The atoms of a physical substance, usually a crystal, are charged up while mirrors at both ends of the laser reflect the energy back and forth to strengthen it.

The "ruby laser," so-called because physicist Theodore Maiman used a ruby rod to make it, was first used on May 16, 1960.

Maiman's first scientific article about the discovery was turned down. While the second was awaiting publication, the laboratory went to the press with the news, prompting scientists who hadn't seen his complete findings to initially dismiss the discovery as insignificant.

There's no way to list everything lasers do. (Although, we do suggest another look at the world's largest laser, currently working to save -- not destroy -- the Earth).

But here's a rundown of just a few applications for lasers, and a nod to where laser technology might go next.

Laser surgery

From a high-tech update to the old nip-tuck to eye treatment that can eliminate the need for glasses or contacts, lasers are often used in surgery.

Carbon-dioxide lasers and others are used to remove unwanted tissue -- from tumors, warts and tattooed skin -- and create incisions that are less intrusive, less painful and leave less scarring than traditional surgery.

Entertainment

At planetarium domes everywhere, starry-eyed fans have enjoyed laser light displays for decades. The shows combine beam effects -- which sweep through the air -- and screen effects, which create images, patterns and shapes on a wall or other fixed object.

At Georgia's Stone Mountain Park, near Atlanta, Georgia, more than 20 million people have watched a laser show projected onto the massive granite mound.

Billed as the world's longest-running laser show, it offers a "dazzling display of neon laser lights featuring characters, stories, graphics and fireworks choreographed to popular musical scores," according to spokeswoman Jeanine Jones.

For the more active set, there's laser tag.

Adopted by the U.S. Army in the late '70s for training, laser tag was offered in crude form in toys around the same time. In 1984, two recreational laser tag centers were opened in Texas.

At most laser-tag venues, teams with laser guns scramble around an indoor course, shooting at each other in the near-dark. Technology varies somewhat, but, generally, laser tag uses infrared signaling to track lasers and determine whether they've hit their target -- usually a vest worn by the player.

Telecommunications

Most of us probably don't think of lasers being involved in our telephone conversations or internet use. But they are.

Fiber optics -- the ultrathin, glass cables used to carry digital information for phones, computers and cable TV -- use laser-generated pulses of light to carry that data at incredibly high speeds.

For computer users, communications companies claim that fiber-optic connections can download music, videos and other files to computers 25 times faster than traditional cable -- at least in the places where it's available.

The fervor over the upcoming Google Fiber project shows that lots of folks are eager to give laser-powered, in-home fiber a try.

CDs and DVDs

Tiny lasers are at work any time you turn on a disc player.

Whether audio or video, these players focus a laser beam on a series of bumps on the disc. The way the different bumps reflect that light determines the sound and images.

And when your CD skips? That's because the laser can't read data through a dirty or scratched outer layer -- although it's probably not the laser's fault that the disc is dirty or scratched in the first place.

So, what's next?

Scientists in all sorts of fields are experimenting with more uses for lasers.

The U.S. Air Force is pondering an airborne laser defense system, albeit one with a high-flying price tag.

Lasers are also being used in technologies such as holographs, new energy sources and space exploration.

And like personal computers, says Bronski, lasers are shrinking.

"Lasers that used to fill up a small-sized room are now the size of a desk," he said. "We'll see that trend continue in the future -- things getting smaller while maintaining their outputs or increasing their outputs."

So, does that mean that handheld lasers could be around the corner? You know -- the kind Han Solo says always trump hokey religions and ancient weapons?

"Those technologies might not be so far off," Bronski said. "At some point, it might be possible to make a much smaller package for these laser devices ... like little phasers or whatever."

The Discovery orbiter is aiming for a final flight in September, with the Endeavour ship scheduled currently to conclude the shuttle programme in November.

Friday's lift-off will be the 32nd for Atlantis. Notable achievements in its 25-year career have included launching interplanetary probes from orbit and leading the Shuttle-Mir programme which saw the ship visit the Russian Mir space station more times than any other ship in the fleet.

The latest mission to the ISS will require Atlantis to carry up a 7m-long (23ft) docking and storage module known as Rassvet (Russian for "dawn").

The shuttle's cargo bay will also contain a large rack structure holding six new batteries for the orbiting platform, as well as a spare communications Ku-band antenna, and a tool tray for the station's Dextre robot system.

These items will be placed on the exterior of the platform during three spacewalks.

The trickiest moment of the mission is likely to come on flight day five when the Rassvet module is attached to the underside of the station. Russian modules are normally flown into their berthing positions, not lifted into place by a robotic arm.

The Atlantis crew has to be sure they apply sufficient pressure with the arm to engage the docking mechanism on Rassvet.

The British-born US astronaut Piers Sellers will be directing robotic operations.

"We're going to be pretending to dock this like a Soyuz or Progress spacecraft," he said.

"We're going to use the arm and very carefully approach the docking cone, and we're going to fool Rassvet into thinking it's docking itself. That's how it's going to activate all its latches and hooks."

Weather forecasters say there is a 70% chance of fine conditions at lift-off time, with low cloud being the one concern.

After it returns from the 12-day mission to the ISS, Atlantis will not go straight to a museum. It will instead be prepared as a standby shuttle ready to go rescue the astronauts on November's Endeavour flight should they get into trouble.

Nasa has not excluded the possibility that it could yet fly out this standby shuttle to take additional spares and supplies to the space station.