Solution to Feynman's reverse sprinkler puzzle also applies to "silly sprinklers"
New study confirms 2024 "momentum flux theory" on how angular momentum of water flows drives rotation.
找到 478 篇相关文章
New study confirms 2024 "momentum flux theory" on how angular momentum of water flows drives rotation.
A dozen state attorneys general are trying to block the $110 billion merger of Paramount and Warner Bros Discovery they warn would raise movie prices and crush cable TV distributors. The states - California, Arizona, Colorado, Connecticut, Massachusetts, Minnesota, Nevada, New Jersey, New Mexico, New York, Oregon, and Washington - filed suit on Monday, arguing […]
Despite a complete lack of evidence, everyone from Russia to Israel and Iran is being blamed for Lindsey Graham’s death.
Despite a complete lack of evidence, everyone from Russia to Israel and Iran is being blamed for Lindsey Graham’s death.
Described as the “feel-good movie of white-boy summer” by one extremist, the movie Citizen Vigilante has been hailed by the far-right as a way to convert moderates to their cause.
Ask most people to name the chip that started modern electronics and they will say the microprocessor. But there is a quieter hero inside almost everything you own that beeps, blinks, or connects to the internet: the microcontroller. And the first one you could actually buy shipped in 1974 as the Texas Instruments TMS1000. Microprocessor vs. microcontroller The distinction matters. A microprocessor, like Intel's famous 4004, is just the processing core. To build anything useful with it you still have to wire up separate memory chips, input/output controllers, and support logic on a circuit board. A microcontroller collapses all of that onto a single piece of silicon: the CPU, the ROM that holds your program, the RAM that holds your data, and the I/O pins that talk to the outside world, all in one package. That is exactly what the TMS1000 did. Designed by Texas Instruments engineers Gary Boone and Michael Cochran, it was a 4-bit device using a Harvard architecture, meaning it kept program memory and data memory in separate spaces so it could fetch an instruction and read data at the same time. One chip in, one chip out, and you had a complete tiny computer dedicated to a single job. Cheap enough to put in everything The genius of the TMS1000 was not raw power, it was economics. In 1974 you could buy the chips in volume for around two dollars each. By 1979, Texas Instruments was selling roughly 26 million of them every year. That price point changed what engineers could build. Suddenly it made sense to drop a small, programmable brain into products that never would have justified a full computer. You have almost certainly held one. The TMS1000 family ran the Speak & Spell, the Big Trak programmable toy vehicle, and the electronic memory game Simon, along with countless calculators, microwave ovens, and appliances. Each one was doing the same fundamental thing an IoT node does today: read some inputs, run a fixed program, drive some outputs. Why this still matters for
If you’ve ever struggled with CALCULATE() or wondered why SUMX() behaves differently from SUM() , this guide is for you. DAX (Data Analysis Expressions) is the language that powers Power BI , Analysis Services , and Power Pivot — enabling dynamic calculations, filtering, and time intelligence. Below is a categorized cheat sheet of essential DAX functions , plus examples showing how to use each in real-world Power BI scenarios. Filtering & Context These functions control how filters are applied and evaluated in your calculations. Function Example Description CALCULATE() CALCULATE(SUM(Sales[Amount]), Region[Name] = "Nairobi") Changes filter context to calculate total sales for Nairobi. FILTER() FILTER(Sales, Sales[Amount] > 10000) Returns a table filtered by condition. ALL() CALCULATE(SUM(Sales[Amount]), ALL(Region)) Ignores filters on Region. REMOVEFILTERS() CALCULATE(SUM(Sales[Amount]), REMOVEFILTERS(Region)) Removes filters from Region. VALUES() VALUES(Customer[City]) Returns unique list of cities. SELECTEDVALUE() SELECTEDVALUE(Product[Category], "All") Returns selected category or “All” if none. TREATAS() TREATAS(VALUES(Temp[City]), Customer[City]) Applies one table’s values as filters on another. KEEPFILTERS() CALCULATE(SUM(Sales[Amount]), KEEPFILTERS(Product[Category] = "Electronics")) Keeps existing filters and adds new ones. ALLSELECTED() CALCULATE(SUM(Sales[Amount]), ALLSELECTED(Region)) Respects user selections in visuals. ALLEXCEPT() CALCULATE(SUM(Sales[Amount]), ALLEXCEPT(Sales, Sales[Year])) Removes all filters except Year. Aggregation Summarize or aggregate data across rows or columns. Function Example Description SUM() SUM(Sales[Amount]) Adds all sales amounts. AVERAGE() AVERAGE(Sales[Amount]) Calculates mean value. COUNT() COUNT(Customer[ID]) Counts non-blank entries. COUNTROWS() COUNTROWS(Sales) Counts rows in a table. DISTINCTCOUNT() DISTINCTCOUNT(Customer[ID]) Counts unique customers. MIN() MIN(Sales[Amount]) Finds smallest sale. MAX() MAX(Sales[Amo
