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Longform articles, the best of what the Hackaday writing crew has to offer.

You Know Pi, But Do You Really Know E?

March 14, 2025 by 29 Comments

Pi Day is here! We bet that you know that famous constant to a few decimal points, and you could probably explain what it really means: the ratio of a circle’s circumference to its diameter. But what about the constant e? Sure, you might know it is a transcendental number around 2.72 or so. You probably know it is the base used for natural logarithms. But what does it mean?

The poor number probably needed a better agent. After all, pi is a fun name, easy to remember, with a distinctive Greek letter and lots of pun potential. On the other hand, e is just a letter. Sometimes it is known as Euler’s number, but Leonhard Euler was so prolific that there is also Euler’s constant and a set of Euler numbers, none of which are the same thing. Sometimes, you hear it called Napier’s constant, and it is known that Jacob Bernoulli discovered the number, too. So, even the history of this number is confusing.

But back to math, the number e is the base rate of growth for any continually growing process. That didn’t help? Well, consider that many things grow or decay through growth. For example, a bacteria culture might double every 72 hours. Or a radioactive sample might decay a certain amount per century. Continue reading “You Know Pi, But Do You Really Know E?” →

Pixel Watch 3’s Loss Of Pulse Detection: The Algorithms That Tell Someone Is Dying

March 12, 2025 by 63 Comments

More and more of the ‘smart’ gadgets like watches and phones that we carry around with us these days come with features that we’d not care to ever need. Since these are devices that we strap onto our wrists and generally carry in close proximity to our bodies, they can use their sensors to make an estimation of whether said body is possibly in the process of expiring. This can be due to a severe kinetic event like a car crash, or something more subtle like the cessation of the beating of one’s heart.

There is a fairly new Loss of Pulse Detection (LoPD) feature in Google’s Pixel Watch 3 that recently got US FDA approval, allowing it to be made available in the US after previously becoming available in over a dozen European countries following its announcement in August of 2024. This opt-in feature regularly polls whether it can detect the user’s pulse. If not found, it cascades down a few steps before calling emergency services.

The pertinent question here is always whether it is truly detecting a crisis event, as nobody wants to regularly apologize for a false alert to the overworked person staffing the 911 or equivalent emergency line. So how do you reliably determine that your smart watch or phone should dial emergencies forthwith?

Continue reading “Pixel Watch 3’s Loss Of Pulse Detection: The Algorithms That Tell Someone Is Dying” →

TrapC: A C Extension For The Memory Safety Boogeyman

March 11, 2025 by 52 Comments

In the world of programming languages it often feels like being stuck in a Groundhog Day-esque loop through purgatory, as effectively the same problems are being solved over and over, with previous solutions forgotten and there’s always that one jubilant inventor stumbling out of a darkened basement with the One True Solution™ to everything that plagues this world beset by the Unspeakable Horror that is the C programming language.

As the latest entry to pledge its fealty at the altar of the Church of the Holy Memory Safety, TrapC promises to fix C, while also lambasting Rust for allowing that terrible unsafe keyword. Of course, since this is yet another loop through purgatory, the entire idea that the problem is C and some perceived issue with this nebulous ‘memory safety’ is still a red herring, as pointed out previously.

In other words, it’s time for a fun trip back to the 1970s when many of the same arguments were being rehashed already, before the early 1980s saw the Steelman language requirements condensed by renowned experts into the Ada programming language. As it turns out, memory safety is a miniscule part of a well-written program.

Continue reading “TrapC: A C Extension For The Memory Safety Boogeyman” →

Inexpensive Repairable Laptops, With Apple Style

March 10, 2025 by 41 Comments

Despite a general lack of real-world experience, many teenagers are overly confident in their opinions, often to the point of brashness and arrogance. In the late 90s and early 00s I was no different, firmly entrenched in a clichéd belief that Apple computers weren’t worth the silicon they were etched onto—even though I’d never actually used one. Eventually, thanks to a very good friend in college, a bit of Linux knowledge, and Apple’s switch to Intel processors, I finally abandoned this one irrational belief. Now, I maintain an array of Apple laptops for my own personal use that are not only surprisingly repairable and hacker-friendly but also serve as excellent, inexpensive Linux machines.

