## Tuesday, May 31, 2011

### Fermi Solution: Settlements in Space

Congratulations to Garystar who came up with just about the same number we did for Friday's Fermi Problem soultion! Garystar, please send us your mailing address to physicscentral@aps.org and we'll send you a prize package of some Physics Central goodies!

As a reminder, on Friday I posed a Settlements in Space Fermi problem based on the painting below of a fictional space station called the Stanford Torus. By guessing the dimensions of the station in the painting below, how many of these torus-shaped space stations would we need to house all of the people on Earth? Here's the solution:

[Rick Guidice's painting of the Stanford Torus space station was commissioned by NASA in the 1970s. Think you'd like to live there? Photo credit: NASA]

After eyeballing Rick Guidice's painting above, I assumed the diameter of the entire Stanford Torus space station was 1 km while the diameter of the interior of the 'doughnut' was 50 m. Since people and houses are seen only on one half of the interior, I considered it as a cylinder with no base or lid, and the height of the cylinder equal to the diameter of the interior.

Using the formula for the area of a cylinder (2*pi*r*h), we get 2*pi*1000m*50m which gives us 160,000 square meters of habitable area inside the Torus.

From looking at the painting, we see that houses don't account for the entire area of the station. I considered 40 percent of the area reserved for houses with the remaining 60 percent used for farming, schools, grocery stores, etc. Forty percent of 160,000 square meters is 64,ooo square meters.

Assuming that the area of the average American house is 220 square meters, this gives us about 300 homes for one station. If each home were occupied by 4 people, then one Stanford Torus could house 1,200 people.

The population of the Earth is about 7 billion. To fit all 7 billion on space stations, we would need just under 6 million Stanford Tori.

[External view of the Stanford Torus by Don Davis. Notice the overhead mirror that reflects sunlight on the station. Photo credit: NASA.]

There are 300 million people in the United States. To house them alone we would need 250,000 stations.

What's more interesting than the number of cushy tori that we would need to house everybody - though it's a lot - is what's going on back here on Earth. Assuming, as we did above, that every person in the world occupies 55 square meters of space (a 220 square meter house divided by 4 people gives us 55 square meters) the world's population could fit in an area the size of Texas.

(Geek out: 55 square meters*7 billion people is 385 billion square meters of required space to house everyone. That's 385,000 square kilometers. Texas is just under 700,000 square kilometers. There would be room to spare.)

That's amazing! Now, here's a parting thought for you to ponder in your free time. If we parked the stations one next to the other, we could walk across them to get to the Moon with millions of stations still to spare - unless, that is, you stacked them like quarters, in which case we would be 128 tori short.

If you're intrigued by the idea of living in space, check out these other conceptual images of the Stanford Torus.

Read the rest of the post . . .

## Friday, May 27, 2011

### Friday Fermi Problem: Settlements in Space

What if something happened to our planet that rendered in inhabitable? We used up all of our resources, let's say. Or for whatever reason we feel the need to abandon our terrestrial home and settle in space. What would that new home look like?

Above is a painting done in the 1970s by an artist named Rick Guidice. The painting, commissioned by NASA, depicts the imagined Sanford Torus. It's a doughnut-shaped space station that rotates to provide Earth-like gravity for its inhabitants.

Here's today's Fermi question: Let's say we built the Sanford Torus for real. (It looks like a nice enough place to live.) Using the painting to guess the dimensions of the station and the settlements inside, how many of these stations would we need to house all of the people of the world?
Read the rest of the post . . .

## Thursday, May 26, 2011

### Corked Bats, Juiced Balls and Humidors

No one should cheat in baseball . . . but if you're going to, you might want to read a recently published paper in the American journal of Physics first.

I think it's safe to say that no sport has been the subject of more physics analyses than baseball. Robert Adair's book The Physics of Baseball is now in its third edition, and remains one of the most popular "Physics of . . ." books on the market.

Adair did a great job analyzing statistics and baseball phenomena, from the challenge of getting a hit to the ideal path around the bases. For the most part, Adair relies on insightful applications of theory to the sport and breakdowns of actual baseball stats. Sometimes, though, to learn about baseball, you're gonna have to hit a few balls.

If you're a careful physicist, however, you don't actually swing the bat - that's too inconsistent. Instead you design a system that makes your experiments as repeatable and consistent as possible. That's exactly what a group of physicists did in a paper appearing in the June issue of the American Journal of Physics. Alan Nathan, Lloyd Smith, Warren Faber and Daniel Russell specifically decided to study three factors affecting the way the ball rebounds off the bat.

Corked Bats

The first experiment they describe involved firing a baseball from an air cannon and hitting either a regular wood bat or a corked bat to test how well the ball rebounded from each. Although some people have speculated that the walls of a hollow bat might act a bit like a trampoline - collapsing a bit and then rebounding to give the ball an extra kick - that doesn't turn out to be the case. The experiment showed that balls bounce better off of solid bats than hollow or corked ones. While it seems likely that the lighter corked bats might help a batter get more hits, the result is likely to be a ball that doesn't fly quite as far because a lighter bat transfers less energy to the ball.

On the other hand, unlike experiments performed on the Myth Busters, corked bats aren't a whole lot worse than solid bats when it comes to hit distance. It seems that home run hitters should stick with solid bats, but a really desperate, mediocre batter may connect more often and more solidly with a lightened bat, perhaps even picking up a homer on occasion. (Of course, they will pay hefty price if they get caught.)

Juiced Balls

In their second experiment, the physicists wanted to determine whether some baseball conspiracy theorists are right in their claims that modern baseballs are livelier (bounce better) than balls of previous eras. So called "juiced balls" are often blamed for the startling increase in home run hits in recent decades.

Once again, the scientists used their cannon to fire a selection of balls at either a bat or a steel plate in order to record how well the balls bounced. Fortunately, they had access to an unopened cache of balls (donated by the family of Oakland As former owner Charlie Finley) from the late 1970s, before the supposed juiced ball period began. In comparing the vintage balls with brand new official balls from Rawlings, they found that the older balls were less consistent, but on average no more or less lively than modern balls.

It's unlikely that the experiment will put conspiracy theorists at ease, but I think it would be wise to look at other explanations for rising home run hit numbers. (Can you say "steroids"?)

Humidors in Denver

The higher you go, the lower the air density, and the farther you will be able to hit a ball on average. That makes the mile high stadium of the Colorado Rockies a great place to be a batter, but a lousy place to be a pitcher.

In order to cool off the hitting a bit at their home town venue, the Rockies decided to try storing baseballs in a humidor, under the assumption that moist balls don't bounce as well, which should in turn keep batted ball distances down.

In order to test that assumption, the researchers turned to their cannon and found, sure enough, that the higher the humidity where the balls are stored, the less well they bounce.

