Tuesday, November 30, 2010

Leaping Lizards? No. Flying Snakes!

Danger from above: Snakes can glide like an airplane. What's more, they can change direction mid-air and sail the length of a tennis court.

The snakes we're talking about are a South and Southeast Asian variety called paradise tree snakes. The snakes are part of a larger genus of airborne serpents called Chrysopelea. They live in a jungle habitat, gliding from tree to tree and can grow to be four feet long. Though they're poisonous, their venom is not harmful to humans.

Jake Socha, a biologist from Virginia Tech, studied the snakes' flying behavior, launching them from a 50-foot tower. The researchers discovered that as a snake falls, it flattens its belly, turning itself into a long wing.

They saw that the snakes angles their bodies 25 to 30 degrees relative to the wind in order to generate lift. This is the same as holding your hand out of a car window at a small angle to have the wind lift it up.

"The snake creates lift using a combination of its flattened cross-sectional shape and the angle that it takes to the oncoming airflow, known as the angle of attack," Socha said to Discovery News.

The flying reptiles also continued their slithering motion during flight, gliding in an 'S' shape. The researchers theorized that the shape might allow the front of the snake to create a wake for its rear, streamlining flight in the same way the 'V' formation aids geese aloft.

Researchers also noticed that the snakes somehow steer themselves and change direction during their flights. The furthest a snake glided during the tests was 79 feet - about the distance of a tennis court, or one fourth of the way down a football field.

The researchers also conducted aerodynamic tests on plastic snakes dipped in a water tunnel and ultimately came up with a mathematical formula to describe the snakes' gliding behavior. The project was funded by the Pentagon and the results might be used to develop something like a flying snake robot used in search-and-rescue missions.

The paper, published in The Journal of Experimental Biology, could also help scientists understand more about other creatures that glide. The research was also presented at the American Physical Society's Division of Fluid Dynamics meeting this November.

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Monday, November 29, 2010

Science Fiction Flowchart

What makes a movie science fiction versus fact-based non-fiction, like Apollo 13 or October Sky, or another genre altogether? It's a tricky question and one that made my colleagues pause for a healthy Monday-morning head-scratching session. Think you know?

Leslie Neilsen - the star of "Don't call me Shirley" fame - died this weekend of pneumonia. He will be missed. Though he was a fantastic comedic actor, Neilsen actually got his start in dramatic films, including one of my favorites - Forbidden Planet.

Musing over the glory days when all science fiction movies had flying saucers* in them, we turned to a question so broad that the only way to solve it was to create a flowchart: What qualifies a movie to be labeled 'science fiction'?

The answer is above. Since no one would agree with me 100 percent on the definition of what constitutes a science fiction film, I welcome your thoughts on where the chart fails (even though it doesn't).

*We also spent a good half-hour harping over the question of "Whatever happened to flying saucers anyway?" The answer: Back in the fifties and sixties, the government was experimenting with making Frisbee-shaped flying machines. They never took off (pun intended), however, because of their inherent lack of stability. There was moderate success with the Avrocar, but it was ditched in favor of a more practical vertical take-off and landing vehicle: The helicopter.

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Wednesday, November 24, 2010

The Physics of Football

Thanksgiving: It's a day dedicated to turkey, dressing, and, of course, football.

Football is a sport almost made for physicists. Newton's three laws of motion are at work during every play and little things like the unpredictable bounce of the "prolate spheroid" - the football - can throw kinks into a game no physicist, player or fan ever saw coming.

Here's how Bill Belichick, head coach of the New England Patriots, described the gridiron in Football Physics: The Science of the Game by Timothy Gay:

The action that happens on a football field involves mass, velocity, acceleration, torque, and many other concepts...

While some observers see only carnage and chaos, brilliant athletic performances and bone jarring collisions, the science-minded see the field as a working laboratory.
Newton's laws of motion are the superstars of pigskin physics, explaining a lot of what goes on on the field. Newton's first law tells us that an object either at motion or at rest tends to stay in that state of motion or rest. The heavier the object, the more it wants to stay in a steady state. Thus, a big linebacker is hard to push around.

How is it then that a little guy like a small defensive player can tackle a bigger running back? It's possible thanks to two things: Torque, or the measure of rotational force, and a player's center of mass, which is explained later.

To understand how torque works, stand next to a swinging door. First, push the door open with your hand on the opposite side from the hinges - about three feet from the axis of rotation or the imaginary line the door swings around. It opens pretty easily.

Now, place your hand very close to the hinges - close to the axis of rotation - and push again. It's much harder this time to open the door. This is because you have more torque when you're at a greater distance from the axis of rotation and a bigger torque is better at moving an object around that axis.

But torque alone isn't responsible for the tackle. A player's center of mass - the point where gravity acts on an object - also has to be considered. A player's center of mass is near his stomach, roughly in the middle of the body. The center of mass is where the torque acts. The axis of rotation, the point the player's body rotates around, is the player's feet touching the ground.

When a player crouches down, keeping low, his center of mass is closer to the ground. Therefore, the potential torque is small. Imagine that the center of mass is like your hand on the door; it's closer to the hinges - or the feet. This gives the player lower towards the ground the advantage. It's harder to push him around his axis of rotation.

When the crouched player, whose center of mass is low, pushes on a standing or running player, whose center of gravity is higher, it's easier to push the upright player around his own axis of rotation, since his center of mass is further away from the axis. More torque.

There are, of course, more forces at work in a tackle, so even the lowest of tacklers can still fail to lay out his target. Understanding torque, though, helps to understand how a little guy can take a big guy.

This is just one example of physics at work in a football play. To see more football physics explained, like why a player with a quick 40-yard dash might be passed over for a player who's quicker off the line, check out these videos jointly produced by NBC and the NFL.

Also, for MythBuster-esque oohs and ahhs, watch Ray Lewis use physics to prove that it's better to hire a linebacker than use a battering ram to bust through a door:

Happy Thanksgiving!

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Tuesday, November 23, 2010

Physicists Mimic Supernovae Formation in the Lab

A trio of physicists from the University of Toronto and Rutgers University have created a laboratory analogue for the type of supernova formed by the explosion of a white dwarf star.

Supernovae can form after the deaths of both giant stars many times the mass of our Sun or from smaller stars called white dwarfs. A white dwarf is a dense star at the end of its life cycle. It heats up over time until, at some point, it reaches a critical temperature that triggers an explosion, called a supernova. (Many, but not all, white dwarfs are thought to form supernovae.)

The initial explosion - called a flame front - starts within the star and balloons out, ejecting matter away from the star's core in a mushroom cloud shape. The highly energetic and super-bright matter wraps around the star and a supernova is born, as demonstrated in this University of Chicago video.

