How Rainbows Work

Rainbows are one of the most beautiful spectacles nature has to offer -- so beautiful, in fact, that they've inspired countless fairy tales, songs and legends. It's a good bet that most of the artists behind these tales were totally mystified by the rainbow phenomenon -- just like most people are today.

But the science of rainbows is really very simple. It's just basic optics! In this article, we'll find out how rain and the sun align to put color in the sky.

Can I get struck by lightning when I'm indoors?

Over 1,000 people get struck by lightning every year in the United States, and over 100 of them die as a result of the strike. Lightning is a very dangerous force that, yes, can even reach you indoors if you're in contact with the telephone or plumbing.

If lightning strikes the phone line outside your house, the strike will travel to every phone on the line -- and potentially to you if you are holding the phone. So, if you are indoors during a lightning storm, stay off the phone. If you must call someone, use a cordless or cell phone -- that way, you're not in contact with any wires that run outdoors.

Stay away from plumbing pipes like your bath tub or shower, as well. Lightning has the ability to strike a house or near a house and impart an electrical charge to the metal pipes used for plumbing. If you're touching those pipes or anything connected to those pipes, that electrical charge has a path to you. This threat is not as great as it used to be, because PVC (polyvinyl chloride) is often used for indoor plumbing these days. If you are not sure what your pipes are made of, wait it out.

And while you're at it, switch off your appliances and electronics before the storm hits. Such devices as your computer, television and air conditioner all provide potential pathways between the lightning and you.

asteroid shower

Dec. 03, 2007: Mark your calendar: The best meteor shower of 2007 peaks on Friday, December 14th.

"It's the Geminid meteor shower," says NASA astronomer Bill Cooke of the Marshall Space Flight Center. "Start watching on Thursday evening, Dec. 13th, around 10 pm local time," he advises. "At first you might not see very many meteors—but be patient. The show really heats up after midnight and by dawn on Friday, Dec. 14th, there could be dozens of bright meteors per hour streaking across the sky."

Right: A Geminid meteor in 2006 photographed by Christopher Colley of Lombard, Illinois. [Larger image]

The Geminids are not ordinary meteors. While most meteor showers come from comets, Geminids come from an asteroid—a near-Earth object named 3200 Phaethon.

"It's very strange," says Cooke. How does an asteroid make a meteor shower?

Comets do it by evaporating. When a comet flies close to the sun, intense heat vaporizes the comet’s "dirty ice" resulting in high-speed jets of comet dust that spew into interplanetary space. When a speck of this comet dust hits Earth's atmosphere traveling ~100,000 mph, it disintegrates in a bright flash of light—a meteor!

Asteroids, on the other hand, don't normally spew dust into space—and therein lies the mystery. Where did Phaethon's meteoroids come from?


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One possibility is a collision. Maybe it bumped against another asteroid. A collision could have created a cloud of dust and rock that follows Phaethon around in its orbit. Such collisions, however, are not very likely.

Cooke favors another possibility: "I think 3200 Phaethon used to be a comet."

Exhibit #1 in favor of this idea is Phaethon's orbit: it is highly elliptical, like the orbit of a typical comet, and brings Phaethon extremely close to the sun, twice as close as Mercury itself. Every 1.4 years, Phaethon swoops through the inner solar system where repeated blasts of solar heat could easily reduce a flamboyant comet to the rocky skeleton we see today.

If this scenario is correct, Phaethon-the-comet may have produced many rich streams of dust that spent hundreds or thousands of years drifting toward Earth until the first Geminid meteors appeared during the US Civil War. Since then, Geminids have been a regular shower peaking every year in mid-December.



3200 Phaethon is now catalogued as a "PHA"—a potentially hazardous asteroid whose path misses Earth's orbit by only 2 million miles. It measures 5 km wide, about half the size of the asteroid or comet that wiped out the dinosaurs 65 million years ago, and can be seen through backyard telescopes—in fact, now is a good time to look:

"3200 Phaethon is flying past Earth just a few days before this year’s Geminid meteor shower," notes Cooke. On Dec. 10th, Phaethon will be about 11 million miles away shining like a 14th magnitude star in the constellation Virgo: ephemeris. That's too dim for the naked eye, he says, but a good target for amateur telescopes equipped with CCD cameras.

Cooke doesn't expect the flyby to boost the Geminids—"11 million miles is too distant to affect meteor rates"—but the Geminids don't really need boosting. "It's always a great shower," he says. "Don't miss it."

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six stroke technology

INVENTION AWARDS
Six Strokes of Genius
After a lifetime of making racecars go faster, Bruce Crower's new engine uses steam to squeeze more mileage from gas

By Dan Carney | May 2007


How do you prevent insurgents from shooting down choppers? How do you keep a cast from itching? How do you reinvent the brick? You sketch. And then you work: nights, weekends—for years, if you have to. You blow all your money, then beg for more. You build prototypes, and when they fail, you build more. Why? Because inventing is about solving problems, and not stopping until your solution becomes real.

