The loss of a fiber optic cable in San Jose, Calif., last year highlighted how crucial lasers have become in our lives. Credit: Henrick5000/iStock

On April 11, 2009, vandals sliced through a handful of fiber-optic cables in San Jose, Calif., a high-tech hub in Silicon Valley.

Instantly, cell phones and land-based phone lines stopped ringing. Internet service crashed. Credit card machines froze. Banks locked their doors. Traffic lights blinked in disarray, snarling traffic. For a short while, no one could call 911.

The reason for the communications breakdown is that most of the information we send and receive, from text messages to Google searches, travels through fiber-optic cables. And the messages racing through these cables are encoded by lasers. So when the cables were cut, so were all forms of communication that are delivered by laser beam.

“Cutting off the lasers was equivalent to having a disaster in that part of the world,” says Thomas Baer, an expert in laser science from Stanford University in California. “That’s how much we depend upon lasers for communicating with one another these days.”

Lasers used in telecommunications blink on and off at blindingly fast speeds of some 10^-12 seconds, or one millionth of one millionth of a second. These pulses create digital codes, sort of like Morse code. The messages are then beamed through fiber-optic cables and carried across classrooms, neighborhoods and oceans. Eventually the messages make their way to our cell phones, televisions and computer screens.

You might be most familiar with laser beams from your teacher’s laser pointer and from Star Wars light sabers. Lasers are remarkable because they are the brightest source of light on Earth, they produce the purest form of color possible, and they can be focused down to the tiniest spot possible. These qualities make them useful for a seemingly endless list of applications.

Now, as scientists this year mark the 50th anniversary of the invention of the laser, it’s clear that lasers have touched and transformed nearly every aspect of our lives.

DVDs contain digital messages that are written by lasers, and those messages are decoded by lasers inside of DVD players. A laser at the grocery store checkout line reads the bar code on your box of cereal. Lasers are used to weld and shape metal. For instance, every major automobile part, from air bags to cloth seats, brakes, clutch and engine is manufactured with the help of lasers. Lasers are used in delicate eye surgeries to improve vision, and they can measure the distance from Earth to the Moon to within a couple of inches. About half the gross domestic product (GDP), the total income of the United States, depends on lasers to manufacture key parts or deliver information, says Baer.

But for all of these practical uses, scientists who are exploring the future applications of lasers — from harnessing the power of the sun for carbon-free energy to altering weather patterns — say that the future of lasers is only getting brighter, and more intense. The next generation of lasers is going to be 10 to 100 times more powerful than present-day lasers.

Light Amplification

Like many scientific discoveries, that of the laser resulted from decades of step-by-step progress. In the early 1950s, during World War II, several teams of scientists were racing to make the first laser. The U.S. military hoped to create a “death ray” that could shoot down missiles. Through trial and error and experimentation with different types of materials, Theodore Maiman at the Hughes Research Laboratories in Malibu, Calif., succeeded in building the first laser in 1960 using a powerful flash bulb wrapped around a short ruby rod about as long as your finger. When the flash bulb fired, it excited atoms in the ruby. Mirrors on the ends of the rod reflected light through the ruby crystal. When some of the light leaked through one of the mirrors, it exited as an intense burst of red light. The first laser was born.

“When these guys invented this, they had a certain application in mind,” says David Fritz, an expert in X-ray physics at the SLAC National Accelerator Laboratory, at Stanford University. “But certainly they didn’t imagine what it would evolve into.”

The word “laser” stands for “Light Amplification by Stimulated Emission of Radiation,” or LASER. In other words, a laser is an intense or “amplified” pulse of light. This pulse results when atoms are stimulated, or excited, by light but then fall down into a lower energy level and give off energy. Atoms can remain in an excited state only for about one-millionth of a second. When atoms return to their usual, non-excited states, they produce photons, which are the basic units of light.

Scientists Yannick Petit and Jérôme Kasparian first tried out their laser in a cloud chamber to see whether water-based clouds could form. Credit: Daniel Giry, Saga Photos

Lasers have unique properties that make them so useful. Ordinary light, such as sunlight, consists of many different colors. In contrast, laser light consists of just one pure color. Light travels in wavelengths with peaks and valleys, just like the waves of the ocean. But while the light waves from sunlight or a flashlight or light bulb scatter in different directions, the wavelengths of a laser flow in perfect formation, sort of like the rows in a marching band. Because the waves of laser light move together so precisely, the light beams can be focused into a tiny area, even much smaller than a pinhead. These qualities create the sharp, powerful beam of light that we recognize as a laser.