Under further research, however, they also showed that there is another factor that affects balls about as much as humidity - temperature. Warming the balls increased their liveliness, regardless of the humidity, and cooling them reduced liveliness. Although it's hardly proof, the revelation adds a bit of credence to the rumor that some unethical managers over the years have attempted to ensure that the opposing team received a chilly batch of balls when they were pitching, and the home team had access to a warmed supply when they were on the mound.

***

Although the published baseball physics paper is available only to subscribers to the American Journal of Physics, you can see a preprint of the paper for free on the physics ArXiv.

Read the rest of the post . . .

## Wednesday, May 25, 2011

### Physics Spinoffs

Sometimes the best discoveries are the ones you aren't looking for.

There's a physicist in Washington today. That's not terribly uncommon, but Steve Gass isn't here to warn us of global warning, beg for research dollars, lobby for/against nuclear power, or many of the other common reasons scientists talk to politicians. He's here to save the fingers of countless shop teachers and wood workers with his invention called the SawStop. Words can't do it justice, so you'll have to check out the video above to see what the Sawstop does.

We featured Steve on Physics Central years ago because we thought it was cool that he would come up with something so useful, which really had nothing to do with his research. Even though it wasn't a physics project, Gass used the problem solving skills and lab experience he gained by studying physics to come up with something so impressive that Consumer Product Safety Commission is advocating that it be included as standard feature on all table saws. They estimate that it will prevent more than 4,000 serious injuries and severed body parts every year.

In case you have doubts about how well it works on anything other than a hot dog, the end of this video shows Steve testing it with his own finger.

Sawstop is only one of countless spinoffs that come out of physics labs. By spinoff, I mean any useful innovation developed by physicists, while not being the focus of a physics project. Here are a few more that come to mind . . .

Lung Flute

Chronic obstructive pulmonary disease (COPD) is a devastating disease that hampers breathing and leads to hundreds of thousands of deaths each year, as suffers literally drown in their own lung mucus. Acoustical physicist Sandy Hawkins applied the physics of sound to develop a simple and elegant way to help people with COPD breath a little easier. The Lung Flute isn't a musical instrument at all - the tone it emits is so low it hardly counts as a note - it's a prescription-only medical device.

Blowing on the Lung flute creates pulses in your airway at a frequency that's just right to shake mucus loose from the hair-like cilia in your lungs, so that you can cough it up. Check out this video from an article about the device by Corey Bins in Popular Science.

World Wide Web

It's hard for me to even wrap my head around what it means to invent the World Wide Web, but invented it was - by Tim Berners-Lee of CERN. Nowadays, CERN is better known as the home of the Large Hadron Collider, which is hot on the trail of the grandest questions in physics. And while many of us want to know why the universe exists in the form we see all around us, the answers to such questions probably won't change your life much.

The Web, on the other hand, changed everything. I'd be willing to bet Berners-Lee wasn't dreaming of YouTube, Facebook, and LOL Cats when he was developing a new system to help scientists share data. The result was beyond the wildest imagination of just about everyone alive at the time.

Berners-Lee was knighted for his accomplishment. Maybe we should cut to the chase and make him a saint.

Medical X-Rays, Microwave Ovens, MRI machines . . .

Yep, these too were fortunate accidents derived from physics research in pursuit of entirely different things. The list goes on an on. But there's only so much time in the day.
Read the rest of the post . . .

## Tuesday, May 24, 2011

### When air just isn't good enough

While munching on my Cheerios yesterday morning, I learned from reading the cereal box that NASCAR teams fill their tires with pure nitrogen gas, instead of regular air. (I also found a toy car prize inside the box which exponentially improved my Monday.)

NASCAR teams aren't the only ones to pump up their rubber with pure nitrogen. The gas is also used in bicycle tires on the Tour de France, in Formula 1 car tires, Space Shuttle orbiter tires and some aircraft tires.

But why nitrogen? What's wrong with regular old air?

To understand why it matters what gas is used in a tire, we have to learn a little about pressure first. Tires are designed to operate under a certain pressure in order to support the vehicle they are carrying. The tire pressure is determined by the amount of air (or other gas) filling the tire. It is measured in psi - pounds per square inch.

An under-filled tire will sag on the ground, creating lots of friction between the tire and the road surface, making it hard for the vehicle to move. An over-filled tire can minimize contact with the road, making handling worse. So, naturally, there is a happy middle ground of ideal tire pressure.
Pressure is also related to temperature. As the tires roll around the race track, the rubber heats up, warming the gas inside the tire. The gas, in turn, becomes more active and pushes against the inside walls of the tire more, increasing the tire pressure. In fact, after two laps around a race track, the pressure in some NASCAR tires can increase by 10 psi. This is a lot when you consider some tires start out filled to a little over 20 psi.

The air we breath is made of about 78 percent nitrogen, 21 percent oxygen, 0.9 percent argon and a fraction of a percent of carbon dioxide and other gasses. One of those other gasses is water vapor - water in gaseous form. The pressure of water molecules can fluctuate a lot with changes in temperature, especially around water's boiling point. Even small changes in temperature can result in big changes in pressure. Therefore, even that small amount of water vapor in regular old air can have a big impact on the pressure inside a tire.

To get around that, race car teams opt to use a "dry" gas - a gas stripped of pesky water vapor. Dry ordinary air is available, but nitrogen is the most common choice since it has even less water than dry air and can be had for a similar price. The nitrogen's pressure also doesn't fluctuate as much with changes in temperature, making it more predictable.

Lastly, nitrogen is also non-flammable. This makes it very attractive for use in riskier environments, like racetracks. Imagine what could happen during a blowout to a tire filled with pure oxygen or hydrogen, both very flammable gases. Argon is another non-flammable gas that some race teams use, but it's more expensive than nitrogen without being much more efficient. So nitrogen is the clear winner.

What if I wanted to try filling my tires with nitrogen? As we've learned, it's more stable and predictable and having properly-filled tires improves gas mileage and safety. Having properly-filled tires, though, is something that will require maintenance no matter what you put in your tires. Having the stability provided by nitrogen is certainly a concern for racing and aviation tires that undergo huge temperature and pressure fluctuations, but unless you take your car to the track a lot, it probably isn't worth it.

Just to be sure, I called a nitrogen provider whose gas can be found at dealerships and automotive shops across the U.S. The woman on the phone told me the cost of filling four automotive tires with their nitrogen varies from dealer to dealer, but that it can range from \$34 to \$200 per car. When you compare that to the cost of a few quarters down at the corner gas mart, regular old air, I think, will be all right for me.

Read the rest of the post . . .

