@4gravitons.bsky.social
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Bluesky for the blog 4gravitons.com
Thereâs something about Symmetry⊠Physicists talk a lot about symmetry. Listen to an article about string theory and you might get the idea that symmetry is some sort of mysterious, mystical principle of beauty, inexplicable to the common man or woman. Well, if it was inexplicable, I wouldnât beâŠ
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Thereâs something about SymmetryâŠ
Physicists talk a lot about symmetry. Listen to an article about string theory and you might get the idea that symmetry is some sort of mysterious, mystical principle of beauty, inexplicable to the common man or woman. Well, if it was inexplicable, I wouldnât be blogging about it, now would I? Symmetry in physics is dead simple. At the same time, itâs a bit misleading.
http://4gravitons.com/2013/04/19/theres-something-about-symmetry/
4 days ago
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In which I have some opinions about exam accommodations:
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Ideally, Exams Are for the Students
I should preface this by saying I don't actually know that much about education. I taught a bit in my previous life as a professor, yes, but I probably spent more time being taught how to teach than actually teaching. Recently, the Atlantic had a piece about testing accommodations for university students, like extra time on exams, or getting to do an exam in a special distraction-free environment.
http://4gravitons.com/2025/12/05/ideally-exams-are-for-the-students/
5 days ago
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Some bonus info for my Quanta piece last week:
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Bonus Info For âCosmic Paradox Reveals the Awful Consequence of an Observer-Free Universeâ
I had a piece in Quanta Magazine recently, about a tricky paradox that's puzzling quantum gravity researchers and some early hints at its resolution. The paradox comes from trying to describe "closed universes", which are universes where it is impossible to reach the edge, even if you had infinite time to do it. This could be because the universe wraps around like a globe, or because the universe is expanding so fast no traveler could ever reach an edge.
http://4gravitons.com/2025/11/28/bonus-info-for-cosmic-paradox-reveals-the-awful-consequence-of-an-observer-free-universe/
12 days ago
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Why do all of those European scholars have teams with cutesy names? The answer may surprise you:
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Mandatory Dumb Acronyms
Sometimes, the world is silly for honest, happy reasons. And sometimes, it's silly for reasons you never even considered. Scientific projects often have acronyms, some of which are...clever, let's say. Astronomers are famous for acronyms. Read this list, and you can find examples from 2D-FRUTTI and ABRACADABRA to WOMBAT and YORIC. Some of these aren't even "really" acronyms, using letters other than the beginning of each word, multiple letters from a word, or both.
http://4gravitons.com/2025/11/21/mandatory-dumb-acronyms/
19 days ago
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reposted by
Sean Carroll
20 days ago
Is the universe bigger on the inside than it looks from the outside? I.e. does a universe contain essentially no global information, but appears to when looked at from internal subsystems? Love this stuff (and have been thinking about related questions). Don't think we have it sorted out quite yet.
add a skeleton here at some point
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I've got a new piece up in
@quantamagazine.bsky.social
, about a puzzle that is fascinating some folks in quantum gravity. Expect a "bonus info" post in a week or two with more info.
www.quantamagazine.org/cosmic-parad...
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Cosmic Paradox Reveals the Awful Consequence of an Observer-Free Universe | Quanta Magazine
Encouraged by successes in understanding black holes, theoretical physicists are applying what theyâve learned to whole universes. What theyâre finding has them questioning fundamental assumptions abo...
https://www.quantamagazine.org/cosmic-paradox-reveals-the-awful-consequence-of-an-observer-free-universe-20251119/
20 days ago
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In which I offer some unsolicited advice:
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Reminder to Physics Popularizers: âDiscoverâ Is a Technical Term
When a word has both an everyday meaning and a technical meaning, it can cause no end of confusion. I've written about this before using one of the most common examples, the word "model", which means something quite different in the phrases "large language model", "animal model for Alzheimer's" and "model train". And I've written about running into this kind of confusion at the beginning of my PhD, …
http://4gravitons.com/2025/11/14/reminder-to-physics-popularizers-discover-is-a-technical-term/
26 days ago
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If you're confused by a scientist, ask yourself: which register are they using?
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Explain/Teach/Advocate
Scientists have different goals when they communicate, leading to different styles, or registers, of communication. If you don't notice what register a scientist is using, you might think they're saying something they're not. And if you notice someone using the wrong register for a situation, they may not actually be a scientist. Sometimes, a scientist is trying to explain…
http://4gravitons.com/2025/11/07/explain-teach-advocate/
about 1 month ago
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For this Halloween, are you afraid of the dark?
