Celebrating its 50th anniversary this year, the laser is now everywhere. Back then, no-one knew what it could be used for. How things have changed. We look at the ten oddest uses for coherent light.
Okay, so they're not going to alert any shepherds or wise men to unusual events - the artificial stars created by lasers fired from observatories such as the Keck on Mauna Kea in Hawaii are not all that bright. But they can be detected by the powerful telescope below and used to calibrate the sensors that collect light from distant stars and process them to remove the blurring effects of the Earth's atmosphere. The artificial star is created by firing laser pulses at a layer 100km above the Earth's surface that is rich in sodium ions. At the right frequency, these sodium atoms emit light that can be picked up from the telescope.
The University of Nottingham is where every upwardly mobile cow aspires to be milked. The robotics researchers there have created a dairy centre that they reckon is 'five-star accommodation' for a cow. Animals queue up to use the automatic milking cubicles. After they have entered, lasers guide the pumps used for milking onto the udders. In the automatic centre, cows even get to choose when they are milked rather than being prodded into place by a farmer.
Scientists have harnessed the electromagnetic radiation created by lasers to produce so-called 'optical tweezers'. By focusing a beam through a microscope lens, it is possible to produce a strong electric field that can trap tiny objects. As you move the beam, the objects caught in the field move with it.
Because these optical tweezers are so sensitive, it's possible to move single molecules of DNA or protein with them. They are also good for moving cells and bacteria from place to place. UCLA researchers reckon this kind of technique could realise the 'smart petri dish' - a laboratory tool for pushing and prodding cells found in saliva to detect diseases.
Hackers have devised many ways to try to get into smartcard chips. A lot of them revolve around tripping the device up while it's performing calculations in the hope that this will reveal how it works. The laser makes it possible for the hacker to home in on specific parts of the chip to a degree that is rarely possible with other approaches. An optical laser aimed at the top surface of a chip, or an infrared laser at the back, can cause the logic gates caught in the beam to make mistakes, as University of Cambridge researcher Sergei Skorobogatov found in the past decade.
Setting the standard for distance
The standard metre stopped being a metal bar back in the 1960s, when it became part of the SI system. Instead it was defined as 1,650,763.73 wavelengths of the orange-red emission line of krypton-86 in a vacuum. That lasted for 20 years when the 17th CGPM redefined the metre in terms of the speed of light - it's the distance covered by light in a vacuum during a tiny fraction of a second. To measure this, however, laboratories still count wavelengths of light along the metre's distance using laser inferometers. Any laser would do but the recommended standard is a helium-neon laser to allow labs to reproduce each others' results.
Laser retreads for your skin
Anything that promises to take years off people has them flocking to private clinics for a dose, even when the development work has been nowhere near a peer-reviewed journal. There is some research to demonstrate that hitting the skin with lasers can tighten it up and knock out shallow wrinkles.
The process works by vaporising some of the excess skin cells with carbon dioxide or helium-YAG lasers. When the skin repairs itself, it should wind up smoother. But be careful, don't go out in the sun for a week or two until the skin heals properly unless you like that blotchy look.
Artworks have also been getting a laser clean-up. Wall paintings in Siena, Italy, were cleaned by a team from the Applied Physics Institute in Florence. The key, say the technique's developers, lies in tuning the laser to the painting and the sort of cleaning it needs.
Back in the 1980s, Jean-Michel Jarre wanted something to spice up his live performances and came up with the idea of the laser harp: a bunch of laser beams and detectors that could play notes when he broke the beams with his hands. The trouble is, with only about ten beams to play with, it can't play a lot and it lacks even the expressive power of synth keyboard because all it can do is register whether the beam is broken or not.
The laser harp is making a comeback, not least in Jarre's own shows. R&B star Kesha played one version on 'Saturday Night Live' in the US in April, and Beamz Interactive is selling a tabletop version that plays samples and sound effects.
To get lightning on demand, you used to have to send a rocket into a cloud, trailing a long wire behind it. That's so last century. Five years ago a team of scientists from France and Germany used powerful but very short laser pulses to ionise air molecules between an artificial thunderhead - in this case a high-voltage electrode - and the ground. The experiment succeeded in triggering megavolt discharges. Moving their work outside a few years later, they found lightning bolts tended to follow their laser-generated paths.
Engraving medals and...beetles
If you need to make medals in a hurry, the laser is there to help. At the Munich Marathon, the 40,000 finishers can get a medal that shows their race time. The quickest way to do it is with a high-powered laser to engrave the name and numbers automatically.
It's not just medals that get laser-engraved. Researchers at the University of Plymouth used gas lasers to engrave tiny serial numbers into the shells of live beetles. The beetles are chilled first to sedate them and then put in a little well while a laser marker gives them their new identity. The beetles were then used in studies of how they hunted.
It was a more intimate intervention for some fruit flies when scientists from the University of California at Berkeley performed microsurgery on their genitalia to see how they performed afterwards. The flies have tiny spines on their penises that the experiment found helped them procreate. Circumcision is a bad idea for fruit flies it seems.
Dr Evil will not be happy: no one has mounted a laser beam on the head of a trained shark. Or, if they have, they aren't telling anyone about the experiment. But lasers have played a role in studying the behaviour of the fish. And the state of their teeth.
Back in the late 1970s, a group from France used laser mass spectrometry to work out what sharks' teeth are made of. More recently, laser-generated light curtains have helped show how leopard and bamboo sharks swim.