## Friday, July 31, 2009

### Fermi Problem Friday: How much energy do you save by having a white roof?

This Friday, in honor of my new facebook friend Steven Chu, I'd like to examine his "White Roofs" campaign through a Fermi problem.

Steven Chu has said that we could all save energy simply by painting our roofs white. The idea is the same one behind why I don't wear a black shirt on a sunny day (and white after Labor Day). Black objects absorb light, and with it, heat, while white objects reflect it. So if you're trying to keep your house cool in the summer, it makes sense to have a roof that reflects sunlight instead of absorbing it. Here's the schpiel:

But how much energy do you save, really?

The Fermi Problem:

The solar flux at Earth's atmosphere is about 1360 watts per square meter. About 0.3 of this is reflected back into space, while the rest is absorbed by the earth. Given the square footage of your roof, how much energy (assumed as heat) would a black roof absorb? How much energy would a white roof absorb?

Now, you could give Secretary Chu the benefit of the doubt and assume that black roofs absorb all of the sun's energy, while white roofs reflect it all. But we're talking getting people to actually paint their roofs white. For reals! So we're going above and beyond the Fermi Problem protocol for this week's problem.

How can we test the difference in absorption between light and dark materials? Let's try placing two thermometers in the sunlight. Procure two boxes. Cover one with white paper, and the other with black paper. Put a thermometer in each box. Go inside and reread a few chapters of Dialogue Concerning Two New Sciences. Then check to see which thermometer reads a higher temperature. Let us know what you find out. Now use this information to calculate the energy you will really save by painting your roof white.

On Monday we'll be posting the results from our own experiment. Send us a photo of your experiment to physicscentral@aps.org with your name and a mailing address, and we will mail you something fun for your scientific efforts!

Now, are you going to do with all the money you save from lower electric bills minus the cost of the white paint? Buy Swedish fish, of course.

Read the rest of the post . . .

## Thursday, July 30, 2009

I've long gotten over the novelty of being able to "add" famous physicists like Isaac Newton, Richard Feynman, and James Clerk Maxwell as friends on Facebook. Fans have their choice of several online impersonators, of varying degrees of convincingness, for each scientific luminary. But in between hanging out with astronauts and watching Toy Box videos, I somehow missed the fact that Secretary of Energy Steven Chu has joined facebook.

Chu must be our most popular and recognizable Secretaries of Energy yet. I mean, can anyone even name a former secretary off the top of their heads? Maybe it's because Chu radiates that ineffable rock star aura known as Geek. He's smart, he bicycles, and he's the first Secretary of Energy who's actually a scientist. And not just your test-tube-shuffling, garden-variety boffin; Chu has a Nobel Prize. (And he's still publishing.)

But part of me raises an eyebrow at such a public figure using such a casual medium to speak to the public. It makes sense for celebrities; Ashton Kutcher has nearly three million fans, no doubt eagerly refreshing his facebook page every few minutes for the latest Ashton news. Barack Obama has over six million fans and uses the page to encourage voters to tweet about issues to congressmen. (He enjoys Stevie Wonder and Bach, and watches Sportscenter.)
Chu's page sits somewhere between the two as far as how engaging it is. His wall features a YouTube video of his recent appearance on the Daily Show, a link to a recent New York Times article about his "white roofs" obsession, and Flickr photos from a trip to China to meet with dignitaries. He's learning how to golf (is golf code for "playing with the other politicians?) and is interested in energy effficiency.

He's got over 5,000 fans—"talk about transparency, this is great" says one wall post. If nothing else, the page gives us this awesome photo of young Chu. (I predict a sudden rush on Buddy Holly glasses.) But is it really transparency? A typo in a recent wall post made me wonder, cynically, if Chu's facebook curator (someone must have the job) would be reprimanded later. On the other hand, when have politicans ever been so accessible?

Read the rest of the post . . .

## Wednesday, July 29, 2009

Yesterday's post generated a lot of great conversation, so I thought I'd respond to some of the interesting points brought up in the comments section. First, are platoons (chains of several cars that are traveling close together) really that bad?