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Fear of the Dark, Physics Version
Happy Halloween! I've got a yearly tradition on this blog of talking about the spooky side of physics. This year, we'll think about what happens...when you turn off the lights. Over history, astronomy has given us larger and larger views of the universe. We started out thinking the planets, Sun, and Moon were human-like, just a short distance away. Measuring distances, we started to understand the size of the Earth, then the Sun, then realized how much farther still the stars were from us.
http://4gravitons.com/2025/10/31/fear-of-the-dark-physics-version/
about 1 month ago
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I have a book review in Science this month, of
@danielwhiteson.bsky.social
and Andy Warner's fun new book, "Do Aliens Speak Physics?" Link here, it's paywalled, but for a one-pager that just means it's a bit pixellated:
www.science.org/doi/10.1126/...
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Extraterrestrials illustrated
A physicist and a cartoonist join forces with an accessible guide to thinking about life in the cosmos
https://www.science.org/doi/10.1126/science.aeb1978
about 1 month ago
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C. N. Yang was a towering figure in physics. And not, for the most part, for his Nobel-winning work.
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C. N. Yang, Dead at 103
I don't usually do obituaries here, but sometimes I have something worth saying. Chen Ning Yang, a towering figure in particle physics, died last week. Picture from 1957, when he received his Nobel I never met him. By the time I started my PhD at Stony Brook, Yang was long-retired, and hadn't visited the Yang Institute for Theoretical Physics…
http://4gravitons.com/2025/10/24/c-n-yang-dead-at-103/
about 2 months ago
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reposted by
Patrick Koppenburg đ§
about 2 months ago
Welcome to @CERN, Ireland.
add a skeleton here at some point
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AGI can be both scientific nonsense and a plausible technological goal.
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AGI Is an Economic Term, Not a Computer Science Term
I ran into this Bluesky post, and while a lot of the argument resonated with me, I think the author is missing something important. Shannon Vallor is a philosopher of technology at the University of Edinburgh. She spoke recently at a meeting honoring the 75th anniversary of the Turing Test. The core of her argument, recapped in the Bluesky post, is that artificial general intelligence, or AGI, represents an outdated scientific concept, like phlogiston.
http://4gravitons.com/2025/10/17/agi-is-an-economic-term-not-a-computer-science-term/
about 2 months ago
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Congratulations to this year's Physics Nobel laureates!
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Congratulations to John Clarke, Michel Devoret, and John Martinis!
The 2025 Physics Nobel Prize was announced this week, awarded to John Clarke, Michel Devoret, and John Martinis for building an electrical circuit that exhibited quantum effects like tunneling and energy quantization on a macroscopic scale. Press coverage of this prize tends to focus on two aspects: the idea that these three "scaled up" quantum effects to medium-sized objects (the…
http://4gravitons.com/2025/10/10/congratulations-to-john-clarke-michel-devoret-and-john-martinis/
2 months ago
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If you've got a theory, you don't just have to test it. You have to make sure it agrees with past tests, too.
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When Your Theory Is Already Dead
Occasionally, people try to give "even-handed" accounts of crackpot physics, like people who claim to have invented anti-gravity devices. These accounts don't go so far as to say that the crackpots are right, and will freely point out plausible doubts about the experiments. But at the end of the day, they'll conclude that we still don't really know the answer, and perhaps the next experiment will go differently.
http://4gravitons.com/2025/10/03/when-your-theory-is-already-dead/
2 months ago
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I suspect academic cheating is more complicated than people think. Anyone know of any good studies?
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Requests for an Ethnography of Cheating
What is AI doing to higher education? And what, if anything, should be done about it? Chad Orzel at Counting Atoms had a post on this recently, tying the question to a broader point. There is a fundamental tension in universities, between actual teaching and learning and credentials. A student who just wants the piece of paper at the end has no reason not to cheat if they can get away with it, so the easier it becomes to get away with cheating (say, by using AI), the less meaningful the credential gets.
http://4gravitons.com/2025/09/26/requests-for-an-ethnography-of-cheating/
3 months ago
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Something bugging me about recent black hole coverage:
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To Measure Something or to Test It
Black holes have been in the news a couple times recently. On one end, there was the observation of an extremely large black hole in the early universe, when no black holes of the kind were expected to exist. My understanding is this is very much a "big if true" kind of claim, something that could have dramatic implications but may just be being misunderstood.
http://4gravitons.com/2025/09/19/to-measure-something-or-to-test-it/
3 months ago
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It's not just a cognitive bias
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What Youâre Actually Scared of in Impostor Syndrome
Academics tend to face a lot of impostor syndrome. Something about a job with no clear criteria for success, where you could always in principle do better and you mostly only see the cleaned-up, idealized version of others' work, is a recipe for driving people utterly insane with fear. The way most of us talk about that fear, it can seem like a cognitive bias, like a failure of epistemology.
http://4gravitons.com/2025/09/12/what-youre-actually-scared-of-in-impostor-syndrome/
3 months ago
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It's been a while since the era you could uncover the laws of the universe by tinkering with rocks.
