Hold out your hands in front of you, palms forward. They look quite similar, but I’m sure you’re all too aware that they’re actually mirror images of each other. Your hands are chiral objects, which means they’re asymmetric but not superimposable. This property is quite interesting when studying the physical properties of matter. A chiral molecule can have completely different properties from its mirrored counterpart. In physics, producing the mirror image of something is known as parity. And in 1927, a hypothetical law known as the conservation of parity was formulated. It stated that no matter the experiment or physical interaction between objects – parity must be conserved. In other words, the results of an experiment would remain the same if you tired it again with the experiment arranged in its mirror image. There can be no distinction between left/right or clockwise/counter-clockwise in terms of any physical interaction.
The nuclear physicist, Chien-Shiung Wu, who would eventually prove that quantum mechanics discriminates between left- and right-handedness, was a woman, and the two men who worked out the theory behind the “Wu Experiment” received a Nobel prize for their joint work. If we think it’s strange that quantum mechanics works differently for mirror-image particles, how strange is it that a physicist wouldn’t get recognized just because of (her) gender? We’re mostly here to talk about the physics, but we’ll get back to Chien-Shiung Wu soon.
The End of Parity
Conservation of parity was the product of a physicist by the name of Eugene P. Wigner, and it would play an important role in the growing maturity of quantum mechanics. It was common knowledge that macro-world objects like planets and baseballs followed Wigner’s conservation of parity. To suggest that this law extended into the quantum world was intuitive, but not more than intuition. And at that time, it was already well known that quantum objects did not play by the same rules as classical objects. Would quantum mechanics be so strange as to care about handedness? Continue reading “There Is No Parity: Chien-Shiung Wu”→
To a ham radio operator used to “short”-wave antennas with lengths listed in tens of meters, the tiny antennas used in the gigahertz bands barely even register. But if your goal is making radio electronics that’s small enough to swallow, an antenna of a few centimeters is too big. Physics determines plausible antenna sizes, and there’s no way around that, but a large group of researchers and engineers have found a way of side-stepping the problem: resonating a nano-antenna acoustically instead of electromagnetically.
Normal antennas are tuned to some extent to the frequency that you want to pick up. Since the wavelength of a 2.5 GHz electromagnetic wave in free space is 120 cm mm, most practical antennas need a wire in the 12-60 cm mm range to bounce signals back and forth. The trick in the paper is to use a special piezomagnetic material as the antenna. Incoming radio waves get quickly turned into acoustic waves — physical movement in the nano-crystals. Since these sound waves travel a lot slower than the speed of light, they resonate off the walls of the crystal over a much shorter distance. A piezoelectric film layer turns these vibrations back into electrical signals.
Ceramic chip antennas use a similar trick. There, electromagnetic waves are slowed down inside the high-permittivity ceramic. But chip antennas are just slowing down EM waves, whereas the research demonstrated here is converting the EM to sound waves, which travel many orders of magnitude slower. Nice trick.
Granted, significant material science derring-do makes this possible, and you’re not going to be fabricating your own nanoscale piezomagnetic antennas any time soon, but with everything but the antenna getting nano-ified, it’s exciting to think of a future where the antennas can be baked directly into the IC.
This is a solution to global warming. This solution will also produce electricity, produce rain in desertified areas, and transform the Sahara into arable land capable of capturing CO2. How is this possible? It’s simple: all we need to do is build a five-kilometer tall, twenty-meter wide chimney. Hot air, warmed by the Earth’s surface, will enter the base of the chimney and flow through turbines, generating electricity. From there, air will rise through the chimney, gradually cooling and transferring energy from the atmosphere at Earth’s surface to five kilometers altitude. This is the idea behind the Super Chimney, It’s an engineering concept comparable to building a dam across the Strait of Gibraltar, a system of gigantic mirrors in Earth’s orbit, or anything built under an Atoms for Peace project. In short, this is fringe engineering.
