T is for Tesla (Coil)

September 09, 2009

Is there anything cooler than a Tesla coil? Ever since Nikola Tesla caused a power outage in Colorado Springs with his gigantic Tesla coil in 1899, science enthusiasts have thrilled to the sight of electrical arcs shooting out like electromagnetic tendrils. It's a staple of science demos, for good reason: people love a good light show, and a small Tesla coil can also cook a hot dog in mere seconds. (Some of us like a bit of charring on the outside.) And some folks get downright creative with the technology.

For instance, Simon Singh is a prolific author -- The Code Book is one of my all-time faves -- but he is also something of a scientific performance artist. He and collaborator Richard Wiseman (psychology professor by day, magician by night) performed a few years ago in Theatre of Science, playing first in London and then briefly in New York City.

The highlight was the "coils of death": two gigantic Tesla coils capable of passing one million volts of electricity in a live, on-stage lightning display. Singh and Wiseman wheeled in the "coffin of terror", a narrow sarcophagus made of chicken wire. Singh got inside, and was "zapped" by two million volts of electricity. He emerged unscathed because the coffin is basically a Faraday cage. The lightning hit the cage, but the charge only  flowed across the metal surface. So long as Singh didn't poke a finger through the chicken wire, he was safe from harm: "Thank god for the laws of physics!"

Austin-based ArcAttack goes one better with their "singing Tesla coils" capable of playing things like the theme from Dr Who:

Per their Website: "These high tech machines produce an electrical arc similar to a continuous lightning bolt which put out a crisply distorted square wave sound reminiscent of the early days of synthesizers. The music consists of original highly dance-able electronic compositions that sometimes incorporates themes or dub of popular songs."

Maybe they can move to Vegas and become featured entertainers at the planned Nevada Lightning Laboratory (h/t: io9). Plans call for two 12-story Tesla coils capable of creating an arc of electricity over 300 feet long. Sure, there'll be some science going on: the coils will be used to test how vulnerable aircraft are to electrical storms, and to conduct "pulsed calibrations of the ionosphere, allowing accurate global weather data."

But there will also be entertainment, including viewing platforms at the top of the towers -- safely encased in Faraday cages, naturally -- complete with a bar and lounge. Project leader Greg Leyh demonstrated his prototype Tesla coils this past June at Dorkbot San Francisco. The spirit of Tesla is alive and well  -- and soon to be a star in Vegas.

DorkbotSF at the Nevada Lightning Lab from Mike Estee on Vimeo.

Always Chasing Rainbows

October 05, 2008

The South Pole is a prime location for scientific research, most notably those who study neutrinos, and those interested in meteorology. That doesn't make it a friendly work environment: it is bitterly cold, with temperatures averaging -40 degrees F during prime research season (and wind chill factors of 100 degrees below zero). Just to get there requires several different airline flights over many days, and the final leg is an 800-mile flight from the coast of Antarctica to the Pole in a cargo plane, which keeps idling as everyone piles out and unloads the cargo, lest it freeze up in the interim. In fact, certain times of year it's not even possible for a plane to land.

But the location has it perks, too, thanks to all the tiny ice crystals scattered throughout the atmosphere. When sunlight reflects and refracts off of them in just the right way, the result is a dazzling ice crystal halo -- the South Pole's version of a rainbow.

I first heard about ice crystal halos many years ago from Robert Greenler, a retired physicist (professor emeritus at the University of Wisconsin, Milwaukee) who became fascinated with the phenomenon, even making three separate trips to the South Pole himself to observe them directly. He's written two books on the subject: a classic introductory text called Rainbows, Halos, and Glories, and more personal memoir: Chasing the Rainbow: Recurrences in the Life of a Scientist.

That's how I learned that the halo effects occur when small droplets of water in the atmosphere freeze into various hexagonal crystalline forms: the two most common are a hexagonal plate crystal, and a cylinder-shaped hexagonal crystal resembling a pencil. When oriented just so, at times when they are plentiful enough, these crystals behave like prisms when sunlight shines through them, refracting the ray by specific degrees (22 degrees and 46 degrees trigger the most common halo effects).

Halo effects are recorded with a device dubbed "R2D2": it contains a video camera operating in time-lapse mode to track the sun around the sky and maintain an extended record of the effects. Nature, of course, is fickle about granting such displays. "You can get all your equipment set up and then you wait. And wait. And wait. Either halos come, or they don't," Greenler admitted.

Ice crystal halos might be Nature's own optical art, but scientifically, they serve a much more practical purpose: mapping the characteristics of crystals in the atmosphere can help with climate modeling. But until recently, the instruments scientists were using to measure them couldn't get decent images of ice crystals smaller than 25 microns. Accurate measurements are critical because the size and shale of the ice crystals have an impact on how much incoming sunlight is absorbed into the atmosphere, and how much is reflected back out into space -- and that in turn affects greenhouse warming.