Lasers for fusion

As long as lasers have existed, scientists have envisioned harnessing their power to create a fusion reaction that could someday produce an almost limitless stream of carbon-free energy. Scientists plan to soon fire up the most powerful lasers in existence to work toward that goal. The National Ignition Facility, part of Lawrence Livermore National Laboratory in Livermore, Calif., houses a 10-story building that spans the length of three football fields. Inside of that building sit 192 of the world’s largest lasers.

When all of the laser beams are activated, they will generate about 2 million joules of energy, which is about the amount of energy contained in a stick of dynamite. That pulse of energy will be delivered to a small pellet of hydrogen ice. The resulting reaction produces “fusion,” a process that occurs when two heavy hydrogen atoms collide, or fuse, into one helium atom. The explosion is very fast and powerful. Imagine the power of an exploding stick of dynamite. Dynamite can blow up mountains. This fusion reaction happens about a million times faster than a stick of dynamite explodes. And while a stick of dynamite is about the size of a large breadstick, the energy of these lasers will be focused, or concentrated, onto a target that is about as wide as a human hair. “The laser in this case acts as a powerful hammer that drives this reaction,” says Baer.

The speed and concentration of this reaction, Baer estimates, will make it about a trillion times more powerful than the explosion of a stick of dynamite.

This fusion reaction is similar to what powers the sun and other stars. It will release a burst of energy so powerful that it’s comparable to making a miniature star on Earth. And scientists believe the fusion reaction could someday be used to produce carbon-free energy.

“No one knows if fusion energy is going to work,” says Baer. “But it is an important area of research, and it allows us to understand new forms of matter in ways we just haven’t been able to access before.”

Lasers for brain research

Lasers are also helping researchers understand what makes the tiniest brains tick. Fruit flies possess brains the size of a grain of salt, yet they can taste and smell, see and walk. These brains can even learn — not unlike the human brain.

Fruit fly brains are complex enough to provide insights into the workings of the human brain, and they are just the right size for scientists to study using lasers. With laser beams precisely pinpointing areas of the flies’ brains, scientists can map individual brain cells and study these cells in action, tracing the flow of information through a fly’s brain.

For instance, it’s possible to learn what happens when flies process information — like when a fly sees and smells a watermelon on a picnic table and makes the decision to land on the watermelon or to pester the picnic guests. And it’s possible to observe how the fly’s brain tells its limbs whether to walk, fly or jump. In other words, scientists can study the patterns of brain waves, or neural activity, inside the flies’ brains.

“We’re looking at this right at the neural level, so we’re reading the actual thoughts of these fruit flies,” says Baer.

Fruit flies are being used as models to study human brain diseases such as Parkinson’s and Alzheimer’s. Scientists hope that learning about the brain circuitry of the flies can help in understanding what causes these diseases and someday to develop cures.

Lasers for rain

Lasers may even play a role in improving weather forecasting and one day in triggering rainfall.

As far back as the 1930s, during a time known as the Dust Bowl when North America was stricken by drought, people have hoped to control weather patterns and create rain.

Current attempts at rainmaking involve “cloud seeding,” using rockets to scatter substances into the atmosphere. These tiny particles provide surfaces, or nuclei, on which water can condense and around which clouds can form. But the process is not very efficient, and there are concerns over the potential toxic effects of these particles in the air, says Jérôme Kasparian, an optical physicist at the University of Geneva in Switzerland.

So Kasparian and his colleagues came up with an alternative. They discovered that lasers can produce charges, or ions, in the atmosphere that act as cloud nuclei. The team recently fired a powerful laser through a cloud chamber the size of a small box. To the researchers’ delight, clouds formed before their very eyes. The clouds were small: just 20 to 30 centimeters in diameter, about the length of two pencils end to end, across the cloud chamber.

“The key point is it works — we shot the laser and saw the clouds forming,” says Kasparian.

To test the experiment outside, Kasparian and his team launched a high-powered laser into the sky. Then they fired a second laser. The laser allowed them to see how much light gets scattered back to the ground by water droplets. When it was really humid out, the scientists were able to trigger formation of clouds in the atmosphere.

The experiment is not yet ready for practical applications, says Kasparian. But soon, the work could be used to improve local weather forecasting, he says. By shooting lasers into the atmosphere and analyzing the size of rain droplets and how quickly droplets are growing, meteorologists could gain a better understanding of the way certain air masses behave. Through “customized” forecasts it could soon be possible to know whether it’s going to rain over a sports stadium during a major event, for instance.

