Desk Top Peltier-Powered Cloud Chamber Uses Desktop Parts

There was a time when making a cloud chamber with dry ice and alcohol was one of those ‘rite of passage’ type science projects every nerdy child did. That time may or may not be passed, but we doubt many children are making cloud chambers quite like [Curious Scientist]’s 20 cm x 20 cm Peltier-powered desktop unit.

The dimensions were dictated by the size of the off-the-shelf display case which serves as the chamber, but conveniently enough also allows emplacement of four TEC2-19006 Peltier cooling modules. These are actually “stacked” modules, containing two thermoelectric elements in series — a good thing, since the heat delta required to make a cloud chamber is too great for a single element. Using a single-piece two stage module simplifies the build considerably compared to stacking elements manually.

To carry away all that heat, [Curious Scientist] first tried heatpipe-based CPU coolers, but moved on to CPU water blocks for a quieter, more efficient solution. Using desktop coolers means almost every part here is off the shelf, and it all combines to work as well as we remember the dry-ice version. Like that childhood experiment, there doesn’t seem to be any provision for recycling the condensed alcohol, so eventually the machine will peter out after enough vapor is condensed.

This style of detector isn’t terribly sensitive and so needs to be “seeded” with spicy rocks to see anything interesting, unless an external electric field is applied to encourage nucleation around weaker ion trails. Right now [Curious Scientist] is doing that by rubbing the glass with microfiber to add some static electricity, but if there’s another version, it will have a more hands-off solution.

We’ve seen Peltier-Powered cloud chambers before (albeit without PC parts), but the “dry ice and alcohol” hack is still a going concern. If even that’s too much effort, you could just go make a cup of tea, and watch very, very carefully.

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Models Of Wave Propagation

[Stoppi] always has interesting blog posts and videos, even when we don’t understand all the German in them. The latest? Computer simulation of wave propagation (Google Translate link), which, if nothing else, makes pretty pictures that work in any language. Check out the video below.

Luckily, most browsers will translate for you these days, or you can use a website. We’ve seen waves modeled with springs before, but between the explanations and the accompanying Turbo Pascal source code, this is worth checking out.

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Determine Fundamental Constants With LEDs And A Multimeter

There are (probably) less than two dozen fundemental constants that define the physics of our universe. Determining the value of them might seem like the sort of thing for large, well funded University labs, but many can be determined to reasonable accuracy on the benchtop, as [Marb’s Lab] proves with this experiment to find the value of Planck’s Constant.

[Marv’s Lab] setup is on a nice PCB that uses a rotary switch to select between 5 LEDs of different wavelengths, with banana plugs for the multi-meter so he can perform a linear regression on the relation between energy and frequency to find the constant. He’s also thoughtfully put connectors in place for current measurement, so the volt-current relationship of the LEDs can be characterized in a second experiment. Overall, this is a piece of kit that would not be out of place in any high school or undergraduate physics lab. Continue reading “Determine Fundamental Constants With LEDs And A Multimeter”

You Are Already Traveling At The Speed Of Light

Science fiction authors and readers dream of travelling at the speed of light, but Einstein tells us we can’t. You might think that’s an arbitrary rule, but [FloatHeadPhysics] shows a different way to think about it. Based on a book he’s been reading, “Relativity Visualized,” he provides a graphic argument for relativity that you can see in the video below.

The argument starts off by explaining how a three-dimensional object might appear in a two-dimensional world. In this world, everything is climbing in the hidden height dimension at the exact same speed.

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Building An Interferometer With LEGO

LEGO! It’s a fun toy that is popular around the world. What you may not realize is that it’s also made to incredibly high standards. As it turns out, the humble building blocks are good enough to build a interferometer if you’re so inclined to want one. [Kyra Cole] shows us how it’s done.

The build in question is a Michelson interferometer; [Kyra] was inspired to build it based on earlier work by the myphotonics project. She was able to assemble holders for mirrors and a laser, as well as a mount for a beamsplitter, and then put it all together on a LEGO baseboard. While some non-LEGO rubber bands were used in some areas, ultimately, adjustment was performed with LEGO Technic gears.

Not only was the LEGO interferometer able to generate a proper interference pattern, [Kyra] then went one step further. A Raspberry Pi was rigged up with a camera and some code to analyze the interference patterns automatically. [Kyra] notes that using genuine bricks was key to her success. Their high level of dimensional accuracy made it much easier to achieve her end goal. Sloppily-built knock-off bricks may have made the build much more frustrating to complete.

We don’t feature a ton of interferometer hacks around these parts. However, if you’re a big physics head, you might enjoy our 2021 article on the LIGO observatory. If you’re cooking up your own physics experiments at home, don’t hesitate to drop us a line!

Thanks to [Peter Quinn] for the tip!

Is Fire Conductive Enough To Power A Lamp?

Is fire conductive? As ridiculous that may sound at first glance, from a physics perspective the rapid oxidation process we call ‘fire’ produces a lot of substances that can reduce the electrical insulating (dielectric) properties of air. Is this change enough to allow for significant current to pass? To test this, [The Action Lab] on YouTube ran some experiments after being called out on this apparent fact in the comments to an earlier video.

Ultimately what you need to make ‘fire’ conductive is to have an appreciable amount of plasma to reduce the dielectric constant, which means that you cannot just use any rapid oxidation process. In the demonstration with lights and what appears to be a (relatively clean-burning) butane torch, the current conducted is not enough to light up an incandescent or LED light bulb, but can light up a 5 mm LED. When using his arm as a de-facto sensor, it does not conduct enough current to be noticeable.

The more interesting experiment here demonstrates the difference in dielectric breakdown of air at different temperatures. As the dielectric constant for hot air is much lower than for room temperature air, even a clean burning torch is enough to register on a multimeter. Ultimately this seems to be the biggest hazard with fire around exposed (HV) electrical systems, as the ionic density of most types of fire just isn’t high enough.

To reliably strike a conductive plasma arc, you’d need something like explosive (copper) wire and a few thousand joules to pump through it.

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Turns Out Humans Are Terrible At Intuiting Knot Strength

We are deeply intuitively familiar with our everyday physical world, so it was perhaps a bit of a surprise when researchers discovered a blind spot in our intuitive physical reasoning: it seems humans are oddly terrible at judging knot strength.

One example is the reef knot (top) vs. the grief knot (bottom). One is considerably stronger than the other.

What does this mean, exactly? According to researchers, people were consistently unable to tell when presented with different knots in simple applications and asked which knot was stronger or weaker. This failure isn’t because people couldn’t see the knots clearly, either. Each knot’s structure and topology was made abundantly clear (participants were able to match knots to their schematics accurately) so it’s not a failure to grasp the knot’s structure, it’s just judging a knot’s relative strength that seems to float around in some kind of blind spot.

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