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Greg Egan

@gregegansf.bsky.social
2.6K followers 119 following 1K posts

SF writer / computer programmer Latest novel: MORPHOTROPHIC Latest collection: SLEEP AND THE SOUL Web site: gregegan.net Also: @gregeganSF@mathstodon.xyz

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Greg Egan @gregegansf.bsky.social · 30/09/2026
Graham’s conjecture (1971): Modulo some prime p, can you find a way to order any subset of {1,...,p-1} so that its successive partial sums are all distinct? www.quantamagazine.org/mathematicia...
quantamagazine.org
Mathematicians Harness Randomness To Crack a 55-Year-Old Conjecture | Quanta Magazine
After a long hiatus, the problem, which was likely inspired by juggling, has finally been resolved by a group of young mathematicians.
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Greg Egan @gregegansf.bsky.social · 29/09/2026
L’adaptation en bande dessinée de la nouvelle Le Coffre-Fort de Greg Egan, sublimée par le graphisme singulier de Clément C. Fabre. Une histoire fascinante autour de l’identité, de la mémoire et des vies que l’on traverse…
Image of a man, with the words "Un jour, j'écrirai mon nom" replacing his face. At the top of the image, Clément C. Fabre, d'aprés Greg Egan.
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Greg Egan @gregegansf.bsky.social · 28/09/2026
Oh, Hostinger, have you no shame?
Superintelligence – SI – is what everyone's suddenly calling AI. And as luck would have it, .si has been a real domain all along, just waiting for its moment.
We got it live. Grab yours before the good names are gone.
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Carl Zimmer @carlzimmer.com · 27/09/2026
Four days ago, a scientist was surprised by the news that Anthropic discovered new virus genes for making DNA. He says he’s been studying them for years—and feeding his data to Anthropic’s AI as part of his own research. Coincidence? Here’s my story. nyti.ms/3VSWayc
nyti.ms
Did Anthropic’s A.I. Really Make a Scientific Discovery on Its Own? (Gift Article)
An expert at the University of Copenhagen said his team had been sharing its research with the company’s A.I. model, Claude, and that its new finding matched their work.
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Greg Egan @gregegansf.bsky.social · 27/09/2026
I was aware of Google announcing an implementation of Shor’s algorithm that needed substantially fewer qubits than previous methods, but I missed the bit where they released a Zero Knowledge Proof of their claim ... www.scientificamerican.com/article/why-...
scientificamerican.com
Why mathematicians are suddenly hiding research results
Google made a major breakthrough in quantum computing. To prevent the results from being misused, the company kept them secret. That backfired
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David Roberts @volts.wtf · 26/09/2026
Class solidarity.
hollywoodreporter.com
The Major Social Media Platforms Are All Rejecting Paid Ads for Alex Gibney’s ‘Musk’ (Exclusive)
YouTube, TikTok and Meta have all turned down the trailer for the Oct. 9 doc, citing "political" content. X won't even take Bleecker Street's calls. The distributor is appealing.
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Greg Egan @gregegansf.bsky.social · 23/09/2026
Let’s hope that it doesn’t turn out that there’s a condition that closely resembles this, to the point where it could easily be mistaken for it, while actually being quite different. en.wikipedia.org/wiki/Pseudop...
en.wikipedia.org
Pseudopseudohypoparathyroidism - Wikipedia
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Greg Egan @gregegansf.bsky.social · 22/09/2026
Breaking: Tilly Norwood, Max Headroom quizzed on their positions re destroying all humanity in Senate confirmation hearings for AI Czar.
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Greg Egan @gregegansf.bsky.social · 22/09/2026
I just had the pneumococcus vaccine [free for people 65+ in Australia]. It contains sugars from 21 types of pneumococcus, linked to CRM197 — a version of diphtheria toxin that is highly immunogenic, but rendered non-toxic by a single mutation, altering just 1 of 535 amino acids.
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Michael Busch @michael-w-busch.bsky.social · 19/09/2026
The large main-belt asteroid 216 #Kleopatra and its moons will have an occultation along a swath from Ireland to Ukraine on 2026 September 22: cloud.occultwatcher.net/event/2090-2... . For anyone who would like to chase the shadows. (It may also be barely visible from Greenland, but at dusk.)
cloud.occultwatcher.net
OccultWatcher Cloud
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Greg Egan @gregegansf.bsky.social · 18/09/2026
Laurie Metcalf as Phyllis Gardner in “The Dropout”: “Don’t ever quote Yoda to anybody ever again.”
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Corey S. Powell @coreyspowell.bsky.social · 16/09/2026
Wow: Giant new impact crater spotted on the Moon! An asteroid the size of an apartment building hit the lunar surface in early 2024 & created 220-meter (730-foot) wide McGetchin crater. It's "the largest contemporary impact crater found in the Solar System." 🧪🔭 science.nasa.gov/solar-system...