“Having very detailed characterization of the atmosphere can feed this kind of forecast,” says Kasparian.

Lasers for biochemistry

This fall, scientists at the SLAC National Accelerator Lab are doing some of the first experiments on the world’s first X-ray laser, which was unveiled in September 2009. Since the wavelength of X-rays is similar to the distance between atoms, this laser can take snapshots of very small stuff, such as, for example, the bonds between atoms in proteins. Proteins are strings of molecules that fold into complex structures and perform lots of services, such as breaking down the food we eat and using it to build muscles. In an upcoming experiment, researchers plan to use the X-ray lasers to study how proteins change shape as one chemical bond is broken and another is formed.

The story of lasers and its many applications illustrates the value of basic research, says Fritz. When the laser was invented, “no one could have envisioned how much of an impact it would have on society.”

POWER WORDS (from the Yahoo! Kids Dictionary)

laser Any of several devices that emit highly amplified and coherent radiation of one or more discrete frequencies.

physics The science of matter and energy and of interactions between the two, grouped in traditional fields such as acoustics, optics, mechanics, thermodynamics, and electromagnetism, as well as in modern extensions including atomic and nuclear physics, cryogenics, solid-state physics, particle physics and plasma physics.

cloud chamber A gas-filled device. In it, particles smaller than atoms form chains of droplets on ions formed in the gas. These chains help show that the particles were present. It is also used to infer the presence of neutral particles and to study certain nuclear reactions.

wavelength The distance between one peak or crest of a wave of light, heat, or other energy and the next corresponding peak or crest.

fiber optics The science or technology of light transmission through very fine, flexible glass or plastic fibers. A bundle of optical fibers.

The fish in the picture is alive and you’re looking inside its head. Really. It’s not a medical freak. Just a kind of fish with a naturally see-through forehead.

A new species, you might think. But no. The story is odder than that.

Meet one of the fish called barreleyes. This kind lives some 600 meters deep or more (that’s more than a third of a mile) in the Pacific Ocean.

A see-through forehead sounds like something you might remember to mention when describing a new fish. But 70 years ago scientists didn’t say a word about it when they gave the fish its official scientific name (Macropinna microstoma).

Those earlier fish scientists probably didn’t know about the clear forehead. They had to work from fish caught in deep nets and dragged up to the surface. The long trip up didn’t leave the samples in such good shape.

Today a scientist can send cameras and other equipment down to study deep-sea creatures where they live. Since 1993, cameras from the Monterey Bay Aquarium Research Institute in California have met these bizarre barreleyes three times in deep water off the coast.

And researchers managed to catch one and bring it to the surface in much better shape than usual.

What a difference meeting a live fish makes. Old reports had talked about some slime on the front of the fish. Now researchers see that the slime was probably the remains of the clear forehead.

The covering is tough and like the clear canopy on a fighter jet that lets the pilot see what’s happening, says Monterey Bay scientist Bruce Robison. In the fish, the rounded window is full of clear liquid and covers the eyes.

Like fighter pilots, these barreleye fish look out through their clear covering. Check the picture for the pair of fat, green domes like the tops of balls, inside the head. Those are the lenses of the fish’s eyes. (In the picture, the green lenses point up, and the fish is looking overhead.)

Each lens sits on top of a short, wide tube, which is the rest of the eye. That’s where the name barreleye came from, and that’s an odd shape for an eye. We hope this won’t happen, but if your eyeball fell out of your head, it would look like a ball. If it were All Planet Drop An Eyeball Day, there would be lots of balls. Cats, dogs, mice, elephants and lots of other animals have round eyes.

A front view of a type of barreleye shows its two nostril-like spots above the small mouth. The glow on the fish comes from the lights of a nearby camera vehicle. A glimmer of green inside the glowing clear forehead shows where the eye lenses are.

© 2006 MBARI

On barreleyes’ short tubes, the part that catches the image is at the bottom. That arrangement had puzzled scientists because tubular eyes should see only what’s straight in front of them and not much at the sides. That’s not very convenient. It would be a bit like looking at the world through the tube from a roll of toilet paper.

But looking at a living specimen, the researchers realized that an eye tube can move. Barreleyes point it upright to look overhead and then swing the lens downward so the tube points straight ahead, like the barrel of a mini cannon.

When the eyes point forward, the fish looks toward its pouty little mouth. Its lips stick out a bit, as if they would be good for picking morsels of food out of small places.