Already-formed supernovae are discovered by the dozens each year, but astronomers rarely observe the initial explosions, having the opportunity to do so only about twice a century.

Now, a group of physicists have created a sort of flame front analogue resembling a lava lamp in their laboratory. The physicists filled a cylindrical container with water and glycerol - a sweet-tasting liquid that sometimes makes its way into low-fat cookies and can be used to thicken up liqueurs (or in this case, water).

They then injected a water-based solution through a small tube at the bottom of the container. The solution reacts with the water-glycerol environment and becomes more buoyant, accelerating slowly to the top of the container.

In their experiment, the physicists observed that with the right water-glycerol mixture, the solution would create the same mushroom cloud shape, producing what they called a "vortex ring" at the top. The vortex ring would eventually detach from the plume of the
injected solution. Then the plume, undergoing a self-sustaining reaction with the water-glycerol mix, would form another vortex ring that would also detach. The process could be repeated several times before the plume reached the top of the container.

The spawning of the doughnut-shaped vortex ring resembles the mushroom cloud ejection of matter during the birth of a supernova. The scientists also found that if they lengthened their container, more vortex rings could form before reaching the top of the container, meaning that the reaction could potentially sustain itself indefinitely.

The high-tech lava lamp could give astronomers and physicists the opportunity to study the genesis of supernovae formation in the laboratory without having to wait 50 years for one to happen out in space.

The physicists' paper is due to appear in the American Physical Society's Physics Review E journal.

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Monday, November 22, 2010

Airport Body Scanners: To Fear or Not to Fear?

It's that time of the year again - when Americans brace for the annual air travel melee on the industry's busiest day of the year - the Wednesday before Thanksgiving. New this year is the increased presence of total body scanners - technology developed to detect explosives stashed in the pants of a would-be terrorist - and the backlash of those who question the scanners' safety. How dangerous are the total body scanners, then?

There is disharmony between the government's official position on the scanners and some scientists' beliefs over the potential health hazards involved with a total body scan.

Air travelers embarking from most major airports in the U.S. this year may find themselves in a security line for one of two types of scanners: A backscatter X-ray unit (the gray and blue rectangular booth) or a millimeter wave unit (the gray cylindrical booth with clear windows).

Both units work by firing a beam of radiation at the person being scanned. An image of the radiation that bounces back is created and viewed by a Transportation Safety Administration worker in another room. For both units, the TSA worker in the side room cannot see the person being scanned and workers operating the machine cannot see the images. If a suspicious item appears on the scan, the person then undergoes a thorough pat-down.

The backscatter X-ray unit is the one generating the most questions. Dr. David J. Brenner, the Higgins Professor of Radiation Biophysics at Columbia University, recently answered x-ray scanner questions during a National Public Radio interview.

"[W]e know that X-rays can damage DNA in cells, and we know that X-rays can ultimately produce cancer. So the concern is about the possibility of inducing X-ray-induced cancer in one of the individuals who's scanned," Brenner said in the interview.

The TSA says that the amount of radiation a person absorbs during a backscatter X-ray scan is equivalent to the same amount a person is exposed to over a period of two minutes when flying in an airplane at cruise altitude.

CBS medical correspondent Dr. Jennifer Ashton reported that if 1 billion people a year go through an X-ray scanner, 10 additional cancer deaths - a fraction of one percent - would result each year.

The government estimates that each scan is the equivalent of one thousandth the amount of radiation in a chest X-ray. Some scientists, however, question the government's figures.

Looking at the images produced by the scanner, Peter Rez of Arizona State Univeristy estimates that the true amount is closer to one one-hundredth or even one fiftieth of a chest X-ray dose. The probability of death, he said, was closer to one in 20 million. While that's still a fraction of a percent, it is a higher risk than the risk of dying from a terrorist attack, which he put at one in 30 million.

Though the scanners could result in deaths, the risk is still far smaller than other risks, like the one in 500,000 risk of being struck by lightning in a given year.

Another group of scientists at the University of California, San Francisco, sent a letter to the President's science and technology adviser arguing that the X-ray scanner poses a greater risk than medical X-rays and the radiation absorbed during a flight. In those two cases, the radiation is distributed evenly throughout the body, the doctors say. The radiation from the scanners, however, is embedded in the skin, resulting in a higher concentration of radiation in a given area.

Questions remain including how the X-ray scanners will affect frequent flyers (including businessmen and flight attendants who could go through security anywhere from 200 to 400 times a year), children, pregnant women and travelers with weakened immune systems. There is also a question of what could happen should a machine get stuck or fail, potentially blasting one point on a person's body with excess X-ray radiation.

The good news about scanners: Millimeter wave scanners, which are also in use at airports around the country, use very far infrared waves, waves at the opposite end of the electromagnetic spectrum from the dangerous ionizing radiation of X-ray waves. X-rays are shorter waves that can penetrate the skin and alter DNA. Millimeter waves, by contrast, are longer waves that penetrate clothes but stop at the skin. The millimeter scan is akin to a heat lamp and is considered to be far safer than X-ray scanners.

The TSA plans to have 1,000 scanners in place at airports across the U.S. by the end of next year and as many as 1,800 in place by 2014 with the goal of making the scanners (or opting out) a mandatory part of security screening.

Passengers can elect to opt-out of either type of scan, but will be required to undergo a thorough pat-down, including an investigation of sensitive areas previously untouched by TSA workers. One website is calling for the day before Thanksgiving to be a national opt-out day, which would force the TSA to do more of the 1-2 minute involved pat-downs versus the 5-7 second body scan and could cause a significant security line logjam.

One Congressman, Ron Paul of Texas, is sponsoring legislation to fight the new scanning requirements, arguing that the examinations are a violation of the fourth amendment protecting U.S. citizens from unreasonable search and seizure.

In any case, as with any new technology prompting health questions, expect for some confusion among travelers facing the new screening devices and plan ahead. The busiest air travel day of the year just got busier.

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Friday, November 19, 2010

Tesla Mad Lib

Nikola Tesla was born in 1856 in the former Austrian Empire. Regarded by some as a mad scientist, his innovation in the field of electrical engineering helped to spur the second industrial revolution. Tesla died in 1943 in New York City. Though he's hardly a household name in the U.S., his work remains a legacy that's ubiquitous in modern life.

To complete the Tesla Mad Lib below, first, print out a copy of this post by going to File -> Print in your browser menu. Then, fill in the blanks at the top of the post with the appropriate parts of speech. Next, fill in the numbered blanks in the story with the words from the list at the top. Read out loud with friends and enjoy!