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The Rocks in the Ground Era of Fundamental Physics
It's no secret that the early twentieth century was a great time to make progress in fundamental physics. On one level, it was an era when huge swaths of our understanding of the world were being rewritten, with relativity and quantum mechanics just being explored. It was a time when a bright student could guide the emergence of whole new branches of scholarship…
http://4gravitons.com/2025/09/05/the-rocks-in-the-ground-era-of-fundamental-physics/
3 months ago
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Scientific fraud is a serious problem. It's also more than one thing, and conflating the two makes science appear much less trustworthy than it actually is.
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Two Types of Scientific Fraud: for a Fee and for Power
A paper about scientific fraud has been making the rounds in social media lately. The authors gather evidence of large-scale networks of fraudsters across multiple fields, from teams of editors that fast-track fraudulent research to businesses that take over journals, sell spots for articles, and then move on to a new target when the journal is de-indexed. I'm not an expert in this kind of statistical sleuthing, but the work looks impressively thorough.
http://4gravitons.com/2025/08/29/two-types-of-scientific-fraud-for-a-fee-and-for-power/
3 months ago
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reposted by
Quanta Magazine
4 months ago
Hundreds of signals from colliding black holes over the past decade show that if black holes are sporting quantum âhair," it must be very short.
@4gravitons.bsky.social
reports:
www.quantamagazine.org/astrophysici...
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Astrophysicists Find No âHairâ on Black Holes | Quanta Magazine
According to Einsteinâs theory of gravity, black holes have only a small handful of distinguishing characteristics. Quantum theory implies they may have more. Now an experimental search finds that any...
https://www.quantamagazine.org/astrophysicists-find-no-hair-on-black-holes-20250827/
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Some bad, but hopefully interesting, ideas to improve AI:
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Some Dumb AIÂ Ideas
Sometimes, when I write a post about AI, I've been sitting on an idea for a long time. I've talked to experts, I've tried to understand the math, I've honed my points and cleared away clutter. This is not one of those times. The ideas in this post almost certainly have something deeply wrong with them. But hopefully they're interesting food for thought.
http://4gravitons.com/2025/08/22/some-dumb-ai-ideas/
4 months ago
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GPS satellites test general relativity constantly. But we need other tests too:
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Technology as Evidence
How much can you trust general relativity? On the one hand, you can read through a lovely Wikipedia article full of tests, explaining just how far and how precisely scientists have pushed their knowledge of space and time. On the other hand, you can trust GPS satellites. As many of you may know, GPS wouldn't work if we didn't know about general relativity.
http://4gravitons.com/2025/08/15/technology-as-evidence/
4 months ago
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reposted by
Philip Ball
4 months ago
Heisenberg on Bohr's occasionally excesssively generous nature. One of the first lessons learnt as a Nature editor about the "fringe" submissions is that this is exactly what will happen if you let it.
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By definition, journalists try to only cover news that is newsworthy. What does that mean for science journalism?
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Newsworthiness Bias
I had a chat about journalism recently, and I had a realization about just how weird science journalism, in particular, is. Journalists arenât supposed to be cheerleaders. Journalism and PR have very different goals (which is why I keep those sides of my work separate). A journalist is supposed to be uncompromising, to write the truth even if it paints the source in a bad light.
http://4gravitons.com/2025/08/08/newsworthiness-bias/
4 months ago
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For those interested in more detail after reading my piece on fermions and bosons, here's a little light topology
add a skeleton here at some point
4 months ago
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Did Einstein do "vibe physics"? Kind of, but not the way you're trying to.
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Microdosing Vibe Physics
Have you heard of "vibe physics"? The phrase "vibe coding" came first. People have been using large language models like ChatGPT to write computer code (and not the way I did last year). They chat with the model, describing what they want to do and asking the model to code it up. You can guess the arguments around this, from people who are convinced AI is already better than a human programmer to people sure the code will be riddled with errors and vulnerabilities.
http://4gravitons.com/2025/08/01/microdosing-vibe-physics/
4 months ago
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reposted by
Opal
5 months ago
With Tom Lehrer's passing, I suppose this is a moment to share the story of the prank he played on the National Security Agency, and how it went undiscovered for nearly 60 years.
