A Low-Cost Spectrometer Uses Discrete LEDs And Math

December 28, 2024 by Dan Maloney 2 Comments

A spectrometer is a pretty common lab instrument, useful for determining the absorbance of a sample across a spectrum of light. The standard design is simple; a prism or diffraction grating to break up a light source into a spectrum and a detector to measure light intensity. Shine the light through your sample, scan through the spectrum, and graph the results. Pretty easy.

That’s not the only way to do it, though, as [Markus Bindhammer] shows with this proof-of-concept UV/visible spectrometer. Rather than a single light source, [Marb] uses six discrete LEDs, each with a different wavelength. The almost-a-rainbow’s-worth of LEDs are mounted on circular PCB, which is mounted to a stepper motor through a gear train. This allows the instrument to scan through all six colors, shining each on the sample one at a time. On the other side of the flow-through sample cuvette is an AS7341 10-channel color sensor, which can measure almost the entire spectrum from UV to IR.

The one place where this design seems iffy is that the light source spectrum isn’t continuous, as it would be in a more traditional design. But [Marb] has an answer for that; after gathering data at each wavelength, he applies a cubic spline interpolation to derive the spectrum. It’s demonstrated in the video below using chlorophyll extracted from spinach leaves, and it seems to generate a reasonable spectrum. We suppose this might miss a narrow absorbance spike, but perhaps this could be mitigated by adding a few more LEDs to the color wheel.

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Experimental sequence for the Ramsey-type phonon anharmonicity measurement. (Credit: Yu Yang et al., Science, 2024)

Creating A Mechanical Qubit That Lasts Longer Than Other Qubits

December 27, 2024 by Maya Posch No comments

Among the current challenges with creating quantum computers is that the timespan that a singular qubit remains coherent is quite limited, restricting their usefulness. Usually such qubits consist of an electromagnetic resonator (boson), which have the advantage of possessing discrete energy states that lend themselves well to the anharmonicity required for qubits. Using mechanical resonators would be beneficial due to the generally slower decoherence rate, but these have oscillations (phonons) that are harmonic in nature. Now researchers may have found a way to use both electromagnetic qubits and mechanical resonators to create a hybrid form that acts like a mechanical qubit, with quite long (200 µs) coherence time.

As per the research paper by [Yu Yang] and colleagues in Science (open access preprint), their experimental mechanical qubit (piezoelectric disc and superconducting qubit on sapphire) was able to be initialized and read out, with single-qubit gates demonstrated. The experimental sequence for the phonon anharmonicity measurement is shown in the above image (figure 2 in the paper), including the iSWAP operations which initialize the hybrid qubit. Effectively this demonstrates the viability of such a hybrid, mechanical qubit, even if this experimental version is not impressive yet compared to the best electromagnetic qubit. Those have managed to hit a coherence time of 1 ms.

The lead researcher, [Yu Yang] expresses his confidence that they can improve this coherence time with more optimized designs and materials, with future experiments likely to involve more complex quantum gates as well as sensor designs.

Taking “Movies” Of Light In Flight

December 25, 2024 by Elliot Williams 10 Comments

This one isn’t clickbait, but it is cheating. [Brian Haidet], the guy behind Alpha Phoenix, has managed to assemble movie footage of a laser beam crossing his garage, using a rig he put together for just a few hundred dollars. How, you ask? Well, for the long version, you’re going to want to watch the video, also embedded below. But we’ll give you the short version here.

Light travels about a foot in a nanosecond. What have you got that measures signals on a nanosecond scale pretty reliably? Of course, it’s your oscilloscope. The rest of [Brian]’s setup includes a laser that can pull off nanosecond pulses, a sensor with a nanosecond-ish rise time, and optics that collect the light over a very small field of view.

He then scans the effective “pinhole” across his garage, emitting a laser pulse and recording the brightness over time on the oscilloscope for each position. Repeating this many thousands of times and putting them all together relative to the beginning of each laser pulse results in a composite movie with the brightness at each location resolved accurately enough to watch the light beam fly. Or to watch different time-slices of thousands of beams fly, but as long as they’re all the same, there’s no real difference.

Of course, this isn’t simple. The laser driver needs to push many amps to get a fast enough rise time, and the only sensor that’s fast enough to not smear the signal is a photomultiplier tube. But persistence pays off, and the results are pretty incredible for something that you could actually do in your garage.

Photomultiplier tubes are pretty damn cool, and can not only detect very short light events, but also very weak ones, down to a single photon. Indeed, they’re cool enough that if you get yourself a few hundred thousand of them and put them in a dark place, you’re on your way to a neutrino detector. Continue reading “Taking “Movies” Of Light In Flight” →

Close up of a Dutch etymology dictionary showing Esperanto, and a candle

Esperanto: The Language That Hoped To Unite The World

December 25, 2024 by Heidi Ulrich 55 Comments

Christmas: a good time to broach a topic of hope. We’re talking Esperanto. This language that spurred the hope it one day could hack the barriers between people, eliminating war and miscommunication. The video below unpacks the history of this linguistic marvel. Esperanto was a constructed language dreamed up in 1887 by Ludwik Zamenhof, a Polish-Russian eye doctor with a knack for linguistics and great ideals. If you’re a little into linguistics yourself, you’ll sure know the name stems from the Latin sperare: to hope.

