Science

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Two very similar diffraction patterns are shown, in patterns of green dots against a blue background. The left image is labelled "Kompressions-algorithmus", and the one on the right is labelled "Licht & Zweibelzellen".

Why Diffraction Gratings Create Fourier Transforms

January 27, 2026 by 8 Comments

When last we saw [xoreaxeax], he had built a lens-less optical microscope that deduced the structure of a sample by recording the diffraction patterns formed by shining a laser beam through it. At the time, he noted that the diffraction pattern was a frequency decomposition of the specimen’s features – in other terms, a Fourier transform. Now, he’s back with an explanation of why this is, deriving equations for the Fourier transform from the first principles of diffraction (German video, but with auto-translated English subtitles. Beware: what should be “Huygens principle” is variously translated as “squirrel principle,” “principle of hearing,” and “principle of the horn”).

The first assumption was that light is a wave that can be adequately represented by a sinusoidal function. For the sake of simplicity (you’ll have to take our word for this), the formula for a sine wave was converted to a complex number in exponential form. According to the Huygens principle, when light emerges from a point in the sample, it spreads out in spherical waves, and the wave at a given point can therefore be calculated simply as a function of distance. The principle of superposition means that whenever two waves pass through the same point, the amplitude at that point is the sum of the two. Extending this summation to all the various light sources emerging from the sample resulted in an infinite integral, which simplified to a particular form of the Fourier transform.

One surprising consequence of the relation is the JPEG representation of a micrograph of some onion cells. JPEG compression calculates the Fourier transform of an image and stores it as a series of sine-wave striped patterns. If one arranges tiles of these striped patterns according to stripe frequency and orientation, then shades each tile according to that pattern’s contribution to the final image, one gets a speckle pattern with a bright point in the center. This closely resembles the diffraction pattern created by shining a laser through those onion cells.

For the original experiment that generated these patterns, check out [xoreaxeax]’s original ptychographical microscope. Going in the opposite direction, researchers have also used physical structures to calculate Fourier transforms.

Continue reading “Why Diffraction Gratings Create Fourier Transforms” →

Astronomy Live On Twitch

January 26, 2026 by 11 Comments

Although there are a few hobbies that have low-cost entry points, amateur astronomy is not generally among them. A tabletop Dobsonian might cost a few hundred dollars, and that is just the entry point for an ever-increasing set of telescopes, mounts, trackers, lasers, and other pieces of equipment that it’s possible to build or buy. [Thomas] is deep into astronomy now, has a high-quality, remotely controllable telescope, and wanted to make it more accessible to his friends and others, so he built a system that lets the telescope stream on Twitch and lets his Twitch viewers control what it’s looking at.

The project began with overcoming the $4000 telescope’s practical limitations, most notably an annoyingly short Wi-Fi range and closed software. [Thomas] built a wireless bridge with a Raspberry Pi to extend connectivity, and then built a headless streaming system using OBS Studio inside a Proxmox container. This was a major hurdle as OBS doesn’t have particularly good support for headless operation.

Continue reading “Astronomy Live On Twitch” →

Environmental Monitoring On The Cheap

January 24, 2026 by 5 Comments

If there is one thing we took from [azwankhairul345’s] environmental monitor project, it is this: sensors and computing power for such a project are a solved problem. What’s left is how to package it. The solution, in this case, was using recycled plastic containers, and it looks surprisingly effective.

A Raspberry Pi Pico W has the processing capability and connectivity for a project like this. A large power bank battery provides the power. Off-the-shelf sensors for magnetic field (to measure anemometer spins), air quality, temperature, and humidity are easy to acquire. The plastic tub that protects everything also has PVC pipe and plastic covers for the sensors. Those covers look suspiciously like the tops of drink bottles.

We noted that the battery bank inside the instrument doesn’t have a provision for recharging. That means the device will go about two days before needing some sort of maintenance. Depending on your needs, this could be workable, or you might have to come up with an alternative power supply.

This probably won’t perform as well as a Hoffman box-style container, and we’ve seen those crop up, too. There are a number of ways of sealing things against the elements.

Polymer Skins That Change Color And Texture When Exposed To Water

January 23, 2026 by 1 Comment

Researchers at Stanford University recently came up with an interesting way (Phys.org summary) to create patterns and colors that emerge when a polymer is exposed to water. Although the paper itself is sadly paywalled with no preprint available, it’s fairly easily summarized and illustrated with details from the Supplementary Data section. The polymer used is poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), which when exposed to an electron beam (electron-beam lithography) undergoes certain changes that become apparent when said water is added.

The polymer is hygroscopic, but the electron beam modifies the extent to which a specific area swells up, thus making it possible to create patterns that depend on the amount of electron beam exposure. In order to ‘colorize’ the polymer, complex cavities are created that modify the angular distribution of light, as illustrated in the top image from the Supplemental Data docx file.

