Category: Physics

John Mather of NASA Goddard Space Flight Center and George Smoot of the University of California, Berkeley, share this year’s Nobel Prize in Physics for their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation.

More on the Nobel site.

As some readers will know, Smoot allegedly let the COBE results out of the bag ahead of the official announcement and so became the name everyone associated with the discovery of the detail in the universe’s microwave background radiation revealed in the picture shown here. There were around 1500 people involved in the research project, including Mather who was coordinator. Divvying up the Nobel Prize of 10m Swedish Krona between them all would give each of them less than $1000. That’s nothing to be sneezed at, but they’d have to club together to buy at least one really decent satellite.

Blue light-emitting diodes (LEDs) are really bright. Too bright for theorists to handle, in fact. Why? Because, the materials from which they are made usually have impurities that should make their glow much duller. Now, an international team of researchers has discovered why this is the case.

Commercially viable blue LEDs are based on the wide band gap semiconductor gallium nitride and indium gallium nitride and were invented by Shuji Nakamura then at the Nichia Corporation in 1993. By the late 1990s, they were widely available and now sit in an important technological niche in the development of large full-colour displays, LEDs for highly energy-efficient solid-state lighting to replace incandescent bulbs, and 400 nanometre laser diodes for optical data storage in high definition DVDs. However, the commonly used indium gallium nitride can only be manufactured at relatively low quality with high levels of impurities. Theoretically at least these impurities should quench the light the device produces, but it does not.

Full story out now, under the Intute Spotlight

The ultrasound equivalent of a laser could lead to important new discoveries in materials science by providing researchers with a non-destructive way to detect even the subtlest of changes, such as phase transitions deep in their samples. Now, researchers at the University of Illinois at Urbana-Champaign and at the University of Missouri-Rolla have built just such an ultrasound analogue of the laser – the uaser, pronounced way-zer.

Light amplification by stimulated emission of radiation devices, lasers, are well known, but a sonic analogue had until now not been developed. Richard Weaver and his colleagues set out to change that and to develop a device that would induce ultrasound amplification by stimulated emission of radiation to produce coherent ultrasonic waves of a single frequency. “A sonic laser has been possible for some time now,” Weaver told us, “our method could have been done earlier. I tend to think it wasn’t for two reasons: first no-one saw an application and second few people are expert at both laser physics and ultrasonics.”

More…

A real physical force that pulls together two metal surfaces separated by empty space does not tug on ships lying close at anchor, according to physicist Fabrizio Pinto, in today’s [email protected].

The “mysterious” Casimir effect is often illustrated by analogy with two ships floating side by side in a heavy swell and being pulled together, at least that’s how it’s been described in popular science articles. The notion apparently stems from a physics article published in 1996, which describes how an 1836 book, The Album of the Mariner, says ships should not be moored too close together because they will be attracted by a mysterious force.

Pinto is out to stem the tide of pseudoscience, however. He told news@nature that the idea is a simple misunderstanding. The Album of the Mariner says this attraction only happens in calm seas, not a heavy swell, points out Pinto. The only way a Casimir-like effect could be responsible is if the boats were moored in a choppy swell.

So the analogy is false, says Pinto. And there may not be any mysterious force at all pulling two ships together, whatever the conditions. “We have caught physicists in the very act of creating a myth,” he says.

So, what is the Casimir effect? Well, it’s not due to gravity, electrostatic charge, nor magnetism. That’s what it’s not. Essentially, it results from the resonance of the energy fields between the two objects. At least that’s what Wikipedia tells us, but what does it mean? Well it boils down to quantum fluctuations in the vacuum between the plates and for a lucid yet detailed description of how that causes attraction check out this PhysicsWeb article on the subject.

Incidentally, how would anyone navigate two ships in a vacuum to begin with?

Two-faced microscopic beads that rotate through a half turn when an electric field is applied to them could be the key to creating electronic paper, according to Japanese scientists. Takasi Nisisako and his team in the Department of Precision Engineering at the University of Tokyo have developed a new technique that allows them to produce these “Janus” particles much more efficiently and with uniform size.

Other researchers have previously developed two-colored beads of between 30 and 150 micrometers diameter (a micrometer is a thousandth of a millimeter) for experimental electronic paper applications. A thin film of these particles is sandwiched between a control grid and a protective surface. Applying a voltage to specific regions of the layer through the control grid can make clusters of individual particles flip over so that they appear black against a background of un-flipped white particles. Such technology could allow a device to display an image, words or pattern that is retained using no additional power until an erase voltage is applied making the particles flip back to white.

Such electronic paper has not yet entered the mainstream electronic gadgetry market because making the particles all the same size and of consistent quality is difficult. Prototype devices based on these Janus particles cannot yet produce a perfect picture. Nisisako and his team have now solved the quality control problem by side-stepping the standard manufacturing approach and have instead turned to microfluidic technology.

The team built a tiny device that comprises a sliver of glass into which is etched a Y-shaped channel. The researchers then seal this beneath a second layer of glass leaving the ends of the channel open. The two starting ingredients are liquid monomers designed to produce particles that respond to an electric current and have a different color on each of their two faces. The team feeds each ingredient into the arms of the “Y” where the materials form a two-color stream at the junction, which travels down the leg of the “Y”. The emerging fluid droplets are all identical and are then “cured” to form solid microscopic particles.

By integrating any number of these microfluidic devices, Nisisako suggests it should be possible to scale-up the manufacture of Janus particles for commercial applications. He adds that their approach is not limited to polymer ingredients and making microparticles from other starting materials such as ceramics or metals should also be possible.

Advanced Materials

A week doesn’t go by without my receiving an email from someone with a new theory that promises to overturn the whole of physics and chemistry. This week’s arrived with just a couple of days to go before April Fool’s Day.

You can check out the website along with movies illustrating the theory here. Please let me know if you get the joke! I’m not sure what those atoms are doing in that movie of two hydrogens colliding to be honest, what’s making them change direction, for instance?

Anyway, the site is here http://phasedparticle.com and I’ve reproduced the basic tenets of the new theory in case anyone can provide some insight:

1. Light is made up of both waves and particles.

2. Protons and electrons are both complete magnets having both a North and South Pole.

3. Heat is an energy field emanating from protons.