1. Adjective _______________
2. Plural Noun _______________
3. Verb _______________
4. Adjective _______________
5. Past Tense Verb _______________
6. Adjective _______________
7. Noun _______________
8. Past Tense Verb _______________
9. Monetary Unit _______________
10 . Adjective _______________
11. Adjective _______________
12. Noun _______________
13. Noun _______________
14. Verb_______________
15. Person's Name _______________
16. Type of Appliance _______________
17. Body of Water _______________
18. Adjective _______________
19. Number _______________
20. Plural Noun _______________
21. Past Tense Verb _______________
22. Adjective _______________
23. City _______________
24. Noun _______________

Nikola Tesla was a (1) ____________ inventor and physicist who developed the energy generators that power our homes and (2) ____________. In 1884, at the age of 28, Tesla moved from his homeland of Croatia to New York City to (3) ____________ with the (4) ____________ inventor Thomas Edison. Tesla (5) ____________ Edison a letter of recommendation written by a mutual friend which said, "I know two great men and you are one of them; the other is this (6) ____________ man."

Edison offered Tesla a $50,000 (7) ____________ if he could make Edison's direct current power system more effective. When Tesla presented Edison with an improved D.C. generator and asked for his bonus, Edison (8) ____________, telling Tesla that he did not understand the American sense of humor about money. Edison never paid Tesla one extra (9) ____________.

Tesla quit Edison's company in disgust. He got a (10) ____________ job at a different electric company and worked on finishing his alternating current generator, far better than Edison's (11) ____________ direct current system. Tesla and Edison then competed to light up the Chicago World's Fair in 1893. Tesla's alternating current (12) ____________ beat out Edison's design and the world got to see the (13) ____________ of the future!

Later, Tesla demonstrated that it was possible to (14) ____________ electricity wirelessly. This invention would allow the average (15) ____________ to power a (16) ____________ from anywhere in a room. Tesla envisioned using wireless energy transfer to send energy across the (17) ____________ from the United States to Europe.

He built a (18) ____________ Tesla coil in New York to start his project, but it was destroyed during World War (19) ____________ because the government suspected it could be used by spies. Some (20) ____________ still dream of fulfilling Tesla's dream, but others oppose his idea, concerned about health risks and the loud noise (21) ____________ by a Tesla coil. The (22) ____________ building still stands in (23) ____________, New York, to this day as a reminder of Tesla's amazing (24) ____________.

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Thursday, November 18, 2010

It'll make you laugh; it'll make you cry. It's...Science!!!

It's okay to be entertained by science. Really, it is. And when it comes to physics especially, science can be very entertaining. Just think about the Discovery Channel and the Science Channel. Think National Geographic , Popular Science, How It Works and Discover Magazine. All are about science. All are entertaining.

A friend once told me that she never watches the Discovery Channel because she feels some sort of obligation to pay attention and retain the information being presented. I can see where she's coming from; science can be intimidating. But my message is simple: It's okay to watch scientific programming simply to be entertained. Just enjoy. I bet, without even knowing it, you'll learn something new without even trying.

Entertaining science is all around and accessible in forms to suit you, your mom and dad, and even your grandma. Take A Short History of Nearly Everything, a book by Bill Bryson. Here's an excerpt from the beginning of his book. Tell me it doesn't suck you in:
No matter how hard you try you will never be able to grasp just how tiny, how spatially unassuming, is a proton. It is just way too small.

A proton is an infinitesimal part of an atom, which is itself of course an insubstantial thing. Protons are so small that a little dib of ink like the dot on this i can hold something in the region of 500,000,000,000 of them, rather more than the number of seconds contained in half a million years. So protons are exceedingly microscopic, to say the very least.

Now imagine if you can (and of course you can’t) shrinking one of those protons down to a billionth of its normal size into a space so small that it would make a proton look enormous. Now pack into that into tiny, tiny space about an ounce of matter. Excellent. You are ready to start a universe.
Here, Bryson is tackling a tricky subject: The Big Bang. His writing is enthralling. It's insulting. And it's deliciously digestible. How about that for a trick? He's entertaining us while serving up a big slice of science. And we don't even care. We're just having fun.

Here's a selection from another older piece from The New Yorker magazine called 'The Mountains of Pi'. It's about two brothers hunting for the last digit of Pi using their home-built supercomputer:
Gregory Volfovich Chudnovsky recently built a supercomputer in his apartment from mail-order parts. Gregory Chudnovsky is a number theorist. His apartment is situated near the top floor of a run-down building on the West Side of Manhattan, in a neighborhood near Columbia University. Not long ago, a human corpse was found dumped at the end of the block. The world’s most powerful supercomputers include the Cray Y-MP C90, the Thinking Machines CM-5, the Hitachi S-820/80, the nCube, the Fujitsu parallel machine, the Kendall Square Research parallel machine, the SX-3, the Touchstone Delta, and Gregory Chudnovsky’s apartment.
I'll warn you, it's a long article, but when I first read it, I couldn't put it down.

If you're not so into the written word, there's always the array of scientific television programming. For example, video from the Discovery Channel show MythBusters - the show that helped to make geek the new chic:

Here's a clip about a physics conundrum that happened in real life during NASA's Apollo 13 moon mission. It's from the incredibly accurate and detailed film Apollo 13 directed by Ron Howard which gained a 97% 'Certified Fresh' rating from Rotten Tomatoes - no mean feat.

And of course, there's the classic YouTube video gone viral (with over 12 million views now):

So there you have it. Try a new TV show. Pick up a new book. Surf the YouTube Science & Technology section. Read a magazine. And enjoy.

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Wednesday, November 17, 2010

Snagging Antimatter Atoms

Anti-hydrogen atoms are collected for the first time.

Researchers announced this week that for the first time they have created and trapped 38 anti-atoms at the CERN laboratory in Geneva, Switzerland.

When a regular atom and an anti-atom meet they annihilate each other, creating a burst of energy. This effect is used on the television program "Star Trek" to accelerate a starship to high speeds. In real life, anti-atoms can be created -- but only in tiny amounts.

Anti-atoms are very scarce in the universe, as far as we know. Indeed, astronomers see little evidence of anti-atoms in the great depths of space. To see them at all anti-atoms have to be made here on Earth at particle accelerators. The trouble is that as soon as you make an anti-atom it drifts away before you can study it. Only with this new announcement can physicists say that they have properly held even a handful of these difficult particles in one place under controllable conditions.

Understanding why there is so much matter but so little antimatter is one of the most pressing issues in science. One way of studying this issue is to make antimatter in the lab.