## Monday, May 23, 2011

### Maurice Goldhaber: A lifetime of physics

Maurice Goldhaber, an Austrian-born American physicist who helped establish the standard model of particle physics and a former American Physical Society president, died at his Long Island, N.Y., home on May 11. Goldhaber was 100.

[Maurice Goldhaber in 1937.]

Goldhaber's studies of subatomic physics helped to establish the standard model of particle physics. In 1934, he and his colleague James Chadwick made the first accurate measurement of the mass of a neutron. Chadwick had first discovered the neutron in 1932. Back then, scientists thought the neutron was a combination of a proton and an electron. The measurements helped show that it is a distinct particle.

Goldhaber also contributed to the understanding of particle spin. Scientists once believed that the spin of a particle would go clockwise as often as it would go counterclockwise. Goldhaber and his colleagues showed in 1957 that neutrinos spin only in one direction. Neutrinos are those elusive particles that zip through matter without being altered or very easily detected. Their discovery changed the way scientists thought about elementary particles.

Goldhaber was the director of Brookhaven National Laboratory from 1961 to 1973. During that time, three major discoveries made at the lab resulted in Nobel Prizes. Though Goldhaber officially retired in 1985, he continued to do research at the lab well after his 90th birthday.

Goldhaber was born in Lemberg, Austria, on April 18, 1911. He was studying at the graduate level at the University of Berlin in the early 1930s. As the Nazi regime took over central Europe, Goldhaber fled to the United Kingdom. There, he worked with Ernest Rutherford, discoverer of the atomic nucleus, at Cambridge University. He earned his Ph.D. in physics from Cambridge in 1936. Goldhaber then went to the United States in 1938 where he joined the faculty at the University of Illinois. He became a senior scientist at Brookhaven in 1950. He served as the president of the American Physical Society (APS) in 1982.

[Brookhaven National Laboratory]

Physics was an integral part of Goldhaber's life and a common thread through generations of family. Goldhaber was married to a nuclear physicist named Gertrude Scharff-Goldhaber. She also fled Europe in the 1930s and worked with him at Brookhaven. Goldhaber's son Alfred Scharff Goldhaber is a physics professor at SUNY Stony Brook. Alfred's son David Goldhaber-Gordon (Goldhaber's grandson) is an assistant professor of physics at Stanford.

Martin Blume, a former editor and chief of the APS journals who used to carpool with Goldhaber, said to The New York Times that the physicist had "an idea a minute."

"I had a hard time keeping Maurice quiet," Blume said to the Times. "He did not have very much sympathy for someone just trying to focus on getting there alive. Sometimes I had to put my hand across his face to stop him from talking."

Peter Bond, the senior adviser to the director of Brookhaven lab, said in a Brookhaven statement that one of his favorite things Goldhaber once quipped is that "Physics teaches old things to new people."

Read the rest of the post . . .

## Friday, May 20, 2011

### The Physics of Blue Jeans

They're a casual Friday staple. Your dad wears them and your mom wears them. Even babies wear them. They're the uniform of the American teenager. They're blue jeans.

[Jeans are so popular, designer labels are sometimes counterfeited, as seen here. Whether counterfeit or legit, there are some that say the only way to clean your fashion jeans is to freeze them. What does physics have to say about that? Read on to find out. Photo credit: Ben Donley]

Did you ever stop to consider the physics behind this ubiquitous garment? If not, then lucky you! Today, we've done the work for you:

Jeans are no stranger to the saddle, being the popular choice for cowboys for decades. The saddle point, a shape known well to mathematicians, is when an object looks like a saddle, curving up in one direction (along the x-axis, if you're a math person) and curving down in the other direction (the y-axis). This can easily be seen in the shape of a Pringles potato chip.

Blue jeans have a saddle point - right in the unmentionables region. The pants curve up to cover the belly and the rump and then also curve down to form the inseam of the right and left pant legs. Why do I care?

Some argue that the universe is a flat endless plane. Others think it is a closed system. (If you traveled in one direction long enough, you would hit yourself in the back of the head.) And some think the universe could be defined by saddle points. So there you are. In the design of your pants is a (maybe) scale model of the universe.

Busting the Myth of Freezing Jeans to Clean Them

Apparently there is a trend of freezing your jeans to clean them. You put your dirty jeans in an air-tight bag, stick 'em in the freezer, come back after a few days and take a whiff. 'The smell is gone', you think. Except, it's not. It will be back.

According to the Department of Agriculture, odor-causing bacteria and molds aren't destroyed when frozen; they're merely inactive. Once the jeans thaw out, the bacteria will turn active again and the odors will return.

This makes sense. We know that vapor pressure - the tendency of a liquid to evaporate or a solid to turn gaseous - is related to temperature. When the temperature decreases, the vapor pressure also decreases. The solid or liquid is less likely to turn to a gas. So, when the jeans cool off, they produce less odor. But as soon as they return to room temperature, they'll be just as smelly as before.

So instead of freezing your jeans, you can try one of two things: 1) Move to the arctic where it's cold all the time and you'll never be stinky, or 2) Pull an old-fashioned trick and air out your jeans on a clothesline.

Durability

On May 20, 1873, Levi Strauss and Jacob Davis were issued a patent for an improvement in fastening pocket openings, or, the reinforcing rivets found on blue jeans. Adding a rivet around pockets and other high-stress areas on blue jeans, Davis discovered, reinforces the seams and makes the jeans more durable.

"The seams are usually ripped or started by the placing of hands in the pockets and the consequent pressure or strain upon them," Davis said in his patent. To reinforce pockets, he suggested using a rivet:
[I]t consists in the employment of a metal rivet or eyelet at each edge of the pocket-opening, to prevent the ripping of the seam at those points. The rivet or eyelet is so fastened in the seam as to bind the two parts of cloth which the seam unites together, so that it shall prevent the strain or pressure from coming upon the thread with which the seam is sewed.
In January, The New York Times did a fashion story in which they compared three pairs of jeans of similar design each made by different manufacturers. They found that it takes almost three times as much force to rip the rear seam on a pair of Levi's than it does on a more costly pair of jeans. I guess Strauss and Davis knew what they were doing.

UV Protection

Those with fair skin may know that it is possible to get a sunburn even through clothes. A plain, white t-shirt, for example, lets through about one-fifth of the sun's rays, giving it an ultraviolet protection factor (UPF) of 5.

Denim, on the other hand, has a UPF of about 1700, blocking a significant amount of skin-damaging ultraviolet radiation from the sun, which gives you a whole new reason to sport the Canadian Tuxedo. (As if you needed one.)

Read the rest of the post . . .

