Category Archives: Electromagnetics

Light pulled out of empty space

You can get something from nothing – as long as you are moving close to the speed of light. The discovery confirms a 41-year-old prediction on how to pull energy from empty space and produce light.

The phenomenon relies on the long-established fact that empty space is not at all empty, but fizzing with particles that pop in and out of existence (see “Out of the ether: the changing face of the vacuum”). This is down to the laws of quantum mechanics, which say that even a vaccum cannot have exactly zero energy but must exhibit small fluctuations of energy. These fluctuations show themselves as pairs of short-lived particles.

The presence of these “virtual” particles, usually photons, has long been proved in experiments demonstrating the standard Casimir effect, in which two parallel mirrors set close together will feel a pull towards each other. This happens because the small space between the mirrors limits the number of virtual photons that can appear in this region. Since there are more photons outside this space, the radiation pressure on the mirrors from the outside is larger than the pressure between them, which pushes the mirrors together.

Now Chris Wilson at Chalmers University of Technology in Gothenburg, Sweden, and his colleagues have gone a step further, pulling photons out of the void in a process called the dynamical Casimir effect. “It was a difficult technical experiment,” says Wilson. “We were very happy when it worked.”

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DIY Transcranial Magnetic Stimulation

Via Grinding

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Tool: Arc Attack’s Singing Tesla Coil Emulator

Arc Attack offers a Singing Tesla Coil Emulator on their website. It also promises the possibility of seeing a VST version of these pitched Arcs at somepoint.

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Sun unleashes X6.9 class flare; Earth spared this time


On August 9, 2011 at 3:48 a.m. EDT, the sun emitted an Earth-directed X6.9 flare, as measured by the NOAA GOES satellite.

This was the largest flare of the current solar cycle, an R3 (Strong) Radio Blackout, alternatively classified as an X6, according to the U.S. NOAA Space Weather Prediction Center.

These gigantic bursts of radiation can disrupt GPS and communications signals. In this case, scientists say the eruption took place on the side of the sun that was not facing Earth, so there’ll be little impact to satellites and communication systems, AP reports.

Space scientist Joe Kunches at the U.S. Space Weather Prediction Center in Colorado says there were reports of brief short-wave radio disruptions in Asia, but little else.

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What You Learned About Static Electricity Is Wrong

For many of us, static electricity is one of the earliest encounters we have with electromagnetism, and it’s a staple of high school physics. Typically, it’s explained as a product of electrons transferred in one direction between unlike substances, like glass and wool, or a balloon and a cotton T-shirt (depending on whether the demo is in a high school class or a kids’ party). Different substances have a tendency to pick up either positive or negative charges, we’re often told, and the process doesn’t transfer a lot of charge, but it’s enough to cause a balloon to stick to the ceiling, or to give someone a shock on a cold, dry day.

Nearly all of that is wrong, according to a paper published in today’s issue of Science. Charges can be transferred between identical materials, all materials behave roughly the same, the charges are the product of chemical reactions, and each surface becomes a patchwork of positive and negative charges, which reach levels a thousand times higher than the surfaces’ average charge.

Where to begin? The authors start about 2,500 years ago, noting that the study of static began with a Greek named Thales of Miletus, who generated it using amber and wool. But it wasn’t until last year that some of the authors of the new paper published a surprising result: contact electrification (as this phenomenon is known among its technically oriented fans) can occur between two sheets of the same substance, even when they’re simply allowed to lie flat against each other. “According to the conventional view of contact electrification,” they note, “this should not happen since the chemical potentials of the two surfaces/materials are identical and there is apparently no thermodynamic force to drive charge transfer.”

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Hand-hacking lets you pluck strings like a musical pro

PossessedHand, being developed jointly by the University of Tokyo, Japan, and Sony Computer Science Laboratories, electrically stimulates the muscles in the forearm that move your fingers.

A belt worn around that part of the subject’s arm contains 28 electrode pads that flex the joints between the three bones of each finger and the two bones of the thumb, and provide two wrist movements. Users were able to sense the movement of their hands that this produced, even with their eyes closed.

