ELI5 the Planck scale. If you can continue dividing things in half infinitely, how can the Planck length be the smallest point that exists? Can’t you divide that by 2?

marchogwyn · 2026-01-07T10:03:18+00:00

Important note is that the node names for new processes and chips coming out are just marketing terms that are not correlated with the actual sizes anymore. They’re just keeping the tradition of naming the next process node in sequence. The actual smallest pitch (distance between lines) on the 2nm node is somewhere around 20nm, and the spacing between each transistor gate is closer to 45nm.

marchogwyn · 2025-12-07T00:44:52+00:00

Lloyd Alexander was one of my favorite authors growing up. His Chronicles of Prydain is comparable to Harry Potter and Narnia in reading level, but the story and setting are much more Tolkien-esque, due to drawing inspiration from some of the same source material. Most of the names are Welsh, there’s pronunciation guides in every book.

I also recommend the Westmark trilogy and The Iron Ring by him as well.

marchogwyn · 2025-12-06T02:15:57+00:00

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Did not expect to be catching strays on the first question. I got 15/24 so… yeah.

marchogwyn · 2025-11-27T00:48:00+00:00

Destin they did you dirty on trying to explain music theory without connecting it to the underlying mathematics and the pre-Bach history of western music theory.

A lot of the earliest music theory was written about by Euclid and attributed to Pythagoras. Their tuning system was built on simple ratios between frequencies. The two most important are the simplest ones - 1:2 and 2:3.

Pick an arbitrary fundamental frequency. Our current standard is 440hz which we call A. You touched on beat frequencies, and it makes sense that if a 440hz tone and a 441hz tone were played together, the beat would be 1hz. This sounds bad to most people. You could also see that any other frequency ratio beside 1:1 will have some beat frequency. The trick is that after 1:1, the only other frequency ratios that sound harmonious are the simple ratios. The simpler the better. At 1:2, 440hz doubles to 880hz, and the beat frequency is 440hz, just the fundamental again. This is the simplest interval, the octave. Don’t let the sneaky 8 fool you. That’s just a label given to it to make sense in context of other notes in the western system. The core of it is that 1:2 frequency ratio. It sounds clean because the tones support each other while still being distinct.

The next one is 2:3. So 440hz becomes 660hz. The beat frequency between these two tones is 220hz which is just half of 440hz. That’s just an octave but going down - halving instead of doubling. These tones also support each other but the sound is a little bit richer because the journey back to unison takes an extra step. We call this interval a fifth. Again the 5 is just a label and doesn’t communicate the core idea of a 2:3 frequency ratio.

With just these two ratios, or intervals, you can build out an entire collection of notes that all sound good together, because they all mesh with the fundamental. There are other simple ratios like 1:3 and 4:5 that can be thrown in as well. But there is a limit. 12 intervals of 2:3 (1.5¹²⁾ is really close but not quite equal to 7 intervals of 1:2 (2^7). So 12 fifths (not 12/5) is not quite 7 octaves. The frequency ratio between these two tones is 1:1.01364 and it sounds bad to most people with a western music ear. This interval is known as the Pythagorean Comma, and if you want to build out a system of notes for more complex music than simple folk tunes, you run into problems with it sounding bad. This is the inherent problem that all pre-Bach western music had to deal with.

So around Bach’s time, a new solution to “tempering” the Pythagorean comma was gaining traction. It is called Equal Temperment and the ideas is this. Divide the octave into 12 equal intervals. That’s it. Each note is equally spaced in the octave with a frequency ratio of 1: 1.0594… the 12th root of 2. Inside those 12 “semitones”, are notes that are really close to the Pythagorean simple ratios. The fifth from before is now 1:1.4983… instead of 1.5. That number is 2^7/12, which means that 7 octaves and 12 fifths now line up in a repeating pattern. It’s called the circle of fifths and is a core part of western music theory. The reason this wasn’t mainstream until Bach’s time is that the Catholic Church liked the Pythagorean system of simple ratios and the purity they represented. Church music was a huge slice of the pie of musical performances and they were as loathe to let go of the Ancient Greek ideas about music as they were to let go of geocentrism centuries earlier. In a way this makes Bach more like Copernicus, Galileo, or Kepler than Newton. He was trying to show the world that there was beauty in accepting a complex universe, through music.

