Tag Archives | technology

The Light Fantastic

I detest sodium-vapor streetlights, whose yellowish glow now colors the night and stains metropolitan horizons everywhere. When I was growing up in suburban California in the 1960s and ’70s, the world after dark was lit by warm incandescence and whitish mercury-vapor street light. Although the latter had a spectral signature with vampiric overtones, turning reds to black and casting a blood-drained pallor on white skin, it still approximated something akin to plain white light.

But after the energy shocks of the 1970s, high-pressure sodium lights gradually took over the night. Following the economic imperative to use the most cost-effective lighting—high-pressure sodium lights consume half as much energy as mercury-vapor lamps and can last up to 16,000 hours longer—transportation departments and cities embraced sodium light. It was as though someone said “Fiat lux sulfurea—“Let there be light from hell.” The relentless spread of sodium streetlights is documented in NASA night photographs from space: New York City and Los Angeles are circuit boards of glowing orange, and Long Beach, one of the world’s busiest ports, is a flare of tarnished gold. It’s even worse in the United Kingdom, where 85 percent of streetlights use sodium. The jaundiced weirdness of sodium light has become a vexing challenge to photographers (one filmmaker, Tenolian Bell, called it “the ugliest light known to the cinematographer”); movie cameras simulate its color by using a gel filter named Bastard Amber. Significantly, retailers have avoided inflicting the unpleasantness of sodium lights on their customers—most commercial parking lots and shopping malls use the costlier white metal halide lights.

Our forced acceptance of sodium light’s ghoulish tint, an accident caused by the electrical vaporization of sodium metal in a gas-filled tube, makes outdoor lighting an example of a “bossy technology,” to borrow a term from Kevin Kelly’s recent book, What Technology Wants. Even worse than this inherent bossiness is the larger problem of light pollution. “Mankind is proceeding to envelop itself in a luminous fog,” wrote the authors of a paper on artificial night-sky brightness in 2001. This “perennial moonlight” that we’ve created enhances our safety and security, but it also dims our view of 10,000 stars and destroys the dance of light and dark.

But now we have a chance to bid good riddance to sodium vapor, and perhaps even resist the heedless trend of adding more and more light. The color of night is changing again.

In the next decade, a large percentage of America’s 37 million streetlights will be equipped with light-emitting diodes, or LEDs, and other kinds of solid-state lighting. Once again, energy-saving is the driving force. “We’re still at the front end of the wave,” says Mark S. Rea, the director of the Lighting Research Center at Rensselaer Polytechnic Institute, “but LEDs are inevitable as a replacement technology.” He predicts that LEDs, which are already 10 to 20 percent more energy-efficient than high-pressure sodium lights, will have a 40 percent advantage within a year or two.

Large-scale streetlight-upgrade programs have already begun in New York, Anchorage, San Jose, Pittsburgh, and many other cities. In Los Angeles, a $57 million project backed by the city’s Department of Water and Power and the Clinton Climate Initiative will replace 140,000 of the city’s 209,000 streetlights. Michael Siminovitch, the director of the California Lighting Technology Center at UC Davis, argues that the true potential and savings of the new lighting are less a matter of the source than of digital “adaptive controls.” Unlike sodium lights, LEDs and other next-generation lights can be tuned to various colors, easily dimmed, arranged into luminous surfaces and shapes, and turned on and off instantly.

Will this versatility translate into self-restraint? “We have the technology to make beautiful, modest night lighting,” says Jane Brox, the author of Brilliant: The Evolution of Artificial Light. “But our relationship to light is not rational. To ask people to live with less light, even if it’s well designed—a lot of people feel like that’s going backward.”

We’ve learned to be that neighbor who leaves a yellow porch light glaring all night long. Perhaps we can now learn, in the words of the lighting designer Rogier van der Heide, “why light needs darkness.”

[This post originally appeared in the July-August 2011 issue of the Atlantic.]

July 1, 2011 at 4:35 pm

Riding the Groove

My all-time favorite explanatory passage from the literature of hi-fi appears in Laura Dearborn’s sadly out-of-print 1987 guide to audio, Good Sound. In it, she contrives to describe what’s happening when a turntable cartridge’s stylus rides an LP groove, and she pulls it off in a way that makes it sound like a marvel akin to a Star Wars jump into Hyperspace. Now and then, when I’m playing a great-sounding record via my trusty Ortofon Kontrapunkt A cartridge I remember Deaborn’s thrilling explication.

So let’s cue up Good Sound:

Visualize the fineness of a record groove, and then consider that it combines two distinct channels of information, each with completely different modulations. Some of the signal modulations in the groove are on the same order of size as a wavelength of light, which means the stylus has to “read” a signal as small as a millionth of an inch…

For the half a mile or so of record groove per LP side, the stylus must precisely trace abrupt changes in the direction of the undulating groove, sometimes traveling at speeds several times the acceleration of gravity, without ever losing contact with either wall or blurring together the modulations.

Groove friction heats the stylus up to 350 degrees Fahrenheit and the groove vinyl momentarily liquefies each time the stylus passes over it. (This is why one should let a record rest for at least 30 minutes before replaying it, and preferably for 24 hours.)

Even though the cartridge tracking weight is commonly set at only about 1.5 grams, the entire weight is supported on the minute edges of the stylus. As a result, the downforce applied to the groove on a per-square-inch basis is several TONS.

Combine these extreme conditions of weight, heat, speed, and need for exquisite maneuverability, then add in the scale of environmental vibrations that interfere with the stylus as it retrieves the music from the groove, and it’s extraordinary that ANY music (as opposed to noise) is heard through an audio system.

For the grand finale of her bravura account of LP playback, Dearborn gets all Brobdingnagian, blowing up the stylus-and-groove action to outsized gynormousness. Technology as minute as an LP record groove is typically measured in microns. One micron equals 0.0039 inch. Dearborn walks us through what would happen if you could convert the micron scale upward to inches, borrowing a thought-experiment originally devised by the Boston Audio Society’s magazine, The Speaker.

Using the inch scale, a stylus is 30 feet long, affixed to a cantilever 50 feet thick and 275 feet long, which extends from a cartridge body 2,000 feet long, sitting 80 feet above the record. The tonearm, 450 feet in diameter, crosses 1,500 feet above the record from its pivot point four miles away… The stylus downforce temporarily deforms the vinyl by as much as an inch (20 times the size of a violin harmonic), leaving a stylus footprint on the groove wall measuring 10 inches long and 4 inches wide. A typical midrange signal demands that the stylus move 16 inches from peak to peak of the wave form. A deep bass note 10 dB louder requires the stylus to move 10 feet 6 inches whereas for a high-frequency harmonic at a very low sound level , the stylus must move only 0.68 inch. Even the simplest piece of music is likely to contain, at any one time, enormous numbers of frequencies at different levels.

The next time you hear someone try to dismiss vinyl as a primitive, antiquarian, and thoroughly Luddite approach to sound reproduction, just remember that analog vinyl sound reproduction is, and always will be, miraculous. Perfect Sound Forever, suckas!

Electron microscope photograph by Chris Supranowitz / Institute of Optics, University of Rochester

October 27, 2010 at 6:56 pm

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