So far in this series, we’ve talked about man-made byproducts — Fordite, which is built-up layers of cured car enamel, and Trinitite, which was created during the first nuclear bomb test.

But not all byproducts are man-made, and not all of them are basically untouchable. Some are created by Mother Nature, but are nonetheless dangerous. I’m talking about fulgurites, which can form whenever lightning discharges into the Earth.

It’s likely that even if you’ve seen a fulgurite, you likely had no idea what it was. So what are they, exactly? Basically, they are natural tubes of glass that are formed by a fusion of silica sand or rock during a lightning strike.

Much like Lichtenberg figures appear across wood, the resulting shape mimics the path of the lightning bolt as it discharged into the ground. And yes, people make jewelry out of fulgurites.

Lightning Striking Again

Lightning is among the oldest observed phenomena on Earth. You probably know that lightning is just a giant spark of electricity in the atmosphere. It can occur between clouds, the air, or the ground and often hits tall things like skyscrapers and mountaintops.

Lightning is often visible during volcanic eruptions, intense forest fires, heavy snowstorms, surface nuclear detonations, and of course, thunderstorms.

In lightning’s infancy, air acts as an insulator between charges — the positive and negative charges between the cloud and the ground. Once the charges have sufficiently built up, the air’s insulating qualities break down and the electricity is rapidly discharged in the form of lightning.

When lightning strikes, the energy in the channel briefly heats up the air to about 50,000 °F, which is several times the surface of the Sun. This makes the air explode outward. As the shock wave’s pressure decreases, we hear thunder.

Of Sand and Rock and Other Stuff

Fulgurites, also known as fossilized lightning, don’t have a fixed composition: they are composed of whatever they’re composed of at the time of the lightning strike. Four main types of fulgurites are officially recognized: sand, soil, caliche (calcium-rich), and  rock fulgurites. Sand fulgurites can usually be found on beaches or in deserts where clean sand devoid of silt and clay dominates. And like those Lichtenberg figures, sand fulgurites tend to look like branches of tubes. They have rough surfaces comprised of partially-melted grains of sand.

When sand fulgurites are formed, the sand rapidly cools and solidifies. Because of this, they tend to take on a glassy interior. As you might imagine, the size and shape of a fulgurite depends on several factors, including the strength of the strike and the depth of the sand being struck. On average, they are 2.5 to 5 cm in diameter, but have been found to exceed 20 cm.

Soil fulgurites can form in a wide variety of sediment compositions including clay-, silt-, and gravel-rich soils as well as leosses, which are wind-blown formations of accumulated dust. These also appear as tubaceous or branching formations, vesicular, irregular, or a combination thereof.

Calcium-rich sediment fulgurites have thick walls and variable shapes, although it’s common for multiple narrow channels to appear. These can run the gamut of morphological and structural variation for objects that can be classified as fulgurites.

Rock fulgurites are typically found on mountain peaks, which act as natural lightning rods. They appear as coatings or crusts of glass formed on rocks, either found as branching channels on the surface, or as lining in pre-existing fractures in the rock. They are most often found at the summit or within several feet of it.

Fact-Finding Fulgurites

Aside from jewelry and such, fulgurites’ appeal comes in wherever they’re found, as their presence can be used to estimate the number of lightning strikes in an area over time.

Then again there’s some stuff you may not necessarily want to use in jewelry making. Stuff that can be found in the dark, dank corners of the Earth. Stay tuned!

When working with limited space or even with limited funding, finding a tool that can do many things for less space or cost than its separate counterparts is a tempting option. The most common downside is that these tools often can’t perform as well as the single-purpose tools they replace, with the obvious example being a pocket-sized multitool or Swiss Army knife. Even things like combination drill and driver tools, adjustable crescent wrenches, or even a kitchen stand mixer can’t quite perform as well as their dedicated counterparts. So when we find a tool that can do two things equally well, like this rock tumbler that can also make a delicious bowl of ice cream, it’s definitely noteworthy.

The project comes to us by way of [North_Stordeur] whose main goal was to create a delicious bowl of ice cream but was deterred by the cost of purpose-built ice cream makers. Making ice cream isn’t a particularly complex process, though, and [North_Stordeur ] realized that grinding down ice for ice cream shares similarities with tumbling and polishing rocks. Normally, the rocks to be polished are placed in a drum with grit and a liquid, then the drum is placed on the tumbler and spun, which causes the rocks to bounce around inside the drum with the grit and smooth out relatively quickly. Replacing sugar for grit, ice for rocks, and milk for the liquid, the ice eventually is worn all the way down, creating an excellent bowl of ice cream.

