Does This Electron Make Me Look Fat? Weighing An Electron

February 12, 2026 by Al Williams 5 Comments

[The Signal Path] shows us how to recreate a classic science experiment to measure the weight of an electron. Things are easier for us, because unlike [J. J. Thomson] in 1897, we have ready sources of electrons and measuring equipment. Check it out in the video below.

The main idea is to trap an electron using a magnetic field into a circular path. You can then compute the forces required to keep it in that circle, along with some other equations, and combine them. The result lets you compute the charge to mass ratio using parameters you can either control or measure, like the radius of the circular path and the electric field.

Helmholtz coils create the magnetic field, and a cold cathode tube provides the electrons. Honestly, the equipment looks a bit like something out of an old monster movie.

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Correlating Electric Cars With Better Air Quality

February 12, 2026 by Maya Posch 75 Comments

Although at its face the results seem obvious, a recent study by [Sandrah Eckel] et al. on the impact of electric cars in California is interesting from a quantitative perspective. What percentage of ICE-only cars do you need to replace with either full electric or hybrid cars before you start seeing an improvement in air quality?

A key part of the study was the use of the TROPOMI instrument, part of the European Sentinel-5 Precursor satellite. This can measure trace gases and aerosols in the atmosphere, both of which directly correlate with air quality. The researchers used historical TROPOMI data from 2019 to 2023 in the study, combining this data with vehicle registrations in California and accounting for confounding factors, such as a certain pandemic grinding things to a halt in 2020 and massively improving air quality.

Although establishing direct causality is hard using only this observational data, the researchers did show that the addition of 200 electric vehicles would seem to be correlated to an approximate 1.1% drop in measured atmospheric NO₂. This nitrogen oxide is poisonous and fatal if inhaled in large quantities. It’s also one of the pollutants that result from combustion, when at high temperatures nitrogen from the air combines with oxygen molecules. Continue reading “Correlating Electric Cars With Better Air Quality” →

Forget Waldo. Where’s Luna 9?

February 11, 2026 by Al Williams 13 Comments

Luna 9 was the first spacecraft to soft-land on the moon. In 1966, the main spacecraft ejected a 99-kg lander module that used a landing bag to survive impact. The problem is, given the technology limitations of 1966, no one is exactly sure where it is now. But it looks like that’s about to change.

A model of the Luna 9 lander with petals deployed.

We know that the lander bounced a few times and came to rest somewhere in Oceanus Procellarum, in the area of the Reiner and Marius craters. The craft deployed four stabilizing petals and sent back dramatic panoramas of the lunar surface. The Soviets were not keen to share, but Western radio astronomers noticed the pictures were in the standard Radiofax format, so the world got a glimpse of the moon, and journalists speculated that the use of a standard might have been a deliberate choice of the designers to end run against the government’s unwillingness to share data.

Several scientists have been looking for the remains of the historic mission, but with limited success. But there are a few promising theories, and the Indian Chandrayaan-2 orbiter may soon confirm which theory is correct. Interestingly, Pravda published exact landing coordinates, but given the state of the art in 1966, those coordinates are unlikely to be completely correct. The Lunar Reconnaissance Orbiter couldn’t find it at that location. The leading candidates are within 5 to 25 km of the presumed site.

The Luna series had a number of firsts, including — probably — the distinction of being the first spacecraft stolen by a foreign government. Don’t worry, though. They returned it. Since the Russians didn’t talk much about plans or failures, you can wonder what they wanted to build but didn’t. There were plenty of unbuilt dreams on the American side.

Featured Art – 1:1 model of the Luna 9, Public Domain.

Why Haven’t Quantum Computers Factored 21 Yet?

February 9, 2026 by Maya Posch 32 Comments

If you are to believe the glossy marketing campaigns about ‘quantum computing’, then we are on the cusp of a computing revolution, yet back in the real world things look a lot less dire. At least if you’re worried about quantum computers (QCs) breaking every single conventional encryption algorithm in use today, because at this point they cannot even factor 21 yet without cheating.

In the article by [Craig Gidney] the basic problem is explained, which comes down to simple exponentials. Specifically the number of quantum gates required to perform factoring increases exponentially, allowing QCs to factor 15 in 2001 with a total of 21 two-qubit entangling gates. Extrapolating from the used circuit, factoring 21 would require 2,405 gates, or 115 times more.

Explained in the article is that this is due to how Shor’s algorithm works, along with the overhead of quantum error correction. Obviously this puts a bit of a damper on the concept of an imminent post-quantum cryptography world, with a recent paper by [Dennish Willsch] et al. laying out the issues that both analog QCs (e.g. D-Wave) and digital QCs will have to solve before they can effectively perform factorization. Issues such as a digital QC needing several millions of physical qubits to factor 2048-bit RSA integers.