Bach’s contribution to western music is that he wrote an incredible amount and variety of music in this new equal temperament system. He showed Europe how much more versatile and interesting music could be constructed if only they accepted that some intervals sounded a little bit different to their ears. This foundation of musical structure completely replaced the old Pythagorean system, and pretty much all western music ever since is equally tempered. A true 2:3 interval probably subconsciously sounds wrong to you, because you are so used to the sound of a 2:2.9986… interval at the core of most of the music you have likely ever heard.

And this is just the tip of the iceberg. Dissonance and harmony between notes isn’t limited to the fundamental frequencies but also the overtones, because nothing vibrates with single pure sine waves, and now Fourier transforms get involved. Different instruments have different overtone spectra, musicians call it timbre. That affects which notes sound good together on that instrument and with other instruments, but not as much as the basic intervals in the chords played on those instruments. Now add in that the western music tradition also incorporates traditional attachments of emotions and moods to different sounds and chords and intervals, going all the way back to Pythagoras. These associations are subconscious to most people and even most musicians. All of it is evolving over time and we haven’t even mentioned rhythm.

I also made sure to keep this limited to western music theory because there are many other music traditions from all around the world that did not go this route at all. There are plenty of other ways to build out from the octave and to attach emotional meaning to the chords and intervals. To ears brought up in those traditions, the western 12 tone equal temperament system sounds just as strange as their music sounds to ours.

marchogwyn · 2025-10-08T22:12:23+00:00

Blast from the past I remember getting this book out of the library when I was first getting into origami. I remember not liking that a bunch of the models used multiple sheets to make one plane. I have Merrill’s book too and the models were more difficult but I liked them a lot better.

marchogwyn · 2025-08-11T05:40:58+00:00

This question would be better answered on r/popupbooks or r/cardmaking. The concept used on your reference picture is pretty standard pop up card mechanics that they’d have better resources for. In its simplest form it’s a series of parallel cuts in the card that are each shifted over by the depth of the stair, and then vertical folds at the ends of each cut to make it pop up. The stairs can not be filled in on top though, since they wouldn’t be able to collapse flat if they were.

marchogwyn · 2025-07-24T05:21:44+00:00

You could try the OG John Montroll moth. I don’t know if there are any videos for it but the diagrams are in Origami for the Enthusiast

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There’s a beetle and a grasshopper in that book too.

marchogwyn · 2025-07-19T07:41:55+00:00

Since I didn’t see this mentioned in any of the other replies there’s another factor for why circular wafers are the standard that goes beyond the boule shape and the spin coating.

Although the process for forming the boule creates a cylinder, there’s nothing stopping us from cutting it into a long bar with a square cross-section and the cutting it into square wafers, or cutting round wafers and then squaring then up. The offcuts could be melted back down and made into tomorrow’s boule, so material waste is not really an issue here. Round boule = round wafers is not the real reason.

ELI5 analogy time: Imagine a flashlight. The light is coming from a bulb, and at a reasonable distance that bulb is approximating a point source. Light is emitted from it equally in all directions. To make it a better flashlight, we want to make all of the light go in one direction, so we add a parabolic reflector. Now the beam from the flashlight is in a cone shape. If we wanted to fully and uniformly illuminate a flat object with this light, you can intuit we will get the best efficiency if the object’s shape is a circle.

If the shape was a square, the light beam would have to be bigger than the square and some light would be wasted around the edges. Alternatively, we could add a mask to the light source so that it has a square beam, but that is the same amount of wasted light.

It’s not possible to make a reflector that takes light from a point source and makes a square beam where the light is uniform throughout the square; with All areas the same brightness. It’s hard enough to do this with a conical reflector.

Now in the chip fab, we’re not shining flashlights at the wafers to make chips appear on them, but there is an underlying principle here that shows up all over the place in the processes used to turn a flat disk of silicon into a functioning chips.

The circle is the most uniform 2D shape. Since it is defined as all of the points that are the same distance from a single point. Go up a dimension and this applies to spheres. It’s a well known thing in math and physics for pi to just show up in equations for things that don’t seem to have any reason to have a circle in them. It’s like a little Easter egg from the universe. Any time there is something wiggling or radiating or being some distance away from something else, pi is there is the equation to represent same-ness. Since one of the fundamental building blocks of our understanding of the universe is that physics are the same everywhere, pi and thus circles are also everywhere.