The simplest conventional atom is the hydrogen atom. It consists of a heavy, positively charged particle called a proton, wedded to a light, negatively charged particle called an electron. Hydrogen is the most abundant element in the universe. Our bodies contain a lot of it, and it participates in myriad chemical reactions such as the digestion of food and the combustion of gasoline.

An anti-hydrogen atom is just as simple, but is harder to come by. It consists of a heavy, negatively charged particle, the antiproton, wedded to a light, positively charged particle, a positron -- the usual name for an anti-electron. Positrons can be obtained from the radioactive decay of certain elements.

Obtaining large numbers of anti-protons is the hard part. First, regular protons must be accelerated to high speeds and smashed into a metal target. These collisions sometimes result in the creation of proton-antiproton pairs, as if they were contrasting twin brothers -- one normal and one anti.

The antiprotons are collected into a separate beam, and then deliberately slowed down. This is ironic since at accelerators the goal is usually to speed particles up. CERN -- the French acronym for the European Organization for Nuclear Research -- is home to the Large Hadron Collider, where acceleration is indeed the theme. But when it comes to antiproton experiments, CERN undertakes a dramatic deceleration. The energy of the antiprotons zipping around deep-underground tunnels is reduced from billions of electron volts, to millions, to thousands, and so forth -- on down to a fraction of an electron volt. According to one of the researchers, Jeffrey Hangst from Aarhus University in Denmark, this is equivalent to cooling the particles from a temperature of 10 trillion degrees to half a degree above absolute zero.

The next tricky step in making anti-atoms is to coax the antiprotons into linking up with the positrons. Slowing these particles to the lowest possible temperatures increases the chances that they will meet and mate.

Several experimental groups at CERN have accomplished this, including one called ALPHA and another deemed ATRAP. The next step is to hold the newly-made anti-atoms in one place. You can't just hold anti-atoms in a conventional bottle since as soon as they come close to a regular atom the two will undergo a mutual annihilation. Therefore, scientists attempt to keep the anti-atoms poised in space using a sophisticated arrangement of magnetic forces.

The ALPHA group is reporting in this week's issue of the journal Nature that they have finally trapped the anti-atoms. Why did they succeed in getting the anti-hydrogen to say put? "There isn't one single innovation; there were lots of them that add up to success," said Hangst, who is the spokesman for ALPHA. The innovations included a special magnet, an improved system for cooling the particles, and a delicate sensor for observing the annihilations that occur when the anti-atoms are finally released from their trap and allowed to drift into the surrounding material.

The ALPHA group observed evidence for 38 anti-hydrogen atoms in their trap. The next step will be to accumulate even more atoms and then to study them in detail. One direct approach is to see if the set of internal energy levels -- the energy spectrum -- of anti-hydrogen is identical to that of hydrogen. If the two species of atoms differ, then some new form of physics would be operating. Physicists find that prospect very exciting.

Gerald Gabrielse of Harvard University in Cambridge, Mass., is the head of the ATRAP group. In an article posted on Nov. 16 in the journal Physical Review Letters, Gabrielse and his colleagues report on a new method for collecting and cooling antiprotons. Although they have not yet been able to trap anti-atoms, they believe that with their new cooling methods they will soon be able to make and trap anti-atoms hundreds or thousands at a time, and at still colder temperatures.

"When in 1987 I first proposed the magnetic trapping of cold anti-hydrogen that was formed from cold trapped antiprotons and positrons I never imagined that 4 substantial international teams would be pursuing the cold anti-hydrogen dream at a storage ring built at CERN for this," Gabrielse said. "I am excited and proud of the 38 atoms that appear to have been fleetingly trapped since they are the latest step towards realizing the dream. Hopefully what we learn from a few atoms will speed us toward accumulating enough trapped anti-hydrogen atoms for precise laser spectroscopy."

Phil Schewe
Inside Science News Service

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Tuesday, November 16, 2010

Baby Black Hole Discovered in Earth's Backyard

Astronomers have found evidence for what they believe to be the youngest black hole existing in our cosmic neighborhood.

The 30-year-old black hole, detected by NASA's Chandra X-ray Observatory, is a remnant of a supernova, or exploded star, called SN 1979C. The supernova is about 50 million light-years away tucked into a galaxy in the Virgo cluster of galaxies that is part of the constellation Virgo. (To put that into perspective, there are anywhere from 1300 to 2000 galaxies in the Virgo cluster.)

The supernova that gave birth to the black hole was first discovered in April 1979 by a teacher moonlighting as an amateur astronomer and astronomers have been observing the area since then.

There is a chance that the supernova has morphed into a dense neutron star instead of a black hole. Researchers are expressing confidence that it is a black hole, however, because for a 12-year period from 1995 to 2007, it emitted X-ray radiation at a constant rate. The amount of radiation emitted from neutron stars would be expected to taper off over time, while a black hole's radiation would remain constant thanks to its steady diet of stellar material.

Though in cosmic terms it is close by, calling the black hole our neighbor is relative. Our Sun is less than a millionth of a light-year away from Earth, an insignificant distance compared to the 50 million light-years stretching between the Earth and Virgo.

It is believed the black hole formed from a star whose original mass was 20 times that of the Sun. Now, the dense black hole looks like it is packing material with a mass about 5 times that of the Sun into an area less than 25 miles across.

In the photograph above, data from the Chandra X-ray telescope is dyed gold. Visible light data from the European Southern Observatory's Very Large Telescope is dyed red, green and blue. Infrared imagery from NASA's Spitzer Space Telescope is also dyed red.

(Incidentally, Chandra and Spizter are two of four satellites comprising NASA's Great Observatories Program which enables astronomers to observe cosmic features across the majority of electromagnetic spectrum. The satellites measure X-rays and infrared light respectively. The Hubble Space Telescope, which measures visible light, and the Compton Gamma-Ray Observatory, which, as you guessed it, observes gamma-rays, are the program's other two satellites.)

The find is significant because it will give astronomers the chance to study a black hole (or a neutron star) from near-infancy. Scientists can follow the progress of the supernova's afterlife to help determine why some supernovas form black holes and others produce neutron stars.

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Monday, November 15, 2010

Who Says Hands Need Five Fingers?

Human fingers are pretty cool: They grip, they pinch, they squeeze. They can crush bugs and hold delicate crystal. They're amazing! Because of all the wonderful things fingers can do, it makes sense that we try to replicate them on our human analogues. But recreating robotic fingers is difficult and can get rather costly. To overcome the challenges that come with creating a robotic hand, one group of scientists ditched human digits altogether and developed something far simpler but just as effective.