Of course, I will have ruffled a few feathers suggesting Apple laptops are repairable and inexpensive. This is certainly not true of their phones or their newer computers, but there was a time before 2016 when Apple built some impressively high quality, robust laptops that use standard parts, have removable batteries, and, thanks to Apple dropping support for these older machines in their latest operating systems, can also be found for sale for next to nothing. In a way that’s similar to buying a luxury car that’s only a few years old and letting someone else eat the bulk of the depreciation, a high quality laptop from this era is only one Linux install away from being a usable and relatively powerful machine at an excellent bargain. Continue reading “Inexpensive Repairable Laptops, With Apple Style” →

Open Source Hardware, How Open Do You Want It To Be?

March 7, 2025 by 43 Comments

In our wider community we are all familiar with the idea of open source software. Many of us run it as our everyday tools, a lot of us release our work under an open source licence, and we have a pretty good idea of the merits of one such document over another. A piece of open source software has all of its code released under a permissive licence that explicitly allows it to be freely reproduced and modified, and though some people with longer beards take it a little too seriously at times and different flavours of open source work under slightly different rules, by and large we’re all happy with that.

When it comes to open hardware though, is it so clear cut?  I’ve had more than one rant from my friends over the years about pieces of hardware which claim to be open-source but aren’t really, that I think this bears some discussion.

Open Source Hardware As It Should Be Done

To explore this, we’ll need to consider a couple of open source hardware projects, and I’ll start close to home with one of my own. My Single 8 home movie cartridge is a 3D printable film cartridge for a defunct format, and I’ve put everything necessary to create one yourself in a GitHub repository under the CERN OHL. If you download the file and load it into OpenSCAD you can quickly create an STL file for your slicer, or fiddle with the code and make an entirely new object. Open source at its most efficient, and everyone’s happy. I’ve even generated STLs ready to go for each of the supported ISO values. Continue reading “Open Source Hardware, How Open Do You Want It To Be?” →

Why 56k Modems Relied On Digital Phone Lines You Didn’t Know We Had

March 6, 2025 by 51 Comments

If you came of age in the 1990s, you’ll remember the unmistakable auditory handshake of an analog modem negotiating its connection via the plain old telephone system. That cacophony of screeches and hisses was the result of careful engineering. They allowed digital data to travel down phone lines that were only ever built to carry audio—and pretty crummy audio, at that.

Speeds crept up over the years, eventually reaching 33.6 kbps—thought to be the practical limit for audio modems running over the telephone network. Yet, hindsight tells us that 56k modems eventually became the norm! It was all thanks to some lateral thinking which made the most of the what the 1990s phone network had to offer.

Continue reading “Why 56k Modems Relied On Digital Phone Lines You Didn’t Know We Had” →

Big Chemistry: Glass

March 5, 2025 by 12 Comments

Humans have been chemically modifying their world for far longer than you might think. Long before they had the slightest idea of what was happening chemically, they were turning clay into bricks, making cement from limestone, and figuring out how to mix metals in just the right proportions to make useful new alloys like bronze. The chemical principles behind all this could wait; there was a world to build, after all.

Among these early feats of chemical happenstance was the discovery that glass could be made from simple sand. The earliest glass, likely accidentally created by a big fire on a sandy surface, probably wasn’t good for much besides decorations. It wouldn’t have taken long to realize that this stuff was fantastically useful, both as a building material and a tool, and that a pinch of this and a little of that could greatly affect its properties. The chemistry of glass has been finely tuned since those early experiments, and the process has been scaled up to incredible proportions, enough to make glass production one of the largest chemical industries in the world today.

Continue reading “Big Chemistry: Glass” →