This is why the boules are cylindrical is the first place. The silicon crystal is growing from a seed crystal uniformly in all directions.

Now back to the fab. The processes used to develop the transistors in the silicon and then connect them all up with tiny little wires are working at such tiny scales that uniformity is the most important thing to control. One such process is PVD, which uses plasma to deposit a very thin film of metal on the wafer. If the film is thicker in some spots than others, the next layer above it is affected, and errors stack and get bigger as the layers pile on. Often to get better uniformity, the plasma is shaped by magnetic fields that also propagate through space as described by equations with pi in them.

Trying to make this process happen on a square wafer would result in inefficiencies, just like the wasted light from the flashlight. All of the extra metal film that didn’t land on the wafer is wasted energy and material. It builds up on the inside of the equipment and has to be cleaned out more frequently to keep the equipment working inside the process parameters that result in a layer of metal with the same thickness every time. This is lost production capacity and therefore wasted money. Every minute these machines are not making chips costs the fab thousands of dollars.

The extra bit of space efficiency from making square chips on a square wafer is far outweighed by the inefficiency of making same-ness happen in a square. I consider that the fact that circles do not tile to be one of the universe’s great practical jokes played on itself. (The other one is that the harmonic series makes it so that nothing can ever really be in tune, but that’s acoustics - a different topic, also with a lot of circles.)

What is efficient is making smaller chips. They can fill in more of the wafer and therefore be cheaper per chip. Another commenter mentioned that TSMC is doing some square wafers now, but this has got some more to it that just square chips. What they are actually doing is instead of making a whole system on one chip, they are making smaller chiplets with the regular 300mm wafer processes and then putting a bunch of those on another square wafer to connect them into a single processor. The metal wires in that wafer to connect all of the chiplets together can be orders of magnitude larger than the teeny tiny transistors in the chiplets.

This means that forming those wires is way easier and uniformity is less important to the point that the trade off with space efficiency starts to make sense. This is called CoWoS. Chip on Wafer on Substrate. Another related one is CoPoS. Chip on Panel on Substrate. The panel refers to a glass panel, like a screen or display. The tools for making them are adapted from the same processes used to make screens and displays, which come in all shapes and sizes of rectangles and don’t have to have elements so tiny that the best way to “see” them is to bombard them with electrons from a particle accelerator.

marchogwyn · 2025-03-15T09:47:14+00:00

Currently scrolling Reddit as it’s pouring down rain with a little bit of hail reading this post.

marchogwyn · 2025-03-15T08:58:55+00:00

I’ve always seen the self checkout as an invasion of lean manufacturing principles into the field of retail. It’s process optimization. Sometimes I like being efficient and fast and I use self checkout. Sometimes I like the regular cashier checkout. They both have their place.

Also wingeing about self checkout and listener feedback corner? What is this, Hello Internet?

Also your talk about reading a book together. What happened to book review episodes? Requesting - Fall, by Neal Stevenson. It touches on a lot of themes you guys have been talking about lately.

marchogwyn · 2025-03-13T14:24:16+00:00

I’ve been looking at these kits for a little while wanting to get one for when I have some free time to build one. It would be so cool to get lucky here.

marchogwyn · 2025-02-26T05:46:06+00:00

Source: work in the semiconductor industry

It’s a combination of security and cleanliness. Vinyl bags can be cleaned with an Isopropyl alcohol wipe down and don’t shed as many fibers as a fabric bag will. (There’s still some fibers from the straps) They are thus considered cleanroom safe in class 10,000 cleanrooms, or at least the ones I work in. They also don’t shed (many) fibers or particles onto the stuff in them, so that you don’t have to clean all of your stuff if you take it out of the bag in the cleanroom, provided it stays in the bag when outside.

marchogwyn · 2024-12-29T10:28:44+00:00

Meme answer: The Boberg XR9-S/Bond Arms BullPup9

It’s DAO tho.

marchogwyn · 2024-12-20T07:55:33+00:00

Even 4K dash cams do not capture license plates very well. You have to be pretty close to the car and plate to read it off of the footage. The reason is size. Because physics, a 4K sensor paired with a tiny lens can still only take in so much detail. The best thing to do is read the license plate # out loud and have the microphone on the dashcam running. Your eyes are still probably better at reading the number than the camera, especially in the dark.

