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The recent book Mathematica by David Bessis attempts to describe this exact topic. One core theme of the book is that math is done by building mental models and using our intuitions that come from. Formalism is then used to shape and refine these models. By spending time developing these models, insights eventually become obvious. These mental models are the essence of mathematics, not theorems. The author explicitly uses neural networks as an example to describe how this negative feedback could work to make these changes to our mental models happen in our brains.

The core premise of the book is to describe how mathematicians work and think and to show that this is a process that everyone can do (although some will be better at it than others). It includes interesting accounts of Grothendieck, Bill Thurston, and Descartes as well as from the author's own research career at Yale and École normale supérieure. The book is targeted at the general reader and at times reads a little like a self-help book, especially in the first third or so. However, I found it to be an enjoyable and fascinating read. It provoked a lot of interesting questions about the nature of learning and provided a framework to begin to answer them (e.g. "How can I have proved something and yet feel no understanding of it?", "How can some people solve problems orders of magnitude faster than other smart people, as if they don't even have to think about it?", "Why do I sometimes watch a presentation on a new topic, follow every step, and come away feeling like I've learned nothing?"(* see except below)). I don't think I'm doing it justice here, so I'll stop by saying I highly recommend it based on your comment.

_______

* I'll use this as an excuse to provide a related excerpt featuring Fields Medalist and Abel Prize winner Jean-Pierre Serre:

One day, I had to give a lecture at the Chevalley Seminar, a group theory seminar in Paris. I didn't have substantial new results to announce, but it was an opportunity to make a presentation even simpler than usual. [...] A couple of minutes before the talk was to start, Serre came in and sat in the second row. I was honored to have him in the audience, but I let him know right off that the presentation might not be very interesting to him. It was intended for a general audience and I was going to be explaining very basic things.

What I didn't tell him, of course, was that his presence was intimidating. Still, I didn't want to raise the level of my talk only to keep him interested. I just kept an eye out to see if he'd taken off his glasses, which would mean he was getting bored and had stopped listening. No worries there—he kept his glasses on till the end.

I gave my presentation as I would have without him there, speaking to the entire audience, especially the students seated in the back, whom I was pleased to see listening and looking like they understood. It was a normal presentation, fairly successful, not very deep but well prepared, clear, and intelligible. At the end of the seminar, Serre came up to me and said—and here I quote verbatim: "You'll have to explain that to me again, because I didn't understand anything."

That's a true story, and it plunged me into a state of profound perplexity.

Apparently, Serre wasn't using the verb to understand the way most people use it. The concepts and reasonings of my talk couldn't really have caused him any difficulty. I'm sure he wanted to say that he understood what I had explained, but he hadn't understood why what I had explained was true.

There are two levels of understanding. The first level consists of following the reasoning step by step and accepting that it's correct. Accepting is not the same as understanding. The second level is real understanding. It requires seeing where the reasoning comes from and why it's natural.

In thinking again about Serre's comment, I realized that my presentation had too many “miracles,” too many arbitrary choices, too many things that worked without my really knowing why. Serre was right; it was incomprehensible. His feedback helped me become aware of a number of very big holes in my understanding of the objects and situations I was working on at the time. In the years that followed, research into explanations for these various miracles allowed me to fill in some of the holes and achieve some of the most important results of my career. (However, some of the miracles remain unexplained to this day.)

But the most troubling aspect was the abruptness, the frankness with which Serre had overplayed his own incomprehension.

Adult Swim's 404 page always has a dark, sometimes surreal, shaggy-dog story that ends with a reference to the page being 404.[1]

The page seems to return the same story each time you access it (at least on the same day). I'm not sure when they change from one story to another. The author has posted some of the other stories on other sites.[2][3][4][5] I still vividly recall reading this one in particular (although this reproduction is missing the bolding of the text in the second to last paragraph).[6]

[1] https://adultswim.com/404

[2] https://www.reddit.com/r/adultswim/comments/l48nii/the_sites...