## Thursday, May 19, 2011

### The Spacerock Saga

Imagine you are hurtling through space at 26,000 miles per hour. You're zipping along, but to you all seems still and peaceful. The stars are so far away they appear stationary and you have no sense that you are crossing the distance of Manhattan every two seconds. Everything around you is black. Darkness cloaks you and it's colder than the arctic on the worst of days.

Ahead, there is a small blue sphere. It glows brightly, silhouetted by the dark background of space. Each day, it grows a little larger and soon you realize you're on a collision course. It is called Earth, and you're headed for a land that will one day be known as Arizona.

[The Meteor Crater, as seen from about 35,000 feet.]

You are a meteor, made of nickel and iron. Once you were a part of the asteroid belt between Mars and Jupiter, but a collision half a billion years ago set you free, ejecting you into the solar system where you've been going it alone ever since.

Eventually, Earth looms before you and you anticipate your impact on the rocky surface below. There is no escape.

Almost as soon as you see it, you are in the planet's wispy atmosphere, slipping through it in seconds. It burns you, stripping you of some rock - solid nickel and iron turned at once into vapor by the heat.

Moments later: Impact. You crash into the Earth's surface with the force of 20 million tons of detonated TNT. Instantly, more of you is vaporized, but the majority of your 150-foot-wide bulk is melted by the force of the collision. The remainder of you that wasn't melted or vaporized is fragmented and mixed in with the surrounding Arizona rock.

Sandstone and limestone are ejected over a mile away. Your impact has left a hole in the Earth 700 feet deep and nearly a mile wide. Giant limestone rocks are piled onto the hole's rim, now 150 feet higher than the surrounding terrain - a new ridge in the Earth where seconds before the land was level.

The intense pressure turns tiny pieces of graphite into diamonds and particles of rock rain down around the crater for minutes. The divot you've created is large enough to house 20 football fields. The residents of Philadelphia could stand on its slopes with room to spare.

Fifty thousand years pass. The crater's walls still loom above the landscape. Arizona is populated and villages and towns, roads and trails settle into place around the crater. No one is really sure why there is a large hole in the ground in an otherwise level part of Arizona. 'Perhaps an ancient volcano?' some wonder.

Daniel Moreau Barringer, a mining engineer from Philadelphia, scouts the site around the turn of the century, pondering its potential as an iron mine. He is one of the first to consider it as the landing side of a meteorite. In 1903, Barringer buys the land surrounding the crater and spends twenty-six years studying it, looking for remnants of a meteor. He dies in 1929, just as his theory to the hole's origin begins to be accepted.

Today, the crater is known simply as "Meteor Crater," and sometimes as "Barringer Crater." When viewed from above at jet-cruising altitude, it's a clear fingerprint of the cosmic pebble that collided with the Earth many thousands of years ago. From above, it's a singular reminder that though the Earth is unique in our solar system, we are just one among many billions of cosmic wanderers zipping through the universe.

View Larger Map

[Can you spot the meteor crater from above using Google Earth? Hint: The crater looks round from above.]

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### Can Killing Trees Save the World?

Here's my solution to yesterday's Fermi problem.

Just to remind you, I'm trying to determine whether it's possible to rely on trees to capture carbon from the atmosphere rather than developing technology to do it. Of course, once a tree pulls carbon dioxide out of the air, you'd have to get rid of the tree in some way that keeps the carbon locked up. (You can't burn it or let it rot, because that would just send carbon back into the air.)

The average US household produces about 7.5 tons of carbon dioxide. That's a bit under 7000 kilograms.

Carbon dioxide consists of one carbon atom and two oxygen atoms. Carbon is a bit lighter than oxygen, and only about a fourth of the carbon dioxide mass is due to carbon. So the average family is responsible for emitting

7000/4 kilograms of carbon = 1740 kilograms of carbon

Which I'll round up to 2000 kilograms to make the math easy . . .

Now, wood is mostly carbon. Precisely how much is carbon, I don't know, and because I'm lazy I'll just guess that it's at least half carbon. By my estimate, approximately 4000 kilograms of wood contains as much carbon as the typical US family releases into the atmosphere each year.

The US has about 300 million people living in it. I would imagine that most live in households with an average of about 3 people in each, which means there are about 100 million households in the US.

So, we put enough carbon in the air to equal . . .

4000 kilograms/household x 100,000,000 households = 400 billion kilograms of wood.

Is that a lot? I'm not sure. Let's see . . .

According to one reference I found, the US produced about 30 billion board feet of lumber in 2008.

A board foot is a one foot wide by one foot long by one inch thick piece of wood. That's about 30 centimeters by 30 centimeters by 3 centimeters, which is 2700 cubic centimeters.

Wood is about half as dense as water (again, I'm lazy, but that seems about right). And water is one gram per cubic centimeter, so one board foot has a mass of roughly 2700/2 grams = 1.35 kilograms, which I'll round to 1.5 kilograms.

In other words, the US timber industry annually produces about . . .

30 billion board feet x 1.5 kilograms/board foot = 45 billion kilograms of wood

Let's round it to 50 billion kilograms of wood.

That's equivalent to one eighth as much carbon as US households produce (based on the estimate of 400 billion kilograms calculated above).

To wrap it up, if we were to use trees to sequester carbon (by throwing them down a salt mine or encasing them in concrete), we would have to grow 8 times as much lumber as the entire US lumber industry produces annually - all for permanent disposal.

My conclusion - nope, it's not feasible to kill trees to solve our carbon emission problems.

Sorry kids. I guess you have some other way to save the planet.

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## Wednesday, May 18, 2011

### Save the Planet - Kill a Tree

Fermi Problem Friday Wednesday

Capturing carbon dioxide from the air would be a terrific way to reduce the causes of climate change, if we ever find a way to do it effectively. Then you could waste all the gas you wanted, leave the air conditioner on 24 hours a day, eat meat imported from halfway around the globe, and still sleep peacefully in your drafty house with single-pane glass and uninsulated attic. Sure you'd be throwing away lots of money, but that's your right, as long as you don't ruin the rest of the planet while you're at it.

Unfortunately, according to a study by the American Physical Society (note: Physics Central and Physics Buzz are produced by the APS), all the carbon capture technologies we know of are way too expensive to be useful today. Best estimates are that it would cost about \$600 per ton to collect carbon dioxide from the air. Considering that the average US household produces 7.5 tons of carbon dioxide a year, that's \$4500 every family would have to shell out every year just to cover their own emissions.

On the bright side (I think), it occurred to me that there are already plenty of living things that capture carbon dioxide, including all plants and trees. Trees in particular are mostly carbon, and often weigh a few tons at full size. All I'd have to do to be carbon neutral is chop down enough trees to equal my carbon load each year, then encase them in concrete and drop them in the ocean, or perhaps toss them into a defunct salt mine. As long as they don't rot and no one burns them, they will take a lot of carbon out of the air. I figure it could probably do that for a lot less than \$600 per ton.