Anonymous said...
The thing about these "platoons" is that when you're driving that close you're not just watching the car in front of you but the car in front of him. You actually end up monitoring a couple of cars ahead. So if you see something happening to the car 2,3 or 4 cars ahead you start easying off and you have more time to brake when the mud really hits the fan.
Strangely enough, Dr. Appert-Rolland told me that the specific expressway she was looking at rarely had accidents, though that wasn't the focus of her study. With such long platoons, it seems like rear-end collisions would happen pretty frequently, so maybe there's something to the above comment. I'd be interested to know why accidents don't happen more frequently here. When I asked her what drivers should do about this platoon effect , she mentioned not only obeying the three-second rule, but trying to look ahead if you can, as the comment above suggests. So perhaps you can fine-tune how closely you follow based on how far ahead you can see, meaning the writer of the comment below should probably stay away from bigger cars:
That's another issue. I can't see a damn thing from my Ford Focus when any SUV is ahead of me. I end up depending on the SUV driver's reaction time and style, which is, generally speaking, horrid.
Obviously the three-second rule is a rough way to keep your distance larger than your reaction time. (One commenter brought up that reaction times are actually less than one second. Anyone have any evidence for that?) But sometimes even that rule needs to be broken, bringing us back to the first paper the article mentions:
the three-second rule means that most people would never be able to enter the highway. If you attempted to merge, you would break everyone else's three second rule behind you and everyone would have to slow down to let you merge. So you can't say "never" because your highway would be at capacity in no time at all.
This comment brings up the fact that any small disruption in the flow of traffic is going to ripple throughout the rest of the system. The closer your headway, the more the car in front of you is going to affect how you drive. If you're, say, driving through the Mojave at midnight, you're not going to worry about the tail lights you can see half a mile ahead of you, but if you're tailgating a car on the 405 south, you're going to slam on the brakes every time you see your leader's brake lights flicker. So I'd argue that if everyone followed the three-second rule, merging traffic would have less effect on the rest of the freeway. Appert-Rolland also mentioned that it might help to display a "suggested speed" that reflects the average speed, helping drivers going too fast or slow to choreograph their driving. She pointed out that simply having shorter headways gets more cars through. The problem is that when you have a heavy flow, there's a higher risk of a jam. And once you're in that jam, she said, it's really hard to get out of it. If you could somehow homogenize the flow, you'd smooth out the bumps...theoretically. According to Minnhagen's research, homogeneity isn't actually that helpful.
Yahktoe said...
For anybody interested in reading Petter Minnhagen's paper (or at least an abstract of it), you can find it here:

Flow improvement caused by agents who ignore traffic rules

I think it's worth noting how stylized the pedestrian rules are in this study. I haven't sprung for the full paper, but I find myself wondering if maybe the rules themselves could have been changed in such a way as to make rule abiding the optimal "solution."
A comment after my own heart: I often wonder whether the proverbial spherical cow eats grass and moos. So here's a bit more detail on the rules of this model world. So we've got our pedestrian-only street, divided into a grid. Each pedestrian is randomly assigned to move either up or down the street, with each square representing a possible move. You try to move forward if you can, but if there's someone in that square, you can move sideways. If you're a good, rule-abiding citizen, you always try to go right first. If that square's occupied too, then you can go left. But if you're a jerk, you're behavior isn't so rigid. You toss a coin to decide whether to go left or right first. You've got more freedom.
Even though we're talking about pedestrians here, and in a computer simulation at that, it's still very surprising that the best possible situation where you have to get a bunch of people to move in a coordinated way is to have quite a few of them acting outside of the norm. Minnhagen said he was completely astounded by the results. "I was also fascinated when I was a kid by occasions when you were able to break the rules," he told me.
Peter Minnhagen's expertise is, broadly, in statistical mechanics, and he said that this was his group's first big foray into traffic problems, inspired when someone brought up the question while they were tossing around ideas. (Sign me up for that group!) Cecile Appert-Rolland studied fluid dynamics for years before she delved into the physics of tailgating. So what I like about these two papers is that they apply the physics approach the infuriating and seemingly irrational phenomena in every day life. I'm definitely looking forward to seeing better models, but I'm also just fascinated by the fact that you can look at these systems with a physicist's eye and start to get some answers.

Read the rest of the post . . .