Creating robotic replicas of human hands is troublesome. It's difficult to get the tension right to grip an object without crushing it. Computers can be strained when controlling multiple joints with umpteen degrees of motion. Instead of trying to replicate our dexterous little fingers, scientists at the University of Chicago and Cornell University opted for another approach, creating a robotic gripper.

The team developed what they called a "universal jamming gripper" out of a latex party balloon filled with ground coffee and a vacuum pump. To operate the robotic appendage, the slack balloon is placed on an object which it surrounds with the loose coffee grinds. Then, the vacuum pump is turned on, sucking out the air inside the balloon. The fluid-like coffee grinds 'jam' into a rigid solid with a fixed grip around the object. Once the pump is turned off, the grains loosen up again and the object is released.

Several types of granular materials were tried in early grippers including sand, couscous, rice and ground up tires. Sand worked the best, but was ruled out for being too heavy. Coffee grinds which jam nearly as well as sand but weigh far less were ultimately chosen.

The gripper can pick up things that have stumped robotic hands in the past like coins and raw eggs. It does have some limitations, struggling with porous objects like cotton balls and failing to lift more than half its own weight.
Even so, the four-inch diameter gripper that was created in the lab could pick up an eight-pound jug of water and the scientists speculate that a gripper with a four-foot diameter could lift a car.

Though it doesn't much resemble a human hand, the gripper could be developed into a new type of prosthetic limb. Since it has only two modes - on and off - it would be easy for users to operate. It could also be used to clean up debris after a catastrophic event, such as the earthquake in Haiti.

To learn more about this cool little gripper, listen to the podcast from PhysicsCentral below:

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Friday, November 12, 2010

Social Media and Science Combine to Explain Cats' Drinking Behavior

Two scientists at MIT used YouTube videos to help supplement their research on how cats' tongues extract water or milk from a bowl. The videos helped prove their formula describing the unique way felines draw liquids into their mouths.

Roman Stocker first got the idea to study how cats drink from watching his own cat, Cutta Cutta, sup breakfast a three years ago. Lapping at 1 meter (or four sips) per second, a cat's tongue is working too fast for humans to see individual sips. To slow it down, Stocker and his colleagues did what any good scientist would do - they whipped out their high-speed camera and got some close-up footage of Cutta Cutta's tongue in action to analyze in the lab.

They observed that a cat's tongue changes into the shape of a capitol 'J' when it is about to touch the surface of a liquid. The tip of the tongue is flattened and draws the liquid up into a column shape, formed by inertia. The cat's jaw closes over the liquid just before gravity acts to pull the liquid back into the dish. The scientists also found that cats naturally lap at the optimal frequency, instinctively maximizing the efficiency of the drinking process.

The scientists used a mechanical analogue of a cat's tongue - a glass disk attached to a piston that they dipped into water - to test the process and get a better understanding of how cats use inertia to overcome gravity. (Interestingly, the project didn't cost the scientists anything. The disk was borrowed from a neighboring lab who had created it for an experiment aboard the International Space Station.)

Stocker and his colleagues then developed a mathematical theory to predict how lapping frequency would change with a feline's mass. Their theory predicted that a cat with greater mass would lap more slowly. To test their theory, the duo turned to Zoo New England who allowed them to film large cats, like lions, tigers and jaguars, as they drank. Stocker then realized that additional data was already freely available on the Internet in the form of YouTube videos of large African cats caught on film during safaris, for example.

After analyzing the data, the scientists found that their theory was correct and that the frequency at which a feline laps water decreases as its mass increases.

To watch an interview of Stocker and colleague Pedro Reis talking about their study, click here. To read the original paper, click here.

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Thursday, November 11, 2010

Solving Two Mysteries at Once

The portions of universe that we can see appear to consist almost entirely matter, rather than an equal balance of matter and antimatter. At the same time, most of the universe seems to be made of something we can't see at all - dark matter. These two facts are among the outstanding puzzles in physics. A new paper proposes that they may actually be two aspects of the same mystery.

Ever since Einstein penned his famous equation, E=mc^2, physicists have known that it's easy to make matter out of nothing but pure energy, provided that you end up with an equal balance of the normal matter and antimatter. Matter, of course, is the stuff you, I, everything around us, and everything we can see in the universe appears to be made of. Antimatter is like matter's Bizarro World twin. An antimatter proton (antiproton), for example, is the opposite of a proton in every way except mass, which means that if one ever runs into a proton, the two will instantly annihilate in a burst of energy.

Because the universe was created out an energetic blast known as the Big Bang, you might expect that half the universe would be matter and the other half antimatter. If that were true, however, everything in the universe should eventually be destroyed as the two types of matter mixed. Instead, we're left with a surplus of normal matter. That's mystery number one.

In recent years, mystery number two reared it's puzzling head. Much of the universe, it seems, doesn't appear to be made of normal matter at all. Instead, the universe is filled with a material so completely alien to us that we call it simply dark matter (for lack of a better name). We know it exists because it affects the orbit of stars and galaxies, and even the structure of the universe. We have yet to make or capture a bit of dark matter, so beyond realizing it's here, we're pretty much in the dark on dark matter.

One solution, which is being proposed in a paper coming out soon in the journal Physical Review Letters, is that the amount of dark matter we can't see balances the matter we do see.

That's not to say dark matter is antimatter. We don't know much about it, but we can tell it's not simply the opposite of regular matter. Otherwise there would be detectable dark matter stars and planets, as well as occasional dark matter meteorites blasting holes in the Earth.

Instead, it may be that dark matter is only the opposite of matter in one way. Specifically, a particle of dark matter may have a negative baryon number. In case you've never heard of baryon numbers, don't worry; it's just a number that we think should be zero for the universe as a whole, but instead appears to be very large. Regular matter particles like protons have positive baryon numbers. If dark matter had the opposite sign of baryon number, everything would add up to give universe the zero overall baryon number that we would expect from the Big Bang. That would be a very tidy answer that ties up two loose ends at the same time, and makes the existence of the universe slightly less mysterious.

The paper is only theory at this point, but its authors suggest at least one experimental test of their proposal. Very rarely, a bit of matter may run across a bit of dark matter and annihilate to produce a signal that looks a lot like a proton spontaneously self-destructing (i.e. proton decay). The problem is, people have been looking for protons actually self-destructing for a long time now, and no one has seen any sign of it happening yet. So it may turn out, right or wrong, that the theory may never be tested. And theory without experimental confirmation is little more than a just-so story, like the tale of how the leopard got its spots, why giraffe has such a long neck, or anything explained by string theory.

To tell you the truth, though, I enjoy a good just-so story every now and then. But it'll be a lot more enjoyable if we can find a way to turn this particular bit of mythology into science.