We're currently rolling out the winners of the 2007 PopSci Invention Awards. We'll be doling out a new innovation each day, so keep checking back for more of what the world's brightest inventors are currently cooking up. And if you just can't wait, pick up a copy of the June issue that just hit the stands.—Eds.

Name: Steam-o-Lene Engine
Inventor: Bruce Crower
Cost to Develop: $1,000
Time: 1.5 years
Prototype | | | | | Product

Bruce Crower's Southern California auto-racing parts shop is a temple for racecar mechanics. Here's the flat eight-cylinder Indycar engine that won him the 1977 Louis Schwitzer Award for racecar design. There's the Mercedes five-cylinder engine he converted into a squealing supercharged two-stroke, just "to see what it would sound like," says the now half-deaf 77-year-old self-taught engineer.

Crower has spent a lifetime eking more power out of every drop of fuel to make cars go faster. Now he's using the same approach to make them go farther, with a radical six-stroke engine that tops off the familiar four-stroke internal-combustion process with two extra strokes of old-fashioned steam power.

A typical engine wastes three quarters of its energy as heat. Crower's prototype, the single-cylinder diesel eight-horsepower Steam-o-Lene engine, uses that heat to make steam and recapture some of the lost energy. It runs like a conventional four-stroke combustion engine through each of the typical up-and-down movements of the piston (intake, compression, power or combustion, exhaust). But just as the engine finishes its fourth stroke, water squirts into the cylinder, hitting surfaces as hot as 1,500°F. The water immediately evaporates into steam, generating a 1,600-fold expansion in volume and driving the piston down to create an additional power stroke. The upward sixth stroke exhausts the steam to a condenser, where it is recycled into injection water.

Crower calculates that the Steam-o-Lene boosts the work it gets from a gallon of gas by 40 percent over conventional engines. Diesels, which are already more efficient, might get another 5 percent. And his engine does it with hardware that already exists, so there's no waiting for technologies to mature, as with electric cars or fuel cells.

"Crower is an innovator who tries new ideas based on his experience and gut instincts," says John Coletti, the retired head of Ford's SVT high-performance group. "Most people won't try something new for fear of failure, but he is driven by a need to succeed." And he just might. Crower has been keeping the details of his system quiet, waiting for a response to his patent application. When he gets it, he'll pass off the development process to a larger company that can run with it, full-steam.

DIAGNOSIS 2.0

By the time a doctor diagnoses you with cancer or a neurodegenerative disease, you may have been living with it for years—a troubling fact, given that early detection is the most important factor in successful treatment. Now, Power3 Medical Products, a biotech firm in Houston, Texas, has developed simple, low-cost blood tests for breast cancer, Alzheimer's and Parkinson's that will allow physicians to spot disease the moment it shows up in a patient's body—years earlier than today's most advanced technologies can catch it. "With our tests, you don't have to wait around for 6 or 10 years [to spot the problem]," says CEO Steven Rash.

Power3's breast-cancer test, to be released early next year, is the first diagnostic to emerge from a fast-growing field known as proteomics that looks for telltale proteins in a person's blood, just as genetic tests screen for disease-causing genes. Genes give instructions, but proteins do the body's work, so although genetic tests can determine whether a person has a gene that increases his or her risk of developing a specific disease (women who carry the BRCA1 or BRCA2 genes run a greater risk of developing breast cancer, for example), proteomic tests like Power3's can tell whether the gene—and thus, the disease—is active, long before physical symptoms appear.

The new breast-cancer test is much less invasive than a mammogram or biopsy. A doctor samples a patient's blood and sends it to Power3's lab, where scientists search for 22 irregular proteins that Power3 has identified as early signs of breast cancer. Initially the test will debut in 40 clinics that treat women at high risk for breast cancer, Rash says. Women under 40 years of age with high-risk genetic or family factors should benefit the most, he adds, because their denser breast tissue makes mammography significantly less effective. Scientists have been working to develop proteomic tests for the past three years, but they were derailed by inconsistent test results. Early data indicate that Power3 has overcome this challenge. In a blind trial of 60 blood samples provided by Mercy Women's Center in Oklahoma City, the test scored a 97 percent rate of identifying cancer in samples from diagnosed patients and a 93 percent rate of correctly identifying healthy women as cancer-free. A second 100-patient trial will be completed by the end of the year. In comparison, mammograms miss up to 30 percent of breast cancers, and 75 percent of the biopsies performed after an irregular mammogram prove benign.

"There's tremendous promise in proteomics," says Lance Liotta, a proteomic scientist at George Mason University. "The early diagnosis and individualized therapy coming out of the science is going to change medicine." But Power3's results are not conclusive, so until further testing confirms the test's reliability, it will just supplement existing tests.

The company is also validating protein-based tests for Parkinson's and Alzheimer's, the latter an affliction for which the only conclusive test is currently an autopsy. Among the possible benefits of a proteomic Alzheimer's test, due out late next year, would be the ability to definitively separate sufferers from those with other neurodegenerative problems, now a major obstacle to running effective clinical trials of drugs for Alzheimer's.