Officially named McGetchin after pioneering lunar scientist Tom McGetchin, the crater formed on the Moon’s eastern edge sometime between April 11 and May 22, 2024, after a comet or asteroid the size of a three- to six-story building hit the surface.
 
The crash left a crater, 728 feet wide, that spans the length of two football fields. And at 141 feet deep, the crater could fit three vertically stacked yellow school buses. Scientists estimate that an impact of this magnitude happens on the Moon about once in a century or even longer.
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Greg Egan @gregegansf.bsky.social · 15/09/2026
Now more than ever we need a Saturday Night Live sketch with Matthew Rhys playing Dario Amodei.
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Greg Egan @gregegansf.bsky.social · 14/09/2026
TIL from @dandkuniverse.bsky.social that you can sometimes hear meteors burning up in the atmosphere *at the same time as you see them*, despite the discrepancy in the speed of light and the speed of sound. How? Here is an abstract from a relevant paper:
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Michael Busch @michael-w-busch.bsky.social · 14/09/2026
When an orbit is eccentric enough that the seasons from eccentricity win over those from obliquity.
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David Ho @davidho.bsky.social · 12/09/2026
I wrote this quickly at a bus stop and didn't realize it would go viral, or else I would have worded it better. But the point is that the media is too credulous about AI killing everyone in 10 years (how?) when climate change is killing people now and will only get worse (we know exactly how).
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Greg Egan @gregegansf.bsky.social · 11/09/2026
Breaking: a team of human mathematicians working in secret over the last 3 years, and at least two frontier AI labs with 7-figure budgets, are believed to be neck-and-neck in a race to determine whether the Birch-Swinnerton-Dyer conjecture was posed by three people, or just two.
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Greg Egan @gregegansf.bsky.social · 10/09/2026
Open Letter about the Mathathon This open letter calling for the cancellation of the Caltech “Mathathon”, has received 471 signatures so far. [Only members of the Caltech community or mathematicians at PhD student level or beyond are eligible to sign.]
docs.google.com
Open Letter about the Mathathon
The full text of the open letter is below. By signing this open letter, you consent to your name, title, and institutional affiliation being publicly displayed beneath this open letter. You can access...
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Greg Egan @gregegansf.bsky.social · 06/09/2026
In the free group generated by four letters, if you remove any two letters (and their inverse) from this product of 16 elements: 𝑎𝑏𝑎⁻¹𝑏⁻¹𝑐𝑑𝑏𝑎𝑑⁻¹𝑐⁻¹𝑑𝑐𝑏⁻¹𝑎⁻¹𝑐⁻¹𝑑⁻¹ it simplifies to 1, but dropping any single letter does not give 1.
A picture bearing the words “This picture hangs insecurely on 4 nails”, hanging from a string that winds in a complicated way around four nails.
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Gro-Tsen @gro-tsen.bsky.social · 02/09/2026
Example of mathematical naïveté: Yesterday I wondered if, when E ⊆ ℝ^m is locally closed (viꝫ. the intersection of a closed and an open set) and of Lebesgue measure zero then, its closure is also of measure zero. “Surely this is true”, I thought. Narrator: “But it was not.”
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Greg Egan @gregegansf.bsky.social · 02/09/2026
I’ve walked past this door (in Sir Charles Gairdner Hospital) a few times, but today I finally gave in to the urge to take a picture, because ... physics! [I once worked in the Medical Physics dept of a different hospital, so I guess this is the same kind of dept, though I’m not actually sure.]
A picture of two grey swing doors with the words WELCOME TO PHYSICS written on them in black tape.
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Greg Egan @gregegansf.bsky.social · 31/08/2026
“A mathematical question is much more than a theorem waiting to be proved; it is a source of momentum. First and foremost, it is a lighthouse in the night: it illuminates and guides mathematicians in their wanderings, both esthetic and scientific.” proofsandprompts.com/2026/08/30/c...
proofsandprompts.com
Care for a little more AI?
Hugo Duminil-Copin, Professor at Université de Genève and IHES Disclaimer. The effects of AI are vast, and there is much to be said about its broader impact on society. One should also remind that …
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Richard Sever @richardsever.bsky.social · 31/08/2026
"When you find yourself writing such a statement about a topic you’re not an expert in, there are only two possibilities: 1. You are not talking to the right people. 2. You are talking to the right people but you’re not listening" blog.genesmindsmachines.com/p/im-sorry-y...
blog.genesmindsmachines.com
I'm sorry, you're not going to die from an AI-engineered supervirus
God save us from economists who think they can competently talk about biology
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Ben Recht @beenwrekt.bsky.social · 30/08/2026
The METR people, who have gone around in public, spouting beyond-insane AGI religious beliefs, found exactly what you'd think they'd find. They anthropomorphised software that is built to emit English. 6/x
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Davide Castelvecchi @castelvecchi.bsky.social · 30/08/2026
Stay tuned for @nature.com coverage by yours truly!