A small piece of brown plastic is held in two pairs of tweezers under a heat gun, and is being twisted.

A New And Strangely Strong Kind Of Plastic

February 9, 2026 by Aaron Beckendorf 10 Comments

As anyone who extrudes plastic noodles knows, the glass transition temperature of a material is a bit misleading; polymers gradually transition between a glass and a liquid across a range of temperatures, and calling any particular point in that range the glass transition temperature is a bit arbitrary. As a general rule, the shorter the glass transition range is, the weaker it is in the glassy state, and vice-versa. A surprising demonstration of this is provided by compleximers, a class of polymers recently discovered by researchers from Wageningen University, and the first organic polymers known to form strong ionic glasses (open-access article).

When a material transforms from a glass — a hard, non-ordered solid — to a liquid, it goes through various relaxation processes. Alpha relaxations are molecular rearrangements, and are the main relaxation process involved in melting. The progress of alpha relaxation can be described by the Kohlrausch-Williams-Watts equation, which can be exponential or non-exponential. The closer the formula for a given material is to being exponential, the more uniformly its molecules relax, which leads to a gradual glass transition and a strong glass. In this case, however, the ionic compleximers were highly non-exponential, but nevertheless had long transition ranges and formed strong glasses.

The compleximers themselves are based on acrylate and methacrylate backbones modified with ionic groups. To prevent water from infiltrating the structure and altering its properties, it was also modified with hydrophobic groups. The final glass was solvent-resistant and easy to process, with a glass transition range of more than 60 °C, but was still strong at room temperature. As the researchers demonstrated, it can be softened with a hot air gun and reshaped, after which it cools into a hard, non-malleable solid.

The authors note that these are the first known organic molecules to form strong glasses stabilized by ionic interactions, and it’s still not clear what uses there may be for such materials, though they hope that compleximers could be used to make more easily-repairable objects. The interesting glass-transition process of compleximers makes us wonder whether their material aging may be reversible.

Pendulum Powered Battery

February 8, 2026 by Ian Bos 21 Comments

While the average person would use a standard charger to top off their phone, [Tom Stanton] is no average man. Instead, he put mind to matter with an entire pendulum battery system.

Using the inductive effects of magnets on copper coils, [Tom] found the ability to power small components. With that in mind, the only path was forward with a much larger pendulum. A simple diode rectifier and capacitors allow for a smoother voltage output. The scale of the device is still too small to power anything insane, even the phone charging test is difficult. One thing the device can do is juice up the electromagnetic launcher he put together a couple years back to hurl an RC plane into the air.

The useful applications of pendulum power storage might not be found in nationwide infrastructure, but the application on this scale is certainly a fun demonstration. [Tom] has a particular fascination with similar projects where practical application comes second to novelty. For a perfect example of this, check out his work with air powered planes!

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A graph of current versus time for circuits with and without inductors

A Deep Dive Into Inductors

February 5, 2026 by John Elliot V 5 Comments

[Prof MAD] runs us through The Hidden Power of Inductors — Why Coils Resist Change.

The less often used of the passive components, the humble and mysterious inductor is the subject of this video. The essence of inductance is a conductor’s tendency to resist changes in current. When the current is steady it is invisible, but when current changes an inductor pushes back. The good old waterwheel analogy is given to explain what an inductor’s effect is like.

There are three things to notice about the effect of an inductor: increases in current are delayed, decreases in current are delayed, and when there is no change in current there is no noticeable effect. The inductor doesn’t resist current flow, but it does resist changes in current flow. This resistive effect only occurs when current is changing, and it is known as “inductive reactance”.

After explaining an inductor’s behavior the video digs into how a typical inductor coil actually achieves this. The basic idea is that the inductor stores energy in a magnetic field, and it takes some time to charge up or discharge this field, accounting for the delay in current that is seen.

There’s a warning about high voltages which can be seen when power to an inductor is suddenly cut off. Typically a circuit will include snubber circuits or flyback diodes to help manage such effects which can otherwise damage components or lead to electric shock.

[Prof MAD] spends the rest of the video with some math that explains how voltage across an inductor is proportional to the rate of change of current over time (the first derivative of current against time). The inductance can then be defined as a constant of proportionality (L). This is the voltage that appears across a coil when current changes by 1 ampere per second, opposing the change. The unit is the volt-second-per-ampere (VsA^-1) which is known as the Henry, named in honor of the American physicist Joseph Henry.

Inductance can sometimes be put to good use in circuits, but just as often it is unwanted parasitic induction whose effects need to be mitigated, for more info see: Inductance In PCB Layout: The Good, The Bad, And The Fugly.

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