This is a fun one - the period of a pendulum outside a Schwarzschild black hole ⌛ arxiv.org/abs/2608.00866
![We determine the small-oscillation period of a simple pendulum in
Schwarzschild spacetime. After transients decay, the displaced rope coincides with a geodesic of the induced spatial metric. This determines the radial lift of the bob to quadratic order in the angular amplitude and leads to the period measured by an observer at the bob's equilibrium position, $r=r_2$, with the fulcrum at $r_1$, \[ T_{(2)}=4\pi\frac{r_2^2}{c r_s}\sqrt{N_2(N_1-N_2)}, \]
where $N_i=N(r_i)$ and $N(r)=\sqrt{1-r_s/r}$ is the Schwarzschild lapse. The result is therefore expressed in terms of the same function that determines clock rates and gravitational redshifts. In the Newtonian limit, we reproduce the classical result $T=2\pi\sqrt{L_0/g}$. We interpret the period close to the horizon in terms of an effective pendulum length. We compare our treatment with the coordinate-length constraint adopted in an earlier study and argue that the two problems are inequivalent away from the classical, weak-field limit.](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:63u4oit6xk73kwpcc776tgap/bafkreicgf7frji6gsfds2mylqq5btuw43srjqx2s4lq7ecyi7s3s44jjse)
Dennis Just 🌵
@sciencepolice.bsky.social
Astronomy and physics professor, former Orbital Mechanic, and officially a Superhuman - cats, spaceflight, 日本語, gardening, and video games.
That wonderful feeling when you find out someone else is a Georges Méliès fan and it's time to geek out 🌙
Explored Mt. St. Helens and transformed it into a Halo Landscape. #landscape #AdobePhotoshop #Halo #Forerunner #ScenicLandscape
Before 99% of people had ever heard of starship/BFR, back when I was doing the podcast I predicted it'd be "shuttle-like": the thing would fly and serve some use, but wouldn't come *close* to achieving what was claimed. I still think I'll be proven right in the end. arstechnica.com/space/2026/0...
Experts warn current Starship heat shield tech is a "dead end" for rapid reuse
NASA has not made substantial investments in thermal protection research for decades.
arstechnica.com
@iwriteok.bsky.social Your latest episodes turning out to be quite topical. "Companies owned by an American government-and-military contractor [and special forces guy] have been operating several planes involved in logistics for the paramilitary Rapid Support Forces in Sudan." (From The Economist)
Oh cool, this was a fun surprise to see in my inbox this morning. Congrats, RayJay! 🔭 www.jpl.nasa.gov/news/caltech...
Caltech Welcomes Astrophysicist Ray Jayawardhana as New President
Taking the helm of the institute that manages JPL for NASA, the distinguished astrophysicist brings a lifelong interest in space exploration and a track record of scientific discovery.
jpl.nasa.gov
CIRIA V. GERRANS Cops coerced a man to fabricate evidence which then convicted a guy of murder. He's later exonerated after 32 years. The question - are the cops entitled to qualified immunity? 9th Cir. says no (thank god), but Trump judge says yes in dissent. law.justia.com/cases/federa...
CIRIA V. GERRANS, No. 24-3308 (9th Cir. 2026)
Joaquin Ciria was convicted in 1991 for the murder of Felix Bastarrica in San Francisco, based largely on the testimony of George Varela, who was 18 at the time and an accomplice to the actual shooter...
law.justia.com
I saw a throwaway reference to the shuttle’s elevons free-floating on-orbit during STS-41C, and my efforts to figure out why didn’t quite pan out 🚀 open.substack.com/pub/dennisju...
J.K. Simmons: What Did We Learn, Palmer?
Alt: J.K. Simmons: What Did We Learn, Palmer?
static.klipy.com
It's a small thing but I'm trying to get back into gardening. I just haven't really had time this past ~year or so 🌱
Hell yea! New Illusory Wall video, for anyone who wants to watch 45 minutes on the smell mechanic from Dark Souls 1 www.youtube.com/watch?v=y4SU...