A siphonophore, a long string of filmy sea creatures, swims through the water (front end to the right) snagging food in its stinging tentacles. Researchers now wonder if the clear-headed barreleye fish steals food from siphonophores. The barreleye’s

© 2001 MBARI

What these barreleyes may do is steal food from creatures called siphonophores (sigh-FAH-nuh-4s), say the Monterey Bay scientists. Siphonophores in the area look like long, skinny, ultrafrizzy scarves made of bits of pale, soft film. Don’t wrap one around your neck though — they sting.

But the scientists think the barreleye might not care about the stings. Its clear forehead protects its eyes. So its mouth could nip off bits of prey that the siphonophores get tangled in their frizz. A clear forehead may actually be like fish goggles.

Power words: (loosely adapted from Yahoo! Kids Dictionary, which is also the American Heritage® Dictionary of the English Language, Fourth Edition)

canopy: a covering

lens: A clear part of the eye that bends the light passing through it so light rays hit the proper place for forming a picture.

siphonophores: sea creatures with clear, filmy bodies and stinging cells that band together in floating colonies. Famous example: the Portuguese man-of-war.

Going Deeper:

People don’t have to go to outer space to make music in new ways. Technologies using computers and sensors are being created that will let people do that right here on Earth.

The musical instruments of the future may be right in front of your eyes and on the tables, walls and windows around you. All it takes to use them is the right hardware, and a little imagination.

In Switzerland, a team of scientists and artists are working together on new technology that can transform almost any surface into a musical instrument. The technology is called MUTE, short for Multi- Touch Everywhere. Using MUTE, a person can use a computer to translate taps on different parts of a table or a wall as different sounds.

For example, you may record and save different sounds on a computer — anything from a snare drum or trumpet to clapping hands or a sneeze. Then, you program your computer to play one of these recorded sound snippets whenever you tap a certain spot on a table top or wall. The left side of a table might play snare drum beats, the right side a melody on a trumpet. If you tap the two sides at the same time, you’ll hear both sounds come together as a song. The system uses a camera and lasers to see where you’ve tapped on the table.

This is the computer program used to assign different sounds to different parts of a surface. Sensors tell the computer when someone taps on one of the colored regions.

Alain Crevoisier / Future Instruments

What’s more, the programmed surface doesn’t even have to be solid — it can float right in front of you, explains musician and MUTE developer Alain Crevoisier. “It can even work in the air,” he says. “Since the lasers are creating a plane of light, what we actually detect is when you cross this plane with either the hands or sticks or mallets.” Imagine, for example, a virtual piano hovering in front of your face.

When the MUTE system is installed on a surface, it also uses acoustic sensors to track the location of a performer’s tap. (For more information on acoustics, see the sidebar below story, “What is acoustics?”) “When you tap the table you generate vibrations,” says Crevoisier, a researcher at the Music Conservatory of Geneva. The vibration travels through the surface as an acoustic wave, and when the vibration strikes the sensor, the sensor sends an electric signal to the computer.

The device is not a musical instrument in the way we normally think about instruments. But that’s part of the beauty of it, says Crevoisier. It allows a person to be creative. “It’s more like we are providing a means for people to design their own instruments,” he says. His system adds a layer of music to already existing sounds. On a regular drum, for example, a drum beat is just the sound of the drum. But on a drum outfitted with MUTE technology, a drum beat could be both the sound of the drum and a control for some other sound layered on top of that.

Crevoisier’s work on new musical instruments grew out of his participation in a project called TAI-CHI (pronounced ty-chee), which stands for “tangible acoustic interfaces for computer-human interactions.” An interface is a device, or a lot of devices working together, that allow people to communicate with machines. A tangible object is one that you can touch. The keyboard of a personal computer, for example, is a tangible interface between you and your computer. So is your mouse.

Sound waves are measured by height, called amplitude, and width, called frequency. At top, the sound waves have a lower frequency and, to our ears, a lower pitch. The bottom image shows a sound wave with a higher frequency, which we would hear as high-pit

NOAA Ocean Explorer

In the TAI-CHI project, Crevoisier and his colleagues showed that acoustics, or the science of sound, could be used to turn any surface into a musical instrument. They also showed that the technology could lead to a new kind of interface.

Here’s how: The sensors pinpoint the place on a surface where a person taps.

One way to do this requires at least three sensors on the surface. When a person taps the table, the sound waves travel to the sensors, and each sensor records the exact time when the waves reached it. By knowing where the sensors are located and what the surface is made of, a computer program can use the waves’ arrival times to figure out exactly where the surface had been tapped.

Another method to pinpoint a tap uses only one acoustic sensor, but it is more complicated. A user needs to fine-tune the device very carefully, and provide the computer with lots of information about the surface material itself.