So, here's the gist of today's problem: is it feasible to grow, harvest, and permanently dispose of trees to pull carbon out of the air? For simplicity, I'm only going to worry about the average US household carbon load. I'll post my solution to the problem tomorrow. Stay tuned to find out if I've saved the planet!!

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## Tuesday, May 17, 2011

### Looking for Hydrocarbons - "Physics Answers These Questions"

As I wrote in an article in APS News, physicists play an integral role in the oil and gas (O & G) industry. Oil is not sitting under the ground in pools waiting for a pipe to suck it up to the surface. It exists in the microscopic pour spaces between rocks, in areas mixed with water and sand. How do you find this oil and extract it safely through an eight inch bore hole? “Physics answers these questions and gets the oil out,” stated Brian Clark, a physicist and Fellow of Schlumberger, a leading oilfield services provider.

At the APS April Meeting, Clark and two of his colleagues in O & G research discussed the latest technologies designed to locate hydrocarbons and access the liquid gold. Clark noted that as a hole is drilled, the “drill pole” (essentially the long “stick” that has the bit at the end) actually contains a series of “laboratories” or tools, to analyze the underground environment. Each tool may look at or use different techniques to examine what is in the space near it. It may collect seismic data, or utilize sonic, magnetic resonance, EM and even nuclear technologies to test for oil.

One of the major challenges of running these “laboratories” down a hole that could be miles deep, is how to ensure the tools operate properly. The tools are self-contained, remarked Clark. They have their own computers, some with 10 processors running at any given time, and are in charge of their own telemetry. “They are basically robots,” he said.

[Photo of Brian Clark, courtesy of Clark and APS]

The laboratories on the drill poles are robust and technologically sophisticated because they have to endure abundant stresses on the job. They must work for hundreds if not thousands of hours at a time
without failing, described Clark. Otherwise, for every broken drill bit or pole, it could cost a company \$1 million a day. When you think about how challenging it is to send these tools down a tiny hole into the Earth and be scientifically certain they will operate correctly under extreme environmental stimuli, it was almost not a surprise to hear Clark utter “This is far more remote than what we send into space.”

While the laboratories on the drill poles perform many functions with limited operator involvement, they are not autonomous. With all the data they collect, process and send to the surface, they still can’t independently instruct an O & G employee to drill in a certain location. “We would like to see these tools more autonomous,” said Clark, “but the geology of the Earth is so complex that it is beyond the decision-making ability of the tools.”

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## Monday, May 16, 2011

### The oil-water-alcohol density timer!

Each year in May the American Visionary Art Museum in Baltimore, Md., hosts the Kinetic Sculpture Race - a race of human-powered sculptures that winds around (and in) the Baltimore harbor. For the second year in a row, the APS Physics Central team built a physics-themed timer for two of the race-day events, the water and mud obstacles. This year, the team was inspired by the mesmerizing display of water interacting with oil.

[Some of the sculptures in action at the 2011 Baltimore Kinetic Sculpture Race.]
To understand why this is so cool, you might first need a little background on density. Here is a Physics Central Physics@Home explanation of the interaction between water and mineral (baby) oil:
Density is the amount of stuff you have in a given space. Something that has a high density means that there is a lot of stuff in the space, where as something with a low density has less stuff in the same amount of space. Objects with a higher density sink when compared to objects of a lower density, which float. Whatever object has the lowest density will float. This explains why when you put a cork in a glass of water, it floats. The cork is less dense than the water. In the case of the baby oil and the water, the baby oil is less dense than the water; therefore, the baby oil floats on top of the water.

[Scale tests of the interaction of liquids with different densities. (Ignore the APS hot sauce collection behind the test tubes. The sauces are for lunch time testing purposes only.)]

After many tests of liquids with different densities, we found a couple of mixtures that separated well: Water and corn oil, and mineral oil and 91 percent rubbing alcohol. In each combination, we needed to use at least one liquid that would float to the top that was also dye-able. Since it is a timer, we went with a green-yellow-red stoplight theme. We dyed the water green, mixing it with yellow corn oil, and then dyed the alcohol red, mixing it with clear mineral oil.

[Equipment used in making the timer. It's surprising the people at Home Depot and CVS don't know the Physics Central team on a first-name basis yet.]

We created two tubes so that one could house the water (green) and corn oil (yellow) mixture and the other could house the alcohol (red) and mineral oil (clear) mixture. Two tubes also gave us more artistic flexibility, a very important consideration for the Race.

[The timer is halfway complete and tests of the corn oil (yellow) and water (green) tube show it takes a little over a minute for the corn oil to rise to the top (right end of the photo) while the water sinks.]

We wrapped the two tubes around a central PVC pipe. When the pipe was flipped end-over-end, the green water sank while the corn oil rose in the skinny tube. To keep the red alcohol from rising right away, we added a valve in the fatter alcohol-mineral oil tube. After the green water sank beyond a certain point, the operator opened the valve and the red alcohol rose to the top. In this way, we were able to make the timer run for two minutes.

[Close-up of the alcohol (red) rising to the top of the tube as the mineral oil (clear) sinks to the bottom.]

Sculptures taking part in the race had to make it through several obstacles on an approximately 15-mile long course. Obstacles included a sand pit, a mud pit, and a short water route through the harbor. If a sculpture got stuck in the mud pit or when exiting the water obstacle, it had two minutes to exit before being dragged out of the obstacle. The APS timer was at the ready for this year's two sticky events, but luckily for the artists, very few sculptures got stuck.

[The APS Wizard was the official timer at the 2011 Baltimore Kinetic Sculpture Race water and mud obstacles. Here, the Wizard posed for a photo-op while the green-yellow tube half of the timer was in action at the water obstacle.]

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## Friday, May 13, 2011

### Physics on the Disneyland Express: There are lots of large worlds after all

My continuing mission is to bump into and engage scientists everywhere I happen to go. The airplane, believe it or not, has produced many such encounters. For some reason, I just happen to always sit next to someone in science or engineering. Case in point: my famous Milan to JFK flight, on which I was not even supposed to be, yielded a seat next to a verbose Italian computer scientist. We talked shop in English and Italian for 6 of the 8 hours we were airborne.

So last week as I prepared to leave the APS April Meeting, held mere blocks from Disneyland, I wasn’t too surprised to see a bushy-headed physicist (I knew he had to be one) get on our bus to LAX. The bus was affectionately called the Disneyland Express and after I began chatting the fellow up, it became the happiest place on Earth.

This physicist was actually an astrophysicist, and was far from shy. He was so excited to talk about his research, he was practically goofy. (Please don’t groan – this post contains puns which are obligated by California law to be included.) So the 1 hour-plus trip practically tilt-a-whirled by as he discussed his passion: exoplanets.