"Power3 won't do it all," says Essam Sheta, the company's director of biochemistry. "But my expectation is that in the next five years, we as a scientific community will be able to develop diagnostic tests for many, many types of diseases."

THE SUN IS BRISTLING WITH X-RAY JETS

12.06.2007


Dec. 06, 2007: Astronomers using Japan's Hinode spacecraft have discovered that the sun is bristling with powerful "X-ray jets." They spray out of the sun's surface hundreds of times a day, launching blobs of hot gas as wide as North America at a top speed of two million miles per hour. These jets add significant mass to the solar wind and they may help explain a long-standing mystery of astrophysics: the superheating of the sun's corona.

"This is awesome and very much unexpected," says Jonathan Cirtain of the Marshall Space Flight Center who was a key figure in the discovery. He recalls how it happened: "We found them a year ago in Nov. 2006. Hinode had just been launched and its instruments were coming online." To calibrate the spacecraft's X-ray Telescope, mission controllers in Japan pointed the telescope at a dark hole in the sun's atmosphere--a "coronal hole." Cirtain analyzed the data and "there they were!"

Above: An X-ray jet recorded by the Hinode spacecraft on Jan. 10, 2007. Quicktime movies: three jets (2.4 MB); many jets in low resolution (4 MB); many jets in high resolution (26 MB).

"After the shock wore off, I ran around dragging other scientists into my office to show them the movie." He likens the appearance of the jets erupting within a coronal hole to "the twinkle of Christmas lights, randomly oriented. It's very pretty."

Cirtain notes that X-ray jets have been seen before, but never in such abundance. The first jets were recorded by a 1st-generation X-ray telescope onboard Skylab in the 1970s. They were called x-ray jets for the simple reason that they were bright at x-ray wavelengths. The phenomenon was later confirmed by a Naval Research Lab ultraviolet telescope that flew aboard the space shuttle in the 1980s as well as by Japan's Yohkoh X-ray Telescope in the 1990s. "All those instruments saw very few jets--typically one or two per day," says Cirtain. X-ray jets were thus regarded as a curiosity of little importance.


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Hinode has changed all that. The spacecraft's advanced X-Ray Telescope can take pictures rapidly enough to catch these fast-moving eruptions. "We now see that jets happen all the time, as often as 240 times a day. They appear at all latitudes, within coronal holes, inside sunspot groups, out in the middle of nowhere--in short, wherever we look on the sun we find these jets. They are a major form of solar activity," says Cirtain.

Each jet is triggered by a magnetic eruption or "reconnection event"--essentially the same process that powers solar flares albeit on a much smaller scale. "The energy in a typical jet is about a thousand times less than the energy of an M-class (medium sized) solar flare," says Cirtain. Individually, jets are weak; en masse, however, they pack quite a punch. "If we add up all the energy jets deposit into the sun's atmosphere, the daily total is on par with solar flares."

Indeed, the jets may contribute significantly to the solar wind. Every day a hot, relentless wind of solar protons and electrons blows against Earth, deflected just before it can reach the atmosphere by our planet’s global magnetic field. Gusts in solar wind can cause bright auroras, power outages and other effects collectively known as "space weather." What drives this wind away from the sun? It's a question that has puzzled physicists for decades. Jets provide at least part of the answer:

"We've added up the mass flowing in these jets and it amounts to between 10% and 25% of the solar wind. That's a significant fraction," he says.

X-ray jets may also contribute to the mysterious heating of the sun's outer atmosphere, the ghostly "corona" seen during solar eclipses.

Right: The sun's outer atmosphere or "corona". Credit & Copyright: Koen van Gorp.

The mystery is this: If you stuck a thermometer in the surface of the sun, it would read about 6000o C. Yet above the surface of the sun, in the corona where intuition says things should be cooler, the temperature rises to millions of degrees. What heats the corona to such extreme temperatures?

X-ray jets seem to help. Cirtain and colleagues have examined four jets in great detail and found that they launch magnetic waves into the sun's upper atmosphere. These waves, called Alfven waves, propagate into the corona where they *crack* like a whip, heating the gas where the crack occurs. (Note: When a whip is cracked on Earth, the sharp sound we hear is a result of energy being transferred from the fast-moving tip of the whip to the air around it. The same basic process is at work with Alfven waves cracking in the corona.) Cirtain doesn't believe jets can wholly explain the super-heating of the corona, but "they make an important contribution."

Another team of Hinode researchers led by Bart De Pontieu of Lockheed-Martin have found evidence for more Alfven waves coming from a layer of the sun's atmosphere called the chromosphere. (The chromosphere is to the sun as the troposphere is to Earth; both are near-surface layers of atmosphere.) These Alfven waves are not launched by jets but rather by turbulent motions within the chromosphere itself. "If we add all the Alfven waves together, the ones from the chromosphere plus the ones from X-ray jets, it may be enough to solve the mystery of coronal heating," says Cirtain.

Even if jets solved no Great Mysteries, however, Cirtain says he's just delighted to have found them. "Jets remind me why I love my job. It's Christmas every day."