[3] https://www.jchristopherarrison.com/crash

[4] https://www.jchristopherarrison.com/bar

[5] https://www.jchristopherarrison.com/departuredate

[6] https://www.reddit.com/r/adultswim/comments/9efd3s/adult_swi...

To provide a bit of context, this article is about Timothy Burke. His most famous work is the compilation video of news anchors on Sinclair-owned local news stations reading the same script about how media bias is "extremely dangerous to our democracy.”[1] He is also known for breaking the infamous Manti Te'o fake girlfriend story.[2] Additionally, he is noted for having a complicated computing setup to monitor, archive, and disseminate videos from dozens of live sources simultaneously. Some of these details appeared in a profile by the New York Times [3] and also appear in this article.

Burke often shares short clips of offbeat moments from sports and news channels. The article states that he has recently shared behind-the-scenes clips of Tucker Carlson on his former Fox show; it appears likely that this raid was related to determining the origin of those clips.

[1] https://www.youtube.com/watch?v=_fHfgU8oMSo

[2] https://en.wikipedia.org/wiki/Manti_Te'o#Catfishing_incident

[3] https://www.nytimes.com/2013/10/22/sports/deadspins-tim-burk...

Janet for Mortals 3 years ago

The prefix notation may be throwing you off or perhaps you have mistaken the function `bottles` for the string "bottles".

The code `(bottles i)` in the loop is calling the function `bottles` (defined at the top) with the argument `i`. The value of `(bottles 99)` is `(string 99 " bottles")` which evaluates to "99 bottles", as expected.

This image is even more worthless than it seems. The post on Wikimedia is an original work. Its description states: "As the percentage of graduates increases the minimum IQ to include at least that percentage of graduates inherently decreases. Since 2000 the intelligence required to be a college graduate has been less than the intelligence required to graduate from high school in 1940, based on a standard distribution."

It seems the author took the the percentage of the population that graduated high school/college each year and then found the corresponding percentile on an IQ bell curve and used those as the y-values. This methodology only makes sense if you assume that high school/college graduates are exactly the highest IQ population and that everyone who does not graduate isn't intelligent enough to do so. This chart also almost certainly doesn't normalize IQ over time, even though IQ is constantly redefined so that 100 is average while raw intelligence scores have increased over time [1].

What this chart actually shows is the highest possible IQ of the graduate with the lowest IQ in a given year, a statistic that seems to have dubious value.

[1] https://en.wikipedia.org/wiki/Flynn_effect

I agree; this story is apocryphal. I was annoyed enough that I did some research into the story. Via this Atlantic article[1], I found the original Valleywag post[2] containing the letter from the employee. It's worth noting that the letter from the employee is pure text (i.e. not a scan of a letter), is only 170 words long, and has a couple of misspellings. The Valleywag post provides a paraphrasing of what the employee told them, followed by what seems to be the entire body of the email that they received.

The Musk detective work is described by Vance in a footnote:

“Musk would later discover the identity of this employee in an ingenious way. He copied the text of the letter into a Word document, checked the size of the file, sent it to a printer, and looked over the logs of printer activity to find one of the same size. He could then trace that back to the person who had printed the original file. The employee wrote a letter of apology and resigned.”

This leaves me a with more than a few questions:

1. Why would this email/letter have been printed out? It's short, informal, and did not seem to contain any corporate materials that would require access from a work computer. Surely, this would be better sent as an email from a personal computer? All I can think of is that the employee did print some kind of private company information (perhaps as proof?) to send to Valleywag. But wouldn't this mean that the print-job sizes wouldn't match since there would be printed materials not made public? It seems beyond insane to physically mail a tip to a gossip site that was built around emailed tips.

2. If this was sent as a physical letter, why would the quote in the article contain the typos? Why would they even take the time to type up the entire letter when the article summarizes every single point that the Tesla employee mentioned? Shouldn't they have taken some care to not verbatim reproduce text that could have gotten their source into trouble? I will say that the minimal journalistic standards employed by former Gawker-network sites provide convenient explanations to these questions, so these aren't particularly damning.

