Leonardo Petrillo
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92sciencemusic.bsky.social
Leonardo Petrillo
@92sciencemusic.bsky.social
260 followers 100 following 200 posts
Physicist (MSc in theoretical physics); scientific blogger (https://scienzaemusica.blogspot.com/); appreciator of music, especially classical-jazz. Expert and theorycrafter on some kinds of videogames, including Diablo, Hearthstone
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92sciencemusic.bsky.social
Leonardo Petrillo @92sciencemusic.bsky.social · Mar 12
🧪⚛️ Update: yesterday the discussion went well...110 cum laude + direct compliments from the counter-rapporteur for the quality of the thesis! 🥳
Here you can find the complete slides of the presentation: docs.google.com/presentation...
Reposted by Leonardo Petrillo
johncarlosbaez.bsky.social
Ever wonder about the math hiding in music? There's a lot of it, and it's really fun! Here's a first take on some of it.

(When you're done, you'll know why musicians have special names for the numbers 81/80 and 128/125.)

johncarlosbaez.wordpress.com/2025/12/26/t...
The Mathematics of Tuning Systems
I’m giving a talk on the math of tuning systems at Claremont McKenna College on January 30th at 11 am. If you’re around, please come! You can read my slides here: • The mathematics…
johncarlosbaez.wordpress.com
December 26, 2025 at 3:18 PM
Reposted by Leonardo Petrillo
johncarlosbaez.bsky.social
New result: you can build a universal computer using a single billiard ball on a carefully crafted table!

More precisely: you can create a computer that can run any program, using just a single point moving frictionlessly in a region of the plane and bouncing off the walls elastically.

(1/n)
Classical billiards can compute Eva Miranda, Isaac Ramos We show that two-dimensional billiard systems are Turing complete by encoding their dynamics within the framework of Topological Kleene Field Theory. Billiards serve as idealized models of particle motion with elastic reflections and arise naturally as limits of smooth Hamiltonian systems under steep confining potentials. Our results establish the existence of undecidable trajectories in physically natural billiard-type models, including billiard-type models arising in hard-sphere gases and in collision-chain limits of celestial mechanics. Significance statement. Billiards are a textbook model of deterministic motion: a particle moves freely and reflects specularly from rigid walls. We show that, even in two dimensions, billiard trajectories can simulate arbitrary Turing machines. This universality implies a sharp limit on prediction: there is no general algorithm that can decide basic questions such as whether a trajectory is periodic. Because billiards also arise as limits of smooth Hamiltonian systems with increasingly steep confining potentials, these algorithmic barriers are not confined to idealized hard-wall models. Our results place undecidability, alongside chaos, as a fundamental obstruction to long-term prediction even in low-dimensional classical dynamics. From here: https://arxiv.org/abs/2512.19156
December 23, 2025 at 10:21 AM
Reposted by Leonardo Petrillo
drnereide.bsky.social
Did you know that a #rainbow makes a full 360 degree circle?

In this photo, an entire rainbow was captured over Cottesloe Beach near Perth by a helicopter.

From the ground, typically, only the top portion...⤵️

➡️ apod.nasa.gov/apod/ap14093...

🔭 🧪 ⚛️ #science #naturephotography #sciart

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Aerial helicopter photo showing a complete circular rainbow arching over a coastal Australian landscape. The bright primary rainbow displays full spectrum colors in a perfect ring, with a dimmer secondary one outside it featuring reversed hues. Below lies sandy shoreline, crashing waves in teal ocean, green fields, urban areas, and a stormy sky lit by setting sun.
December 26, 2025 at 9:54 PM
Reposted by Leonardo Petrillo
drnereide.bsky.social
This #Christmas🎄, instead of leaving Tiny Tim locked in a potentially dangerous box, we choose the more humane path: carefully removing every risk & helping him emerge safe & sound.

A gentle reminder that true science goes hand in hand with compassion💜, & that kindness🌺 always lights up the world✨
astrokatie.com Katie Mack @astrokatie.com · 2d
[breathing a sigh of relief as I carefully remove the poison, hammer, Geiger counter, and radioactive source before helping Tiny Tim out of the box]
December 25, 2025 at 9:11 AM
Reposted by Leonardo Petrillo
drnereide.bsky.social
"Christmas is not in tinsel and lights and outward show.