Now, however, scientists from the Universities of Hartfordshire and Manchester in England, collaborating with Colorado State University, have developed a new optical scattering instrument that can measure ice crystal halos down at that teensy micron level (it's comparable to the smallest cells found in the human body). There are two versions: a ground-based instrument, and a second instrument tat fits under the wing of a research aircraft and measures the cloud particles directly. Rather than trying to take a full image of an ice crystal, the instruments record the detailed pattern of scattered light from each crystal and then extrapolate backward, interpreting those recorded patterns and matching them to effects associated with known ice crystal shapes.

The equipment has only been tested in the lab to date, and those results appeared in Optics Letters, but the next step is to send the instruments into actual clouds to make some real-world measurements. They don't necessarily need to go to the South Pole, however: the scientists are especially interested in studying ice crystals in high-altitude cirrus clouds, which cover more than 20% of the Earth's surface on any given day. Still, for anyone willing to brave the wind chill factor, the new instruments might be able to shed more light not just on climate modeling, but the less well-understood variations of ice crystal halo effects.

Photo: An ice crystal halo. Source: NASA Astronomy Picture of the Day. Taken by Jean-Marc LeCleire.

MapQuest for Mars

June 18, 2008

It's summer, time for the great American tradition of the family vacation road trip! When I was a kid, our entire family criss-crossed the country one summer, from Seattle to Maine, in an old Buick station wagon, stopping off at Yellowstone National Park, the Grand Canyon, and a few other landmarks along the way. But mostly, I recall the tedium of 8-hour drives, punctuated by arguments between me and my siblings: "Are we there yet?" "Mom, he keeps looking at me!" Even my parents had their share of arguments, usually while looking over a map in the gigantic atlas that weighed more than my baby sister. Because of course my father wouldn't dream of asking for directions (that's my mom's story and she's sticking to it).

These days, the standard big atlases of my youth are pretty much obsolete, thanks to online resources like MapQuest and GoogleMaps -- both of which I use regularly. But what's a plucky space explorer to do when trying to land a spaceship on Mars (or the moons of Jupiter) sometime in the distant future? Our current "maps" of the red planet leave a lot to be desired in terms of the minute details, especially changing variables like wind speed, atmospheric pressure, and temperature. Sure, our little space probes have done an outstanding job giving us a rough idea of Martian topography, but frankly, the resolution just isn't good enough yet. You don't want to confuse a big boulder with a small pebble -- not when you're trying to land a multi-million-dollar space craft.

What we need is a 3D "super road map" giving us location-specific, detailed information about changing planetary surfaces and conditions. If only we had an imaging technique capable of producing such a map! Lucky for our future astronauts, scientists at the Rochester Institute of Technology (RIT) in upstate New York are developing such an imaging system based on LIDAR (Light Detection and Ranging), in collaboration with MIT's Lincoln Laboratory.

LIDAR is very similar to radar in concept, except it uses laser light instead of radio waves to determine distances, by measuring the time it takes for light to travel from a laser beam to an object and then back again. Not only could such a system prove invaluable for mapping out the surface of the moon, Mars, or other planetary surfaces and atmosphere, it can also probe the environments of comets or asteroids. The RIT scientists will test their prototype system under conditions that mimic those likely to be encountered during NASA space missions.

Improved resolution is the key. Generally speaking, we can usually only image objects roughly the same size as the wavelength of light being used, or larger. The radio waves used in radar, for instance, are terrific at detecting metallic objects, but rocks, or even raindrops, might not produce much in the way of detectable reflections, so these sorts of things would be pretty much invisible to radar. LIDAR uses much shorter wavelengths (eg, in the optical and ultraviolet regimes of the electromagnetic spectrum), and thus the system can detect very small objects, even tiny particles in the atmosphere. In fact, LIDAR is already being used to study atmospheric conditions here on Earth.

Lasers also have a very narrow, focused beam, so LIDAR enables the mapping of physical features with much higher resolution than conventional radar. Its "footprint" can be less than one meter, making it possible to map the floor underneath a thick forest canopy in the Amazon, or details in narrow urban canyons obscured by tall buildings. Such systems were used in the aftermath of the terrorist attacks on September 11, 2001, to map out the debris from the collapsed World Trade Center at Ground Zero in New York City. The resulting detailed topographical "maps" helped rescue workers navigate the often treacherous terrain by identifying unstable areas likely to shift or collapse. The maps also showed the locations of foundation-support structures, elevator shafts and so forth. (You can read more about LIDAR and its many terrestrial applications here.)

According to RIT scientist Donald Figer, his team's LIDAR imaging detector will be able to distinguish topographical details of a planetary surface that differ in height by as little as 1 centimeter. And its imaging system will be able to swiftly capture wide swaths of entire scenes as the laser beams sweep across the terrain. Current LIDAR systems use a single pixel, which must be moved across a scene bit by bit to slowly build up an image. Accuracy is important in space navigation, but so is speed: you've got to be able to adapt to changing conditions quickly, after all. That's why Figer believes his team's LIDAR system could become "a workhorse for a wide range of NASA missions" -- thereby sparing our future astronauts the embarrassment of having to ask local planetary inhabitants for directions.

Photo: LIDAR image of Ground Zero in New York City, September 27, 2001. NOAA/U.S. Army JPSD