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reposted by
Ben Brubaker
5 months ago
Missed opportunity for a perfect headline: "I believe that Claude believes in God"
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Claude Finds GodâAsterisk
â»[Perfect stillness]â»
https://asteriskmag.com/issues/11/claude-finds-god
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There is a type of theory that isn't meant to be tested. How do physicists evaluate them?
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Value in Formal Theory Land
What makes a physics theory valuable? You may think that a theory's job is to describe reality, to be true. If that's the goal, we have a whole toolbox of ways to assess its value. We can check if it makes predictions and if those predictions are confirmed. We can assess whether the theory can cheat to avoid the consequences of its predictions (falsifiability) and whether its complexity is justified by the evidence (Occam's razor, and statistical methods that follow from it).
http://4gravitons.com/2025/07/25/value-in-formal-theory-land/
5 months ago
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We all hate hype. But it's not as easy to define as you'd think:
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Hype, Incentives, and Culture
To be clear, hype isn't just lying. We have a word for when someone lies to convince someone else to pay them, and that word is fraud. Most of what we call hype doesn't reach that bar. Instead, hype lives in a gray zone of affect and metaphor. Some hype is pure affect. It's about the subjective details, it's about mood.
http://4gravitons.com/2025/07/18/hype-incentives-and-culture/
5 months ago
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reposted by
Daniel Green
5 months ago
In fact, the reason the SPT result is lower than previous ones is that they use a different value for the optical depth (there are multiple values that come from Planck that are just slightly different ways of analyzing the low-ell data). The SPT data isnât actually driving this.
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reposted by
Daniel Green
5 months ago
The really critical point is that âmore dataâ is not a solution. Because of the peculiar nature of the neutrino mass measurement, it is limited by measurements that will be very difficult to repeat and may not happen again for 15 years
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The South Pole Telescope did not just rule out massive neutrinos. But here's why it might look that way:
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Did the South Pole Telescope Just Rule Out Neutrino Masses? Not Exactly, Followed by My Speculations
Recently, the South Pole Telescope's SPT-3G collaboration released new measurements of the cosmic microwave background, the leftover light from the formation of the first atoms. By measuring this light, cosmologists can infer the early universe's "shape": how it rippled on different scales as it expanded into the universe we know today. They compare this shape to mathematical models, equations and simulations which tie together everything we know about gravity and matter, and try to see what it implies for those models' biggest unknowns.
http://4gravitons.com/2025/07/11/did-the-south-pole-telescope-just-rule-out-neutrino-masses-not-exactly-followed-by-my-speculations/
5 months ago
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Some bonus info for my (three!) pieces last week:
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Bonus Info on the LHC and Beyond
Three of my science journalism pieces went up last week! (This is a total coincidence. One piece was a general explainer "held in reserve" for a nice slot in the schedule, one was a piece I drafted in February, while the third I worked on in May. In journalism, things take as long as they take.) The shortest piece, at Quanta Magazine, was an explainer about the two types of particles in physics: bosons, and fermions.
http://4gravitons.com/2025/07/04/bonus-info-on-the-lhc-and-beyond/
5 months ago
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I have a piece with Physics Today, about discussions over CERN's next big collider project:
pubs.aip.org/physicstoday...
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Europeâs particle-physics community weighs its next collider
Looking to solidify their post-LHC plans, CERN and its partners are considering an ambitious project that would stretch to the end of the century.
https://pubs.aip.org/physicstoday/online/44387
6 months ago
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Did you see the muon headlines? What actually changed?
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Why Solving the Muon Puzzle Doesnât Solve the Puzzle
You may have heard that the muon g-2 problem has been solved. Muons are electrons' heavier cousins. As spinning charged particles, they are magnetic, the strength of that magnetism characterized by a number denoted "g". If you were to guess this number from classical physics alone, you'd conclude it should be 2, but quantum mechanics tweaks it. The leftover part, "g-2", can be measured, and predicted, with extraordinary precision, which ought to make it an ideal test: if our current understanding of the particle physics, called the Standard Model, is subtly wrong, the difference might be noticeable there.