According to Dr. M, as I will refer to him, there are many, many exoplanets – ok, yes we know this. In fact, the Extrasolar Planet Encyclopedia states that there is currently 548 known exoplanets. More info can also be found at exoplanets.org. So big deal – there’s a few planets more than a few light years away – how does this impact my life?

[This artist's concept shows a cloudy Jupiter-like planet that orbits very close to its fiery hot star.NASA/JPL-Caltech/T. Pyle (SSC), from NASA]

Dr. M explained to me that his studies of exoplanets allows him and his astro-colleagues to better understand the formation of the proto-planetary disks that existed before the actually gas-n-stones-particulates bound together and took shape as planets surrounding a star. And with “a few more planets being discovered everyday,” said Dr. M, there is more opportunity to better understand how planets, and more importantly solar systems, form.

This is not Mickey Mouse science. I sat on the bumpy bus listening to Dr. M wax on about how most of the exoplanets are mostly like Jupiter, with odd, jumpy orbits, and how the Kepler Mission is examining 150,000 stars over a three year period with a goal of finding Earth-like planets with Earth-like orbits. He didn’t mention any mission determined to find Pluto-like non-planets. Aw, shucks.

But he did reveal that at least 10% of the stars that we know of have Jupiter-like planets orbiting them, and Kepler may even lead us to discover that that number is more in the 20-30% range.

We soon arrived at LAX and our conversation came to an end. But the fire in Dr. M’s eyes told me that we will be hearing more about this subject in many places, including more APS meetings. In fact, he suggested to me that as an astrophysicist with an expertise in X-rays, he was surprised himself to be speaking at this conference, which doesn’t usually delve into this particular area of astrophysics. But if there are so many worlds out there, there surely will be more conferences at which to present. In fact, maybe one of those conferences is happening right now on a so-called “Jumping Jupiter”. Aw, shucks.

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## Tuesday, May 10, 2011

### Writing Science Fiction: Trying to Avoid “The Button” (Physics in Hollywood, Part 2)

In the future, which may include mean aliens destroying our planet and us migrating to another world, or wacko aliens eating our brains and completely obliterating our existence, or warm and fuzzy aliens who want to “friend” us on Facebook, there will be problems. Mo’ aliens, mo’ problems, as they say.

But in science fiction, when writing about the future, while you may not want to shun aliens, you definitely want to avoid “the button”, said Bill Prady, Co-Creator and Executive Producer of the TV hit “The Big Bang Theory”. He spoke at a session at the recent APS April Meeting about one of the biggest problems in scifi – “if there’s a button that solves everything [say on a spaceship or in an underground bunker of the future], there’s no conflict,” and conflict, of course, is what makes all forms of fiction interesting.

So whether you are writing much delayed fan fiction for Star Trek or Star Wars, or a script for the newest blockbuster concerning beautiful physicists who are also secret assassins, make sure you don’t include “the button”. Rather, write your characters as if they were, um, people, solving their own challenges. And if you can, said Prady and the panelists, do your best to make sure the science is accurate.

Science plays an important part in Prady’s hit, as well as other shows such as “Eureka” and “Star Trek: The Next Generation”. But there must be a reason for the science to be present and there must be some (even a modicum of) understanding of it by the public. “Eureka” is set in a town in the future, populated by geniuses, and therefore has some flexibility in terms of the science they explore and exploit. But the audience has to relate to the characters and understand why they are conducting this measurement, or building that black hole, stated the panelists. Bruce Miller, Executive Producer of “Eureka”, explained that the character of the sheriff, who does not possess the technical expertise of the rest of the hamlet’s inhabitants, acts as a guide for the audience to understand what the heck is going on and why it is important to the story.

This insight led John de Lancie, who played Q on “Star Trek”, to comment on knowing when to say when, when you write science into a script. de Lancie’s opinion was that in science fiction, sometimes the best “technobabble” in a script allows the audience to “almost” understand what is going on. This is enough for the public to enjoy the show. But for a more seasoned audience, say one that consist of scientists, there is a different level of expectation. Even though the majority of viewers of “The Big Bang Theory” are not physicists, Prady was well aware that there would be a few watching. He joked that in deciding how much physics to include and what specific scientific subjects to mention, “I wanted [the physicists watching] to have a little cringe, but not a big one.”

The panelists also opined about the many reasons to write for television, especially when a show involves science. Prady recalled that David Saltzberg, the science consultant to “The Big Bang Theory”, once told him that “'if you are reading a script on an airplane, women will talk to you…'", to which Prady added jokingly, "that’s why we do this.”

But there is another motive that seems to tug at writers, particularly those who value science and/or have a science background themselves. As Prady puts it, “I am offended by the anti-intellectualism that seems to be part of this country…I enjoy being in a world where science is [correct] on TV.” No need to hit any button when you have an Executive Producer who shares that conviction.

[Photo of David Saltzberg, science consultant to "The Big Bang Theory", used with permission]

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## Monday, May 09, 2011

### Facebook and Forest Fire Prevention

Less is more when it comes to preventing forest fires, according to a new analysis that explains why aggressive fire fighting in the US may make the risk of severe forest fires worse.

Many people have speculated that land management policies in the US could be contributing to the severity of wildfires that seem to plague the country's broad swaths of wilderness each year. The argument is that routinely putting out small fires leads to the accumulation of unburnt fuel - leaves, sticks, and fallen trees - just waiting for that one, big, late season fire to come along.

A new model presented in a paper published in the journal Physical Review E shows that it's not so much the amount of fuel that's the problem, but instead the connections between flammable areas that are to blame.

University of California researchers (Mark Yoder, Donald Turcotte, and John Rundle) studied forest fires in the same way that other researchers study the flow of rumors through Facebook connections, or the spread of diseases in populations.

If you consider Facebook-spread rumors, for example, the more connections between a group of people, and the larger the number of people in the group, the faster and farther rumors travel. One way to put a stop to a rumor, at least in theory, is to sever some connections (i.e. make some people de-friend a certain number of folks in their Facebook friend list). It's fairly easy to determine how many connections have to be cut in order to make sure rumors peter out and die rather than spreading like . . . well, like wildfire.

Similarly, if you could remove sections of flammable forest litter in a park, you could make sure that the fires can't spread very far. As it turns out, the researchers' model shows that letting small fires burn during the moist seasons each year gets rid of little patches of fuel, which breaks connections between portions of forest that may burn during the dry season.