How Enemies Detect You in Dark Souls: Part 2 - Smell
YouTube video by illusory wall
youtube.com
Go Cats!!
404 Media@404media.co · 3mo agoFormer Google CEO Eric Schmidt was booed throughout this commencement speech at the University of Arizona for his praise of AI. This comes just a week after another commencement speaker who mentioned AI was booed at a school in Florida. Read more: www.404media.co/ucf-ai-comme...
Nice on-orbit shot of Hubble ! "Collected on April 23, 2026, by one of Vantor's WorldView Legion satellites, this remarkable non-Earth image showcases Hubble from just 61.8 km away" Source: Vantor on the other site.
At the present moment I am not interested in anything politically beyond the destruction of the Republican Party as a viable political force. If we don't break the back of the conservative movement nothing else really matters. Whatever good shit you want to do won't happen.
The juxtaposition on arxiv is the best part of April 1st - you'll have "Protoplanetary Disk Evolution in a Low-Metallicity Environment: JWST's First Mid-Infrared Census of Low-Mass Stars" followed by "On The Detection of Digiorno-like Objects in the Flavor Zone" 🍕
As an already nervous flier, I really really hope navigating ORD is easy enough this week.
Dominique Baker@bakerdphd.bsky.social · 5mo agoI don't know what O'Hare did but I thank them for the nearly nonexistent lines today
My collaborator and friend's group is featured in this article on developing structures within lunar lava tubes. A number of my community college students have worked with him and gone on to do great things. Very cool! 🌙 www.asce.org/publications...
Lava tubes could make life on the moon possible
The structures, set deep beneath the lunar surface, are safe, efficient, and habitable with the right strategies and tools.
asce.org
Anyone with eclipse shades (or a welder's mask) and clear skies should check out this massive sunspot 4466. 10x larger than the Earth, you can see it's *shape* with the naked eye. Incredible ☀️
As far as I can tell, the Schmidt Observatory System is essentially “what are the best next-gen facilities coming online in the future? Ok yea let’s just build all of them nice and fast and synergize them w the rest of the community.” Incredible 📡🔭🔭🛰️
Schmidt Sciences@schmidtsciences.bsky.social · 7mo agoPacked splinter session at #AAS247 for the announcement of The Eric and Wendy Schmidt Observatory System—a modular, rapid-response network of four novel observatories designed to democratize access to the cosmos. Read more about the initiatives here: www.schmidtsciences.org/focus-area-a...
How cool is this - Cal Poly Pomona and SLO's float, the only one designed and built entirely by students, won the Rose Parade. The float's message is about the dangers of climate change, with a bunch of cute woodland animals repairing a damaged robot 🤖 www.cpp.edu/news/content...
Hey Martians, did I mention we now also have a video of epic Phobos passing over a Martian dust storm near Pavonis Mons? 🌪️🌋🥔 Video & full info: flic.kr/p/2rNN8wk Credit: ESA/DLR/FUBerlin/AndreaLuck CC BY @esa.int Mars Express HRSC 300 MP Photo quoted below Easy zoom: easyzoom.com/image/674026
Andrea Luck@andrealuck.bsky.social · 8mo ago1/n 2 NEW epic images of Phobos over Mars just released by @esa.int Mars Express This view is especially striking, with Phobos between the Tharsis volcanoes and Noctis Labyrinthus–Valles Marineris Full resolution 300MP(!) & info on: flic.kr/p/2rMW4so Credit: ESA/DLR/FUBerlin/AndreaLuck CC BY 🧪🔭
I'm very happy I woke up at 4am this morning to catch 3I/ATLAS right before its closest approach to Earth (today!) This interstellar visitor is traveling over 60 km/s ☄️ At 269 million km (1.8 AU), I took a series of 2.5 min exposures with my Seestar 🔭
Just a little PSA - if you have any solar eclipse shades (or a welder's mask), you should try and check out the massive sunspot group that has rotated into view these past few days. It looks so big it may be naked-eye visible, which is pretty neat!
Today’s big Thanksgiving goal is to finally, after all these decades, beat 7th Saga 🎮 🐈⬛