Truly, the only downside we could see with a build like this is that the drum in the National Geographic rock tumbler that [North_Stordeur] chose for this project looks like it would only make a single serving at a time. However, with picky eaters around who like their own additions to ice cream, this might be a perk as everyone can make exactly the style they like with their own choice of flavors. It’s an excellent discovery for anyone already grinding and polishing rocks or someone who has already built a DIY ball mill for any number of other uses.

You might think the game of Rock Paper Scissors is just the random chance, but that’s not true. There is a strategy for Rock Paper Scissors, multiple ones in fact, and the best human players can consistently beat any Joe Schmoe off the street. But what about computers? [Paul] answered that question with a tiny little keychain dongle that can beat you at Rock Paper Scissors.

This is a neural network, and you need to train a neural network, so where did [Paul] get all that data? roshambo.me offers thousands of paper rock scissor games, and trained the network on more than 85,000 human games, along with about 10,000 simulated games. Rock Paper Scissors isn’t a complicated game at all, and the entire neural network is stored on an ATtiny1614 microcontroller. The calculations are done as floats, even. That’s how non-computationally intensive this project is.

Building a neural network is one thing, but putting it in a handy keychain enclosure is something else. This handsome device fits on a PCB just larger than a 2032 coin cell battery and is enclosed in a 3D printed case. The buttons are 3D printed as well, with some clever application of fiber optic as light pipes for the LEDs. The end result is something that is slightly better than random chance at Rock Paper Scissors and shows off some matrix programming skills. Check out the video below.

Single board computers are great, but what we really need are cheap single board computers. Running Linux on anything isn’t as good as running Linux on everything, and all that. To that end, here is the Rock Pi S, a $10 single board computer with Ethernet, WiFi, and it costs $10.

This one comes from the boffins at Radxa, already behind the footnote-worthy Rock Pi 4, a single board computer that appears to be heavily derived from the Raspberry Pi but with a 4 in the name so it’s obviously better. It also has 4 GeeBees of RAM, so it’s got that going for it too. Their latest product is the Rock Pi S, a board that seems as though it’s taking inspiration from the C.H.I.P.. The biggest selling point is of course the price: $10 for the version with 256MB of RAM and without WiFi or Bluetooth. Various other incarnations exist with permutations of 256MB or 512MB of RAM, and with or without WiFi and Bluetooth. The highest spec variant costs $16, but is sold out at the moment.

This tiny little single board computer fills a need in the marketplace; the Raspberry Pi Zero is cheap and small when it’s available, but sometimes you need Ethernet for various reasons and a real USB A port is great to have. We’re looking forward to the builds this tiny board enables and all the fantastic creations that will come from a community so very interested in single board computers.

[Steve Hoefer] pulled together a great hack for the friendless. This glove will play a heated game of rock-paper-scissors against you. [Steve] realized that the middle and fourth fingers are all that need to be monitored to decide which of the three signs you are making. He used flex sensors on the back of these fingers as an input. There is also an accelerometer to judge the three shakes that lead up to the shoot.

The small screen you see displays what the glove chose and is a hack in itself. This idea adapts from an Evil Mad Scientist project, using three sheets of acrylic etched with the different icons and edge-lit with LEDs. All of this, along with a speaker and scoreboard, connect to an Arduino. The icing on the cake? [Steve] coded an adaptive learning algorithm that observes your playing style to gain an advantage.

See this in action after the break. Once you’ve mastered rock-paper-scissors you should consider building other glove-based peripherals.

[youtube=http://www.youtube.com/watch?v=GwvRWdWMy_E]

[Thanks Zokier]

Anyone with children will understand the value of this project immediately. This is an Arduino controlled sound activated crib rocker. [Lars] built a custom suspension system for his baby’s crib which allows a servo, mounted to the floor to rock it gently back and forth. Ok, maybe it’s a vigorous rocking, but that’s what some kids want. At least he’s safe and moderately immobile. He had to make a custom amplifier circuit to get his microphone working with the Arduino. It seems to all work perfectly now, triggering to begin rocking when it detects the baby’s cries. This should buy them a few extra minutes of sleep until the baby is truly hungry or annoyed. You can see a video of it in action and download the Arduino code on the project page.

[via littlebridceo]