Having successfully hijacked a hand, the researchers tried to teach it how to play the koto, a traditional Japanese stringed instrument. Koto players wear different picks on three fingers, but pluck the strings with all five fingertips, so each finger produces a distinctive sound.

PossessedHand does not generate enough force to pluck the koto strings, but it could help novice players by teaching them the correct finger movements.

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Antiproton ring found around Earth


Antiprotons appear to ring the Earth, confined by the planet’s magnetic field lines. The antimatter, which may persist for minutes or hours before annihilating with normal matter, could in theory be used to fuel ultra-efficient rockets of the future.

Charged particles called cosmic rays constantly rain in from space, creating a spray of new particles – including antiparticles – when they collide with particles in the atmosphere. Many of these become trapped inside the Van Allen radiation belts, two doughnut-shaped zones around the planet where charged particles spiral around the Earth’s magnetic field lines.

Satellites had already discovered positrons – the antimatter partners of electrons – in the radiation belts. Now a spacecraft has detected antiprotons, which are nearly 2000 times as massive.

Heavier particles take wider paths when they spiral around the planet’s magnetic lines, and weaker magnetic field lines also lead to wider spirals. So relatively heavy antiprotons travelling around the weak field lines in the outer radiation belt were expected to take loops so big they would quickly get pulled into the lower atmosphere, where they would annihilate with normal matter. The inner belt was thought to have fields strong enough to trap antiprotons, and indeed that is where they have been found.

Piergiorgio Picozza from the University of Rome Tor Vergata, Italy, and colleagues detected the antiprotons using PAMELA, a cosmic-ray detector attached to a Russian Earth-observation satellite. The spacecraft flies through the Earth’s inner radiation belt over the south Atlantic.

Between July 2006 and December 2008, PAMELA detected 28 antiprotons trapped in spiralling orbits around the magnetic field lines sprouting from the Earth’s south pole. PAMELA samples only a small part of the inner radiation belt, but antiprotons are probably trapped throughout it. “We are talking about of billions of particles,” says team member Francesco Cafagna from the University of Bari in Italy.

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Augmented instruments add virtual input to live music

They look like just another three-piece band, with drums, violin and guitar. But stop and listen to Edgar Berdahl and his colleagues, and you’ll notice things aren’t quite what they seem. Strange tones emerge from their instruments, sometimes without any of the performers moving, as an abstract soundscape washes over you.

The Haptic Drum, Overtone Fiddle and Feedback Resonance Guitar are all examples of what Berdahl, who researches technology in music at Stanford University in California, calls actuated instruments.

Berdahl and his colleagues have modified traditional instruments by adding electromagnets and other sensors that can both detect and induce vibrations, blurring the line between physical and computer-generated sounds. The instruments can essentially play themselves, while also allowing a person to control them. This allows very different sounds to be created. “The manner in which the external energy is injected into the instrument enables and even compels the performer to interact in new ways,” says Berdahl.

Take the Overtone Fiddle, created by Dan Overholt at Aalborg University, Denmark. It can be played like a regular violin, but signals can also be pumped directly into the instrument’s body, causing it to resonate and produce a wider variety of sounds. An iPod Touch controls the signals, allowing the performer to modify effects on the fly, while a bow fitted with a position sensor provides another form of input that can be used to modify the sounds.

The Feedback Resonance Guitar follows a similar construction, using electromagnets to vibrate each of the instrument’s six strings at a variety of frequencies. Notes can be artificially sustained, and the guitar can also play traditional rock “feedback” tones without the usual corresponding rise in volume – handy if you want to avoid blowing your amp.

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Eric Giler demos wireless electricity

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Solar flare eruptions set to reach Earth

“Our current view is that the effect of the solar flare is likely to reach Earth later today Thursday GMT, possibly tomorrow morning,” said Alan Thomson, head of geomagnetism at the British Geological Survey BGS.

He told BBC News: “In the scientific community, there’s a feeling that it’s not as intense as we first thought it might be. But it’s possible still that it could be a large enough event for us to see the northern lights in the UK.”

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