Acoustic sensors could be used to build new kinds of computers that look nothing like traditional desktop models. Unlike a keyboard and mouse, which require a user to remain in front of a computer screen, acoustic sensors would allow a user to interact with the computer almost anywhere. You could use your fingers to draw a picture on a wall, for example, and record the drawing with your computer.

This device, built with TAI-CHI technology, is called the Sound Rose because when a person taps on the table, a colorful flower appears. A person’s taps are tracked using acoustic sensors, and the images are projected from the ceiling.

Alain Crevoisier / Future Instruments

Or, imagine a restaurant owner, who could glue menus to the top of his tables and install acoustic sensors underneath. Diners could then order simply by tapping on the menu. The vibration from the tap would be picked up by the sensors, which would be able to figure out where the tap came from. A computer could match that location to a dish on the menu and send the order to the kitchen.

In another example, perhaps someone in a wheelchair could mark a spot on the wall, a table top or the arm of a chair to serve as a switch. It might be for turning on or off a light, for turning up or down the volume on a television or even for sending out a distress alarm. A simple tap on the spot could trigger the sensors, which could relay the information to a computer. The technology would allow people to make any surface into an interface to control some action.

Crevoisier isn’t the only one looking at ways to use acoustic sensors in future devices. Another European company, for example, is finding ways to use them to make a “smart apartment,” where any surface — mirrors, tables, counters, walls — can be used to interact with the house computer, to do tasks like change the lighting, turn on the television or raise the temperature.

The Touch Wall, created by Microsoft Corporation, made its debut in May of this year.

Microsoft

Other researchers around the world are developing other kinds of new tangible interfaces, though not all of them use acoustic sensors. The computer company Microsoft has developed a device called TouchWall, for example, which converts almost any surface to a computer interface by using sophisticated laser trackers, cameras and a projector.

Look around again. The future of computing and of musical instruments may be all around you.

Going Deeper:

News Detective: What is Acoustics?

Additional Information

Questions about the article

But this is no Hollywood blockbuster—at least not yet. It’s a real-life mystery being tackled by a team of engineers, art historians, and computer scientists.

They’ve come to a centuries-old church to look at sections of an old and valuable picture painted onto the church’s stone walls. Local residents uncovered this painted mural in the church of St. Jean the Baptist in Vif, France. It had been hiding beneath layers of painted plaster for hundreds of years.

Everyone wanted to know: How big was the full mural and what did it look like? And they wanted to find out the answer without removing any more of the painted plaster that still covered much of it.

A few years ago, this job would have been impossible. Not any more.

U.S. researchers brought a new type of scanning device with them. It allows them to “see” right through layers of solid materials—including plaster. It relies on a type of electromagnetic energy known as “terahertz radiation.”

This type of radiation may one day take credit for everything from finding terrorists to identifying potentially catastrophic hidden flaws on spacecraft.

A centuries-old mural peeks out from behind paint and plaster on the walls of a very old church in France. Researchers recently traveled to France with a T-ray scanning device. It will allow them to view the entire mural, without removing any of the plast

Irl Duling

T-rays—bridging the gap

Every time you talk on a cell phone, microwave a bag of popcorn, or turn on a lamp to read, you rely on electromagnetic radiation (see sidebar: “Understanding Electromagnetic Radiation”). Elements of this radiation move as waves. Terahertz rays are emissions of energy that have waves from less than a tenth of a millimeter to several millimeters long.

The detective team that went to France carried a device that emits terahertz radiation. Its energy lies between microwaves and infrared radiation, on the low-energy end of the electromagnetic spectrum. Unlike microwaves and X-rays, scientists didn’t know until very recently how to make terahertz radiation, also known as T-rays, explains Daniel Mittleman, an electrical engineer at Rice University in Houston.

“We’ve known for a long time how to generate and detect microwave and infrared radiation,” he says. “But there’s a gap in the middle, and that’s where terahertz is.”

That gap is beginning to disappear now that scientists have begun making T-rays and testing what they can do.

The research team traveling to France, for instance, is using a device about the size of a printer for a home computer. It makes and detects T-rays. Before traveling, the team tested it.

They made paintings with the same kinds of paint pigments that artists would have used hundreds of years ago, and then they covered them up with several layers of plaster, says John Whitaker. He’s a research scientist at the University of Michigan who led the test.

By scanning the fake art with the T-ray device, Whitaker and his colleagues displayed the original paintings behind the plaster—without removing the plaster. The hidden images show up only in black and white at this time. In the future, however, engineers hope to figure out how to distinguish between pigments and then reconstruct the hidden images in color.