OrbitLens Ace → ace.orbitlens.io A busy quarter is easy to stage. Code that's still there in two years isn't. Pick any metric a team has ever used to judge people, and someone has quietly figured out how to move it without doing the underlying thing. Lines of code rewarded typing, so people typed. Commit counts rewarded committing, so commits got smaller and more frequent. Velocity rewarded closed points, and points drifted upward until a "3" meant nothing. DORA measured how often you deploy, so teams shipped trivial changes just to move it. Even churn — the number the "code health" tools lean on — is something you can lower on purpose, which means you can manage the number instead of the mess underneath it. None of that requires dishonest engineers. It's Goodhart's law doing what it always does. Every one of those numbers is a measure of activity , and activity is cheap to produce. Once you're paid for activity, the fastest way to get paid more is to produce more of it — not more of whatever the activity was supposed to be a sign of. So the question worth asking isn't which activity metric is least bad. It's whether a git history contains anything at all that you can't move just by being busier. It turns out there's one. And it's not because we were clever — it's because of what the thing is actually made of. What lasts isn't something you do Take everything a person wrote, wait a while, and ask a smaller question than "did they work hard." Ask whether the specific lines are still there. Not reverted, not rewritten, not quietly swallowed by someone else's refactor. Still holding weight at HEAD. That's survival. We read it with time-decayed git blame : a line's weight fades month by month unless the line keeps existing, and it counts for more once other people have built on top of it instead of leaving it as a private island. Survival that others have built on is what we call gravity — the structural pull that outlives the person who created it. Try to game it and w
Oregon Attorney General Dan Rayfield had been seeking documents from Paramount related to its takeover of Warner Bros. Discovery. Rayfield also asked a state circuit court judge to delay the closing of the deal by 60 days so that his office could review the documents. But according to Deadline and Variety, he's now dropped his […]
Harvard astrophysicist Avi Loeb will head the UAP Science Advisory Council established by the White House, the Pentagon, the Office of the Director of National Intelligence, the FBI, and "the intelligence community." The Council will provide scientific reports and advice to the UAP Governing Board, in an effort to "resolve the nature of UAP," or […]
It's unclear how the planet avoided its star's bloated red giant stage.
Adapted from an appendix of my MS thesis. Markov Chain Monte Carlo Almost as soon as computers were invented, they were used for simulation. Markov chain Monte Carlo (MCMC) was invested as Los Alamos, Metropolis et al (1953) simulated a liquid in equilibrium with its gas phase. Their tour de force was the realization that they did not need to simulate the exact dynamics, they only needed to simulate some Markov chain with the same equilibrium distribution. The Metropolis algorithm was widely used by chemists and physicists, but was not widely known among statisticians until after 1990. Hastings (1970) generalized the Metropolis algorithm, and simulations following his scheme are said to use the Metropolis-Hastings (MH) algorithm [1]. A special case of the MH algorithm was introduced by Geman et al (1984) discussing optimization to find the posterior mode rather than simulation. Algorithms following their scheme are said to use the Gibbs sampler. It took some time for the spatial statistics community to understand that the Gibbs sampler simulated the posterior distribution, thus enabling full Bayesian inference of all kinds. Gelfand et al (1990) made the wider Bayesian community aware of the Gibbs sampler, and then it was rapidly realized that most Bayesian inference could be done using MCMC, whereas very little could be done without MCMC. Green (1995) generalized the MH algorithm as much as it could be generalized [1]. Theoretical Foundations A sequence X 1 , X 2 , … of random elements of some set is a Markov chain if the conditional distribution of X n + 1 given X 1 , … , X n depends on X n only. The set in which the X i take values is called the state space of the Markov chain. A Markov chain has stationary transition probabilities if the conditional distribution of X n + 1 given X n does not depend on n . This is the main kind of Markov chain of interest in MCMC. The joint distribution of a Markov chain is determined by the following [1]. The ma
Reinforcement learning uses error information to adjust control algorithms.