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Greg Egan @gregegansf.bsky.social · 28/08/2026
Every time they played “Nine to Five” on the radio this week it turned into an unstable earworm that kept slipping into the adjacent attractor in music-space for “Heart of Glass”. But now I just learned that Dolly Parton did a *cover* of “Heart of Glass” in 2023 featuring Debbie Harry …
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ESA Space Science @science.esa.int · 25/08/2026
T – 5️⃣ days to #NASARoman launch day   Like ESA’s Euclid, Roman will study: ✔️dark matter ✔️dark energy & expansion of the Universe ✔️exoplanets Read more 👉  www.esa.int/Science_Exploration/Spa…  🔭🧪 #cosmology #exoplanets
Artist’s impression of the Roman Space Telescope depicting the spacecraft floating against a vivid purple background studded with distant galaxies.
CREDIT: NASA Goddard Space Flight Center 
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Greg Egan @gregegansf.bsky.social · 24/08/2026
The first improvement in the “Komlós combinatorial discrepancy problem” in ~30 yrs (and it wasn’t done with AI). Given N unit-length vectors in R^d, partition them into two subsets, A and B, so the sum of the vectors in A and in B differ in every component as little as possible.
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Greg Egan @gregegansf.bsky.social · 20/08/2026
Wow, not only have astronomers found a star that comes so close to the black hole at the centre of our galaxy that a detailed study of its orbit over the next decade should be able to quantify the black hole’s spin, there is a chance that future spectroscopic analysis will show…
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Greg Egan @gregegansf.bsky.social · 20/08/2026
Just had my 1st dose of shingles vaccine. A few relatives have had shingles in the last few years, and it was *very* unpleasant. In Australia, the Shingrix vaccine is now free for 65+, so if you don’t want your childhood chickenpox infection waking up to torment you again ...
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Greg Egan @gregegansf.bsky.social · 19/08/2026
If you pick 3 points at random on a unit sphere, the average radius, R, of the circle that contains them is 7/6. For 3 points on a flat disk of radius ρ, mean(R) diverges. However, the curvature, κ = 1/R, has a finite mean which can be computed exactly: 16 (3 – 16/π^2) / (15ρ)
A disk in light blue with radius rho, and a black circle of radius R that intersects it along an arc whose half-angle is a. The centre of the black circle is a distance r from the centre of the disk. Three points are marked along the arc, labelled phi 1, phi 2 and phi 3.
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Greg Egan @gregegansf.bsky.social · 18/08/2026
TIL about “cancellous bone”. I’d previously misunderstood what the solid sample taken in a bone marrow biopsy was composed of; I thought it was part of the outer, “cortical” bone. But today the doctor doing the biopsy showed me the sample and explained exactly what it was.
A micrograph of cancellous bone, looking a bit like a river junction with the solid parts like land and the softer parts like a pink river.
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Greg Egan @gregegansf.bsky.social · 13/08/2026
AIs hallucinating that the patients whose medical notes they are transcribing used illegal drugs. What could possibly go wrong? www.abc.net.au/news/2026-08...
abc.net.au
Doctor forced to apologise after AI makes 'scary' error about illegal drugs
Artificial Intelligence is listening to many people's medical appointments, but it is not always hearing things correctly.
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Michael Busch @michael-w-busch.bsky.social · 11/08/2026
I first heard planetary scientists argue about when Pluto's atmosphere would freeze 20 years ago. The outer solar system is great for learning patience.
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Greg Egan @gregegansf.bsky.social · 10/08/2026
Breaking: Mark Zuckerberg reveals that Meta plans to create Artificial Super Intelligence by redrawing the scale on the Intelligence knob so it goes up to 11.
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Clarkesworld @clarkesworldmagazine.com · 09/08/2026
Ok folks, Sheila and her family need our help. You might know her as the editor of Asimov’s, but she's also a good friend and one of the best people in the field. If you can, please... www.gofundme.com/f/help-irene...
gofundme.com
Donate to Help Irene's Parents Get Skilled Nursing Care, organized by Irene Bruce
Hi - This is Irene and Juliet, the daughters of Sheila and David. As many of… Irene Bruce needs your support for Help Irene's Parents Get Skilled Nursing Care
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Greg Egan @gregegansf.bsky.social · 09/08/2026
A conference in honor of Jean-Pierre Serre on the occasion of his 100th birthday will be held in Paris on September 15 and 16, 2026. Speakers: Pierre Deligne, Ramon van Handel, Peter Sarnak, Maryna Viazovska, Don Zagier and possibly Jean-Pierre Serre. www.reddit.com/r/math/comme...
reddit.com
From the math community on Reddit
Explore this post and more from the math community
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Claudine Monteil @claudinemonteil.bsky.social · 09/08/2026
Yes my father is still active mathematically every day. He will be 100 in one month and will give a talk at a colluquium in his honor on September 15.