The secret lies in an inner glow.

It's lighting a fire inside the heart.
[...]
It's glorious dream in the soul of man."

~ W. A. Peterson in 'The Art of Living'

#MerryChristmas everybody✨🎄🎅

➡️ eso.org/public/image...

🔭 🧪 #Universe
#ESO pic of the NGC 2264 region that includes the #Christmas Tree Cluster. You've got these young stars shining like bright blue ornaments on a cosmic tree made of reddish and greenish gas clouds. Down there's the dark Cone #Nebula sticking out like a shadowy cone. They built this color image using four filters – B, V, R, and H-alpha – with the Wide Field Imager at ESO's La Silla Observatory up in the Chilean Andes.
December 24, 2025 at 3:56 PM
Reposted by Leonardo Petrillo
drnereide.bsky.social
Running a bit late on solstice cheers, but this #Hubble image alone is pure gold: breathtaking face-on view of spiral galaxy NGC 1309. 🔭

Bonus — it has helped us nail down the cosmic distance ladder using Cepheids and Type Ia supernovae.

Definitely worth your time — go read the article! 🧪📖
philplait.bsky.social Phil Plait @philplait.bsky.social · 4d
I gripe a little bit about the ambiguity of the word "day" — astronomically speaking, of course — and also present you with a *gorgeous* Hubble shot of a face-spiral galaxy that turns out to be part of the puzzle that tells us how the universe expands.

badastronomy.beehiiv.com/p/happy-sols...

🔭 🧪
Happy solstice, and a gorgeous galaxy with which to measure the Universe
The longest night is now behind us, and a Hubble image of a galaxy used as a ruler
badastronomy.beehiiv.com
December 23, 2025 at 9:54 AM
Reposted by Leonardo Petrillo
drnereide.bsky.social
🧵
Westerlund 2 looks just like a holiday scene in this new, magical image from the JWST.

Those red and orange gas clouds and thousands of bright stars recall the #Christmas vibe.

➡️ esawebb.org/images/potm2...

🔭 🧪 #Webb #Universe #galactic #JWST

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Image Description (from the source linked in the thread): "A cluster of stars inside a large nebula. The clouds of gas and dust are predominantly bright red in colour and wispy, akin to flames. They are clumped in the bottom-left corner. Other clouds, deeper in the cluster behind many of the stars, appear pale pink. The stars are concentrated in the top half of the image and are mostly small, bright white and six-pointed. They cast blue light over the nebula. Other stars with very long spikes surrounding them lie in the foreground."
December 22, 2025 at 7:16 PM
Reposted by Leonardo Petrillo
drnereide.bsky.social
Today, the December solstice occurred at 15:03 UT. 🔭

Although the #solstice itself lasts only a moment, the term also refers to the day on which it occurs. It marks the shortest and longest day of the year respectively in the Northern & Southern Hemisphere. 🧪

➡️ www.youtube.com/watch?v=kS57...

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December 21, 2025 at 4:35 PM
Reposted by Leonardo Petrillo
drnereide.bsky.social
"On that blue dot, that's where everyone you know and everyone you ever heard of, and every human being who ever lived, lived out their lives."

― #CarlSagan

December 20, 1996: Carl Sagan passed away.

🔭 🧪 #PaleBlueDot #Voyager1 #HistSci #Science

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It's the 2020 remastered version of that famous Pale Blue Dot pic —taken by Voyager 1 from about six billion kilometers out in space. The picture shows a bluish vastness, broken up by faint vertical streaks of light that got scattered inside the camera. Right there in one of those rays—just a little to the right of center—hangs the famous tiny pale blue speck, barely even a full pixel. That's Earth highlighted by a simple, added arrow. Across the image you may read Carl Sagan's words: "Look again at that dot. That's here. That's home. That's us.
December 20, 2025 at 6:27 PM
Reposted by Leonardo Petrillo
drnereide.bsky.social
Picture a stellar newborn that, between one hiccup and the next, launches jets of gas at insane speeds, leaving behind a trail of rings like footprints in the cosmos. 🔭

That's the story told by the recent discovery on SVS 13, a protostar...

➡️ www.almaobservatory.org/en/press-rel...

