John F Wu
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jwuphysics.bsky.social
John F Wu
@jwuphysics.bsky.social
3.6K followers 630 following 1K posts
Tenure-track astronomer at STScI/JHU working on galaxies, machine learning, and AI for scientific discovery. Opinions my own. He/him.

Website: https://jwuphysics.github.io/
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jwuphysics.bsky.social
Took a break from wrangling NSF grant application spreadsheets and instead decided to wrangle MLB team sentiment spreadsheets...
A giant matrix showing how MLB teams feel about other MLB teams. Based on survey data from Reddit's r/mlb. A block-diagonal highlights the divisional rivalries quite well.
November 12, 2025 at 3:30 PM
jwuphysics.bsky.social
Me when my 14-month old throws up and interrupts my first full week of work since September
"that wasn't very cash money of you" meme with a dinosaur wearing shades
November 5, 2025 at 6:57 PM
jwuphysics.bsky.social
Honestly I'm just glad he shut up for a bit
"Schumer won't say who he voted for in New York City mayoral race"
November 5, 2025 at 2:51 AM
jwuphysics.bsky.social
Looking At NJ governor election results and... What is going on with Gen Z.
Huge disparity in voting between men 18-29 (54% D) vs women 18-29 (80% D)
November 5, 2025 at 1:17 AM
jwuphysics.bsky.social
Obscure question for #Ravens fans and journalists: I have this T-shirt that references "Splash '98 Funky Jungle" presented by the Baltimore Ravens.

What event was this?

Google search, ChatGPT turned up nothing...
The aforementioned Splash'98 funky jungle shirt. It has a green/black toucan design on it as well.
November 1, 2025 at 2:36 PM
jwuphysics.bsky.social
Every year my wife always has the greatest family costume ideas

This year for Halloween: pollinators & friends 🐝🦋🌻🤠
My family dressed in: monarch butterfly (wife), flower (baby), bee (older kid), beekeeper (me)
October 31, 2025 at 10:18 PM
jwuphysics.bsky.social
Okay first of all rude
Gmail summary from Fidelity: Disclosure About Your ASS...
October 31, 2025 at 2:31 PM
jwuphysics.bsky.social
New blog post introducing a recently accepted NeurIPS ML4PS workshop paper. 🔭

Post: jwuphysics.github.io/blog/2025/10...
Paper: arxiv.org/abs/2510.23749
Screenshot of my blog post at https://jwuphysics.github.io/blog/2025/10/euclid-galaxy-morphology/
October 29, 2025 at 9:07 PM
jwuphysics.bsky.social
This is what they're flying into, by the way: a still-intensifying major hurricane #Melissa
October 27, 2025 at 3:57 AM
jwuphysics.bsky.social
2spooky4u
My lil guy
October 26, 2025 at 2:06 AM
jwuphysics.bsky.social
"I love all the exotic vegetables in Asian grocery stores."
Always has been meme template: Astronaut looking at earth: Wait, so it's all brassica rapa? Astronaut behind them, pointing gun: Always has been
October 25, 2025 at 4:44 PM
jwuphysics.bsky.social
all the while solo parenting our 1 and 4 year old kids during spouse's two work trips these two weeks, during which the kids got sick, of course.*

My body: *gets sick*

Me:
Shocked Pikachu face meme
October 19, 2025 at 10:32 PM
jwuphysics.bsky.social
Fantastic work on the size–mass relation for low-mass galaxies, led by Yasmeen (@yasmeenasali.bsky.social)!

arxiv.org/abs/2509.25335

🔭🌌🧪
A sneak preview of Figure 6 in the paper, which shows size (r-band radius) vs stellar mass for SAGA satellites, SAGA background galaxies, and SDSS isolated galaxies. They all obey the same trends but have small offsets, which appears unlikely to be driven by SFR but *does* seem to be driven by environment!
October 1, 2025 at 1:54 PM
jwuphysics.bsky.social
An Arp-like messy merger at z=0.03.

www.legacysurvey.org/viewer?ra=17...
A merger galaxy system that look Arp-like. https://www.legacysurvey.org/viewer?ra=171.8432&dec=-5.4983&layer=ls-dr9&zoom=14
September 29, 2025 at 4:18 PM
jwuphysics.bsky.social
Anyone else going to COLM? Give me a shout!