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Greg Egan @gregegansf.bsky.social · 07/08/2026
No laser? No problem? “Here, we demonstrate, for the first time, that sunlight … can produce entangled-photon pairs via [spontaneous parametric down-conversion] despite its lack of optical coherence.” www.scientificamerican.com/article/phys... Open-access paper: opg.optica.org/optica/fullt...
scientificamerican.com
Sunlight could be the key to making quantum computers less energy-hungry
A proof-of-principle experiment used concentrated sunlight to produce entangled photons
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Greg Egan @gregegansf.bsky.social · 06/08/2026
Not sure why I need to provide my parents’ occupations on the form for donating my body to the local medical school. It’s not as if we’re living in a medieval village where John, son of the blacksmith John, needs to be carefully distinguished from John, son of the innkeeper John.
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Greg Egan @gregegansf.bsky.social · 06/08/2026
There was a viral joke recently about the 3 largest cities in Germany all lying on a circle … but whether that made you laugh or groan, it gives me an excuse to mention 3 non-trivial things about the circle through 3 points on 3 kinds of surface.
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Greg Egan @gregegansf.bsky.social · 06/08/2026
Data centres powered by gas or coal should be 100% steampunk, full of hissing, clanking Babbage engines, tended by grimy-faced urchins who risk being crushed between the gears as they clear out all the sparrow's-nest malware with chimney-sweep brushes. www.abc.net.au/news/2026-08...
abc.net.au
Commonwealth says it will block gas-fired data centres
The NT government has rejected a federal plan to mandate the use of renewables for new large-scale data centres, but the Commonwealth says it will block proposals that rely on gas.
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Lana Sinapayen @sinalana.eurosky.social · 05/08/2026
Watch moon impact live: www.youtube.com/watch?v=-PRp...
youtube.com
AICO Falcon9 Lunar Impact Livestream_Aug 5 2026
YouTube video by YorkUObservatory
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Greg Egan @gregegansf.bsky.social · 03/08/2026
The fatal Hendra virus was an infamous spillover from bats to horses to humans in Australia in the 1990s. Since then, ecologists, bat experts and virologists have learned a lot about these events, perhaps including mitigating strategies. www.theguardian.com/science/2026...
theguardian.com
A mystery virus started killing horses. Then humans. Was this the moment our coronavirus era began?
In the 1990s, scientists in Australia began searching for the origins of a new disease showing up in places hundreds of kilometres apart. They discovered the origin: bats. And found a way to reduce th...
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Greg Egan @gregegansf.bsky.social · 03/08/2026
“All previous identifications of asteroids with a neck have been interpreted as ‘bilobates’, having just two lobes, but (44) Nysa has a unique ‘trilobate’ structure.” www.eso.org/public/video...
eso.org
Unmasking an unusual asteroid
Unmasking an unusual asteroid
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Clarkesworld @clarkesworldmagazine.com · 01/08/2026
Clarkesworld has recently discovered that their August issue successfully breached containment and gained access to the Internet, where it is presently hacking reader's minds. "Oh no, what will we do? Who knew that stories could be so powerful?" said Neil Clarke, when approached for comment.
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Greg Egan @gregegansf.bsky.social · 01/08/2026
I quite like “Sugar” but honestly they could have just made him a quirky cinephile detective with some other secret than [redacted as might still be a spoiler for some people], which is completely ridiculous and has no effect on 90% of what happens.
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Rodney Brooks @rodneyabrooks.bsky.social · 31/07/2026
1/3 How do you feel about living in a world full of rude robots that have been trained to navigate from watching first person shooter games and to treat you as an NPC (non player character)? [Admittedly, in such a game it is better to be an NPC...] I asked Gemini about this new set of startups:
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Lana Sinapayen @sinalana.eurosky.social · 31/07/2026
Nobody even glanced at the slop before sending it in. No one saw the left arrow turning in itself and thought "mmm", wondered why Cote d'Ivoire has no coast. They are not simply incompetent, they don't care at all, probably because they know every sentence they ever say is a lie anyway
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Greg Egan @gregegansf.bsky.social · 30/07/2026
When setting a default name for the PDFs your customers download for their records, maybe try to find a Goldilocks zone between Mercury ("getPDF.pdf" for every file) and the Oort Cloud ([64 hex digits guaranteed unique across the universe, and utterly meaningless to humans].pdf)
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