🧪 #Science 1/9
The Hubble background shows a dramatic dark cavity carved through the nebula by the outflow from young star SVS 13. Toward the lower right, a few soft orange-red glowing spots mark the Herbig-Haro knots—places where the invisible jet hits gas and makes it shine.A plain white box picks out the zoomed area. ALMA adds colored outlines of the molecular gas in the jet's brightest bullet. Deep red marks slower material (about 35 km/s), warming to orange and yellow, then sharp blue for the fastest (up to 97 km/s). The bluer the color, the smaller and farther southeast the rings get, clearly sketching thin curved shock shells from the jet's varying pulses. Hubble's visible light meets ALMA's hidden radio view here.
December 19, 2025 at 2:25 PM
Reposted by Leonardo Petrillo
drnereide.bsky.social
Emblematic anecdote!

Pauli, an undisputed genius, here stumbles in one of his rare failures of intuition – and what a failure!

Wu’s experiment gave him a memorable lesson: even the “scourge of God” of physics is not infallible.

By the way, Pauli was a ruthless...

⚛️ 🧪 #histsci

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johncarlosbaez.bsky.social John C. Baez @johncarlosbaez.bsky.social · 8d
When Lee and Yang suggested there's a fundamental difference between left and right, Pauli wrote:

"Ich glaube aber nicht, daß der Herrgott ein schwacher Linkshänder ist."

(I do not believe that the Lord is a weak left-hander.)

2 days later, Wu's experiment showed that Lee and Yang were correct!
December 18, 2025 at 2:51 PM
Reposted by Leonardo Petrillo
drnereide.bsky.social
🧵
Ever wonder what the baby universe looked like—just 800 million years after the Big Bang?

JWST has given us an amazing glimpse via a galaxy called Virgil, hidden in the iconic Hubble eXtreme Deep Field.

➡️ news.arizona.edu/news/monster...

🔭 🧪 #extragalactic #science #cosmology #JWST

1/11
A deep-space image from the James Webb Space Telescope shows a small patch of sky filled with thousands of distant galaxies as faint, diffuse spots and streaks in shades of blue, white, and subtle reds against a black background. An inset box zooms in on the reddish, compact galaxy Virgil, seen as it existed 800 million years after the Big Bang, highlighting its hidden supermassive black hole shrouded in dust.
December 16, 2025 at 3:06 PM
Reposted by Leonardo Petrillo
drnereide.bsky.social
🧵
This aurora and SAR arc (according to the author Graeme Whipps), taken on Dec. 1, 2023 at Chapel of Garioch (Aberdeenshire, Scotland), give us a view of rare beauty.

The SAR arcs, or Stable Auroral Red arcs, were discovered only in 1956.🔭

spaceweathergallery2.com/indiv_upload...

🧪 #science

1/4
Oh man, this photo Graeme Whipps took on December 1, 2023, in Chapel of Garioch, Scotland, just blows you away. It's that rare moment when a delicate green aurora down low mixes with a quiet, steady red SAR arc up high. Softly snowy fields lie dark and hushed in the foreground, dotted with a few farm buildings and faint lights far off on the horizon. The sky starts with soft green glows near the ground, fades into deep pinks higher up, and then there's this broad, calm red band stretching peacefully overhead. A scatter of stars peeks through, and the whole thing feels almost unreal—like the universe quietly showing off its magic.
December 13, 2025 at 7:51 PM
Reposted by Leonardo Petrillo
drnereide.bsky.social
🧵
Here is Messier 106 (or NGC 4258), a true cosmic marvel in the constellation Canes Venatici.

Image Credit: NASA, ESO , NAOJ, Giovanni Paglioli; Assembling and Processing: R. Colombari and R. Gendler

➡️ apod.nasa.gov/apod/ap19031...

🔭 🧪 #science #universe #extragalactic #astronomy

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The image features Messier 106, a big spiral galaxy. Its center glows bright white from a huge black hole gobbling gas. Blue arms full of young stars sweep out wide, crossed by dark red dust lanes and pink hydrogen clouds near the middle. Faint reddish extra arms hint at hidden jets. It stretches approximately 135,000 light-years across in the dark sky.
December 12, 2025 at 5:01 PM
Reposted by Leonardo Petrillo
drnereide.bsky.social
🧵
Here's Ellen Harding Baker's "Solar System" quilt.🧪

This is the story.🔭

Back in 1876, an Iowa mom with 7 kids, E. H. Baker, decided that cooking & raising children wasn’t enough for her.