This is also, ‘saving the world with wacky waving inflatable arm flailing tube men.’
The idea of building tens of thousands of fabric chimneys, placing them all around the globe, and cooling the Earth while sequestering carbon dioxide is fantastic. Ideas are simple, implementation is something else entirely. There are also obvious problems with the physics presented in the Super Chimney presentation, but these problems don’t actually make a Super Chimney impossible. We need more eyes on this, so we’re opening this one up as an Ask Hackaday. What do you think of this audacious scheme, and is it even possible?
What’s tiny and on track to be worth $22 billion dollars by 2018? MEMS (Micro Electrical Mechanical Systems). That’s a catch-all phrase for microscopic devices that have moving parts. Usually, the component sizes range from 0.1 mm to 0.001 mm, which is tiny, indeed. There are some researchers working with even smaller components, sometimes referenced as NEMS (Nano Electrical Mechanical Systems).
MEMS have a wide range of applications including ink jet printers, accelerometers, gyroscopes, microphones, pressure sensors, displays, and more. Many of the sensors in a typical cell phone would not be possible without MEMS. There are many ways that MEMS devices are built, but just to get a flavor, consider the cantilever (see right), one of the most common MEMS constructions.
[PhysicsGirl] posts videos that would be good to use in a classroom or homeschool environment. She recently showed a 200KV capacitor made from a cake pan, a bowl, and some other common items (see video, below).
One of the most interesting things about the project was how they charged the capacitor. A PVC pipe and some common hardware made a wand that they’d charge by rubbing a foam sleeve up and down against the dome formed by a metal bowl. We might have used a cat, but there’s probably some law against that.
To discharge, they used the end of the wand and were able to get a 10 cm spark. Based on the dielectric constant for air, they estimated that equated to a 200KV charge. They also discharged it through someone’s finger, which didn’t seem like a great idea.
We’ve talked about [PhysicsGirl’s] videos before. Granted, a lot of this won’t help the experienced hacker, but if you work with kids, they are a great way to make physics interesting and approachable. We wish she’d spent more time on the actual construction (you’ll need to slow it down to see all the details), though. If you really want a capacitor for your high voltage mad science, you might find these more practical. We’ve seen many homemade capacitors for high voltage.
We’ve learned a lot by watching the talks from the Hackaday Superconferences. Still, it’s a rare occurrence to learn something totally new. Microwave engineer, professor, and mad hacker [Toshiro Kodera] gave a talk on some current research that he’s doing: replacing natural magnetic gyrotropic material with engineered metamaterials in order to make two-way beam steering antennas and more.
If you already fully understood that last sentence, you may not learn as much from [Toshiro]’s talk as we did. If you’re at all interested in strange radio-frequency phenomena, neat material properties, or are just curious, don your physics wizard’s hat and watch his presentation. Just below the video, we’ll attempt to give you the Cliff’s Notes.
Do you remember Gilligan’s Island? For many people of a certain age, “The Professor” was our first impression of what a scientist was like. Even in those simpler times, though, you probably couldn’t find anyone like the professor; a jack of all trades, he sort of knew everything about everything (except, apparently, how to make a boat).
Real scientists tend to hyper-specialize. Getting grant money, publication pages, and just advancing the state of the art means that you get more and more focused on more obscure things. It is getting to the point that two scientists in the same field may not be able to really understand each other. You see the same thing in engineering to some degree. Not many digital designers can talk about the frequency dependence of Early effect in bipolar transistors, but not many device gurus can talk intelligently about reservation techniques for superscalar CPUs.
There’s now a website that lets you guess if a physics paper title is real or if it made up jibberish. The site, snarXiv, gets the real titles from arXiv, the site that contains many preprint papers. For example, we were asked to guess if “Brane Worlds with Bolts” was a real paper or if it was “Anthropic Approaches to the Flavor Problem.” (For the record, it was the one about branes.) Give it a whirl!