Magnetic self-assembly in slow motion
90 1/8″ small magnets arranged in a 9×10 matrix with a larger magnet brought close. Beautiful self-assembly occurs
Slower and slower motion, so you can see what’s happening.
Category Archives: Physics
What's in Your Toolbox?
America's First Great Astronomer
Just got my copy of Physics Today, and noticed that the cover looked familiar. It’s a drawing from a photo, depicting Simon Newcomb at the USNO’s 26″ telescope, and the article inside, Simon Newcomb, America’s first great astronomer, was co-written by a colleague. And it’s one of the free stories.
A complete account of Newcomb’s many achievements in astronomy, mathematics, physics, and economics is beyond the scope of this article. Indeed, the collection of his works held in the Library of Congress contains more than 46 000 items. We focus on Newcomb’s contributions to one of the central astronomical issues of his time: accurately determining the astronomical unit, the distance from Earth to the Sun. Newcomb did everything he could to ensure the success of massive American campaigns to better determine the astronomical unit by observing the transits of Venus in 1874 and 1882. Yet he also set out independently on a different path to reach the same goal. Ultimately, he succeeded in deriving a more accurate value sooner, at a tiny fraction of the cost, and without leaving Washington.
(I got to see the transit of Venus in 2004, with one of the views being through one of the telescopes that has been used to observe these 19th century transits)
Nerd Alert!
Zapperz has stumbled across the ideal gift for that geek who loves to play prime-number-card stud, or superconducting supercollider hold ’em, or even CP-symmetry-not-conserved (e.g. deuces wild) games.
Physicist playing cards at the AIP store. “Historic” deck and “modern” deck.
I already have the Periodic Table playing card decks.
Call Him Neo
Hi, I’m Rob Gallagher and I’m a MagnetNerd.
[…]
Neodymium Magnets are just plain cool. It’s totally amazing how something so small can have such strong magnetic forces. I enjoy showing others the amazing things that can be done with Neodymium Magnets. So far I have created 53 Videos of my experiments and designs on YouTube and have incorporated most of them into this website.
More magnet-relates stuff than you can shake a magnetic stick at.
Adaptive Optics
$20 Self Adjustable Pump-Action Glasses
The lenses comprise flexible membranes containing silicone oil. Using syringes (seen in the picture), the amount of oil can be adjusted and the refractive index of the lenses changed. The syringes are detachable.
This is big, because it means a single, uniform product can be mass produced and then tweaked at its destination without specialized equipment.
The goal is to distribute these in countries where ground glass (or plastic) lenses are too expensive and doctors are in short supply.
From The Telegraph,
His aim is to eventually reach 100 million people a year, with a target of one billion in total by 2020
Also see the writeup in the Washington Post
It's About Time, Part II
Super clocks: More accurate than time itself
An article discussing the progression of atomic clock technology, and also relating to something I posted earlier, a discussion of what happens when the next generation of atomic clocks is deployed: the clocks won’t be the limiting factor in determining the time.
To tell the time consistently, all clocks need to be at a known height relative to Earth’s “geoid”, an imaginary surface that links points at which the gravitational field has the same strength. But the height of this geoid varies over time at any given place by up to 20 centimetres, because of effects such as tectonic movements, glacial melting and changes in ocean levels, and varying atmospheric pressure. Changes of that magnitude could wreak havoc with any attempt to establish a global time standard at an accuracy of 1 part in 1018 or better
One of the things that always glossed over in these discussions is that almost everything that is called a clock is actually a frequency standard, which is part of a clock. Clocks run continuously, because you are measuring a phase, and frequency standards don’t. Now, there’s a caveat here in “running continuously,” because even commercially-available clocks will skip measurement cycles to do self-diagnostics. During those skips in measurement, as with the time between measurements, the frequency is maintained with some oscillator. Usually this is a quartz crystal, which typically has excellent short-term stability. The important point becomes how long the clock is running on the “flywheel” oscillator and what kind of degradation that introduces. The latest generation of frequency standards run for several hours, but then are shut down for extended periods of time, which is not surprising for a cutting-edge kind of experiment. But while the frequency standard is not running, the clock’s performance approaches whatever the flywheel performance is, whether that’s cesium beam clocks or hydrogen masers, etc., or some ensemble made up of several clocks.
So when these stories appear touting the great performance of cutting-edge clocks, there’s an unwritten implication that we will be getting an improvement in the flywheel operation as well, to be able to leverage this improved frequency-standard performance.
Listen Up!
A phonon is a quantized sound wave – a collective vibrational mode of a solid (or liquid). In a crystalline solid, the idea is that the atoms in the solid are displaced, at any given instant, from their equilibrium positions. For a single phonon, the instantaneous displacements are periodic in space (that is, there is some wavelength, where atoms separated by an integer number of wavelengths are displaced the same amount). The displaced atoms feel restoring forces due to their interactions with neighbors, and will tend to oscillate in time around their equilibrium positions.
There’s more, though.
Also see What is a plasmon?
Chubby Checker Physics
Quantum twist: Electrons mimic presence of magnetic field
[O]n the surface of certain materials collective arrangements of electrons move in ways that mimic the presence of a magnetic field where none is present. The finding represents one of the most exotic macroscopic quantum phenomena in condensed-matter physics: a topological Quantum Spin Hall effect.
Quantum Biology
The Quantum Dimension Of Photosynthesis
In the initial steps of photosynthesis, the energy from a solar photon is transferred through the protein by sequentially exciting electrons in the organic molecules and is eventually delivered where it’s needed. Biologists have long thought that the energy moved like a hot potato: an excited electron in one molecule passes its energy to an electron in another, nearby molecule, and so on.
However, laser-based experiments have suggested other possibilities. In 2007 a team hitting a photosynthetic protein with laser pulses and measuring the time variation in the output light found strong evidence that some of the electrons were coherently coupled. The quantum wave nature of the electrons seemed to be connecting some of the chlorophyll-like molecules and helping energy flow through the protein like a wave on a string.