By varying the concentration of IPA versus water, the intermediate swelling states can be controlled. Although this sounds pretty advanced, if you look at the supplementary videos that are already sped up a lot, you can see that it is a very slow process. Compared to an octopus and kin whose ability to alter their own skin texture and coloring is legendary and directly controlled by their nervous system, this isn’t quite in the same ballpark yet, even if it’s pretty cool to watch.

A red silicone cupcake pan sits on a black glass inductive stove cooktop. The word induction is written in white text on the glass of the stove.

Silicone Bakeware Might Be Bad For Your Liver

January 19, 2026 by 38 Comments

Silicone bakeware has become a staple in many kitchens due to its flexible, yet temperature-tolerant nature. New research from Canada shows it could be causing trouble for your liver and lungs, however.

The siloxanes that make up silicone bakeware can target “the liver through oral exposure, as well as the liver and lungs through inhalation exposure.” The fat content of the food being baked is also a factor as these compounds are lipophilic, so higher fat foods will absorb more siloxanes than lower fat foods.

Don’t throw out all your silicone yet, though. The researchers say, “the results showed a consistent decreasing trend in migration levels across consecutive weekly baking sessions, with no increase after the seven-month interval.” So, that dingy looking silicone mat you’ve used a hundred times is safer than a brand new, brightly-colored one.

This seems like an example of how glass and (non-heavy) metal are usually the best way to go when handling food. While we’re talking about ovens, do they really need to run a connectivity check? They certainly could be improved with a DIY thermometer or by making a more practical solar-powered example.

How To Use Tiny Open Loop Actuators For A Living Mirror

January 19, 2026 by 5 Comments

How do you go about making a mirror with 128 segments, each of which can be independently angled? That was the question that a certain bloke over at [Time Sink Studio] found himself pondering on, to ultimately settle on a whole batch of mini-actuators bought through AliExpress. These stepper-based actuators appear to be akin to those used with certain Oppo smartphones with pop-up camera, costing less than half a dollar for a very compact and quite fast actuator.

The basic design is very much akin to a macro version of a micromirror device, as used in e.g. DLP projectors, which rely on a kinetic mirror mount to enable precise alignment. With the small actuators travelling up to 8 mm each, the mirrors can cover 73 mm at a distance of 4 meters from a wall.

With the required angle of the mirror being effectively just the application of the Pythagorean theorem, the biggest challenge was probably calibrating these linear motors. Since they’re open loop devices, they are zeroed much like the steppers on 3D printers, by finding the end limit and counting steps from that known point. This doesn’t make drift impossible, but for projecting light onto walls it’s clearly more than good enough.

Continue reading “How To Use Tiny Open Loop Actuators For A Living Mirror” →

A red-and-blue image of a nebula is shown, shaped somewhat like an eye, with a plume of gas emitting from the center.

Is The Theory Of Special Relativity Wrong?

January 15, 2026 by 17 Comments

There’s an adage coined by [Ian Betteridge] that any headline ending in a question mark can be answered by the word “No”. However, Lorentz invariance – the theory that the same rules of physics apply in the same way in all frames of reference, and an essential component of special relativity – has been questioned for some time by researchers trying to unify general relativity and quantum field theory into a theory of quantum gravity. Many theories of quantum gravity break Lorentz invariance by giving photons with different energy levels very slightly different speeds of light – a prediction which now looks less likely since researchers recently analyzed gamma ray data from pulsed astronomical sources, and found no evidence of speed variation (open-access paper).

The researchers specifically looked for the invariance violations predicted by the Standard-Model Extension (SME), an effective field theory that unifies special relativity with the Standard Model. The variations in light speed which it predicts are too small to measure directly, so instead, the researchers analyzed gamma ray flare data collected from pulsars, active galactic nuclei, and gamma-ray bursts (only sources that emitted gamma rays in simultaneous pulses could be used). Over such great distances as these photons had traveled, even slight differences in speed between photons with different energy levels should have added up to a detectable delay between photons, but none was found.

This work doesn’t disprove the SME, but it does place stricter bounds on the Lorentz invariance violations it allows, about one and a half orders of magnitude stricter than those previously found. This study also provides a method for new experimental data to be more easily integrated into the SME. Fair warning to anyone reading the paper: the authors call their work “straightforward,” from which we can only conclude that the word takes on a new meaning after a few years studying mathematics.

If you want to catch up on relativity and Lorentz invariance, check out this quick refresher, or this somewhat mind-bending explanation. For an amateur, it’s easier to prove general relativity than special relativity.

Top image: Crab Pulsar, one of the gamma ray sources analysed. (Credit: J. Hester et al., NASA/HST/ASU/J)