Mobiles may also appeal, Schmitt suggests, because they are not as intellectually demanding as much modern art. "A lot of art tries to express ideas or requires interpretation," he says. "What I strive for in the mobile, it's an object you want to have in your home. It enriches your environment. You don't have to analyze it."
Not that there isn't plenty to analyze. Alexander Calder (1898-1976), the Philadelphia artist-engineer who gave mobiles to the world in the 1930s, spent time with the French Surrealists and was equally fascinated with chance procedures and the unconscious.
A mobile, Howe suggests, "is almost like a structure that references a dream activity. They are bodies floating in space, they are planetary, they are like cloudscapes or thought bubbles floating above your head."
Frazier says the appeal is simple. "They make people happy."
Schmitt enjoys the unpredictable way they move. "They're almost like a goldfish you don't have to feed," he says.
"Because it's dynamic," he suggests, "it adds a personality to a space you don't get with a static object. In a corner of an atrium, it really sets off the space."
Mobiles work well in modern houses, Frith says, because high, open-beamed ceilings benefit from the energy of mobile art. "Eichlers have angled roofs, so they're perfect to hang a mobile," she says.
Matt Richards, who began his mobile-making ten years ago, building ten-inch table models he hawked over eBay, still sells some production mobiles through Design Within Reach, but focuses instead on large scale, individually designed commissions -- many for hospitals.
Mobiles succeed in hospitals for the same reason they succeed above cribs -- they're relaxing. Many of his mobiles hang in hospital lobbies and atriums. "Patients or family members sit and look out," he says. "It's slowly moving, just a little movement. In the end it gets mesmerizing. You spend ten minutes gazing at it. That's something other art doesn't do, it doesn't allow you to get lost in it."
About half of Brad Howe's mobiles go into people's homes, often to mobile collectors, who number maybe a thousand worldwide, he estimates, with up to 200 in Los Angeles. "Some people love their mobiles like pets," Howe says. "They're very, very fond of them."
While there is general agreement that a 'mobile' has to move and has to hang, and that its movement must be generated by wind or a breeze generated by passersby and not by a motor, definitions vary.
Many say a 'mobile' must involve interconnected pieces, one hanging from another.
"A suspended interconnected, balanced sculpture," is Howe's definition, "with elements that are cantilevered, with linkages that allow for more or less rotation before the next link can move."
Others use the term in a broader sense to mean art using "anything that might move," Richards says, interconnected or not.
Richards uses a broader term 'hanging kinetic art,' within which 'mobiles' are a subset.
Whatever you call them, mobiles have a natural affinity with mid-century modern design.
Calder and other pioneers of kinetic art -- the Russian Constructivist Naum Gabo in the 1920s and the American-born Scotsman George Rickey in the 1950s -- produced one-of-a-kind, avant-garde artworks.
During the 1950s, mobiles went mass market, with production by several European and American firms, including the Danish company Flensted, which remains in business.
Many sculptors from the early 1940s through the 1960s produced a wide variety of mobile sculptures, including the San Franciscan Robert B. Howard, the Frenchman Jean Tinguely, and Otto Piene, who focused on inflatables. French artist Jackie Matisse worked with kites.
Later mobile artists of note include Timothy Rose of Sausalito and Jerome Kirk, who settled in Healdsburg.
Meanwhile, many advances were made in the much broader field, 'kinetic art,' which ranges from mechanically controlled robots to electronics and sound sculptures.
One of the world's most unique creators of mobile sculptures is San Franciscan Ruth Asawa, whose freeform, basket-like wire designs, which she began in the 1950s, have become iconic. Asawa was married to architect Albert Lanier, who designed mid-century modern homes.
The connection between mobiles and mid-century modern design is acknowledged by many current mobile makers. "A lot of my clients come from that mid-century modern mindset," Matt Richards says.