How do the researchers know their model is accurate? By comparing wildfires in two similar, adjacent regions that have very different land management systems in place: Southern California (wildfire central in the US) and Baja California Norte, Mexico. In Baja, there's rarely any attempt to put out small fires that occur through out the year, and there are very few massive wildfires. Just across the border, small fires are quenched immediately, but raging forest fires make national news nearly very year. In both cases, the frequency and severity of the fires fit well in the new physics model of fires spreading across highly-connected and poorly-connected networks.

Will the new model have any effect on US land management policies? Who knows, but maybe I'll send a complimentary copy of the April issue of Physical Review E to the Bureau of Land Management, considering that they probably don't already subscribe.

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## Friday, May 06, 2011

### Phriday Fizzicts Phun!

Here's some Phriday Fizzicts Phunnies for you. Know any good ones? Leave them in our comments section below!

A Higgs Boson walks into a bar. The bartender looks up and says "Hey! You just missed some guys who were in here looking for you!"
---
Erwin Schroedinger is driving down the autobahn when he gets a flat tire. He pulls over to the shoulder and inspects the damage. As a theorist by trade, though, he's not sure how to change a tire. Many hours pass before a police officer shows up to help. Looking for the spare, he asks Schroedinger to pop his trunk.

Policeman: "Did you know you have a dead cat in here?"

Schroedinger: "Well I do NOW!”
---
Q: Who was the first electricity detective?
A: Sherlock Ohms
---
Q: Where does bad light end up?
A: In a prism.
---
Does a radioactive cat have 18 half-lives?
---
In Munich, there's a sign that says, "Heisenberg might have slept here."
---
(So old, yet so good...)
Two atoms are walking down the street. One stops and exclaims: I think I lost an electron.

The other replies: Really? Are you sure?

The first replies: Yes, I'm positive.
---
The neutron walks into the bar and asks how much for a beer, and the bartender says: For you, no charge.
---
More jokes from: Jupiter Scientific & NPR.

[Physics at the University of Maryland]

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## Thursday, May 05, 2011

### Q and A with Q, et al re: Physics of Hollywood, Part 1

One of the unique benefits of holding the APS April Meeting in Anaheim, California, is that the city is just down the road from LA. A tertiary, confidential, semi-reliant “informant” specifically told me that he/she estimated that the likes of Tom Cruise, Samuel L. Jackson and Madonna had all expressed a grand desire to attend the conference, but unfortunately their schedules did not permit them to do so. However, despite their absences, the close proximity to Tinsletown did provide the impetus for a very clever set of sessions about the physics of Hollywood and an appearance by a few other celebrities.

Bill Prady, Executive Director and Co-Creator of the TV show, “The Big Bang Theory,” Bruce Miller, Executive Producer of the show “Eureka,” and John de Lancie, who played “Q” on “Star Trek: The Next Generation” participated in a plenary session entitled “The Physics of Hollywood”, which was emceed by Jennifer Ouellette, science writer and former executive director of the Science and Entertainment Exchange. The evening event (coupled with a shorter afternoon session) delved into how physics has impacted television. (That's me with de Lancie in the picture)

“The Big Bang Theory” centers around the lives of physicists. Prady, who has a background in computer science, described how he based some of his characters on people he knew, who recognized and celebrated their own “sense of odd”. But he didn’t make the characters into computer scientists because they would always be looking down at their computers and “that’s bad TV,” he said. He wanted people writing on blackboards, but he also wanted scientific accuracy, unlike other shows such as “Star Trek: The Next Generation” or “Futurama”, where entertainment in many ways trumps science. Whether his characters are bantering about physics, reading physics books, or standing in front of a poster from a physics conference, there is a sense of reality in what they are doing.

Prady stated that when he watched the show “Friends”, he disliked the fact that the character of Ross, a paleontologist, only spoke about his science at a 7th grade level. He aspired for something better for his show, he said, so he hired Dr. David Saltzberg, a physics professor at UCLA to serve as science consultant. Prady described how the show incorporates science in three ways: 1) He will leave sections of the script for dialogue about certain areas of physics, which is filled in by Saltzberg; 2) He and his writers come up with a scenario, for example, the characters travel to a cabin in a cold environment, and consult with Saltzberg about what the scientific reason would be for their adventure; 3) He and his writers think of something in physics or related to it and consult with Saltzberg to find out if they are correct.

Prady and Miller are mainly writers, so it was also a treat to hear from de Lancie, who as an actor, has a unique perspective in weaving science into a narrative on TV. de Lancie, who revealed that he didn’t learn to read until he was 14 due to dyslexia, became entranced with science fiction when he read his first book, Jules Verne’s The Mysterious Island. He explained how as Q, he sought to embody the elements of science fiction and engage the audience with a bit of mischief, even when viewers didn’t know the full extent of his actions. For example, he described how in one scene with Captain Picard he put his hands in a puddle of goo and allowed it to drip down below the camera’s viewpoint. What the viewers didn’t know was that he was dripping the viscous liquid onto the head of a crew member.

Stay tuned for Part 2…

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## Wednesday, May 04, 2011

### Mystery Force May Be Due To Mirrors

40-year old NASA space probes are still heating up the field of astronomy after identifying mysterious 'anomaly'.

[Photo credit: NASA]

Portuguese physicists report that they have identified the unknown force whose influence on outward bound interplanetary space probes has puzzled scientists since 1998.

Until now, theorists speculated that this "Pioneer anomaly," -- affecting NASA's Pioneer 10 and 11 -- is caused by unseen matter in space, the gravity of an unknown planet, or even new principles of physics: beyond even Einstein's theory of general relativity.

This anomaly is one of a long line of mysterious motions in our solar system, many of which were resolved when investigators discovered new objects or physical effects.

Case in point: In the 19th century, Uranus deviated from its calculated orbit and the gravity of an unknown planet was suggested as the cause. In 1846, the discovery of Neptune solved the mystery. Astronomers blamed a quirk in Mercury's orbit on the influence of undiscovered matter near the sun, perhaps in the form of a small planet, or on a problem with Newton’s theory of gravity. The third suggestion panned out in 1915 -- Albert Einstein's general theory of relativity -- an advance beyond Newton, explained the Mercury effect.

Johann Encke, a 19th century German astronomer, found that a comet returned 2.5 hours early on each 3.5 year orbital trip. Encke suspected that the comet -- now named after him -- was plowing through a thin, resisting medium that was pulling it slowly toward the sun, making the orbit slightly smaller and the round-trip faster. However, some comets arrive later than expected, not early. The once mysterious force that causes the comets to belie their timetables was identified in 1950 by American astronomer Fred Whipple: gases streaming from a comet act like rocket propulsion, advancing or decreasing the comet's motion, depending on stream direction.