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Wednesday, November 10, 2010

A Milky-Way Shaped Bubble Wand of Death*

The Milky Way: It's just a giant bubble wand, blowing colossal gamma-ray bubbles that extend tens of thousands of light-years from the center of our galaxy.

Scientists who have been examining images of the Milky Way taken by NASA's Fermi Gamma-Ray Space Telescope announced yesterday that they've discovered two high-energy balloon-like structures protruding from the top and the bottom of the Milky Way's core.

The radiation-emitting orbs extend a total of 50,000 light-years above and below the center of the galaxy. Traveling the length of just one of the spheres would be the equivalent of traveling to the Moon and back about 6.1 trillion times.

Astronomers at the Harvard-Smithsonian Center for Astrophysics in Massachusetts, where the bubbles were discovered, said they don't yet understand the nature of the spheres, nor how old they are or how they were created.

The astronomers processed data taken by the telescope to filter out a gamma-ray fog that permeates the Milky Way. The resulting image revealed the two orbs filled with significant amounts of high energy radiation. The orbs also appear to have edges, suggesting they were created by a single massive, rapid release of energy.

Perhaps they were formed by the black hole at the center of the galaxy. It may have spewed a particle jet over a period of a few tens of thousands of years as other black holes have been known to do. Or perhaps the bubbles are remnants of several million years of star formation, when huge, short-lived stars formed and then exploded releasing massive amounts of energy. Or maybe both. As with many new discoveries, for the scientists, there are more questions than answers.

If you look anywhere between the constellations Virgo and Grus in the night sky, then you're looking right at the giant bubbles. Too bad gamma-rays aren't a part of the visible spectrum. The orbs would have revealed themselves years ago. It just goes to show that there's still a lot we have to learn about our own galaxy.

If you're feeling really peckish, check out the full paper published today in The Astrophysical Journal. Fair warning: It's 46 pages long.

*There isn't any need to fear. The bubbles could be deemed deadly simply because they are made up of gamma-rays, a form of electromagnetic radiation harmful to humans. Luckily, Earth's atmosphere protects humans from space-bound gamma-ray invaders.

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Tuesday, November 09, 2010

Virtually Project Yourself In 3D

Materials science breakthrough leads to a new type of holographic display.

In 1977, Star Wars introduced popular culture to holographic projections with Princess Leia's famous distress message to Obi-Wan Kenobi. Since then, countless science fiction films have recycled the idea by having characters project themselves via hologram. Now, a team of physicists at the University of Arizona has taken a step towards making it a reality.

The physicists claim that their holographic 3-D display can refresh color images every two seconds and say it's the closest thing to a real time holographic projection ever created.

“What we have come up with is a new technique to do three dimensional telepresence, which means that we can take objects from one location and show them in another location in 3-D,” said Nasser Peyghambarian, director of the National Science Foundation's Center for Integrated Access Networks.

Peyghambarian said that a movie like Avatar creates a 3-D image with just two different perspectives, or one for each eye. However, by surrounding an object with cameras in a semi-circle, this technology creates a multitude of perspectives in the display that allow the image to actually change as you move your head.

“You look at the display like you look at your computer screen, but if you shift around, you see a different perspective,” said Pierre-Alexandre Blanche, an assistant research professor at the University of Arizona in Tucson.

The breakthrough was possible because of a material called a photorefractive polymer film, on which a 3-D image can be recorded and erased, and then replaced with a new image in nearly real time.

“Polymers have existed for a long time, what's new is that we have refreshable material now,” said Blanche.

An image -- whether real or computer generated -- is recorded in the polymer by high energy lasers firing frequent pulses. As the laser's light is absorbed in the film, it modifies the film's optical properties and creates a 3-D image in high definition. Best of all, the process eliminates the need for silly glasses.

The hologram still exists inside of a flat frame rather than being projected into thin air, but like a sheet of magical glass it allows you to see all sides of an image as the frame is rotated. This sets it apart from seemingly 3-D projections like those used by CNN in its election night coverage, which still only show one perspective.

For now, the hologram is only about 4 square inches -- or as Peyghambarian said, about the size of the Princess Leia hologram, but the group plans to make a version that is large enough to be more useful. They have already demonstrated a prototype that is about a square foot and in the next few years they expect to have a 6-foot square screen that is capable of the same speed as video, has a higher resolution than even HDTV and can produce a wider range of color.

Michael Bove, who heads a media laboratory team at the Massachusetts Institute of Technology in Cambridge, Mass., is working on their own holographic video technology. They agree that such devices will soon be commercially available, but said it might not be this group's technology that makes it into the market. Bove compared holographic video to the early days of television, where many different approaches were competing to be accepted.

“I think there are a half dozen technologies that could have holographic video into people's living rooms in ten years,” Bove said. “What they've done is largely a materials science advance. There's nothing about their overall display architecture that makes it more suited (than other technologies) to do telepresence.”

But Blanche said that the device is a huge improvement over what they had before, which only allowed updated images every five or six minutes in a four inch frame. He added that achieving a video speed is a must before the technology can be widely marketed for entertainment and said it could also be used for things like telemedicine, advertising, manufacturing and military applications.

“In our everyday life we see hundreds of perspectives with our naked eye and this technology is the closest one to that,” said Peyghambarian. “We have demonstrated the concept that it works, so it's no longer something that is science fiction, it's actually something that you can do today.”

Eric Betz, ISNS Contributor
Inside Science News Service

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Monday, November 08, 2010

X-Ray Vision: It's Not Just for Superman

Thanks to today's Google Doodle, we're reminded that Nov. 8 is the 115th anniversary of the discovery of the X-ray! If you do a Google search for "X-ray," it will turn up the usual suspects: A mock X-ray photo of Homer Simpson's head, a handful of articles and websites detailing the use of X-rays in medicine, and even art, like the image above taken by photographer Nick Veasy. What isn't as prominent and what some might forget is the role x-ray photography has played in our understanding of the Universe.

Visible light, the wavelengths of light that human eyes can see, make up only a very small portion of the electromagnetic spectrum. Our eyes enable us to see the sun and, at night, stars and planets - all emitters of visible light. The universe, though, isn't concerned with what we're designed to see. It emits light (anything on the EM spectrum is a form of light) at all sorts of wavelengths. Developing the technology to see and interpret it gives us all sorts of ways to learn more about the Universe around us.

X-rays were discovered by Wilhelm Rontgen, a German physicist, in 1895. He was messing around with electromagnetic radiation, shooting an electron beam through a tube. Rontgen noticed that when his beam of radiation was turned on, a fluorescent screen in his lab starting glowing. He put his hand between the tube and the screen and saw his bones projected onto the screen. Just like that, X-ray photography was born!