You’d never guess just by looking at it, but there is a painting of a butterfly underneath the painted square (top image). Scientists covered the butterfly with layers of plaster and squares of paint. Yet when scientists scanned the art with terahertz rad

J. Bianca Jackson

How did the T-rays recognize the hidden images?

The terahertz device sends a pulse of energy at the covered-over test object, Whitaker says. Materials in the buried painting absorbed some of the T-rays’ energy. Some of the energy was also reflected away.

Different materials reflect or absorb T-rays in different—but predictable—ways, Whitaker says. For example, each of the different pigments behind a layer of plaster will reflect the rays differently. The T-ray device measures how T-rays reflect back from the object. With this data, the researchers can recreate a picture of the hidden items.

The way researchers detect objects with T-rays is analogous to the way we perceive color with visible light, Mittleman explains.

Each color of visible light radiates in waves that have a different frequency—meaning energy waves that repeat a certain number of times per second. What your eye perceives as color is its detection of that energy.

For instance, Mittleman says, “the pigment in your shirt absorbs visible light at a certain frequency. So the light that comes back to you has a certain frequency missing because it was absorbed by the pigments.” Your eye notices that and tells your brain that it has seen a particular color.

The T-ray device does much the same thing. It detects a certain frequency of reflected energy and reads it as a color.

Security, screening, and safety

Just as T-rays can help identify pigments beneath a layer of plaster, they also can identify chemicals—like bombs or illegal drugs—hidden inside suitcases or other items, says Xi-Chen Zhang, a physicist and electrical engineer at Rensselaer Polytechnic Institute in Troy, N.Y.

“If you have a suspicious material, you’d like to know: Is it explosive? Is it a biological or chemical threat? We could use a device to send a T-ray into it,” Zhang says. “By measuring how the ray returns, we can identify certain materials, like explosives or biological materials.”

Zhang is a member of an international organization with the mission to develop a T-ray device to detect explosives. The technology for this particular purpose is now being developed. One of Zhang’s students has invented a portable T-ray generator, which should make such tasks easier.

Called the Mini-Z, it’s about the size of a few stacked laptop computers and only weighs a few pounds. Unlike earlier T-ray generators, this one is very portable. So one could carry it and use it to scan people, equipment, or artwork—without hurting any of them. A company in New York called Zomega Terahertz Corporation manufactures this device for scientists who want to test new uses for T-ray technology.

Scanning a china teapot with T-rays will show you whether it’s empty or full. When it’s empty, the rays bounce off the back of the teapot and reflect back to the scanning device, producing an overall light color. Water absorbs T-rays, so rays striking the

Xi-Chen Zhang

Zhang has used this type of T-ray system to look for defects in the kind of foam that insulates parts of the space shuttle. “The shuttle is covered with thermal insulation to prevent it from being damaged,” Zhang says. “But how can we guarantee it is free of defects? We can send T-rays through it.”

T-rays are ideal for this kind of job because they work where other imaging systems can’t, Mittleman says.

“If there’s an air bubble in the middle of a block of foam, how would you know it was there? You can’t see it,” Mittleman says. “You can’t use X-rays, because foam is mostly air and the X-rays would ignore those holes. That’s why terahertz is perfectly suited. With terahertz, you can detect differences between foam and air.”

Finding bubbles in foam might not sound like a very significant aspect of spaceflight. But researchers now believe defects in foam insulation caused the space shuttle Columbia to overheat and then explode in 2003. All seven astronauts aboard the spacecraft died.

Recently, the National Aeronautic and Space Administration, or NASA, has begun scanning the surface of its shuttle spacecraft using a T-ray device produced by a Michigan company called Picometrix.

Rensselaer Polytechnic Institute

Picometrix also works with drug manufacturers who want to use T-rays to test the quality of the medicines they make. “We are developing ways to weigh tablets to make sure every tablet has exactly the right amount of ingredients,” says Irl Duling. He is the director of terahertz programs at Picometrix.

To measure how much medicine a tablet contains, you target the pill with a pulse of T-rays. “When you hit the tablet, you get a reflection from the front surface and the back surface—it’s two little pulses,” Duling explains. The difference in time that the two pulses take in being reflected back to the T-ray device relates to the amount of matter between the front and back of the tablet. “You can measure the time delay between the two pulses very accurately,” he says, and use that to calculate how much medicine the pill contains.