## Tuesday, July 28, 2009

### Jerks actually reduce the risk of traffic jams

The next time someone cuts you off on your morning commute, don't be so quick to call the driver a jerk; you may have a reason to say thanks. According to the latest physics research, rule-breakers—drivers passing you on the wrong side or changing lanes too close to the intersection—actually help smooth the flow of traffic for the rest of us.

"The interesting finding is that if most of the people are law-abiding, and you have a certain amount of people who are breaking the rule, then you are actually getting the minimum chance of a [traffic] jam," said Petter Minnhagen, a physicist at Sweden's Umea University and an author of the paper published in the journal Physical Review E.

Physicists at the school uncovered this phenomenon while constructing a computer model of how a crowd of people move across a confined space, such as a pedestrian-only street. They divided the space into squares, like a chessboard, and randomly placed pedestrians in some of the squares. Like real people, the model pedestrians had a certain small probability of momentarily pausing, as if they had run into a friend or had bent down to tie a shoelace.

To make things more interesting, the researchers then tossed a few mavericks into the mix, who didn't follow the rules the other pedestrians used. The physicists ran the simulation over and over, each time boosting the percentage of rule-breakers. At first pedestrian deadlocks worsened. But as more and more rule-breakers joined the fray, something entirely unexpected occurred: traffic flowed best when only about 60 percent of pedestrians were obeying the rules.

Simple interactions of individual cars, people, or molecules add up to large patterns in a system. The high concentration of pedestrians in a small area increases the chances of a jam, but rule-breakers made the crowds spread out.

Morris Flynn, a University of Alberta professor who uses computational methods to study car traffic, agrees with the explanation. Because rule-breakers "carve out their own path," Flynn said, they dilute large concentrations of rule-abiders moving in the same way. He pointed out an example familiar to anyone who has driven on a two-lane road: breaking the speed limit to pass a slow vehicle prevents a long chain of cars from forming.

However, there is one rule you shouldn't break, according to a new analysis of how high-volume traffic flows along a highway. Cecile Appert-Rolland, a physicist at the University of Paris-Sud, looked at the tailing distances between cars traveling on a busy two-lane expressway in the suburbs of Paris. Most people have heard of the "three-second rule" for following distances; after the car ahead of you passes a point on the road, count to three. If you pass the same object before you get to three, you're following too closely. This time-based measure of the distance between cars is what Appert-Rolland terms the "time headway."

Her research showed that tailgating drivers were more likely than a non-tailgater to have a car in the lane next to them, so they weren't just speeding up in order to change lanes. She also found that these short time headways tended to extend across several vehicles, creating a platoon.

"We can identify at least seven or eight cars where they have time headways of half a second," she said. Considering that a driver's reaction time is about one second, these platoons are disastrous pileups waiting to happen. "If the first one brakes, the second one has to brake harder, the third one even harder, and the last wouldn't be able to brake hard enough."

So while unexpected behavior may help with congestion, always follow the three-second rule—because if you're tailgating, chances are you won't be the only one.

-Lauren Schenkman

Read the rest of the post . . .

## Monday, July 27, 2009

### Physicists at TED Global Conference

The hallowed halls of Oxford University have been echoing with even more good ideas than usual lately. Last week the venerable institution hosted the 2009 TED Global Conference. A sort of variety show for the mind, the conference featured talks by innovators, thinkers, musicians, artists, architects, scientists, and even British Prime Minister Gordon Brown (warning before you click: his talk is about pretty tough stuff, and includes photos from war zones in the first few minutes.)

If you haven't heard of TED, go right to the website. There you can find videos of talks by anyone from famed primatologist Jane Goodall to engaging string theorist Brian Greene, and former UN director Louise Fresco to aspiring millennium man Ray Kurzweil. The brainchild of WIRED editor-in-chief Chris Anderson, TED stands for Technology, Entertainment, and Design. It's like a mini-YouTube for the most daring, unusual, thought-provoking ideas (and thinkers) out there. Think of it like the Harvard classics, except fast paced—each talk lasts less than twenty minutes—and in living color, often with props and not-your-average PowerPoints.