Rontgen's first X-ray photograph was of his wife's hand. Today, medical doctors use X-rays to check for broken bones and locate swallowed pennies. In the same way, physicists detect X-rays coming from space, capturing images of celestial matter that, just like broken bones, human eyes alone could not see.

Stars, star systems, black holes and the remnants of supernovae are just some of the things in space that emit X-ray radiation. X-ray astronomers use telescopes in orbits high above the Earth to take pictures of high energy, high temperature cosmic objects like this X-ray image of our own Sun taken by the Hinode satellite. Scientists must use satellites because the Earth's atmosphere prevents x-rays from reaching the Earth's surface. (Though this is bad news for scientists, it's good news for the rest of us, since a prolonged bombardment of X-ray radiation can be harmful to humans.)

The Chandra X-Ray Observatory, in an elliptical orbit that ranges from 10,000 to 83,000 miles above the Earth, is another satellite spying on celestial X-ray emitters. The Chandra satellite took the image of two colliding galaxies at the top of this post and also the photo below of a suspected supernova.

X-ray telescopes uncover layers of phenomena whose visible spectrum signatures don't tell the whole story. They can detect gas left over from an exploded star (a supernova). They can 'see' radiation lurking just outside a black hole. They're high-orbit detectives who give scientists another set of eyes with which to see and study the Universe.

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Friday, November 05, 2010

Be very, very quiet; I'm Hunting Radioative Rabbits

A radioactive rabbit that was on the loose this week in the Hanford former nuclear reactor site in Washington state prompted state Department of Health workers to hunt for contaminated rabbit droppings in the area.

The radioactive rabbit was among several bunnies captured over the last few days (a scene which calls to mind an iconic moment in Monty Python and the Holy Grail) at the site near Richland, Wash. The hopping critters were rounded up for testing after contaminated rabbit droppings were found last week. Only one rabbit tested positive for radiation contamination.

State department of health workers used hand-held radiation-detecting instruments to look for contaminated droppings. After capturing the afflicted rabbit, the amount of tainted droppings they found decreased, leading them to believe only one rabbit was affected. None of the droppings, so far, have been found in areas accessible to the public.

Washington Closure Hanford, the group responsible for cleaning up the former nuclear reactor site, thought the rabbit was most likely poisoned near the recently demolished 327 building. The building had been used during the Cold War to test highly radioactive materials in the process of creating plutonium for the United States' nuclear weapons program.

Workers think the rabbit probably drank water containing radioactive cesium that had pooled in the building's basement. They had sprayed water to keep dust at bay while demolishing the building about a month ago.

Radioactive cesium is one of the more potent types of radioactive materials. Though it washes out of the human body fairly quickly in sweat and urine, small doses (of 4.1 micrograms) have proven to be lethal to dogs who died within a few weeks of exposure to it.

To keep animals out, Washington Closure workers installed a chain-link fence around the building and scented the perimeter with fox urine to discourage burrowing animal visitors. The workers also removed vegetation that might attract hungry animals and covered suspected areas of contamination with gravel and steel plates.

For years, animals have wandered onto the site from time to time and become contaminated. In 2003, workers removed radioactive mud dauber wasps' nests that were found scattered across six acres of the site. The wasps had used sullied mud created from water sprayed at another demolition site to build their nests.

In 1998, radioactive gnats and flies munched on discarded banana peels and apple cores in trash that was then taken to the Richland landfill. Thirty five tons of rubbish that might have mixed with the contaminated Hanford waste had to be unearthed and returned to the nuclear reactor site.

Sadly, the unfortunate rabbit involved in the latest contamination calamity was euthanized and disposed of as radioactive waste.

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Thursday, November 04, 2010

Less Fiction, More Science - Too Bad

Maybe Scientists don't make the best science fiction advisers after all.

Call me a purist. Call me an old fogie. Call me anything you want, but don't call classic science fiction "Roddenberrian nonsense." For some inexplicable reason, that's what Battle Star Galactica producer Ronald Moore thinks of classic Star Trek. It also finally makes it clear to me why I HATED Star Trek Voyager, which Moore also wrote for.

Compared with Star Trek (classic and Next Generation), Voyager seemed to me to be a bunch of psychobabble, which would have worked much better as part of a daytime soap opera rather than a spin-off from one of history's ground breaking SF television shows. In keeping with his anti-Roddenberry approach, Moore has hired NASA scientist Kevin Grazier to make sure that all of the science on a forthcoming Battle Star Galactica series is in line with contemporary knowledge. (Grazier is also author of a book explaining exactly why the science of BSG is so lame how the science of BSG works.)

Great, terrific, outstanding, if you're making a movie about the present or near future. By 'near future', I mean the next twenty years or less. If you're looking out any farther than that, then you're gonna have to bend, stretch, or outright break what we think of as conventional science.

Consider how completely alien our world would seem to someone from 1900. We have jumbo jets, computer piloted trains, tiny portable phones, giant flat-screen TVS, and countless other things they could hardly imagine. If movie producers had followed Moore's approach in making science fiction in the old days, Buck Rogers would have talked on a land line phone, fired bullets rather than lasers rayguns, and traveled mostly by horse cart or Model A Ford. In other words, Buck would have been a cowboy instead of a space traveler.

The upcoming series Battlestar Galactica: Blood & Chrome apparently is supposed to take place in the distant future, but Grazier's job is to make sure none of the science and tech in it is too different from modern stuff. That's absurd because, at the rate that things are changing these days, I suspect that the technology we'll be using by the time I retire will be more alien than the stuff of BSG:B&C.

Now, I'm not saying that we can ever hope to accurately predict what things will be like in the distant future. But I firmly believe that fans of science fiction want more than Moore is willing to give us. I'm also convinced that the weird science and tech, that Moore felt weighed down Star Trek, is precisely the sort of thing that inspires people to study science and stimulates the imaginations and hopes of everyone who watches futuristic shows and movies.

Come on Moore, lighten up, use your imagination to stimulate ours. And don't let Grazier throw cold water on visionary fiction just because modern science can't explain/understand/predict it.

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Wednesday, November 03, 2010

Particle Accelerators in Earth's Atmosphere

Our atmosphere is very active electrically, evidenced by lightning forming during thunderstorms. Though we can't see it, another short-lived and equally as interesting atmospheric phenomenon occurs alongside lightning in thunderstorms, and this one can create gamma rays, the most energetic type of electromagnetic radiation.

In 1994, scientists first discovered that gamma rays, typically created by cosmic events in space, were also being created in thunderstorms. The events causing the gamma rays were called terrestrial gamma ray flashes (TGFs) and unlike lightning, they last only a few milliseconds (if that).

