Thread by @MalvagioMarco

Even if I post about history because that's the current obsession for my brain squirrels, I'm a nuclear physicist.
My field and roman history don't really overlap much.
Except sometimes.
⚛️A THREAD ABOUT ROMAN SHIPWRECKS AND NUCLEAR PHYSICS⚛️
(I'm science I swear it's legit)

This story begins a real, real long time ago. About two minutes after the birth of the universe.
The newborn universe was cooling from "so hot numbers make no sense" to "Much hotter than you could ever understand".
So, cool enough for matter to form.
Pic: a helpful timeline.

We know how that works, mostly. You *can* create matter out of nothing, given enough energy, and the early universe had plenty - for twenty minutes, the whole universe was hotter than the heart of of Sun.

But, there's a but. When you create matter, you make its evil twin, too: antimatter.
Antimatter is... basically exactly like matter.
Except if they touch, they destroy each other ("annihilate", I love the word), releasing a huge amount of energy in the process.

In the early universe, matter and antimatter were created, destroyed each other, released energy that formed new matter and antimatter... again and again, while the universe expanded and cooled.
See a diagram of the process with familiar particles: popes and anti-popes.

It's easy to see how the game should end: no matter, no antimatter.
Sooner or later in this cycle the universe should become too rarefied for the resulting energy to creat new matter.
And the cycle ends, with an universe that is nothing but void and gamma rays.

The vast majority of matter created in the first furious seconds of the universe annihilated with antimatter.
But a minuscule fraction - about one in a billion - was left when all the antimatter was burned. That fraction is us.
(like most things, it's best explained with popes)

We're made of matter, and so is pretty much everything - cats, the world, the Sun, all the stars in the sky and every galaxy for billions of light-years. No substantial amount of antimatter seems to exist anywhere.
Fun facts: most anti-popes were actually made of matter.

How did that happen? If creating particles you make the same exact amount of matter and antimatter, how could antimatter run out first?
That's a major issue for particle physicists.
It's not entirely a mystery, but not yet settled either.

Long story VERY short, there are some processes which can create, by the tiniest amount, more matter than antimatter.
One such process goes by the very human-friendly name of "neutrinoless double beta decay".
The name is a mouthful, so I'll call it "Bob".

Basically, if it actually exists, it means an element becomes a different element, creating two electrons - without antimatter to balance.
Problem is, we don't know if this process really exists!

If it exists, beside making alchemists happy, its existence would prove Important Physics Stuff I Won't Try to Explain, and possibly contribute to the matter\antimatter unbalance.

...so, where do the Romans come into play?
See, Bob is a very, very rare process. The only way to see it happen is to gather a lot of the material that COULD decay (for example the element Tellurium)... and wait.
If Bob happens, it will release a tiny, tiny amount of energy.

Problem is: A LOT of things release energy! Imagine you're looking for the faintest spark of light imaginable, and you have no way to tell it apart from any other light source. Stars, mobile phones, fireflies... anything would look brighter.

You'd go to a very dark room, of course. And that's what physicists do.
Detectors for this kind of rare events are built deep underground, where miles of rock stop not only light, but cosmic rays.
pic: a typical source of noise for underground experiments

That's not enought, though! Heat generates some light, too. So the detector must be cooled almost to absolute zero.
One of the detectors for the "Bob" process, CUORE, is the coldest chunk of matter that we know of in the whole universe. Because THAT'S how cold you need it.

And it still isn't enough. See, the experiment must be shielded with lead to stop even the tiniest possible amount of radiation.
But lead itself emits a minuscule amount of radiation!

That's because there are radioactive isotopes (close nuclear brothers) of lead that slowly decay into regular lead. This radioactive lead is produced by trace amounts of Uranium in lead ore, so all lead in the world has some.

But, with time, radioactive lead decays. It takes 22 years to halve - so lead which has ben refined centuries ago has much less radioactivity than the one recently mined.
Lead mined *2000 years ago* is basically perfect.

Ancient romans didn't know much about particle physics [citation needed].
But they were REALLY into metallurgy! They mined incredibly high amounts of iron, lead and copper - much more than any later preindustrial society in the West.

Given how much they traded in the mediterranean, a substantial amount of lead sunk in shipwrecks. And it's still there, underwater - millennia old lead, almost perfectly pure.

Roman lead from ancient shipwreck makes the shielding for the CUORE experiment.
The detectors are deep under a mountain, kept colder than interstellar space, surrounded by ancient lead.
Sounds like it could double as a demon's prison tbh.

CUORE so far did not find any "Bob" event, but set the world's most stringent limits on their frequency ("if there were more than X events, we'd know by now"), advancing our understanding of reality.

Retrieving the roman lead was a joint venture between physicis and history research agencies - historians kept all the parts with writings or other historically significant data, physicists kept the rest.

I'll tell the truth, the historians involved weren't thrilled about it - they weren't happy about melting down roman lead.
But while I'm REALLY passioned about preserving history, for once I don't care tbh: it was literally shapeless lead.

Not everything old is of great historical value. On the other hand, as a particle shield that lead is a literally irreplaceable resource.
I like the idea of something so ancient directly contributing to something so modern.

Well, that was is. Sorry for the long-ass thread.
Also, whoever AKSHUALLIES me about physics will be utterly ignored, I know I made simplifcations - particle physics really isn't a newbie friendly topic.

Well, this was an unusual thread, but if you enjoyed it, here there are some more human-friendly ones!
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