3. Is this really all the text that was sent to Valleywag? The quoted part of the letter provides no salutation or signature. Sending this text exactly as quoted as a physical letter seems bizarre, even for an anonymous tip.

4. Would the sizes of the files sent to the printer even match up considering the document metadata? This actually seems somewhat plausible.

5. Would the print-job really be the best way to figure out who the leaker was? In October 2008, before the letter was written, Tesla only had 363 employees[3] and may have laid off a few dozen of them before this letter was written. This employee claims to have joined in 2004. A Wired article from 2006[4] mentions a meeting of 30 Tesla employees and board members in December 2004. It seems like there are a very small number of people who could have been the potentially leaker. How many of those people were using the corporate printers the day after the mentioned all-hands meeting to print a single page document?

--------

I imagine that this story was told to present Musk as smarter than everyone else while also threatening disloyalty, which seems to be a frequent Musk bugbear. The bit about the caught employee writing a letter of apology and then resigning (amidst large-scale layoffs at Tesla in 2008!) also seems a little too cute, in a chain-email-atheist-professor-humiliated-by-freshman-Albert-Einstein kind of way.

--------

[1] https://www.theatlantic.com/technology/archive/2018/06/elon-...

[2] https://www.gawker.com/5071621/tesla-motors-has-9-million-in...

[3] https://www.latimes.com/archives/la-xpm-2008-oct-25-fi-tesla...

[4] https://www.wired.com/2006/08/tesla-3/

Moving to Estonia 4 years ago

I really enjoyed the second example of paying Netflix by the second. The blockchain has invented movie rentals.

I wasn't thinking about that when I commented, but you're absolutely right. I definitely missed the point.

I don't think there is any way to generalize the algorithm in the article to work on the method I described. However I was able to find an alternate algorithm to find the initial node of the cycle. It also has linear time complexity and constant storage, but it requires that the pointers in each node be mutable. It is also worse than Floyd's algorithm in almost every way. The algebra gets a little annoying, so I've just provided the informal algorithm below.

0) Find the meeting point as described above.

1) Find the cycle length.

2) Find the distance to the meeting point k+x (where k is the length of the linear portion and x is the number of nodes from the start of the cycle to the meeting point).

   2a) If the hare speed is double the tortoise speed and the tortoise speed is less than the cycle length, this can be found directly.

   2b) Otherwise, we can send a probe from the head until it reaches the meeting point.
This unfortunately this isn't enough information to find the initial node of the cycle, so more drastic measures are needed.

3) Reverse all of the nodes of the cycle (We can actually do this during step 1 if we want to be more efficient, although some care needs to be taken (e.g. that step 2b is performed first).)

4) Send a probe from the head and count the steps until it reaches the meeting point node. This will have gone k + m - x steps.

5) Now we use some algebra to get x in terms of k and known values. We can substitute this into our equation that gives a known value for k+x (from step 3) to find k.

6) Reverse all the nodes of the cycle so they are back to how they originated.

7) Advance k times to reach the first node of the cycle; return this node.

The additional steps have a linear order complexity with respect to the number of nodes of the linked list. And like the OP algorithm, only a constant amount of storage is necessary, although reversing the list will require a couple more pointers to nodes. I'm not sure if there are many cases where this would perform better, but if they do exist they seem like they would be extremely rare.

If you check every node that the hare enters, you don't need the relative speed to be coprime to the cycle-length. This eliminates the need for the hare and tortoise to finish a round on the same node; the hare passing the tortoise is sufficient evidence to detect a cycle.

This change adds a performance penalty with the extra equality checks, but can reduce the total number of steps in certain contexts (e.g. lists with long cycles that appear at an early node can benefit from a much faster hare).

In addition to its annoying layout, this site bizarrely decides to mix public domain works from the various different major copyright systems together (life + 50 years, life + 70 years, the old American system of 95 years). For example, Nabokov's first novel in Russian, Mary, is listed because it was published in 1926; he died in 1977 which means in virtually every non-American country, that work will still be copyrighted until 2028.

