Displaying The Rainbow

February 20, 2026 by Al Williams 23 Comments

True or false? Your green laser pointer is more powerful than your red one. The answer is almost certainly false. They are, most likely, the same power, but your eye is far more sensitive to green, so it seems stronger. [Brandon Li] was thinking about how to best represent colors on computer screens and fell down the rabbit hole of what colors look like when arranged in a spectrum. Spoiler alert: almost all the images you see of the spectrum are incorrect in some way. The problem isn’t in our understanding of the physics, but more in the understanding of how humans perceive color.

Perception may start with physics, but it also extends to the biology of your eye and the psychology of your brain. What follows is a lot of math that finally winds up with the CIE 1931 color space diagram and the CIE 2012 system.

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The History Of The View-Master

February 19, 2026 by Al Williams 27 Comments

We are going to bet that as a kid, you had a View-Master. This toy has been around for decades and is, more or less, a handheld stereoscope. We never thought much about the device’s invention until we saw a recent video from [View Master Travels and Peter Dibble]. It turns out that the principle of the whole thing was created by the well-known [Charles Wheatstone]. However, it was piano repairman [William Gruber] who invented what we think of as the View-Master.

[Gruber] didn’t just work on normal pianos, but complex player pianos and, in particular, the pianos used to record player piano rolls. He was also, as you might expect, a stereo photography enthusiast. Many of the ideas used in automating pianos would show up in the View-Master and the machines that made the reels, too. In the 1930s, stereoscopes were not particularly popular and were cumbersome to use. Color film was also a new technology.

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The Requirements Of AI

February 19, 2026 by Al Williams 77 Comments

The media is full of breathless reports that AI can now code and human programmers are going to be put out to pasture. We aren’t convinced. In fact, we think the “AI revolution” is just a natural evolution that we’ve seen before. Consider, for example, radios. Early on, if you wanted to have a radio, you had to build it. You may have even had to fabricate some or all of the parts. Even today, winding custom coils for a radio isn’t that unusual.

But radios became more common. You can buy the parts you need. You can even buy entire radios on an IC. You can go to the store and buy a radio that is probably better than anything you’d cobble together yourself. Even with store-bought equipment, tuning a ham radio used to be a technically challenging task. Now, you punch a few numbers in on a keypad.

The Human Element

What this misses, though, is that there’s still a human somewhere in the process. Just not as many. Someone has to design that IC. Someone has to conceive of it to start with. We doubt, say, the ENIAC or EDSAC was hand-wired by its designers. They figured out what they wanted, and an army of technicians probably did the work. Few, if any, of them could have envisoned the machine, but they can build it.

Does that make the designers less? No. If you write your code with a C compiler, should assembly programmers look down on you as inferior? Of course, they probably do, but should they?

If you have ever done any programming for most parts of the government and certain large companies, you probably know that system engineering is extremely important in those environments. An architect or system engineer collects requirements that have very formal meanings. Those requirements are decomposed through several levels. At the end, any competent programmer should be able to write code to meet the requirements. The requirements also provide a good way to test the end product.

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Ancient Ice Production

February 18, 2026 by Al Williams 53 Comments

Today, we take ice for granted. But having ice produced in your home is a relatively modern luxury. As early as 1750 BC, ancient people would find ice on mountains or in cold areas and would harvest it. They’d store it, often underground, with as much insulation as they could produce given their level of technology.

A yakhchāls in Yazd province (by [Pastaitkaen] CC BY-SA 3.0).

By 500 BC, people around Egypt and what is now India would place water in porous clay pots on beds of straw when the night was cold and dry. Even if the temperature didn’t freeze, the combination of evaporation and radiative cooling could produce some ice. However, this was elevated to a high art form around 400 BC by the Persians, who clearly had a better understanding of physics and thermodynamics than you’d think.

The key to Persian icemaking was yakhchāls. Not all of them were the same, but they typically consisted of an underground pit with a conical chimney structure. In addition, they often had shade walls and ice pits as well as access to a water supply.

Solar Chimney

The conical shape optimizes the solar chimney effect, where the sun heats air, which then rises. The top was typically not open, although there is some thought that translucent marble may have plugged the top to admit light while blocking airflow. yakhchālThe solar chimney produces an updraft that tends to cool the interior. The underground portion of the yakhchāl has colder air, as any hot air rises above the surface.

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Retrotechtacular: Mr. Wizard Jams With IBM

February 16, 2026 by Al Williams 29 Comments

You may not remember [Mr. Wizard], but he was a staple of nerd kids over a few decades, teaching science to kids via the magic of television. The Computer History Archives Project has a partially restored film of [Mr. Wizard] showing off sounds and noise on a state-of-the-art (for 1963) Tektronix 504 oscilloscope. He talks about noise and also shows the famous IBM mainframe rendition of the song “Daisy Bell.” You can see the video along with some extras below.

You might recall that the movie “2001: A Space Odyssey” paid homage to the IBM computer’s singing debut by having HAL 9000 sing the same song as it is being deactivated. The idea that HAL was IBM “minus one” has been repeatedly denied, but we still remain convinced.

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Microfluidic Display Teaches The Basics

February 15, 2026 by Al Williams 8 Comments

We’ve always been interested in fluidic logic and, based on [soiboi’s] videos, he is too. His latest shows how to use silicone and a vacuum to build a multiplexed dot matrix display. This is a fascinating look at how you design with air instead of electrons.

Just like a regular display, it isn’t efficient to control each element separately. Usually, it’s better to multiplex such that 16 “pixels” need only row and column air valves. Just as you might use transistors, the project uses “air transistors” to build logic gates.

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The WalMart Atomic Clock

February 14, 2026 by Al Williams 28 Comments

In the realm of first-world problems, your cheap wall clock doesn’t keep time, so you have to keep setting it. The answer? Of course, you connect it to NTP and synchronize the clock with an atomic time source. If you are familiar with how these generic quartz clock movements work, you can probably guess the first step is to gut the movement, leaving only the drive motor.

The motor is somewhat like a stepper motor. The ESP8266 processor can easily control the clock hands by sending pulses to the motor. The rest is simple network access and control. If the network time is ahead, the CPU gooses the clock a little. If it is behind, the CPU stalls the clock until it catches up.

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