immune scores of people who had already volunteered in other studies, they found that the IHM seemed to align with other measures of health, such as how people respond to diseases, treatments, and vaccines. The study was published in the journal Nature Medicine last year.
The researchers behind it hope that a test like this could one day help identify people who are at risk of cancer and other diseases, or explain why some people respond differently to treatments or immunizations.
But the test isn’t ready for clinical use. If, like me, you’re finding yourself curious to know your own IHM, you’ll just have to wait.
This article first appeared in The Checkup, MIT Technology Review’s weekly biotech newsletter. To receive it in your inbox every Thursday, and read articles like this first, sign up here.
Monero’s “Fluorine Fermi” update enhances privacy by fighting nodes that try to link user IP addresses to their transactions.
Proof of Search’s Kevin Gibson said the job market looks very different from 2021, when entry-level jobs were easier to land.
Democratic senators have been criticized for pitching a counter-proposal to the market structure bill that could effectively “kill DeFi.”
Super.money, the fintech arm of Flipkart, is looking to raise a round of funding at a $1 billion valuation, after securing $50 million from Flipkart to date.
Read more Microsoft CEO Satya Nadella offered a glimpse of the “first of many” massive Nvidia AI systems it is rolling out, starting now.
Read more