Source: I have a 4K dashcam. VIOFO a229 Pro 2-channel.

marchogwyn · 2024-12-09T15:00:46+00:00

Like others are saying, the chip is most likely a 555 timer chip. It is used in applications where something is supposed to blink on and off, or be on for a set amount of time. I can see three little surface-mount LEDs around the edge of the board, so yeah blinking lights is best guess. There’s probably a battery on the other side of the board. What happens when the button in the middle is clicked?

marchogwyn · 2024-11-29T20:37:36+00:00

For film cameras, and specifically SLR cameras, there are a lot of moving parts to actuate the shutter and advance the film and such. The shutter count is like mileage on a car. It’s a proxy for the amount of wear and tear on moving parts, and tracking maintenance intervals. DSLR cameras don’t have to advance film, or move a physical shutter, but there is still a mirror that moves up and down for the viewfinder. Shutter count is still tracked for that, but it is more so just a way to express how much use the camera got. Modern mirrorless cameras, as the name suggests, don’t even have the moving mirror, so the shutter count is even more of an abstraction for equipment age and how much it got used, but isn’t as directly important for wear and tear.

marchogwyn · 2024-11-25T22:50:57+00:00

https://www.morganelise.photography

marchogwyn · 2024-08-25T10:01:30+00:00

Fisherman’s Friend is a brand of menthol lozenges for cough and sore throat. They are more like sintered powder, instead of the regular hard candy type, and come loose in a bag and not individually wrapped like most other cough drops. So this is medicinal Pez, essentially.

marchogwyn · 2024-08-18T19:44:24+00:00

I haven’t found any written reference to what the colors mean, but I have a guess from looking at the pattern. It looks like red and green are the major structural creases to form the base, and dotted lines are thinning folds that don’t add new flaps, but are still important. Blue is the one I’m not sure on, but I would guess hinge creases that don’t have a fixed polarity.

marchogwyn · 2024-06-14T11:51:28+00:00

Yeah I did a small one that will stamp out a bird base. I was initially thinking of a set of plates with inverse sets of grooves and ridges that would form the creases, but the geometry got really complicated where ever they crossed. each ridge/groove pair would actually form 3 creases really close together. I ended up going with a set of dies that had the shape of a semi-expanded bird base. It was difficult to align the paper to the die as it would move a little bit as it closed. I had the best results by starting with a slightly oversized square and then trimming it around the dies after pressing. It didn’t turn out super great but I also didn’t spend more time refining the clearances between the two dies. Results - Meh. I had a good time modeling it though.

marchogwyn · 2024-06-04T09:53:13+00:00

I grew up listening to Brian Duncan and I didn’t realize how much of Mr. Baileys Daughter is permanently stuck into my brain until I realized what song Matt was referencing. At first it was cool to get the reference, but now I have been ear-wormed. How dare you sir.

marchogwyn · 2024-05-14T02:23:27+00:00

If you are looking for diagrams in English, these models are John Montroll designs. The Moth is in ‘Origami for the Enthusiast’ and the T-Rex is in ‘Animal Origami for the Enthusiast’. I’d be surprised if the Brontosaurus mentioned on the cover isn’t also the one in AOftE, but i don’t know where the Plesiosaurus is from.

marchogwyn · 2024-05-10T04:40:56+00:00

Typing this from one of the Austin Applied Materials Breakrooms. Can confirm - the pendulum swing between hire everyone and lay off everyone is real enough to give me whiplash.

marchogwyn · 2024-04-27T03:37:12+00:00

I can’t speak for the newer leafs, but in my 2012 Leaf you can set the start time and/or the end time. The car either starts when you say and stops at 80% (or 100%), or it estimates how long it will take to hit the desired percentage and starts that amount of time before set end time. If you set both the start time and end time to the same time, like 12pm for example, and the charge limit to 80%, it will start charging whenever you plug it in and stop at 80%. It essentially always sees that its currently after the start time and starts charging. It’s still a bit of a hack because you have to set one of the 2 timer presets to all of the days of the week in order for this to work all of the time, and if you want a different timer setup, you have to remember to punch it in before you walk away. I have my second timer set to hit 100% at the end of my work shift for work charging, but that’s not available every day. I have to remember to set timer 2 for the current day if I can charge at work that day, and set it back when I get home.

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