davidsuculum

johncarlosbaez, 9 days ago (edited 9 days ago) to random

The precise location of the boundary between the knowable and the unknowable is itself unknowable. But we 𝑑𝑜 know some details about 𝑤ℎ𝑦 this is true, at least within mathematics. It's being studied rigorously in a branch of theoretical computer science called 'meta-complexity theory'.

For some reason it's hard to show that math problems are hard. In meta-complexity theory, people try to understand why.

For example, most of us believe P ≠ NP: merely being able to 𝑐ℎ𝑒𝑐𝑘 the answer to a problem efficiently doesn't imply you can 𝑠𝑜𝑙𝑣𝑒 it efficiently. It seems obvious. But despite a vast amount of work, nobody has been able to prove it!

And in one of the founding results of meta-complexity theory, Razborov and Rudich showed that if a certain attractive class of strategies for proving P ≠ NP worked, then it would be possible to efficiently crack all codes! None of us think 𝑡ℎ𝑎𝑡'𝑠 possible. So their result shows there's a barrier to knowing P ≠ NP.

I'm simplifying a lot of stuff here. But this is the basic idea: they proved that it's probably hard to prove that a bunch of seemingly hard problems are really hard.

But note the 'probably' here! Nobody has 𝑝𝑟𝑜𝑣𝑒𝑑 we can't efficiently crack all codes. And this too, seems very hard to prove.

So the boundary between the knowable and unknowable is itself shrouded in unknowability. But amazingly, we can prove theorems about it!

https://www.quantamagazine.org/complexity-theorys-50-year-journey-to-the-limits-of-knowledge-20230817/

davidsuculum, 11 days ago to climate

This could be a nice set of resources for using Python in #climate, #climatology and #meteorology.

I link a tutorial for extreme values. It doesn't include "peak over threshold" analysis, but you have pyextremes for that (and R).

Tutorial 4: Return Levels Using Normal and GEV Distributions — Climatematch Academy: Computational Tools for Climate Science
https://comptools.climatematch.io/tutorials/W2D4_ClimateResponse-Extremes%26Variability/student/W2D4_Tutorial4.html

davidsuculum, 16 days ago to random

The association of Stack Overflow and chatGPT is exactly a proof of what it has already been said: the knowledge created by many people for free and to help others will be served to you for the cost of a premium account.

ColinTheMathmo, 1 month ago to random

Kurt Vonnegut tells his wife he's going out to buy an envelope:

“Oh," she says, "well, you're not a poor man. You know, why don't you go online and buy a hundred envelopes and put them in the closet?"

And so I pretend not to hear her. And go out to get an envelope because I'm going to have a hell of a good time in the process of buying one envelope.

I meet a lot of people. And see some great looking babies. And a fire engine goes by. And I give them the thumbs up. And I'll ask a woman what kind of dog that is. And, and I don't know. The moral of the story is - we're here on Earth to fart around.

And, of course, the computers will do us out of that. And what the computer people don't realize, or they don't care, is we're dancing animals. You know, we love to move around. And it's like we're not supposed to dance at all anymore.

---

Let's all get up and move around a bit right now... or at least dance.

johncarlosbaez, 1 month ago (edited 1 month ago) to random

"Nature in Descending Regions" from Levi Walter Yaggy's 1887 𝐺𝑒𝑜𝑔𝑟𝑎𝑝𝘩𝑖𝑐𝑎𝑙 𝑃𝑜𝑟𝑡𝑓𝑜𝑙𝑖𝑜—𝐶𝑜𝑚𝑝𝑟𝑖𝑠𝑖𝑛𝑔 𝑃𝘩𝑦𝑠𝑖𝑐𝑎𝑙, 𝑃𝑜𝑙𝑖𝑡𝑖𝑐𝑎𝑙, 𝐺𝑒𝑜𝑙𝑜𝑔𝑖𝑐𝑎𝑙, 𝑎𝑛𝑑 𝐴𝑠𝑡𝑟𝑜𝑛𝑜𝑚𝑖𝑐𝑎𝑙 𝐺𝑒𝑜𝑔𝑟𝑎𝑝𝘩𝑦. This popular set of maps and charts was intended for use in classrooms. Each page was 2 feet by 3 feet in size!

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davidsuculum, 1 month ago to random

To be honest, I've always thought that Newton's Third Law is something arcane.

Why what the Münchausen baron did to escape a swamp (pulling himself up from the hair) doesn't work in real life? Or why a lot of fans in a sailboat can't push it forward?

The reason is Newton's Third Law, in the previous cases the force and its reaction cancel out because they have the same application point. To me this seems a little bit of a medieval, alchemist explanation. But I don't know how to do it better, not even appealing to more modern or fundamental concepts.

davidsuculum, 1 month ago to random

It's curious how you can plot a curve in "Asymptote". In libraries like matplotlib you plot (sin(x)) giving many values for x in an interval.

In "Asymptote" you get a very decent sinusoidal curve giving three points, for instance ((0, \pi/2, \pi)) and the tangent vector there. I had never seen it.

davidsuculum, 1 month ago to random

I watched a movie of the Marx Bros tonight. Besides the humour, Chico and Harpo were masters playing the piano and the harp, respectively.

davidsuculum, 1 month ago to physics

A physicist friend of mine has sometimes expressed that Einstein is shown as if after GR he achieved nothing, and that that seems hard to believe. Even acknowledging his stubbornness despising quantum mechanics, it seems unreasonable that there's nothing relevant or at least interesting in what he was doing after 1920.