She started working on a wool quilt showing the solar system.

americanhistory.si.edu/collections/...

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1883 wool quilt by Ellen Harding Baker: a vast black sky with a blazing yellow Sun at center. Mercury, Venus, Earth with its Moon, and Mars orbit it. Four clumps of objects beyond Mars represent asteroids. Jupiter shows its four Galilean moons, Saturn its rings, Uranus six moons, Neptune one. Top left: streaking Coggia’s Comet. Hundreds of stars dot the darkness. Hand-stitched by an Iowa mom.
December 10, 2025 at 11:21 PM
Reposted by Leonardo Petrillo
drnereide.bsky.social
Mind-blowing new paper just out! 🧪

A research team used #Gaia to create the most detailed 3D census to date of OB associations within ~1000 ly from the Sun.

Result? 🔭

57 groups of massive stars — twice as many as we knew before — that were born together and are now slowly drifting apart.

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alexis-space.bsky.social Alexis Quintana @alexis-space.bsky.social · 19d
A new census of OB associations with Gaia!

In this study, we took advantage of my OB stars map to find new OB associations within 1 kpc. The goal was to create a useful reference catalogue for this era, and to trace the star formation and structure of the local Milky Way.

#stellarastro #galactic
December 9, 2025 at 9:47 AM
Reposted by Leonardo Petrillo
johncarlosbaez.bsky.social
Just when you thought you had 'em figured out.
When you realize, sadly, that derviatives don't always act like fractions: Suppose u,v,w are functions on the plane and you can take any two as coordinates and write the third as a smooth function of the other two. Then partial u/partial v|_w partial v/partial w|_u partial w/partial u|_v = -1
December 8, 2025 at 2:44 PM
Reposted by Leonardo Petrillo
drnereide.bsky.social
🧵
Admire this fascinating JWST picture.

The cluster MACSJ0159.2-0849, here featured, is a monster made of hundreds of galaxies, ~4.5 billion light-years away.

But the real magic? This galaxy cluster works as a gigantic, natural magnifying glass.

🔭 🧪 #extragalactic #cosmology

1/7
landru79.bsky.social Landru79 @landru79.bsky.social · 21d
James #Webb Space Telescope #JWST

Vast Exploration for Nascent, Unexplored Sources
High-redshift Galaxies and the Distant Universe

TARG: #MACSJ0159-0849
2025-12-01
PI: Fujimoto, Seiji
NIRCAM 444 410 300 277 210 200 150 115 090

yuval-harpaz.github.io/astro/jwst_l...

NASA/ESA/CSA/STScI/j. Roger
December 8, 2025 at 5:01 PM
Reposted by Leonardo Petrillo
drnereide.bsky.social
Admire this fantastic pic, dominated by the diffuse blue light of the M78 nebula.

Igor Chekalin, by processing the raw data for the original image uncovered in ESO's archives, claimed first prize in the ESO's Hidden Treasures 2010 contest with his final work.

➡️ www.eso.org/public/news/...

🔭 🧪 1/9
Picture a deep dark sky, where a vast, intense deep-blue cloud with two main luminous lobes stands out. Right in the middle two sharp white stars shine, throwing their light onto the dust around them so everything turns that soft milky blue. A wide, dark dusty streak runs diagonally from the top-left corner down to the bottom-right, cutting the view in two and blocking the stars behind it.Down near the lower-right edge there’s a sudden bright patch shaped like an open fan, glowing pale pink and white – that’s McNeil’s Nebula, almost like someone suddenly turned on a light inside the cloud. Close by, thin pink curls and little streaks shoot out, the trails left by brand-new stars still buried in their dusty cocoons. Here and there faint warm red spots flicker against all the cool blue, giving the whole thing a quiet, living feeling, like watching a nursery where stars are just waking up.
December 7, 2025 at 3:30 PM
Reposted by Leonardo Petrillo
drnereide.bsky.social
Another stunning Martian sunset!

(I reiterate what I wrote in another post a few days ago.)

Fine dust strongly scatters red light away in all directions (Mie scattering).
At sunset, when the Sun is low, its light travels hundreds of km through the dusty Martian atmosphere— almost...

