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Alex Nelson

@pqnelson.bsky.social

Mathematician, software engineer. Obsessed with everything about proof assistants. AMS Subject Class.: 68V15, 68V20, 20Exx.

785 Posts83 Follower38 Folgt
Alex Nelson@pqnelson.bsky.social · 7d ago

David Gross estimated that there is a 2% probability humanity will kill itself each year, due to nuclear weapons, or a bio-weapon out of control, or some other catastrophe. This estimate was *before* AI became a thing. Saying there's a 10% probability humanity will die out per year seems possible.

John C. Baez@johncarlosbaez.bsky.social · last wk.

Did you hear about the UK government report on ecosystem collapse? 𝗧𝗵𝗲 𝗸𝗲𝘆 𝗷𝘂𝗱𝗴𝗲𝗺𝗲𝗻𝘁: 𝗶𝘁 𝗮𝘀𝘀𝗲𝘀𝘀𝗲𝘀 𝘄𝗶𝘁𝗵 𝗵𝗶𝗴𝗵 𝗰𝗼𝗻𝗳𝗶𝗱𝗲𝗻𝗰𝗲 𝘁𝗵𝗮𝘁 𝗲𝘃𝗲𝗿𝘆 𝗰𝗿𝗶𝘁𝗶𝗰𝗮𝗹 𝗲𝗰𝗼𝘀𝘆𝘀𝘁𝗲𝗺 𝗶𝘀 𝗼𝗻 𝗮 𝗽𝗮𝘁𝗵𝘄𝗮𝘆 𝘁𝗼 𝗰𝗼𝗹𝗹𝗮𝗽𝘀𝗲 - 𝗶𝗿𝗿𝗲𝘃𝗲𝗿𝘀𝗶𝗯𝗹𝗲 𝗹𝗼𝘀𝘀 𝗼𝗳 𝗳𝘂𝗻𝗰𝘁𝗶𝗼𝗻 𝗯𝗲𝘆𝗼𝗻𝗱 𝗿𝗲𝗽𝗮𝗶𝗿. It was going to be released in October 2025, but Starmer blocked it.

Critical ecosystems are at risk of collapsing (1) If current rates of biodiversity loss continue, every critical ecosystem is on a pathway to collapse. An ecosystem collapses when it passes beyond a critical threshold or tipping point, after which it can no longer maintain essential functions or structure, leading to extensive shifts to its size and composition. The ecosystem transitions irreversibly from one stable state to another. For instance, the Amazon basin collapse would see it shifting to a drier savannah state. Collapse impairs an ecosystem’s ability to provide vital services including clean water, food production, and climate regulation. This could accelerate climate change and biodiversity loss and have catastrophic implications, including the collapse of major food sources and fundamental changes to global weather patterns and the water cycle. As biodiversity loss and degradation continue, impacts become more severe and the likelihood of ecosystems collapsing increases. It is likely that ecosystem collapses would happen concurrently given their shared drivers and feedback loops. There is a high degree of uncertainty around the timing and pathways of ecosystem collapse. The drivers of ecosystem degradation are approaching the known thresholds for collapse - for example, the Amazon is likely to collapse at 20-25% deforestation when combined with temperature rises and forest fires; it is currently at 17%. 9-13 But the thresholds for collapse could be higher or lower than the science has been able to identify: we could be closer to, or further away from, the thresholds than we think; and there could be additional thresholds that we do not know about yet. There is a realistic possibility that trends to date mean we have unknowingly crossed thresholds already and irreversible collapse of some ecosystems is inevitable (for example coral reefs), though we may not see the impacts for several years. There is a realistic possibility some ecosystems start to collap…
Evan Greer@evangreer.bsky.social · 2w ago

Age verification makes everyone less safe. Age verification makes everyone less safe. Age verification makes everyone less safe. Age verification makes everyone less safe. Age verification makes everyone less safe. Age verification makes everyone less safe.

Hackers Had A Live Feed Of Every ID This Verification Company Scanned. For Over A Year.

From the very beginning of this recent obsession with identifying everyone online (yes, they like to call it "age" verification, but it always ends up as identity verification), we've been pointing out that it was a huge privacy nightmare waiting to happen. Or maybe it wasn't waiting. Maybe it was already happening. This week a...

techdirt.com

Alex Nelson@pqnelson.bsky.social · 2w ago

In programming, when you transform an object into a string representation, that's called 'serialization' (and reconstructing the object from the string is 'deserialization'). More generally, what's the verb for taking something in the metalanguage and describing it in the object language?

Alex Nelson@pqnelson.bsky.social · 2w ago

The Sedonions are an "algebra" with a norm, but the norm is incompatible with the algebra structure. Namely, the norm has degeneracies: there are nonzero elements, which are not zero divisors, whose norm is zero.

Alex Nelson@pqnelson.bsky.social · 3w ago

Megan McArdle certainly sounds like the "I have a pet theory, and everything is neatly explained by it. And even when it's wrong, it's secretly correct."-type of "thinker"...

Alex Nelson@pqnelson.bsky.social · 3w ago

Yeah, it seems like "extensible structures" is an under-studied subject of proof assistants, and first-class extensible structures seems to have been re-invented multiple times independently.

Alex Nelson@pqnelson.bsky.social · 3w ago

Fun fact: quaternionic Hilbert spaces are naturally one-sided (either a "left module over the quaternions + an inner product" or a "right module over the quaternions + an inner product"), but there is a way to make it 2-sided in a *VERY NON-CANONICAL* manner.

Alex Nelson@pqnelson.bsky.social · last mo.

"The most potent weapon any opposition has against an authoritarian regime is the charge of corruption, and that charge rings hollow when every desperate plea sent under the party’s name validates the cynical belief that both parties are corrupt." True, and heart breaking.

Adam Bonica@adambonica.bsky.social · last mo.

I wrote this because most journalists facing this pressure can’t. The paper we count on to check authoritarianism spiked an investigation into the Democratic Party because the party’s lawyers threatened to sue. Holding authoritarians accountable starts with holding your own side accountable.