They also include Jim Morrison who died in 1971, whose death is only relevant to the countries still on the life + 50 years system. However, it seems like very few of the Doors' songs give just Morrison songwriting credit. This means that only a small handful of Doors songs will be in the public domain in those countries and most likely this will not apply to the recordings either.

For American readers, the best way to find out what will be entering the public domain is to go directly to the Wikipedia pages for the "1926 in literature"[1], "1926 in film"[2], etc.

[1] https://en.wikipedia.org/wiki/1926_in_literature

[2] https://en.wikipedia.org/wiki/1926_in_film

That's a really good method. I think one of the reasons why this works so well is that it makes the student think about the "why". Most people are more likely to follow rules they understand (so long as they agree with why they exist).

Telling someone to not drink on a boat is a prescriptive rule. Telling someone not to drink on a boat because being drunk will make it easier for them to drown is too vague. Including specific reasons might help, but it is easy for the student not to internalize these explanations, especially since they would likely prefer to not think about drowning.

Turning this around puts the negative outcome, drowning, in the forefront. This puts the focus on the reason why the rule was created. By thinking about why being drunk will increase their chances of drowning, they will better understand why they should follow the "no drinking" rule. In your case, it sounds like you even have them derive the rule itself. This requires at least some thought about the issue and should make it more likely that they will both remember and follow the rule.

I would guess that this technique is most effective when the negative outcome is severe and/or something the student doesn't want to think about (e.g. dying). By focusing on how to cause these negative outcomes, the student is forced to think about things they may otherwise try to avoid.

It also seems that this technique is effective when the positive outcome is the negation of the conjunction of the negative outcomes. For example, consider the goal of "staying safe while boating". Being safe is easiest to define as not doing any of the things that increase the chance of danger, or, in other words, "not being unsafe". Being unsafe in general is the conjunction of all the ways of being unsafe specifically ("NOT being drunk while boating" AND "NOT entering the water without a life jacket" AND ...). Being safe requires avoiding unsafe outcomes. By flipping the goal, it becomes more clear that we need to figure out what the unsafe outcomes are. Once these are determined, we can start to come up with ways to avoid them.

I also thought this was odd. This site alleges malfeasance based purely on analysis of data but then alludes to a person's thoughts on specific dates without citation.

I also found this article on 2020/12/21 where Pelosi says she wanted more stimulus, but the $600 checks were significant.[1] So it seems all the more unlikely that she said she was against further stimulus at any point on the 22nd.

[1] https://news.yahoo.com/nancy-pelosi-wanted-more-600-22542493...

It's tough to come to any conclusion from looking at eBay listings. Especially when many of the listings are from possible scammers.

Sort by "most bids" and set the minimum value to $100. Only a few have even a single bid, with just a couple having multiple bids. Also, the most expensive single-bid items all have sellers with no feedback. The market price is one that buyers are willing to pay, not just one sellers are willing to list.

You should probably call your mom anyway though. I'm sure she'd appreciate the chance to talk to you.

It's worth noting that Matt Levine has a lot of other good writing on SPACs. (And economics in general. To anyone reading this comment, I highly recommend his daily newsletter "Money Stuff", which is where these excerpts come from).

On how SPACs can end up giving more money to banks than IPOs:

"But for another thing, a lot of people are dissatisfied with the process for selling stock; they think that investment banks make too much money and do not have issuers’ interests at heart, and so they are looking for ways to sell stock more cheaply and to cut out the role of the investment banks. And the ways that they have discovered, the methods that they tout to cut out the middleman and free companies from the tyranny of Wall Street banks, all involve (1) hiring Wall Street banks and (2) paying them tons of money. It’s so good!

[...]

Venture capitalists and SPAC sponsors sometimes suggest that this is a way to cut out Wall Street and avoid expense, but that is not true. Not only is the SPAC expensive because its sponsor—the person who sets up the shell company and searches for a target to take public—charges for her efforts, but the SPAC also has to pay banks to do its own IPO. And maybe to search for the target, execute the merger, and otherwise be around to provide banking services. And so, unsurprisingly, banks love SPACs.

