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Model-Based Machine Learning (2023)

https://mbmlbook.com/toc.html
1•Tomte•57s ago•0 comments

Probabilistic Models of Cognition

https://probmods.org/
1•Tomte•1m ago•0 comments

What Are People Still Doing on X?

https://www.theatlantic.com/technology/archive/2025/05/stop-using-x/682931/
1•_tk_•2m ago•0 comments

B2B SaaS Growth Strategies from Business Classics Applied to AI Startups

https://guptadeepak.com/10-proven-growth-strategies-for-b2b-saas-lessons-from-business-classics-applications-for-ai-startups/
1•guptadeepak•3m ago•1 comments

Sammy's Sensation: Pausing to See If a New Pattern Has a Name

https://sampatt.com/blog/sammys-sensation
1•SamPatt•3m ago•0 comments

Be the first to apply to new jobs with this tool

https://firstonjobs.com/
1•gpopmescu•6m ago•1 comments

Securing a Form on the Internet: Still Pretty Difficult

https://serverascode.com//2025/04/12/securing-a-form-on-the-internet.html
2•todsacerdoti•9m ago•0 comments

HEY is finally for sale on the iPhone

https://world.hey.com/dhh/hey-is-finally-for-sale-on-the-iphone-a08cb218
2•saikatsg•11m ago•0 comments

Show HN: DoubleMemory – more efficient local-first read-it-later app

https://doublememory.com
5•randomor•11m ago•1 comments

NASA Ames Research Center Archives

https://www.beautifulpublicdata.com/nasa-ames-research-center-archives/
1•jonathanmkeegan•11m ago•1 comments

Show HN: Preview / Generate Website from Reactive Resume JSON

https://gsingh704.github.io/rx-resume-web/
1•gsingh704•11m ago•1 comments

Canvas Medical's Deep Unified Architecture

https://www.canvasmedical.com/articles/deep-unified-architecture
1•mooreds•12m ago•0 comments

The Monster-Slaying Game You Can Play Almost Anywhere

https://www.nytimes.com/2025/05/21/arts/play-doom-ports.html
1•jaredwiener•17m ago•0 comments

Is a Piece of Software Ever Done? (2024)

https://www.mooreds.com/wordpress/archives/3679
2•mooreds•18m ago•0 comments

The Academic Pipeline Stall: Why Industry Must Stand for Academia

https://blog.sigplan.org/2025/05/19/the-academic-pipeline-stall-why-industry-must-stand-for-academia/
1•rbanffy•18m ago•0 comments

Droplet Outbursts from Onion Cutting

https://arxiv.org/abs/2505.06016
1•m463•18m ago•0 comments

Show HN: Business Intelligence Agent

https://github.com/vladkol/crm-data-agent
1•vladkol•19m ago•0 comments

Emacs dired-mode as a file manager

https://lynn.sh/guix-emacs-file-manager.html
1•todsacerdoti•19m ago•0 comments

Big Problems From Big IN lists with Ruby on Rails and PostgreSQL

https://andyatkinson.com/big-problems-big-in-clauses-postgresql-ruby-on-rails
1•Ocha•20m ago•0 comments

Show HN: Hcker.news – an ergonomic, timeline-based Hacker News front page

https://hcker.news
10•postalcoder•22m ago•1 comments

The computer revolution hasn't happened yet [video] (1997)

https://www.youtube.com/watch?v=oKg1hTOQXoY
1•fidotron•23m ago•0 comments

Google's AI Mode is 'the definition of theft,' publishers say

https://9to5google.com/2025/05/22/google-ai-mode-theft-publisher-opt-out-controls/
2•ironyman•23m ago•0 comments

Epic Bus Journey-Bus to London with Adventures Overland

https://bustolondon.in/
1•thunderbong•24m ago•0 comments

Anthropic's AI resorts to blackmail in simulations

https://www.semafor.com/article/05/23/2025/anthropics-ai-resorts-to-blackmail-in-simulations
3•Stratoscope•26m ago•0 comments

Recreating the Webtable in Rust

https://fjall-rs.github.io/post/recreating-webtable/
2•alex_hirner•27m ago•0 comments

Kermit the Frog gives commencement speech at University of Maryland

https://apnews.com/article/kermit-frog-university-of-maryland-commencement-7976fbba353fef1bb2ca818944f9728d
2•ChrisArchitect•29m ago•2 comments

Swad 0.11 – auth service for Nginx and Anubis alternative

https://github.com/Zirias/swad
1•Zirias•29m ago•1 comments

The Fortress That China Built for Its Battle with America

https://www.wsj.com/world/china/china-us-technology-economy-advancements-bb8d7439
4•bookofjoe•30m ago•1 comments

Types of optical systems in a lens designer's toolbox (2020)

https://www.pencilofrays.com/lens-design-forms/
11•picture•33m ago•0 comments

Kuo: Jony Ive's Futuristic OpenAI Device Like a Neck-Worn iPod Shuffle

https://www.macrumors.com/2025/05/22/ming-chi-kuo-on-openai-device-design/
1•m463•33m ago•0 comments
Open in hackernews