Inspired by the chaos of multilingual strife in his hometown, Zamenhof created Esperanto to unite humanity under a single, simple, easy-to-learn tongue. With just 16 grammar rules, modular word-building, and no pesky exceptions — looking at you, English — Esperanto was a linguistic hack ahead of its time.

But Esperanto wasn’t just a novelty—it almost became the lingua franca of diplomacy. In 1920, Iran proposed Esperanto as the official language of the League of Nations, but the French vetoed it, fearing their language’s global dominance was at risk. From there, Esperanto’s journey took a darker turn as both Nazi Germany and Stalinist Russia persecuted its speakers. Despite this, Esperanto persisted, surfacing in quirky corners of culture, from William Shatner’s Esperanto-only horror film Incubus to its inclusion on NASA’s Voyager Golden Record.

Fast-forward to the digital age: Esperanto is thriving on online learning platforms, where over a million learners explore its minimalist elegance. It appears at places in various editions of Grand Theft Auto. It has even inspired modern makers to create new constructed languages, like Loglan, Toki Pona, and even Klingon. Could Esperanto—or any reimagined language—rise again to unite us? For curious minds, watch the video here.

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Apollo Lunar Surface Experiments Package of the Apollo 16 mission (Credit: NASA)

ALSEP: Apollo’s Modular Lunar Experiments Laboratory

December 23, 2024 by Maya Posch 13 Comments

Down-Sun picture of the RTG with the Central Station in the background. (Credit: NASA)

Although the US’ Moon landings were mostly made famous by the fact that it featured real-life human beings bunny hopping across the lunar surface, they weren’t there just for a refreshing stroll over the lunar regolith in deep vacuum. Starting with an early experimental kit (EASEP) that was part of the Apollo 11 mission, the Apollo 12 through Apollo 17 were provided with the full ALSEP (Apollo Lunar Surface Experiments Package). It’s this latter which is the subject of a video by [Our Own Devices].

Despite the Apollo missions featuring only one actual scientist (Harrison Schmitt, geologist), these Bendix-manufactured ALSEPs were modular, portable laboratories for running experiments on the moon, with each experiment carefully prepared by scientists back on Earth. Powered by a SNAP-27 radioisotope generator (RTG), each ALSEP also featured the same Central Station command module and transceiver. Each Apollo mission starting with 12 carried a new set of experimental modules which the astronauts would set up once on the lunar surface, following the deployment procedure for that particular set of modules.

Although the connection with the ALSEPs was terminated after the funding for the Apollo project was ended by US Congress, their transceivers remained active until they ran out of power, but not before they provided years worth of scientific data on many aspects on the Moon, including its subsurface characteristics and exposure to charged particles from the Sun. These would provide most of our knowledge of our Moon until the recent string of lunar landings by robotic explorers.

Heading image: Apollo Lunar Surface Experiments Package of the Apollo 16 mission (Credit: NASA)

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Illustrative models of collinear ferromagnetism, antiferromagnetism, and altermagnetism in crystal-structure real space and nonrelativistic electronic-structure momentum space. (Credit: Libor Šmejkal et al., Phys. Rev. X, 2022)

Nanoscale Imaging And Control Of Altermagnetism In MnTe

December 21, 2024 by Maya Posch No comments

Altermagnetism is effectively a hybrid form of ferromagnetism and antiferromagnetism that might become very useful in magnetic storage as well as spintronics in general. In order to practically use it, we first need to be able to control the creation of these altermagnets, which is what researchers have now taken the first steps towards. The research paper by [O. J. Amin] et al. was published earlier this month in Nature. It builds upon the team’s earlier research, including the detection of altermagnetism in manganese telluride (MnTe). This new study uses the same material but uses a photoemission electron microscope (PEEM) with X-rays to image these nanoscale altermagnetic structures.

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Measuring A Well With Just A Hammer And A Smartphone

December 19, 2024 by Dan Maloney 38 Comments

What’s the best way to measure the depth of a well using a smartphone? If you’re fed up with social media, you might kill two birds with one stone and drop the thing down the well and listen for the splash. But if you’re looking for a less intrusive — not to mention less expensive — method, you could also use your phone to get the depth acoustically.

This is a quick hack that [Practical Engineering Solutions] came up with to measure the distance to the surface of the water in a residential well, which we were skeptical would work with any precision due to its deceptive simplicity. All you need to do is start a sound recorder app and place the phone on the well cover. A few taps on the casing of the well with a hammer send sound impulses down the well; the reflections from the water show up in the recording, which can be analyzed in Audacity or some similar sound editing program. From there it’s easy to measure how long it took for the echo to return and calculate the distance to the water. In the video below, he was able to get within 3% of the physically measured depth — pretty impressive.

Of course, a few caveats apply. It’s important to use a dead-blow hammer to avoid ringing the steel well casing, which would muddle the return signal. You also might want to physically couple the phone to the well cap so it doesn’t bounce around too much; in the video it’s suggested a few bags filled with sand as ballast could be used to keep the phone in place. You also might get unwanted reflections from down-hole equipment such as the drop pipe or wires leading to the submersible pump.

Sources of error aside, this is a clever idea for a quick measurement that has the benefit of not needing to open the well. It’s also another clever use of Audacity to use sound to see the world around us in a different way.

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