[...]

This is really the kind of business you want to be in, the kind where (1) it is so lucrative that your customers are constantly complaining that you make too much money, but (2) when they want to disrupt your business, they come to you to disrupt it and pay you even more money."[1]

Another article mentions that companies sometimes prefer merging with SPACs than having an IPO in volatile markets due to the uncertainty involved in an IPO:

"Compared to an IPO, the SPAC is much less risky for the company: You sign a deal with one person (the SPAC sponsor) for a fixed amount of money (what’s in the SPAC pool 2 ) at a negotiated price, and then you sign and announce the deal and it probably gets done. With an IPO, you announce the deal before negotiating the size or price, and you don’t know if anyone will go for it until after you’ve announced it and started marketing it. Things could go wrong in embarrassing public fashion.

In volatile times, that certainty is worth a lot more, so companies are looking for it.

[...]

There is a problem, a risk: Companies want to go public, but they are worried about the risk of the market collapsing. There is a solution, a holder of the risk: A SPAC will take a company public in a fully sold deal with a fixed price and size, so they don’t have to worry about the market collapsing. There is a price: The SPAC doesn’t take this risk because it is nice, or foolish; it takes this risk because it expects to make much more money than a typical IPO investor. In normal times, the risk is low, the compensation is low, and the tool is not used that much. In volatile times, the risk is high, the compensation is high, and people talk about SPACs a lot." [2]

He then goes on to note that SPACs have their risks too, including the same kind of public embarrassment that an IPO can bring. The share-holders of the SPAC can vote against an announced merger, which happened last year when the investors of the SPAC Far Point decided against merging with the company Global Blue.

"Ordinarily, in a public-company merger, if a board of directors changes its mind like this it needs to pay the other side a big termination fee, but SPACs are just pots of money held in trust for public shareholders so its harder to do that; the Far Point merger agreement has no termination fees. Just as in an IPO, the deal isn’t really done until you get the cash, and while you’re more likely to get the cash in a SPAC merger than in an IPO, there’s still some risk." [2]

[1] https://www.bloomberg.com/opinion/articles/2020-07-30/kodak-...

[2] https://www.bloomberg.com/opinion/articles/2020-07-14/everyo...

European newspapers can be even worse. Le Monde, one the biggest French newspapers, requires its customers to unsubscribe via registered mail. This is even the case for digital-only subscriptions.

I found a link to a video with a large portion of the debate[1], though I can't vouch for whether watching it is worthwhile. From quickly comparing bits of it to a transcript[2], it seems like at least some of the debate has been cut out. However, to the video's credit, it does have the full visual effects of Leary's presentation in color.

[1] http://openvault.wgbh.org/catalog/V_0669B2FE8ADC4F80A8D89CB5... [2] https://www.swt.org/oshare/Lettvin-Leary/Lettvin-Leary-LSD-D...

The two blues are identical: the CSS has them both colored as "dodgerblue."

Facebook appears to be the only one in the "Proprietary" category. The rest of the blue ones are all "Chrome."

Org-Capture creates a temporary buffer, inserts its template string, processes the special escape sequences (called "%-escapes")[1], and then lets the user edit the buffer before adding it as an entry. Where the entry goes is specified by the code that sets up the template.

The power here comes from the %-escapes, which range from asking the user for a prompt and pasting it in that location ("%^{PROMPT}") to arbitrary code execution ("%(EXP)") that can include text input from the user from other %-escapes. There are escapes to insert the file name ("%f") and the full file path ("%F") of the file that was visited when the template was triggered.

I think it's a lot easier to evaluate this kind of thing in action rather than in screenshots, so I've added an example screen recording[2] with a keylogger to show what a capture using a fairly simple template looks like. This Imgur album has both the screen recording as well as what the resulting entry looks like after it is saved.

[1]https://orgmode.org/manual/Template-expansion.html [2]https://imgur.com/a/l8jwbnN

In Emacs, an org-capture template[1] can be used to quickly and easily append new items to logs. It can prompt the user to enter text in multiple locations, eliminating the need to navigate around boilerplate to write entries. It can also prompt for tags to help make organization and searching easier. Additionally, it has the benefit of being callable anytime and anywhere within Emacs.