Caesar's Last Breath

https://charliesabino.com/caesars-last-breath/
90•charliesabino•4h ago

Comments

lkmill•4h ago
isnt the half life of most types of molecules in air far shorter than 2k years? maybe i am nitpicking, but would it not be more to correct to say we are breathing the same atoms as those in caesers last breath?

edit: itchy trigger finger, think i subconsciously wanted to be the first to comment. it is stated quite early that molecules preservation is assumed. still think it would be more correct and just as interesting to discuss atoms, not molecules.

edit 2: quick research has taught me that nitrogen gas, n2, and naturally occurring isotopes do not even have a half life. they do not radioactively decay. til.

oatsandsugar•4h ago
I don't think so — Nitrogen, the most common part of air, is stable in its most common isotope
lkmill•4h ago
indeed it seems so, i thought all atoms (except hydrogen) had some kind of decay. i thought so called stable atoms still had half-lives of 10^{very large number} years.
tgv•4h ago
In this scenario, you can think of a reaction as terminating a molecule's life. So if there's a 50% chance that an H2O (or CO2) molecule reacts in a certain period, that could be its half-life time.
SJC_Hacker•3h ago
If you buy into the Big Rip, then all particles in the universe (including protons and neutrons) will eventually disintegrate
jasongill•2h ago
your post made me laugh because it makes the theory sound like propaganda that is sponsored by Big Rip
kjs3•2h ago
Big Bang, Big Rip, Big Crush. Cosmologists like Big Things.
cyberax•2h ago
If we're talking about these kinds of scales, N2 molecules are not stable because there's a non-zero probability for the atoms to fuse into a heavier element through tunneling. And this will release more than enough energy to break the chemical bonds, of course.
hnuser123456•2h ago
Maybe you saw this story recently?: https://phys.org/news/2025-05-universe-decay-years-sooner-pr...

Also, bismuth was once thought to be the most massive "fully" stable element, but turns out does decay with a half life of 10^19 years, compared to the universe's age of ~10^10 years.

Neutrons decay into a proton/electron pair after 15 minutes when not part of a nucleus.

Protons appear to be fully stable for any practical considerations, however they might decay after 10^30 years.

pvg•4h ago
What's the 'half-life' you're thinking of? Your basic gas molecules will last a lot longer than 2k years short of being involved in some reaction or another. And a lot of these reactions aren't that easy in atmospheric conditions- e.g. pulling nitrogen out of the atmosphere https://en.wikipedia.org/wiki/Nitrogen_cycle
victorNicollet•3h ago
I have seen the similar assertion "some of the water molecules you drank today were once part of a dinosaur", which is false because water molecules do not last very long when in liquid phase (they continuously swap protons, turning into hydronium ions and back).

The O-O and N-N bonds are much stronger than H-O bonds, but there are still atmospheric processes that can break them. For instance, O2 undergoes photodissociation under ultraviolet light and recombines into O3 ozone, and N2 likely also undergoes photodissociation. And obviously, the fact that living beings breathe O2...

satvikpendem•39m ago
People should instead say atoms, not molecules. Or maybe even say quarks.
hilbert42•4h ago
This is sn oldie but it beautifully illustrates orders of magnitude and how many atoms there really are.
ninalanyon•4h ago
Estimation without any attempt to quantify the distribution of each of the components of the formula doesn't give me much confidence in the result.
d--b•4h ago
What? There is 10ˆ22 breaths in the atmosphere? I guess the atmosphere is huge.
lkmill•4h ago
i guess this also means there are around 10^23 farts in the atmosphere. a quick empirical study just showed there around 10 farts to a breath.
dudeinjapan•3h ago
So we're also breathing Caesar's last fart.
d--b•2h ago
Well, once every 10 breaths on average.

But on the other 9 breaths, you get to breath quite a lot of his other farts... So... your breath is really never Caesar-fart-free.

But as a consolation, most of humanity will breath your farts on every breath, so...

shmeeed•1h ago
Empirically, my buddies' farts seem to weigh in way above 0.1 breath.
xixixao•4h ago
But do the molecules really disperse like that? The molecules were all in Caesar's mouth before he released them in his last breath. Is the movement of molecules such that they are now, roughly 2000 years later, about equally spread around the Earth? Is there more of them in Rome? In Italy? In the norther hemisphere?
pvg•4h ago
The dispersion assumption tends to make the estimate more rather than less conservative.
horsawlarway•3h ago
I think the contention is that I don't have an intuition for how molecules actually disperse, but I do know that general climate trends certainly aren't "random dispersion".

Ex - we see consistent, long term, patterns in weather that make it unlikely that this dispersion is anything close to "ideal gas in a chamber" style dispersion.

Further - we have all sorts of compounding effects. Ex - atmospheric escape is a real thing, plants do nitrogen fixation, hydrogen and oxygen can be bound up in the oceans, etc...