I agree with my friend, so I looked for something and found this: what Einstein wrote in 1928, he was looking at the spacetime using the "vierbein" formalism, a kind of square root of the metric that I think it's used to introduce matter fields in spacetime.

(I think this could change at any moment. One day a researcher or a science historian could republish a result from those years of Einstein, perhaps linking it to a contemporary question, and then everybody would be super interested in Einstein from 1925 onwards). #physics

https://arxiv.org/abs/1106.2037

davidsuculum, 2 months ago to math

Do you know what software can I use to generate beautiful explanatory images at the style of this one? Preferably not TikZ. Source: https://youtu.be/T0V08u4t-cg?si=n486IrxVtnpEOQe0
#math #physics

Johannab, 2 months ago to random

Hey there Wandering.shop regulars … @AstroKatie over on her Bsky account has a “can anyone find me the title/author of this story… “ question and allowed me to share her request over here.

https://bsky.app/profile/astrokatie.com/post/3knta6oj2gt2y

Does this ring a bell for any of you hardcore SF&F writers/readers?

ColinTheMathmo, 2 months ago (edited 2 months ago) to random

This must be a solved problem ...

A group I'm in is reviewing and revising a document. It's a word document, because some of them are seriously, seriously technically challenged, and that seems to be the only thing they can cope with.

But making comments on and passing copies around of a Word document is just a completely nightmare, and it ends up ... as you will all know ... a mess of formatting, wrong versions, just ... urgh.

If there is a website with the document visible and little boxes spread throughout into which people can type comments to be collected and collated, that would be much easier.

Is there such a thing?

davidsuculum, 2 months ago to random

In "Metazoa", by Peter Godfrey-Smith, I've been reading about thr Ediacaran period. It was before the more famous Cambrian period. The Ediacaran is famous for its relative calm, there was no signs of predation, of any defensive or offensive structure (there's no evidence of claws or thorns).

Some lifeforms were like worms, others like bags, disks... Wikipedia says it's not clear if some of them were animals or big protists, and perhaps many of them were lines of the tree of life that didn't continued. It seems that connecting many Ediacaran lifeforms with the posterior life of the Cambrian is not easy.

The book is interesting. Since the focus is the origin of the consciousness, the origin of life, perhaps 3800 millions of years ago, is not analyzed. I should look for other book for that.

davidsuculum, 2 months ago to random

A Japanese mathematician claims that he has found a formula for the weekday that is simpler than the already existing ones. Probably, the best solution so far was the one proposed by John Conway.

A Simple Formula for the Weekday – ThatsMaths
https://thatsmaths.com/2023/06/22/a-simple-formula-for-the-weekday/

appassionato, 3 months ago to books

A Random Walk in Physics: Beyond Black Holes and Time-Travels by Massimo Cencini et al.

This book offers an informal, easy-to-understand account of topics in modern physics and mathematics. The focus is, in particular, on statistical mechanics, soft matter, probability, chaos, complexity, and models, as well as their interplay.

@bookstodon
#books
#nonfiction
#physics
#mathematics
#science

gregeganSF, 3 months ago to random

Me: Opening the doors and windows overnight will help cool the house down and get me through tomorrow’s expected 43°C!

Air outside, at 10pm: OK, I’m 30°C, is that helpful?

davidsuculum, 3 months ago to random

I've just known that Christopher Priest died three days ago. A great storyteller, in the British tradition of H. G. Wells. I want to read more by him. RIP.

davidsuculum, 3 months ago to random

I was talking the other day about wavelets and I found this, from @johncarlosbaez 's blog "Azimuth". Here, John and a colleague used the Gabor transform, very related to wavelets, to analyze the Milankovich cyles, an important concept in climate science.

It's really interesting. The Gabor transform, as the wavelets, show information in both frequency and temporal domain, contrary to a Fourier transform that takes you completely to the frequency world or the temporal one.

For a signal whose components may have changed through time, the Gabor can help more than a Fourier analysis. This in fact is what happened with Milankovich, where "recently", in the last million years aprox. the eccentricity seems to be the stronger signal.

Milankovich vs the Ice Ages | Azimuth
https://johncarlosbaez.wordpress.com/2013/01/30/milankovich-vs-the-ice-ages/

johncarlosbaez, 4 months ago (edited 4 months ago) to random

Camembert is an endangered species! It relies on a mold that had lost the ability to reproduce sexually... and now, thanks to inbreeding, this mold has also lost the ability to reproduce using spores. Roquefort is also in trouble, but for Camembert it's worse:

"The world over, this other symbol of French gastronomy is inoculated exclusively with one single strain of Penicillium camemberti, a white mutant that was selected for Brie cheeses in 1898 and Camemberts in 1902.

The problem is that ever since then the strain has been replicated by vegetative propagation only. Until the 1950s, Camemberts still had grey, green or in some cases orange-tinged moulds on their surface. But the industry was not fond of these colours, considering them unappealing, and staked everything on the albino strain of P. camemberti, which is completely white and moreover has a silky texture. This is how Camembert acquired its now-characteristic pure white rind.

Year after year, generation after generation, the albino strain of P. camemberti, which was already incapable of sexual reproduction, lost its ability to produce asexual spores. As a result it is now very difficult for the entire industry to obtain enough P. camemberti spores to inoculate their production of the famous Norman cheese.

Worse still, while the Roquefort PDO (Protected Designation of Origin) standard retains a degree of microbial biodiversity, the PDO specifications for Camembert require farmers and other producers to use P. camemberti exclusively."

What to do about it? Switch to eating American cheese, or Velveeta? Read on....

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