Picometrix also makes the T-ray scanner that is on its way to France to look at the partially hidden mural. While it’s at the church, researchers will use it to look for any other paintings that might have been similarly plastered over during the past centuries. Re-discovering such murals might help explain why they were covered over in the first place.

“Artworks may have shown something that fell out of favor,” Whitaker says. Throughout European history, new leaders took control in different regions. When a new group moved in, it often had people paint right over art representing the religious views or leaders of an earlier society, he says.

“Uncovering hidden artworks could provide insights into current events at the time a painting was made,” Whitaker says. “We could learn about how the people saw their god or what they thought about medieval saints.”

This project is just the beginning of a new technological approach to art history, Duling says. “In many churches, it’s just a matter of asking: Is there a painting here we don’t know about?” With thousands of churches scattered around Europe, there are plenty of opportunities to search for other hidden treasures.

Understanding Electromagnetic Radiation

Energy travels throughout the universe at the speed of light in the form of electromagnetic radiation. What that radiation is called depends on its energy level.

At the really high-energy end of the spectrum, you’ve got gamma rays. You’re probably familiar with a close cousin to these: X-rays. They’re the ones doctors and dentists use to probe for unusual structures inside your body. Radio waves fall at the extreme other end. Those radio waves are the ones that deliver music and news broadcasts to your home radios.

Ultraviolet rays, visible light, infrared radiation, and microwaves fall at energy levels in between.

Together, all of these types of radiation make up one long, continuous electromagnetic spectrum. Its energy travels in what’s usually referred to as waves.

What separates one type of electromagnetic radiation from another is its wavelength. That’s the length of a wave of that type of radiation. To identify the length of a wave of water in the sea, you would measure the distance from the crest (upper part) of one wave to the crest of another. Or you could measure from one trough (bottom part of a wave) to another.

It’s more difficult to do, but scientists measure electromagnetic waves the same way—from crest to crest or from trough to trough. In fact, each segment of the energy spectrum is defined by this wavelength. Even what we refer to as the heat given off by radiators is a type of radiation—one that has wavelengths in the infrared portion of the spectrum.

Sometimes these segments of the electromagnetic spectrum are also described in terms of frequency. A radiation’s frequency will be the inverse of its wavelength. So the shorter the wavelength, the higher its frequency. That frequency is typically measured in hertz, a unit which stands for cycles per second.—Janet Raloff

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Word Find: Terrific T-Rays

Going Deeper:

Even so, I didn’t plunge into the water right away. I watched the waves and studied surfers in action. I tried to figure out how big the swells were, which way the wind was blowing, and where the waves were breaking.

Winds can stir up large waves, which break when they approach shore.

National Oceanic and Atmospheric Administration

I soon learned that every day was different. Conditions changed constantly. Tides came and went. Winds shifted. No two waves were alike. How, I wondered, do surfers know what to expect?

“It’s 100-percent science,” says Vic DeJesus, a meteorologist and surf forecaster for WaveWatch. Wave predictions have become so reliable, he says, that many surfers check Web sites such as WaveWatch several times a day. And, as scientists continue to analyze the movement of water around the globe, predictions keep improving.

The research is helping make life safer and more fun for surfers, to be sure, but they aren’t the only ones who care about wave forecasts. Accurate information is also useful for lifeguards, boaters, biologists, engineers, and other people who need to know what the ocean is doing.

Predicting waves

Predicting waves, for the most part, depends on reading winds. To see why, fill a tub with water. Wait until the liquid becomes still. Then, blow across its surface and watch the ripples.

Like your breath, winds create ripples in the ocean. With enough wind, ripples form waves that crash when they hit the shore or a shallow reef. Near the shore, the ground causes the bottom of the wave to slow down, which makes the top curl over and break.

Surfing on the North Shore, Oahu, Hawaii.

Commander John Bortniak, NOAA Corps

The stronger the wind, the bigger the waves, says Jerome Aucan, a surfer and oceanographer at the University of Hawaii in Honolulu.

“There are three main factors in surf forecasting: wind speed, area over which the wind blows, and how long it blows,” says Aucan.

Winds are most powerful when storms are brewing, Aucan says, and waves can travel a long way. Swells that hit the west coast of Mexico often start as squalls as far away as New Zealand, thousands of miles away. The best waves in France often begin as major storms called nor’easters, which sweep across the coasts of New York and New England.

Better forecasting

Wave forecasting began during World War II, when the U.S. military was planning attacks from the sea and needed to know the size of the surf, Aucan says. Oceanographers started by creating wind maps and observing the connection between wind patterns and swell size.