Also, check out our poster on evaluating LLMs for astronomy research. This work came out of our 2024 JSALT research and was jointly led by undergrads Alina Hyk and Kiera McCormick!
Screenshot of our abstract from the COLM schedule page, printed below Thursday, October 9th Title: From Queries to Criteria: Understanding How Astronomers Evaluate LLMs 11:00 AM – 1:00 PM 710 Authors: Alina Hyk, Kiera McCormick, Mian Zhong, Ioana Ciucă, Sanjib Sharma, John F Wu, J. E. G. Peek, Kartheik G. Iyer, Ziang Xiao, Anjalie Field Abstract There is growing interest in leveraging LLMs to aid in astronomy and other scientific research, but benchmarks for LLM evaluation in general have not kept pace with the increasingly diverse ways that real people evaluate and use these models. In this study, we seek to improve evaluation procedures by building an understanding of how users evaluate LLMs. We focus on a particular use case: an LLM-powered retrieval-augmented generation bot for engaging with astronomical literature, which we deployed via Slack. Our inductive coding of 368 queries to the bot over four weeks and our follow-up interviews with 11 astronomers reveal how humans evaluated this system, including the types of questions asked and the criteria for judging responses. We synthesize our findings into concrete recommendations for building better benchmarks, which we then employ in constructing a sample benchmark for evaluating LLMs for astronomy. Overall, our work offers ways to improve LLM evaluation and ultimately usability, particularly for use in scientific research.
September 27, 2025 at 7:54 PM
jwuphysics.bsky.social
Thanks Baltimore DOT for penalizing 40+ mph speeders more harshly, but by that point shouldn't you be revoking their driving license?
Baltimore new tiered speeding fine structure, ranging from $40 (<15 mph over), $70 (16-19 mph), $120 (20-29 mph), $230 (30-39 mph), and $425 (40+ mph)
September 24, 2025 at 7:25 PM
jwuphysics.bsky.social
Two things about this paper.

1. This is legitimately useful information
2. The supplementary material shows the experimental set up... and they perform all experiments in a Bialetti Moka pot box, because of course they did
Supplementary Fig 1 of the paper, showing the schematic of the heating equipment (left) and image acquisition set up (right) Supplementary Fig 1 of the paper, showing the actual heating equipment (left) and image acquisition set up (right). The right-side shows a camera mounted over an illuminated box. The box is the outside packaging of the popular Bialetti moka pot.
September 19, 2025 at 4:37 PM
jwuphysics.bsky.social
Thanks to UMaryland Astro for inviting me to give the Center for Theory and Computation Seminar!
A snapshot of the Illustris TNG simulation, showing stellar light, with the text "Is there a better way to quantify environment?" as the slide title. It then shows the environmental "parameterizations": spherical overdensity (a blue circle of fixed radius), DisPerSE (a topological data analysis technique), and Graph Neural Networks (which uses the subhalo catalog as a point cloud and connects them within a fixed linking length). There is also an example of a subvolume shown as a graph neural network.
September 10, 2025 at 4:42 PM
jwuphysics.bsky.social
Ma'am this is a ML x Astro/Cosmology email d-list
September 9, 2025 at 12:47 AM
jwuphysics.bsky.social
Fun little blob at the end of the tidal tail associated with NGC 3628.

Tidal dwarf? It's detected in HI and certainly has young stars!

Source: www.legacysurvey.org/viewer/cutou...
A smattering of diffuse blue nebulosity with some brighter blue stars (or star clusters).
September 5, 2025 at 1:26 PM
jwuphysics.bsky.social
Another fantastic paper that arose from our @kitp-ucsb.bsky.social GalEvo23 program.

This one is from the inimitable Kartheik Iyer, who also shared a fantastic takeaway figure on how simulated feedback affects galaxy star formation histories.

#AstroSci #extragalactic
Cartoon showing how galaxy SFH is affected by different things at different epochs: (a) galaxies assemble in overdensities at early times, dominated by cosmological parameters; (b) galaxies and BHs grow along with their host halos, impacted by SNe feedback and halo accretion at high-z; (c) star formation regulated by feedback until quenching, dominated by SNe/AGN feedback and baryon cycling processes. Image by Kartheik Iyer, who also led the paper.
September 2, 2025 at 5:38 PM
jwuphysics.bsky.social
I've received lots of crackpot physics emails, and this 200 page manifesto looks like every other 200 page "retired engineer" crank manifesto...

But this is the first one I've seen which claims an endorsement from Marx.
Screenshot from this email with the text: 2.5 The Dialectical Materialist View of the Ether Marx was a firm supporter of the ether doctrine. He believed that Descartes' view that "wherever there is extension and space, there is a thing", "there is no difference between space and a thing in fact", "there is no thing that does not occupy space", "extension is entity", and "vacuum is not empty", that is, materialism and dialectical thinking of infinite extension of matter, was "the property of real natural science".
August 16, 2025 at 2:26 AM
jwuphysics.bsky.social
Happy nine years of marriage to us!
Selfie of my wife and me, seated on a park bench in front of some green shrubbery.
August 11, 2025 at 11:17 AM
jwuphysics.bsky.social
Check out my new blog post discussing graph neural networks for astrophysics—specifically, how galaxies relate to their dark matter subhalos in the context of their cosmic environments.

jwuphysics.github.io/blog/2025/07...

#astrosci
Results figure showing how the stellar mass prediction error decreases when (a) we use GNNs, shown in purple, and (b) add environmental context on very large scales out to 10 Mpc.
July 31, 2025 at 11:48 AM
jwuphysics.bsky.social
When you and your spouse are enjoying a Friday night with a bottle of pinotage but you hear your 4 year old scampering around upstairs so you decide to investigate
A froggy squishmallow and Elmo tucked under covers in your bed
July 19, 2025 at 2:16 AM