Another cheap little toy I recently acquired is a keychain containing a multicolor LED that rapidly flashes between red, blue and green. It looks white (almost) to the naked eye when it’s stationary, but when it’s moving quickly enough, persistence of vision allows you to see the different colors. My webcam frame rate is timed such that it picks this up as well.
It’s been a reasonable distraction for when I’m put on hold by tech support or customer “service.”
Specialized nanoparticles floating in water make a fluid that can be switched between two states with different thermal properties, according to the 13 March Physical Review Letters. If the particles start out evenly distributed throughout the fluid volume, heat transfers more rapidly through the fluid than if they are more concentrated close to the heat source. The flow pattern is not fixed like the steady rolling produced in pure water, which suggests more complicated physics than researchers had previously predicted. But the team hopes some version of their fluid can be used to improve the regulation of heat flow in future devices.
Lasers Provide Antimatter Bonanza
Hui Chen and Scott Wilks of the Lawrence Livermore National Laboratory in California and their colleagues now report that they have generated copious amounts of positrons with intermediate energies–in the range of a million electron-volts. They fired picosecond pulses with intensities of around 1020 watts per square centimeter from the Titan laser at Livermore’s Jupiter laser facility onto millimeter-thick gold targets. Positrons were produced via the “Bethe-Heitler” process, in which part of each laser pulse creates a plasma on the surface of the target, and the remaining part of the pulse then blasts electrons from the plasma into the solid. Next, the electrons are slowed down by gold nuclei, an interaction that generates gamma-ray photons. The gamma rays then interact with more gold nuclei and transform into electron-positron pairs.
Machines that Almost Fall Over
A system of sculptures that is constantly on the brink of collapse. My intention was to capture and sustain the exact moment of impending catastrophe and endlessly repeat it.
While at rest, or with the hammer slowly moving, the pieces stay upright because the center-of-mass is located somewhere over the base. The key is to make sure the impact doesn’t change that.
Also, there’s Conversation Piece
Film editor Walter Murch, who edited many of Francis Ford Copolla’s films, developed a theory about edits while working on The Conversation (1974) He noticed that in many cases, the best place to make a cut was when he blinked. Subsequently, Murch wrote about the human blink as a sort of mental punctuation mark: a signifier of a viewer’s comfort with visual material and therefore, a good place to separate two ideas with a cut.
This sculpture is a physical test of Murch’s principle. I watched The Conversation while wearing a custom device that recorded the pattern of my blinks during the film. Using this information, I created a display in which the left mallet taps out the paattern of my blinks, while the right mallet taps out the pattern of Murch’s edits. When the two match up, the cymbal chimes for success.
Beat notes, sort of.
Welcome to Who Wants to be an Atomic Physicist?
Is It a Gas, Fluid, Solid, or All of the Above?
Because rubidium is magnetic, however, Stamper-Kurn and his Berkeley colleagues thought that the magnetic interactions between rubidium atoms in the gas might nudge them to adopt a type of regular spacing like atoms in a solid.
To look for this ordering, Stamper-Kurn’s team used a conventional laser trapping technique to confine a gas of millions of rubidium atoms in an oblong, surfboardlike trap. They then cooled the sample to below 500 nanokelvin. Lastly, they hit their collection of rubidium atoms with a beam of circularly polarized light, which is reflected differently by atoms with a different magnetic orientation and can, therefore, reveal the magnetic orientation of the atoms in the sample. What they saw was that within their optical trap, the rubidium atoms ordered themselves into an array of 5-micrometer-square domains, inside which all of the atoms adopted a similar magnetic orientation. What’s more, these domains adopted a crystalline-like ordering, with alternating domains with different magnetic directions. This ordering wasn’t perfect like the regular lattice of sodium and chlorine atoms in table salt. But it’s not random either (see picture). “There is some emergent order which shows up in this system,” Stamper-Kurn says.
Once the Berkeley researchers spotted the ordered makeup of the atoms, they decided to check whether the gas was coherent as well. Using another laser, they nudged two groups of rubidium atoms already in their trap. They found that the atoms interfered with each other in the same way that two coherent light beams create an interference pattern of light and dark stripes, an unmistakable sign of their wavelike quantum nature.
This was a nit that may have bothered only me (and my ilk. My ilk is somewhat sensitive to such things). In this past week’s episode of NUMB3RS, there’s a scene where Liz and Nikki go to arrest some 350-pound badassMF™. One of them tries some FBI-fu on him, is thwarted, and the other (I forget which did which) grabs a fire hose and knocks him over with the jet of water and a cliché. Except that momentum is conserved, or is supposed to be. The impulse from the water leaving the hose should knock the person holding it back, and given that either of these characters has somewhere around a third of the mass of the target, should have not been able to easily wrangle such an instrument of havoc.
This is similar to the magic shotgun, that is recoil-free to the wielder, but is able to knock the target a meter or so backward when struck.
Fiber. As in fiber-optic cables.
A short report on fiber optic cables for beginner level physics
$35,000 NitroCream Liquid Nitrogen Ice Cream Maker
Sure, it’s designed for restaurants, but there’s nothing stopping you from getting one. Other than the price tag, of course.
I’ve had liquid-nitrogen ice cream — we did it in grad school. It’s good. The fast freezing means you get small ice crystals, so it’s smooth, and the nitrogen just boils away. But it cost several orders of magnitude less to do it by hand.
A UV LED flashlight. Just checking on what fluoresces. Among the more interesting, we have the security stripe of a $20 bill
A Mr. Clean bottle shows both the label and the cleaner fluorescing
and some vitamin B complex (I think the B-12 is the main culprit here), dissolved in some vinegar, and spilled on the counter in the shape of a guitar. Worship the fluorescent guitar!
(I’ve previously noticed that vitamin B gives the appearance of remaining fluorescent even after digestion. Not that I’ve checked this with the flashlight. )
U.S. Naval Observatory IYA 2009 Open House
In celebration of the 400th anniversary of Galileo’s first use of the telescope, the International Astronomical Union and UNESCO have declared 2009 to be the International Year of Astronomy (IYA 2009). As part of a world-wide celebration of this event, the U.S. Naval Observatory (USNO) will be sponsoring a free-admission Open House on Saturday, 4 April, from 3:00 pm to 10:00 pm. During that time the Observatory’s telescopes will be open for inspection, scientists will explain the mission of USNO’s Master Clock, exhibits will display the Observatory’s history and present work, and local amateur astronomers will share views through their telescopes.
The event is planned regardless of weather, although predominantly cloudy conditions may limit observing activities. Additionally, heavy or persistent rain may result in cancellation. Be sure to watch the website for updates.
More details in the press release
I’ll be there, helping out, meetin’ and greetin’. I announced this on the local geocaching bulletin board, since USNO time supports GPS, so I hope to hang out with fellow geocachers for a while (there’s actually a geocache at the Observatory, which normally requires you to take the public tour), and then I’ll probably be helping out with the Time Service display. If you’re in the area, come on by. If you can’t make it, you can still commemorate your nonvisit with a Navel Observatory shirt