Now, more than 50 years later, computer programs do most of the work. These models rely on data that come from ocean buoys and space satellites, both operated by the National Oceanic and Atmospheric Administration (NOAA).

A buoy measures wave height and wind speed, transmitting the information to satellites.

National Weather Service Forecast Office, Portland, Maine

Floating buoys measure the height of wave surges, the distance between waves, and wind speed. Satellites use altimeters and other tools to calculate wave height from above. Ocean depth and topography (the shape of the ground underwater) also affect waves.

Scientists plug in as much data as possible into the models, which spit out charts that show where the waves are going and how they will probably change as they move. Professional wave forecasters such as DeJesus use these charts in combination with other methods.

“I get up between 4:30 and 5:00 a.m.,” DeJesus says. “I call friends, people I hire. They tell me if it’s windy, good, bad, ugly, whatever. The rest of the day, I go through weather charts, wave models, and I prepare forecasts for the next 48 to 96 hours and up to a week later.”

Oceanographers are still tweaking the models, but the short-term formulas already work pretty well. “Within 24 to 36 hours, you can usually hit anywhere between 90- and 100-percent accuracy,” DeJesus says. After that, the accuracy of forecasts drops rapidly.

Weather conditions

Better long-term forecasts will depend on better predictions of the wind’s behavior and closer attention to geographical details, Aucan says. Scientists are working on these questions. Ultimately, though, forecasting will never be perfect, because weather conditions can always change without warning.

The beach and waves off the west coast of Mexico.

E. Sohn

Still, surfers would rather rip it up on smooth, clean waves than fight 50 mile-per-hour winds. To that end, wave forecasts help determine whether or not it’s worth waxing up the board. In the meantime, surfers often become experts of the ocean.

“I think surfers end up being kind of like scientists,” says Julie Cox, a 26-year-old competitive surfer and surf instructor from Santa Cruz, Calif. “Surfing involves wave prediction, meteorology, astronomy, the sun, the moon, tides, seasons, geography, and topography. You learn about the chemistry of the water, temperature, salinity, and animals, like stingrays, seals, otters, and whales.”

Surfing is more than a sport. It’s a scientific education. After a week of “fieldwork” in Mexico, I realized how much more I have to learn. And because catching waves is such a rush, it’s a class I’ll get up early for any day.

Going Deeper:

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Scientists are developing “smart” lenses that sense where your eyes are looking and automatically focus to help you see more clearly.

Electric signals from microchips in the black boxes attached to these experimental eyeglasses change the focus setting to improve vision.

Guoqiang Li et al./Proceedings of the National Academy of Sciences

The main market for the glasses is adults older than 45—perhaps your parents or grandparents. At this point in life, most people start to get worse at seeing things that are close to them, such as books and computer screens.

When the decline begins, people usually start wearing reading glasses. Or, they get bifocals, which have divided lenses—a top part for seeing far and a bottom part for seeing near. Some kids with vision problems have to wear such glasses, too.

University researchers are working with a company called PixelOptics, in Roanoke, Va., to replace bifocals with electric lenses that can switch quickly from one type of focus to another.

“You don’t have just the bottom half of your eyeglasses” for close vision, says electrical engineer David L. Mathine of the University of Arizona in Tucson. He’s one of the inventors. “You get the whole view,” he says.

Each lens is made from two layers, and each layer is made up of two sheets of glass, with a thin layer of fluid sandwiched between the sheets. The fluid contains a transparent type of material called a liquid crystal, which is made of molecules that are shaped like rods. To change a lens’ focus, scientists apply electricity to the inner surface of one of the glass sheets in each layer.

In response to the electricity, the crystal rods rotate. Their direction determines how quickly light passes through the liquid-crystal layer. The process allows the material to focus light so that a crisp image forms inside the viewer’s eyes.

An image is out of focus when a special, electrically controlled lens is off (left) but clear when the lens is on (right).

Guoqiang Li et al./Proceedings of the National Academy of Sciences

Scientists had made similar, electrically controlled lenses before, but these earlier lenses couldn’t focus well enough or change focus quickly enough to be useful in eyeglasses, the inventors say.

PixelOptics has announced that it also plans to make a version of the glasses that will help people achieve extrasharp vision—even better than normal 20/20 eyesight.—E. Sohn

Going Deeper:

Weiss, Peter. 2006. Switch-a-vision: Electric spectacles could aid aging eyes. Science News 169(April 22):243-244. Available at http://www.sciencenews.org/articles/20060422/fob2.asp .

You can learn more about smart glasses at www.gravitysedge.com/pixeloptics/ (PixelOptics).