I've only recently gotten around to using them, but they're really nice for quickly logging things that I was too lazy to do otherwise (e.g. recipes I have tried).

[1]https://orgmode.org/manual/Capture-templates.html

I use MIPAV[1] which can run on Linux (or any OS with a new enough Java Runtime Environment). I don’t have a lot of experience with other DICOM viewers and have somewhat limited use cases for it, but it seems to have a good number of features.

It’s completely free, but accessing the download (or the source) requires (free) registration.[2] Filling out the form should take you straight to the download links (i.e. you should not have to wait for a manual approval to download).

[1] https://mipav.cit.nih.gov/ [2] https://mipav.cit.nih.gov/clickwrap.php

I took the (Penn) Calculus sequence by Robert Ghrist and really enjoyed it as a review of single variable calculus. He uses Taylor series as the basis of his explanations which I felt was really clean way to provide intuition for some of the more complicated theorems and formulae. The lecture videos have high quality animations and are broken into digestible chunks (around 10-15 minutes each). The downside is that only a few example problems are shown being worked out, but I only found this to be an issue for a few of the lectures (mainly in the applied calculus section of the course).

The course also covers some interesting, non-standard topics. In particular, I liked the lecture on a discrete version of calculus (https://www.youtube.com/watch?v=NHa8UgWigZk) which can be used to find easy solutions to series and recurrence relations (e.g. the "discrete anti-derivative" can be used to provide quick closed-form solutions to sums of the form "n^k from n=1 to K" - an example occurs at the 5:28 mark of the linked lecture, but some background from earlier in the video will be necessary to follow along).

The lecture videos are available on Youtube (https://www.youtube.com/playlist?list=PLKc2XOQp0dMwj9zAXD5Ll...), but I would recommend working through the problems on Coursera (especially the challenge problems) as well. I would also recommend that viewers watch the videos as 1.5x speed or faster. Dr. Ghrist speaks so slowly in these videos that I found it distracting.

For those who have some knowledge of the standard intro calculus textbooks, the level of rigor and difficulty in this course is above the Stewart book that many universities use, but below the Spivak/Apostol/Courant type of book that an honors course may use.

This used to be a single course, but Coursera split it up into 5 pieces, with somewhat unhelpful names. The sequence is "Part 1 - Functions"[1], "Part 2 - Differentiation"[2], "Part 3 - Integration"[3], "Part 4 - Applications"[4], and "Part 5 - Discrete Calculus"[5]. The first four parts names are reflected in their Coursera titles, but the "Discrete Calculus" course is titled "Single Variable Calculus" instead since it contains the final exam for the overall sequence.

It's also worth mentioning that Dr. Ghrist also has other video lectures available on Youtube (https://www.youtube.com/c/ProfGhristMath) for other math courses including a sequence on multivariable calculus called "Calculus Blue."

[1] https://www.coursera.org/learn/single-variable-calculus

[2] https://www.coursera.org/learn/differentiation-calculus

[3] https://www.coursera.org/learn/integration-calculus

[4] https://www.coursera.org/learn/applications-calculus

[5] https://www.coursera.org/learn/discrete-calculus

I'm not sure why Sartre is quoted in Italian here, but this seems to be a spurious quote all the same. I could only find two sources with a version of that quote in French and neither had a citation of the original source. In fact, the only real quote from him I could find on soccer was «Au football, tout est compliqué par la présence de l'équipe adverse» ("In football, everything is complicated by the presence of the other team.").

Interestingly, during my search I found an apt quote for this discussion from another 20th century French philosopher. Camus once said «Ce que je sais de la morale, c'est au football que je le dois» ("What I know about morality, I owe to football"). I guess he would be missing the point here too.

[dead] 6 years ago

He also has the incontrovertible proof of a screenshot anyone could have taken from any account that copied Trump's profile and cover photos.