Will M Farr

Astrophysicist, formerly of @unibirmingham & @UoBIGWaves, currently lead gravitational wave group at @flatironCCA, Assoc. Prof @stonybrooku.

[Will M Farr @farrwill]

At the prompting of @cplberry , a thread about LIGO's recent H0 measurement. It will be long (but hopefully informative). Gird yourselves!

[Ruth Angus @ruthangus]

To find life on another world, we first need to know what a lifeless planet looks like. But a talk last week showed just how difficult that is. Now I’m feeling pessimistic about our chances of finding life out there. My first post on substack(!) goes into more detail. Link below.

[Will M Farr @farrwill]

@dilanesper Excellent question! At least on large scales (galaxies and bigger) there is a good, natural way to define “the same place” even though the universe is expanding: keeping your relative position fixed with respect to all the other galaxies, the CMB, etc.

[Daniel Litt @littmath]

I gave the Bott lectures at Harvard last week, about some topics (around the arithmetic of differential equations) that I've been thinking about recently. You can watch the first one, which starts out relatively elementary, here: https://t.co/K7XhcKWSuO

[Flatiron Institute @FlatironInst]

🌌 Last call! Applications are due this week for our postdoctoral research positions in computational astrophysics. Apply before October 31st: https://t.co/vTK1zWnIwW

#science #astrophysics #FlatironCCA

[Dan Roberts @danintheory]

We are announcing three new discoveries in mathematics, computer science, and physics about harmonic analysis, complexity theory, and quantum field theory.

https://t.co/9BX8HWQDTJ

[Flatiron Institute @FlatironInst]

Applications are due soon for postdoctoral research positions at our Center for Computational Astrophysics: https://t.co/vTK1zWnIwW

#science #astrophysics #FlatironCCA

[Martin Bauer @martinmbauer]

Ordinary, stable atoms can only exist in a Universe with 3 space dimensions

The argument is very straightforward:
Stability in atoms is a balance between kinetic energy and potential energy of the electrons

🧵 1/6

[Fiona H. Panther @FiPanther]

Seeing as this was an absolute banger, I did it properly, with some help from Claude to speed up messing around with scraping the Nobel website:

[Greg Egan @gregeganSF]

Don’t you hate it when someone mixes up the Nobel Prizes and inserts ion channels in your neurons that open when exposed to neutrinos instead of light, and your brain just goes pffzzz ....

[The Nobel Prize @NobelPrize]

BREAKING NEWS
The Royal Swedish Academy of Sciences has decided to award the 2026 #NobelPrize in Physics to Francis Halzen “for decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin.”

[Fiona H. Panther @FiPanther]

Which subatomic particle has produced the most Nobel prizes:
Electron: 10 directly associated
Neutrino: 5
Quarks/gluons: 5ish
Neutron: 3ish?
Proton: 2ish, more if you fold in quarks/antiproton
Higgs: 1
W/Z, Pion: 2 each
Tau: 1, but shared with neutrino
Technically 0 for muons

[Flatiron Institute @FlatironInst]

Come do a postdoc at our Center for Computational Astrophysics! We're #hiring for research positions through October 31st: https://t.co/vTK1zWnIwW

#science #astrophysics #FlatironCCA

[Brandon Bright-Barker, PhD✨ @AstroBarker]

News: we moved to New York! I’m excited to share that I am joining @FlatironInst Center for Computational Astrophysics as a research software engineer supporting MESA and broader software needs. Software is a pillar of sci. infrastructure and I am elated to continue to support it

[Giovanni Maria Tomaselli @gimmytomas]

On the surface, my second year @the_IAS mirrored the first: four new papers (which I recap below), an amazing time overall, and a summer holiday hiking volcanoes.

In reality, the arrival of AI changed everything. The future seems both exciting and unpredictable! (1/5).

[Andrew Gelman et al. @StatModeling]

A nonlinear effect plus measurement error in x becomes close to linear: A simulation study
https://t.co/MHbHmIUuud

[Akshat @star_stufff]

How do these people do it man, really promising work here
https://t.co/qkNhl6rpjO

[Will M Farr @farrwill]

@WKCosmo @WKCosmo in what sense is this *not* Platonist? (Legit confused---and have some vague understanding of Platonism, so maybe it's just that I'm not getting it.)

[Ruth Angus @ruthangus]

The 14 Herculis planetary system shouldn't exist: 2 massive planets with elliptical, misaligned orbits? @FlatironInst's Tiger Lu thinks the system once had a 3rd planet which perturbed the orbits of the inner 2. That 3rd planet likely got ejected https://t.co/QmdfgY1FUF

[Niko @NikoSarcevic]

@WKCosmo "If you are confused about p(A|B) and p(B|A) consider if A=pregnant and B=female. p(A|B) is a few percent, p(B|A) is unity" 😂😂😂😂😂

[Will Kinney @WKCosmo]

A bit of history for the youngs.

The custom of distributing preprints started out in high-energy physics. In the old days, pre-publication papers (literally on paper) would be sent out to university libraries by postal mail, often even prior to submission to journals, certainly before acceptance. Because this was expensive, the practice was mostly limited to national labs and other large institutional groups. The labs even had distinct letterhead for their preprints, and an internal numbering system for indexing. The libraries would then put them in a display rack once a week, and to update yourself on the latest, you would go into the library and sit at a table and read them. (They could not be checked out!) This was how it was when I started as a grad student. It was an informal and collegial system for communicating the latest science that flew under the radar of the journal system.

In the early '90s, Paul Gisparg and Joanne Cohen (who is often left out of the story) set up a server to distribute preprints by email. You would receive a daily list of papers by email, and could request the TeX source via email commands, then compile it yourself locally. Being of a hacker-ish bent, I was one of the first in my department to embrace this wild new idea.

Note that this was before the release of the first widely used web browser, NCSA Mosaic. The Wold-Wide-Web at the time was one stub site at CERN that you could find on Gopher. When Mosaic came out and the https://t.co/ykbC6DWZZa server went live with its Jolly Roger logo amd you could download preprints directly in Postscript format and print them on your department's expensive laser printer, the world changed forever.

But it was never about papers already accepted for publication.