http://4gravitons.com/2025/06/27/why-solving-the-muon-puzzle-doesnt-solve-the-puzzle/
6 months ago
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I had a piece a couple days ago in Ars Technica, about a young researcher's quest to change how the LHC analyzes data:
add a skeleton here at some point
6 months ago
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I have a new short "explainer" piece with
@quantamagazine.bsky.social
, on two words you can hear physicists use for...well, pretty much everything.
add a skeleton here at some point
6 months ago
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reposted by
Brittany Bennett
6 months ago
Well this is fâin sad
#ASMicrobe
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Amplitudes 2025 was this week, and I've been skimming slides in my free time. Here's the highlights:
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Amplitudes 2025 This Week
Summer is conference season for academics, and this week held my old sub-field's big yearly conference, called Amplitudes. This year, it was in Seoul at Seoul National University, the first time the conference has been in Asia. (I wasn't there, I don't go to these anymore. But I've been skimming slides in my free time, to give you folks the updates you crave.
http://4gravitons.com/2025/06/20/amplitudes-2025-this-week/
6 months ago
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I have another piece up with FirstPrinciples! For this one, I interviewed the president of the Sloan Foundation, one of the US's most prestigious foundations that funds scientific research.
www.firstprinciples.org/article/how-...
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How the Sloan Foundation picks scientific winners
Sloan Foundation president Adam Falk is stepping down this year after seven years leading the iconic organization. He spoke with FirstPrinciples about how the foundationâs philosophy has given it an o...
https://www.firstprinciples.org/article/how-the-sloan-foundation-picks-scientific-winners
6 months ago
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Some bonus details for my two pieces last month:
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Bonus info for Reversible Computing and Megastructures
After some delay, a bonus info post! At FirstPrinciples.org, I had a piece covering work by engineering professor Colin McInnes on stability of Dyson spheres and ringworlds. This was a fun one to cover, mostly because of how it straddles the borderline between science fiction and practical physics and engineering. McInnes's claim to fame is work on solar sails, which seem like a paradigmatic example of that kind of thing: a common sci-fi theme that's surprisingly viable.
http://4gravitons.com/2025/06/13/bonus-info-for-reversible-computing-and-megastructures/
6 months ago
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reposted by
Tania Lombrozo
6 months ago
Laypeople often learn about science from expert explanations & those explanations often contain JARGON. Does jargon make explanations better or worse? In a paper out today in Nature Human Behaviour,
@cruzf.bsky.social
and I find that jargon can support illusions of understanding...
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This week I started on a new type of science writing work: communications consulting.
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Branching Out, and Some Ground Rules
In January, my time at the Niels Bohr Institute ended. Instead of supporting myself by doing science, as I'd done the last thirteen or so years, I started making a living by writing, doing science journalism. That work picked up. My readers here have seen a few of the pieces already, but there are lots more in the pipeline, getting refined by editors or waiting to be published.
http://4gravitons.com/2025/06/06/branching-out-and-some-ground-rules/
6 months ago
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reposted by
Sean Carroll
6 months ago
Postscript: David Chalmers organized a poll, by which we have established that not all Philosophy is Natural. I always suspected that some philosophy is Unnatural.
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I had a piece up last week in Scientific American! A few bonus details in this post:
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In Scientific American, With a Piece on Vacuum Decay
I had a piece in Scientific American last week. It's paywalled, but if you're a subscriber there you can see it, or you can buy the print magazine. (I also had two pieces out in other outlets this week. I'll be saying more about them...in a couple weeks.) The Scientific American piece is about an apocalyptic particle physics scenario called vacuum decay.
http://4gravitons.com/2025/05/30/in-scientific-american-with-a-piece-on-vacuum-decay/
6 months ago
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And another piece this week! This one in
@quantamagazine.bsky.social
, about a counterintuitive approach to computing:
www.quantamagazine.org/how-can-ai-r...
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How Can AI Researchers Save Energy? By Going Backward. | Quanta Magazine
Reversible programs run backward as easily as they run forward, saving energy in theory. After decades of research, they may soon power AI.
https://www.quantamagazine.org/how-can-ai-researchers-save-energy-by-going-backward-20250530/
6 months ago
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I have another piece out with FirstPrinciples! This was a fun one, about the math behind some classic science fiction concepts:
www.firstprinciples.org/article/engi...
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Engineering the implausible? Paper explores stable Dyson spheres and ringworlds
Artificial structures surrounding an entire star were thought to be impossible. A new calculation shows that they could be supported by the gravity of a second star.
https://www.firstprinciples.org/article/engineering-the-implausible-paper-explores-stable-dyson-spheres-and-ringworlds
7 months ago
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