🔭 🧪

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hourlycosmos.bsky.social Hourly Cosmos @hourlycosmos.bsky.social · 22d
Sun setting behind Gale crater wall - sol 956 - From Thomas Appéré (thomasappere.bsky.social) - https://flic.kr/p/snMQzS
Picture 4 of 6 taken by MastCam 100mm on sol 956 at 6:28 pm Martian local time. Sunsets are blue on Mars. Dust in the atmosphere scatters efficiently red light in all directions which results in an orange sky during the day. Blue light is scattered by dust in the forward direction. During sunset, only blue light penetrates to the surface. Picture was debayered, cleaned from instrumental artifacts and colors corrected. ---------------------------------------------------------------------------------------------- Image 4 sur 6 acquise par la MastCam 100mm au sol 956 à 18h28 heure locale martienne. Les couchers de soleil sont bleus sur Mars. La poussière présente en abondance dans l'atmosphère martienne diffuse efficacement la lumière rouge dans toutes les directions, d'où un ciel orangé en journée. Par contre, la lumière bleue est diffusée dans la direction avant. Au coucher du soleil, seule la lumière bleue parvient à la surface. L'image a été débayerisée, nettoyée des artefacts instrumentaux et les couleurs ont été corrigées.
December 5, 2025 at 4:05 PM
Reposted by Leonardo Petrillo
drnereide.bsky.social
🧵
The #JWST has recently given us one of the most beautiful images of late years: the stellar system Apep, a trio of massive stars surrounded by four perfect dust spirals that look almost drawn by hand.

➡️ science.nasa.gov/missions/web...

🔭 🧪 #science #stellarastro #astro

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December 5, 2025 at 12:25 AM
Reposted by Leonardo Petrillo
johncarlosbaez.bsky.social
Lie groups and Noether's theorem are the tools that let 20th-century physicists wield *symmetry* as a powerful tool to study crystals, molecules, atoms, and elementary particles.

(1/n)
December 5, 2025 at 3:28 PM
Reposted by Leonardo Petrillo
drnereide.bsky.social
Look at this galaxy going absolutely feral!

NGC 1792 is popping out stars like 10× faster than ours?

Apparently its neighbor NGC 1808 keeps yanking on it.

The result?
Fireworks of baby blue stars and glowing red clouds.

Space is really wild.

🔭 🧪 #extragalactic #science #Hubble
esa.int European Space Agency @esa.int · 26d
📷 This NASA/ESA #Hubble Space Telescope image shows a stormy spiral galaxy ⛈️

NGC 1792 is a starburst galaxy with spiral arms rich in star-forming regions. 🧪🔭

Read more 🔗 esahubble.org/images/potw2...

@science.esa.int @stsci.edu
December 1, 2025 at 7:43 PM
Reposted by Leonardo Petrillo
drnereide.bsky.social
🧵
Under a dark sky, the Milky Way looks like a bright band interrupted by black rivers.

Those rivers are not empty space; they are curtains of tiny dust grains that swallow nearly all the starlight trying to reach us.

➡️ apod.nasa.gov/apod/ap25111...

🔭 🧪 #galactic #science #MilkyWay

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December 2, 2025 at 6:37 PM
Reposted by Leonardo Petrillo
drnereide.bsky.social
🧵
This colorful composite image features NGC 6357, a diffuse nebula located some 5,500 light years away in the constellation Scorpius.

➡️ www.nasa.gov/image-articl...

Image credit: X-ray: NASA/CXC/PSU/L. Townsley et al; Optical: UKIRT; Infrared: NASA/JPL-Caltech

🔭 🧪 #science

1/5
This pic of NGC 6357 is wild: a huge cloud lit up in deep purple from super-hot gas caught by Chandra and ROSAT X-rays, mixed with rusty-orange infrared dust from Spitzer and cold blue starlight from ground telescopes. In the middle there’s a tight pack of brand-new, blazing stars that look like someone spilled diamonds on velvet. Long, thin streamers of gas drift away like smoke, and all over the place you’ve got big empty bubbles hollowed out by radiation, stellar winds and ancient supernovas. It’s basically several star clusters being born at once, loud and quiet at the same time.
December 1, 2025 at 12:27 AM