Scientists have thought since then that the Earth-based gamma rays are created in conjunction with a burst of cosmic rays entering our atmosphere. The incoming rays strip electrons off of molecules. When the electrons are combined with a lightning strike, an electric field is created, and an "avalanche" of stray particles form into a narrow beam projected out towards space.

Particle accelerators on earth do roughly the same thing, using electromagnetic fields to propel charged particles at high speeds. Though the process is the same, particle accelerators created by man produce beams with energies of many billions of electron volts while TGFs result in radiation amounting to only a few million electron volts.

Models for the creation of TGFs expect the atmospheric avalanche to result in about 10 MeV (mega, or million, electron volts) of radiation production in the form of gamma rays. New research by a group of Italian scientists, however, has recorded observations of TGFs producing ten times the amount of radiation at 100 MeV, suggesting that scientists' understanding of how TGFs are created may be incorrect.

Using the Italian Space Agency's AGILE satellite, the Italians detected multiple TGF events resulting in nearly 100 MeV of radiation using separate instruments. Their findings challenge current understandings of TGFs and suggest that more may be going on during the event, including the creation of neutrons which is already known to happen during lightning strikes. The Italian scientists hope that their new observations will reinvigorate interest in studying this elusive type of atmospheric phenomenon.

TGFs are typically found in tropical (equatorial) regions where thunderstorms and lightning occur more frequently. They're found between the altitudes of 33,000 ft. (where airliners cruise) and 65,000 ft. - well below the U.S. defined 'edge of space' at 262,000 ft. Estimates say anywhere from 100 to 1,000 TGFs occur every day. (Compare that to about 8.5 million lightning strikes on the average day.)

Though gamma ray radiation can alter human DNA, the radiation generated in TGF events is not significant enough to affect those on the ground. The gamma rays also mostly dissipate at the edge of Earth's atmosphere so astronauts are also safe from the newly-generated radiation, though satellites in low orbit could potentially be affected.

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Tuesday, November 02, 2010

'R2' Robot Ready for Launch

Space shuttle Discovery is on launchpad 39A, ready and waiting for tomorrow afternoon's launch. Inside the cargo bay a 7th astronaut is also waiting, already strapped in, and ready to make spaceflight history. After tomorrow's launch, Robonaut 2 - 'R2' for short - will be the first-ever humanoid robot in space.

R2 was designed as a prototype and not originally scheduled to go up into space but when he was revealed in February (I'll reference R2 as a 'he' since I've never seen a woman quite so burly as he), NASA was so impressed that they made room for him on the second to last shuttle flight. Though he'll be restricted to staying inside the International Space Station (ISS) for now, R2 had to be hastily redesigned to withstand the harsh environment of space and also modified to meet requirements for those living aboard the ISS.

R2's processors were upgraded to increase his tolerance for radiation - a persistent threat to any human or machine operating in space. His original skin was replaced with non-flammable materials and he was given extra shielding to reduce electromagnetic interference. Quieter fans were installed to keep the robot within the ISS's noise requirements and his power system was rewired to work with the station's direct current power supply rather than the alternating current used on Earth.

In 2007, General Motors partnered with NASA to develop R2 in hopes that the new robot design would benefit both manned spaceflight and auto manufacturing plants. Though the robot's nickname, R2, brings to mind a certain trashcan-shaped droid, the machine looks more like a legless Boba Fett than Luke Skywalker's rolling sidekick. He weighs over 300 pounds, has an 8 foot wingspan and senses depth through an infrared camera mounted in his mouth. He thinks with his stomach (cameras are mounted behind his visor to enable him to see so his 'brains' were housed in his torso) and can hold up to 20 pounds in his arms.

For now, R2 will be restricted to the Destiny laboratory where he will undergo tests to see how he reacts to space. Once engineers see how R2 functions in orbit, he can then get hardware and software upgrades (including legs!) to enable him to work outside in the vacuum of space. Ultimately, learning how to beef up R2 to better withstand the constant onslaught from solar flares and cosmic radiation could enable similar robots to survive long-term spaceflight either in earth's orbit, where they can repair and maintain satellites, or on long journeys through deep space.

"This project exemplifies the promise that a future generation of robots can have both in space and on Earth, not as replacements for humans but as companions that can carry out key supporting roles," John Olson, director of the Directorate Integration Office in the Exploration Systems Mission Directorate at NASA Headquarters said in a NASA press release. "The combined potential of humans and robots is a perfect example of the sum equaling more than the parts."

To watch the launch of STS-133 live, click here for streaming NASA TV.

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Monday, November 01, 2010

Packing in Your Morning Joe

What's the best way to pack rice, coffee beans, or other granular materials? It's an important question for companies selling grain products or people in a rush to buy coffee, nuts or raisins who want to pack as much into a bag as quickly as they can.

In the past, scientists typically only worried about two things when packing granular materials in a container: The number of grains and the volume of the container. However, new theories arose saying the amount of stress in the system ought to also be considered.

Imagine you have a large can half full of coffee beans and you tap it very gently. After each tap, you will see the beans bounce very little before settling back into place. In this case, the beans fall from a short height and the stress they place on one another (or how much they press against each other) after the fall is said to be small. If, however, you give the can a good thump, the beans will bounce much higher and fall much farther allowing you to pack them tightly in less time.

To test the theory, a group of scientists from Argentina, Spain and Venezuela built a mock 2D container about an inch long and almost six inches tall and filled it with one thousand beads, each about the diameter of a grain of rice. The container was just wider than the diameter of one bead, allowing the beads enough wiggle room to slip from the sides of the container.

The team used an mechanical shaker to tap the container at different intensities. At a high intensity, the beads settled into place after just a few taps. However, when the intensity was reduced to about a fifth of the original strength, it took almost 100 taps to reach the same packing.

The experiment was repeated in a 3D container and had the same results. A few strong taps could settle granular material as efficiently as many small taps. The same behavior can be seen at home with a plastic container of trail mix. After a few hefty taps, the nuts and raisins will pack together tightly. Loosen them up and give them a hundred tiny taps and they'll pack together again, but at the expense of time.

Accordingly, this new data might help companies packing granular materials pack just as effectively as before but in less time. A formula considering stress as well as the number of granules and the volume of the container could also help someone interested in packing less material in a give volume, like a filter manufacturer, since the formula can give the optimal tapping strength for a particular density.

Though this discovery is something you might have stumbled upon in your own kitchen, it did come as a surprise to some in the granular physics community where little experimental research has been done. The next time you're alone with a can of coffee or a tub full of trail mix, give it a few taps to see it for yourself.

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