It feels a bit like something that might have been issued by Q branch. In fact, it's on sale at Boots the chemist. When you press a little gold button on the back, a prismatic pseudopod slides up behind the blades. From its top shines a tiny red eye of the sort you might have seen in "The Lord of the Rings" had it dealt with malevolent fruit flies rather than disembodied demigods. A perfect red line is projected across my cheekbone. My laser-guided beard trimmer is ready.
The difference between a laser and any other light is, on the face of it, minimal: a laser's light is all one wavelength and all the waves are in step with each other. Other than that it's the same as the stuff we get from a lightbulb. But that small distinction opens up big possibilities. The obvious ones have to do with power. When the first laser was turned on in 1960, imaginations primed by decades of fictional ray guns saw it as a weapon. The laser's natural home in James Bond films was not as an aid to male grooming (M detested facial hair anyway) but as a threat, whether aimed at the superspy's crotch by Auric Goldfinger or, in a symbolically isomorphic move, at America’s nuclear missiles by Ernst Stavro Blofeld. But it hasn't been as a projector of power that the laser has made an impact on real life.
That's not to say the world lacks powerful lasers. They come in handy for cutting up metal plate. And the military does have an interest in them. In the 2000s the US Air Force mounted a monstrous one in a jumbo jet to see if it could shoot down a missile in flight. It could—but not from far enough away to be worth developing. Less ambitious laser weapons, though, may yet be able to knock out mortar rounds in mid-air.
The greatest laser of all fills up the National Ignition Facility, a building the size of an arena at America's Lawrence Livermore National Laboratory. Livermore is in the nuclear-explosions business, and the NIF is designed to produce tiny little ones by squeezing pellets of hydrogen with laser light. When I walked its hangar-like halls, the ambition of the undertaking—192 beamlines that can focus 500 trillion watts of laser power—made me feel physically faint, the scientific equivalent of Stendhal syndrome.
If you are astutely wondering how those NIF lasers can use 200 times more electricity than is generated by all the power plants in the world put together, the answer is that they operate at that ludicrously high level only in remarkably short bursts. The light is turned on and off again so quickly that each blast contains only enough energy to boil a few dozen kettles. And it is the fact that laser light can be controlled at such high speeds, rather than its sheer power, that has allowed the laser to transform the world.
This control lets lasers squirt data by the gigabyte from continent to continent by means of fibre-optic cables. By exploiting the laser’s precision, DVD and Blu-ray players tease symphonies and TV series from the patterns of tiny pits on the spinning discs within them. Every year humankind produces a billion little lasers to pull data out of the real world—by reading bar codes, for instance—and move it round the digital one.
Lasers also help get data back out again. Some 3D printers depend on the ability of lasers to trigger chemical reactions that turn liquids into solids, producing finely wrought designs from vats of formless goo. In a crude way, that's what the laser in the shaver does, too: it takes a pure, Euclidean plane and projects it onto the fleshier geometry of my face. Idea is thus given form, or at least the chance to guide it.
In commercial and everyday terms, lasers matter most as transmitters and transformers of information. Perhaps their most inspiring applications, though, come not from their power or ubiquity but from their stability and precision. Whether it is in measuring the minuscule or the vast, the perfectly ordered, perfectly reliable light from lasers is vital. It allows engineers to build atomic clocks so accurate they could run for the age of the universe and only be out by a couple of hours. It allows astronomers to measure the quivering of the surface of a distant star to within a centimetre a second. Lasers can continuously monitor the distance between mirrors kilometres apart to within a fraction of the width of a single atomic nucleus. This allows physicists to watch for distortions in the fabric of space and time, as predicted by Einstein but never yet observed in the lab.
And the precision goes beyond measurement: it extends to manipulation. Lasers can help to hold solitary atoms in traps. They can be used as tweezers to pull on single coils of DNA, precisely calibrating the elasticity of the double helix. With the help of genetic engineering, which can add light-sensitive switches to genes, lasers can switch on and off individual pathways, and even cells, in the brain of a mouse. Again, laser light weaves together matter and information—but now it does so inside a mind.
The changes lasers have wrought are everywhere, from the manufacture of silicon chips to the removal of unwanted tattoos. But it is when unleashed from pragmatism by the scientific quest for ludicrous precision that their capabilities are most dazzling.
As an aid to shaving, though, one has now given me marginally more rectilinear sideburns.