Every camera-equipped connected device you build today, from a smart doorbell to an ESP32-CAM streaming frames over Wi-Fi to a factory machine-vision rig, is a descendant of one clunky, toaster-sized prototype: the first digital camera , built at Eastman Kodak in December 1975. It weighed about 8 pounds, took 23 seconds to capture a single 0.01-megapixel black-and-white image, and recorded that image to a cassette tape. It looked like a science-fair project, but it proved a radical idea that underpins the entire IoT sensing industry: an image could be captured, digitized, and stored as data with no film at all. An engineer, a side project, and a CCD The camera was built by a 24-year-old Kodak engineer named Steven Sasson . His manager had handed him a loose assignment: could the newly invented charge-coupled device (CCD) image sensor be used to build a camera with no moving film? The CCD, developed at Bell Labs in 1969, converts light falling on an array of tiny capacitors into electrical charge, pixel by pixel. Sasson took a Fairchild 100-by-100-pixel CCD, bolted it to a lens from a Super 8 movie camera, added a digitizer, and wired the output to a portable cassette recorder. The result captured just 0.01 megapixels, a grid of 10,000 pixels. To view a photo, Sasson's team built a custom playback rig that read the tape and painted the image onto a television screen. That first image, a Kodak lab technician, took 23 seconds to write to tape and several more to display. Crude, yes, but it was the first fully electronic, filmless photograph. Why Kodak shelved the future Here is the twist that every embedded engineer should remember. Kodak owned the patent on the first digital camera, but the company made its money selling film, chemicals, and photo paper. Executives saw a filmless camera as a threat to that business, so the project was quietly set aside. Kodak did file the patent in 1978 and collected licensing revenue for decades, but it never led the digital transiti
The Earth may not be that massive, but it still distorts space-time.
Meta is in breach of the EU's Digital Services Act (DSA), a preliminary investigation has found, over the "addictive" design of Instagram and Facebook. It's likely to be forced to redesign both apps and could face a fine of up to $12 billion. The European Commission said Meta "did not adequately assess the risks of […]
Searching billions of documents for a phrase and getting ranked results in tens of milliseconds looks like magic. It is not. It comes down to two ideas working together: an index that maps words to documents instead of scanning documents for words, and a way to spread that index across machines so each holds only a slice. Understand both and full-text search stops being mysterious. The core problem A database scans rows. If you ask a plain database to find every document containing a word, it reads documents and checks them, which is linear in the amount of data. That is fine for exact key lookups and hopeless for free-text search across huge corpora. You need the opposite mapping. Instead of "given a document, what words does it have", you want "given a word, which documents have it". That inversion is the whole trick. The second problem is size. One machine cannot hold the index for billions of documents, and one machine cannot serve the query load. So the index has to be split across nodes, and a query has to find the right nodes and combine their answers. Key design decisions Build an inverted index. At index time, each document is broken into tokens by an analyzer that lowercases, splits on word boundaries, and often strips or stems words. For every token, the engine keeps a posting list: the set of document ids that contain it, often with positions for phrase matching. A query for a word becomes a direct lookup of its posting list, not a scan. A multi-word query intersects or unions posting lists, which is fast because the lists are sorted. Store the index in immutable segments. New documents go into small new segments rather than editing existing ones. Segments are immutable, which makes them cache-friendly and safe to read without locks. A background process merges small segments into larger ones over time. A delete is just a marker; the document is removed for real during a later merge. Split an index into shards. An index is divided into shards, each a sel
Amid live coding sessions and Silicon Valley optimism, the UN’s AI for Good summit wrestled with an increasingly urgent question: Can global governance catch up before the technology races beyond its control?
Building Educational Software for Mandarin Chinese and Interlingua IALA Language-learning software is most useful when it makes structure visible. I’m Ian Blas, a developer based in Buenos Aires, Argentina, and I build educational tools around Mandarin Chinese, Interlingua IALA, etymology, morphology, writing systems, and open-source language learning. Two projects, one educational approach My work currently takes two complementary forms. Chety is an educational app for Mandarin Chinese. It approaches characters and words through their structure, etymology, morphology, historical development, and use in context. Schola Interlingua is a free, open-source learning platform for Interlingua IALA. It brings together lessons, readings, review tools, and progress-oriented study on multiple platforms. The languages are different, but the design question is similar: how can software help a learner notice the patterns that make a language readable and memorable? Learning through structure For Mandarin Chinese, a character is not only a unit to memorize. It can open a path into components, historical forms, pronunciation, word formation, and reading. That perspective guides Chety’s tools for exploring characters and vocabulary. For Interlingua IALA, the focus shifts toward transparent vocabulary, reading, morphology, and sustained practice. Schola Interlingua is designed to make that learning path approachable without separating learners from the materials and tools that support it. In both projects, the goal is practical: make language learning more legible. Etymology and morphology are useful when they give learners better ways to connect forms, meanings, and usage. An open educational practice I care about software that can be examined, shared, and improved. Schola Interlingua’s development is available through its GitHub repository , and my broader work can be found on GitHub . I also write and share updates through Medium and Substack . Explore the projects Chety — Chines
Today on Uncanny Valley, we unpack the political debacle unfolding in Maine surrounding the campaign of Democratic candidate Graham Platner.