Maybe 2000 years is enough time for real random dispersion, maybe it's not. But it's a huge assumption baked into this that doesn't feel especially reasonable to me.

All we have is this:

>If we assume that a breath diffuses evenly throughout the atmosphere and that these molecules are preserved over time (a reasonable assumption—nitrogen is relatively inert)

Which... I challenge is likely not a particularly reasonable assumption to base this on.

kortilla•3h ago
Long term climate patterns are much slower than dispersion.
pvg•2h ago
we have all sorts of compounding effects.

It's still an atmosphere mostly made of nitrogen, on a scale vastly exceeding 2000 years.

I don't have an intuition for how molecules actually disperse, but I do know that general climate trends certainly aren't "random dispersion".

Big volcano eruptions make for pretty sunsets across the world. Nuclear testing fallout is detectable in everything since atmospheric nuclear testing began. Everywhere we find the K-P boundary, we find iridium. The counter-assumption (which may well be true!) is the counter-intuitive one.

hnuser123456•2h ago
The jetstream moves north and south over the US in somewhat predictable ways each year. But the molecules in the jetstream never stop flowing, and the jetstream tends to diverge after it reaches the Atlantic ocean. Sometimes it does another tight lap around the artic circle, sometimes it veers down towards Africa, sometimes it splits and goes both ways:

https://en.wikipedia.org/wiki/File:Aerial_Superhighway.ogv

The jetstream blows at around 110 mph, and Earth's circumference at mid-northern latitudes is around 12500 miles, so it takes 12500/110=114 hours or just under 5 days for the jets to complete a lap around the planet, assuming we choose a molecule that doesn't take a diverging path on that lap. That's 73 laps per year, so 2000 years is nearly 150,000 times that the faster parts of the atmosphere have circled the globe, twisting, breaking, and reconnecting paths the whole time.

lkmill•3h ago
i believe so, https://en.wikipedia.org/wiki/Maxwell%E2%80%93Boltzmann_dist....

2k years is a long time for gas dispersion in such a "small" volume as the earth's atmosphere. early weather behaviour probably affected the distribution unevenly, but by now it should be relatively evenly distributed across the globe. no more or less in rome or italy. this is, however, as we say in sweden, a "guy's guess".

pugworthy•2h ago
Not gas dispersion, but it's crazy how fast some compounds can disperse in the human circulatory system when introduced by IV. If you've ever had IV saline flush you may know that metallic taste that seems to show up in your mouth almost instantly.

Similarly, there is a sensation from Adenosine for chemical cardioversion that creates a hot flushing feeling inside your body as it spreads, and it's quite the sensation to feel it going from your chest down to your extremities in a few seconds.

munchler•4h ago
> If we assume that a breath diffuses evenly throughout the atmosphere and that these molecules are preserved over time

In other words, let’s hand-wave away the most interesting part of the question, and then come up with a trivial answer to whatever’s left.

symmetricsaurus•3h ago
Well actually, air molecules (N2, O2) are indistinguishable. This means that they are fundamentally interchangeable with each other and it’s not well defined what ”same” molecules mean. You can’t label the individual molecules.

It’s of course possible to track a single molecule if you really try hard. But this hasn’t been done since Caesar's time and the molecules have mixed. Even if we knew the exact state of the universe right now and could play back time perfectly it would be impossible to say that some particular molecules were part of his last breath.

fedeb95•3h ago
doesn't this assume both the external layer of the atmosphere and all of the earth to be impermeable to breath molecules?
jamesgill•3h ago
"Obviously, many simplifying liberties were taken."

Yes, I would agree. Perhaps too many. But it's a fun exercise.

cm2012•3h ago
Super neat. Did not expect the math to work.
seydor•3h ago
Well now every salad is Caesar's salad
diego898•3h ago
Purely empirical observation, in my own life, make no claim as to humanity/society/etc.:

It's interesting how often fermi estimation problems are used as proxy's for "intelligence". Something like: 'let's assess how well "they can think" - how many golf balls fit in a baseball stadium?' etc.

Often, doing well in these kinds of problems can more than makeup for a lack of specific knowledge in something someone is interested in assessing!

miobrien•1h ago
This reminds me of a question from my first interview as a college grad: estimate the number of taxis in New York City. I was totally baffled by it.
BubbleRings•3h ago
How many breaths do I have to take, to pull in an oxygen atom that used to be part of a dinosaur, and was also in Caesar’s last breath? Could we turn this number into a unit of measure, so we can name it the…Caesaur? Caesarasaur?
tempodox•3h ago
I fell for it, I thought it was καὶ σύ, τέκνον (“you too, child”), to Brutus.
dimitrios1•2h ago
technically, the diminutive τεκνίον would be more appropriate in this context. Teknon was more formal, and in its colloquial usage was used commonly in the stereotyped phrase "women and children", which in the ancient world was a symbol of low social status. The diminuative would indicate a different usage, more affectionate, friendly, etc.