To astronomers, the new breed of hand-held laser pointer is a way to write in the sky, its two-mile-long beam allowing them to trace constellations and point out individual stars. To a lost hiker, the laser is a lifeline to a search and rescue team overhead. To a "Star Wars" fan, it is a prop for playing a lightsaber-wielding Jedi knight.
But to a pilot in a darkened cockpit, the pointer's bright green beam could be something very different -- a disorienting and even blinding blast of color.
A green laser is used to point out stars and constellations. Pointed at an aircraft, a green laser can be dangerous.
Laser Basics: A laser creates, amplifies and transmits a narrow, concentrated beam of light. Laser is an acronym for light amplification by stimulated emission of radiation.
"It's kind of like a flashbulb going off in your face," said Steve Luckey, chairman of national security for the Air Line Pilots Association.
Over the past month, pilots have reported more than 30 incidents of laser beams being trained from the ground into their aircraft, prompting warnings from federal authorities and new reporting guidelines. One of the incidents occurred in Anne Arundel County, where a man is charged with shining a laser beam at a police helicopter on New Year's Eve.
The controversy has led to a new focus on the beam machines -- gizmos seemingly stolen from science fiction that recently have become both cheap and readily available in stores and on the Internet.
Lasers are ubiquitous in American life. A laser tells a grocery clerk the price of a loaf of bread. Lasers are used in stores to keep track of inventory, in homes to help hang pictures straight, on automobile assembly lines for welding, in operating rooms, in the military for laser-guided weapons and in everyday electronic devices such as CD players.
The government does not regulate sales of lasers, and no laws restrict their use, though laser pointers have been banned from many public places, such as sports arenas.
The Food and Drug Administration regulates the manufacture of laser products and rates them in four categories based on the power of the beam. Beams in CD and DVD players are in category 1, the lowest. Laser pointers are in category 3, and industrial laser equipment is in category 4.
What's changed is the availability of powerful laser pointers. About a dozen years ago, a pointer with a red beam sold for about $600. Today, consumers can get a similar one for a key chain for $3.95 -- batteries included.
The popularity of red laser pointers is now being overtaken by green pointers, which are visible over a much longer range.
"The human eye responds to the green light approximately 50 times better than the red laser pointer, and that is why it appears so bright," said Richard Hughes, a member of the Florida-based Laser Institute of America, who has a doctorate in physics and holds 23 patents in the field of lasers.
The difference is striking: The old red pointers had a range of about a half-mile at best, experts say. The new green ones -- powered only by AAA batteries and no bigger than a Sharpie marker -- can send their beams more than two miles.
In recent years, prices of green lasers have fallen steeply -- from $400 each in 2002 to as little as $59 now.
As the lasers have become less expensive, they have become far more popular, said John Mueller, president of Beam of Light Technologies in Clackamas, Ore. Mueller said he is selling 1,500 to 2,000 a month.