In the 1980s, the Naval Observatory searched telescopically for a hypothetical Planet X, to explain possible discrepancies in the orbit of Uranus, finding nothing. But an astronomer at NASA's Jet Propulsion Laboratory, John D. Anderson, hunted X in another way: he searched for deviations in the trajectories of Pioneer 10 and 11 that could be due to the gravity of the supposed planet.

The Pioneer satellites were launched in 1972 and 1973, respectively. By March of 1997, Pioneer 10 was already far beyond Pluto, a little more than 6 billion miles away from the sun. Anderson’s Planet X hunt failed, but in 1998 he and coworkers announced the discovery of the Pioneer anomaly: the probes were moving outward less rapidly than planned. By 2007, the Pioneers were about 250,000 miles short of their predicted distances from the sun, according to "The Hunt for Planet X" by Dutch writer Govert Schilling.

The Portuguese physicists -- including Orfeu Bertolami and graduate student Frederico Francisco of the Instituto Superior Technico in Lisbon -- said that the mystery force originated in the Pioneer spacecraft themselves.

Bertolami's team calculate that infrared radiation from warm parts of each spacecraft, notably the radioactive thermal generators that powered them, and the main equipment compartment, where electrical power from the generators was used to operate electronics, bounces back and forth between exposed surfaces and exerts pressure on the back of each spacecraft's 9 foot wide onboard parabolic radio antenna pointing toward Earth. Seen from a great distance, the Earth is very close to the sun in the sky, and so pressure on the antenna represents a force on the spacecraft in the direction of the sun.

The possibility that onboard heat causes the Pioneer anomaly was considered and dismissed by Anderson in 1998. Jonathan Katz, a physics professor at Washington University in St. Louis, Mo., disagreed, suggesting in 1999 that indeed heat is the culprit. The Portuguese physicists used detailed computer modeling to produce the most precise simulation of Pioneer heat flow yet, including both mirror-like and diffuse reflection from spacecraft surfaces. In their paper, they conclude that heat does the trick and "unless new data arises, the puzzle of the anomalous acceleration of the Pioneer probes can finally be put to rest."

Katz said that if he were the referee on the Portuguese paper, "I'd recommend publication."

Alan Stern, a former head of space science at NASA and the Principal Investigator of the New Horizons spacecraft that’s now en route to Pluto, said that "I don't think there is any longer any credible evidence" that the Pioneer anomaly originates from anything but heat.

The Pioneer effect will likely be just a footnote in the history of space exploration, but for now, at least it's the end of one mysterious anomaly.

By Stephen P. Maran
Inside Science News Service

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## Tuesday, May 03, 2011

### New possible signal of dark matter subject of debate

Dark matter detection experiment CoGeNT has seen a possible signal of dark matter, similar to the much-disputed DAMA/LIBRA collaboration result, it's spokeperson announced yesterday at the American Physical Society April meeting in Anaheim, California. Whether or not it is really a sign of dark matter is still very much open to debate but it presents an intriguing possibility that is leading to heated discussion in the dark matter community.

The germanium detector at the heart of the CoGeNT dark matter
detector. Photo courtesy of the CoGeNT experiment.

CoGeNT spokesperson Juan Collar presented data that showed an excess of low energy interactions in their germanium crystal detector that couldn't be explained by any known cause. Something seems to be hitting the germanium atoms and making them recoil. That something is a mystery, but possibly dark matter. The hits are coming at a rate of about 3 per day which is higher than expected based on other dark matter searches but is still consistent with the DAMA/LIBRA experiment. That experiment has been conducting its search for nearly a decade and claims to have seen a real signal of dark matter.

The DAMA/LIBRA experiment is controversial because it infers the presence of dark matter by looking for a difference in the number of interactions in their sodium iodide crystals between summer and winter when the Earth is moving against or with the supposed cosmic flow of dark matter. But searches by other experiments for dark matter particles of that mass and interaction strength turn up empty. Many physicists believe that there is some unidentified factor that changes seasonally but is not dark matter. Yet, nobody can identify that factor. Making the issue even more difficult is that others can't attempt to replicate the DAMA/LIBRA experiment as they have not made their sodium iodide crystals available to others.

Now that a second experiment has seen an identical seasonal variation in an independent configuration, the mystery has only deepened. Collar is not saying whether he thinks his experiment has observed dark matter but comments, "We're making all the data available to others so they can make their own interpretation."

Physicists from the XENON100 experiment in particular don't seem impressed by the result as they believe their search covers the same territory but turns up nothing at all. Collar contended in his presentation that the XENON100 search doesn't cover quite as much territory as they think it does and that there is still a gap where dark matter could be living.

University of Chicago theorist Dan Hooper finds the result "very exciting" but admits that he is biased in it favor as a recent theoretical development of his predicts the existence of a particle that has properties consistent with the CoGeNT result.

CoGeNT was recently shut down as result of a fire in the Soudan, Minnesota, mine where it is located. Collar doesn't know if it will be operational when they try to restart it in the next few weeks but crosses his fingers as he hopes that he still has an experiment to run. CoGeNT will try to make a more definitive statement about their signal once they have more data but it seems that the dark matter mystery will be the subject of debate for some years yet.

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## Monday, May 02, 2011

### Sights from the APS April Meeting

Here are some sights from the APS April Meeting held Sat., April 30 through Tue., May 3 at the Hyatt Hotel Orange County in Anaheim, Calif. Research on nuclear physics, particle physics, and astrophysics among other topics was presented at the meeting.

[Peace, love, and neutrinos: One researcher handed out buttons related to her research at the APS April Meeting held April 30 through May 3 at the Hyatt Regency Orange County in Anaheim, Calif.]

[Physicists stroll through the lobby of the Hyatt Regency Orange County, site of the APS April Meeting.]

[A large crowd filled the room for the meeting's first session celebrating 100 years of sub-atomic physics. Topics included the Large Hadron Collider and the search for dark matter.]

[Benson Way, a graduate student at the University of California, Santa Barbara, reads through the schedule of APS April Meeting events.]

[The APS April Meeting spanned the weekend of April 30 and included research on nuclear physics, particle physics, and astrophysics among other topics.]

[David E. Snead, center, and Lior Burko, left, talk in the hotel lobby about Snead's research on measuring particles in free fall. Marc Sher, right, looks on.]

[Lyn Evans, former project leader of the Large Hadron Collider, checks out the wares APS store.]

[Yu Zheng, a graduate student at Purdue University, speaks on the phone while flipping through her April Meeting schedule of events in the lobby of the Hyatt Hotel.]

[Becky Thompson, of APS, hands out free Physics Central posters and activity books to passers by.]

[Crystal Baily and Ted Hodapp, both of APS, dance in front of the Hyatt Hotel to celebrate May Day, May 1, during the APS meeting.]

[Friends old and new chat in the lobby of the Hyatt Hotel during a break between meeting sessions.]

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