Of course, wherever great thinkers gather you will also find physicists. This year's global conference included several physicists, astronomers, mathematicians and inventors in their lineup. It's only fitting; what could be more daring, innovative, and "out there" than quantum computing or energy from plasma fusion? TED will be posting the videos on their site in the next few weeks, so I've highlighted some of the ones to look out for:

Marcus du Sautoy is an Oxford mathematician, author, and science ambassador. I like him because he writes and talks about math puzzles and ideas the way the rest of us go on and on about a favorite food. He writes a maths (yes, plural, because he's British) column for the Times called Sexy Maths, which I find to be an incredible feat in itself, though I'm bewildered as to why it appears online in the women's section next to articles about casual fashion and divorce parties.

Steven Cowley is a plasma physicist and director of the UK Atomic Energy Authority's Culham Laboratory. Forget about cold fusion; Cowley's trying to turn fusion into a source of energy, really. That means working with 150-million-degree gases. He says electricity from fusion might be only 20 years away, if we can muster the brain power and the dollars. Because my reaction is initially, "Yeah, that and every other enewable energy idea," I can't wait for his talk to go online. I'm looking forward to being convinced.

Garik Israelian is an astrophysicist and is in charge of the world's largest telescope, located on one of Spain's Canary Islands. It was inaugurated on Friday under the auspices of the king of Spain, and Israelian had to cut out early from TED in order to celebrate. His talk was about spectroscopy--how matter interacts with electromagnetic radiation. (Israelian's t-shirt in the video just linked says it all.) Astronomers peer at the universe in infrared, visible, UV, X, and gamma radiation, hunting for the signatures of different elements, our sharpest clues to what's happening millions of lightyears away.

William Kamkwamba doesn't have a Ph.D. (he's only 19, after all), but he's got all the characteristics of a great physicist--imagination, ingeniousness, and resourcefulness. He's also living proof of the aphorism, "necessity is the mother of invention." Kamkwamba, who hails from Malawi, couldn't afford to go to high school but figured out how to build a scrap-metal windmill to power his house just from looking at a few outdated physics books from the library. I'm really looking forward to seeing his talk. And great news for anyone who wants to meet him: he'll be making an appearance at Science Chicago's Labfest on August 21st!

Finally, physics was even part of the musical repertoire of the conference. Lydia Kavina, who, according to her site, "began studying the theremin at the age of 9 under the direction of her great-uncle Léon Theremin himself," performed for the conference on the world's only touch-free instrument:
The theremin-player moves his hands near two antennas. The proximity of the right hand to the vertical antenna changes the electromagnetic field thus changing the pitch of the sound over a six-octave range. Left hand controls the volume.

Read the rest of the post . . .

## Friday, July 24, 2009

### Fermi Problem Friday

Hurry back guys! Time to head to Pluto.

We recently celebrated the 40th anniversary of the Apollo 11 moon landing, we're airing a special edition of Fermi Problem Friday in honor of Buzz, Neil, and Mike (you know, Michael Collins, the guy who drew the short straw and had to stay in lunar orbit).

Here is the problem:

It took the Apollo 11 crew four days to reach the moon, blasting off from the Kennedy Space Center on July 16, 1969 and arriving at the moon on July 20. What planet would they be closest to today, about 40 years later, if they'd decided to skip the moon and head out into the solar system?
Extra credit: How many Swedish Fish would it take to form a ring around Saturn that the astronauts could see as they flew by, if they made it that far?

Share the problem with friends, try it out on your blind date tonight, and remember, all you need is your common sense, intuition, and a vague idea of how fast our intrepid crew was traveling.
Read the rest of the post . . .

## Thursday, July 23, 2009

### Electricity From Salty Water

The Mississipi delta, where the freshwater river pours into the salty Gulf of Mexico, would be an enormous source of energy if we could tap it.

A device that gleans usable energy from the mixing of salty and fresh waters has been developed by University of Milan-Bicocca physicist Doriano Brogioli. If scaled up, the technology could potentially power coastal homes, though some scientists caution that such an idea might not be realistic.

Extracting clean, fresh water from salty water requires energy. The reverse process—mixing fresh water and salty water—releases energy. Physicists began exploring the idea of extracting energy from mixing fresh and salty waters, a process known as salination, in the 1970s. They found that the energy released by the world’s freshwater rivers as they flowed into salty oceans was comparable to "each river in the world ending at its mouth in a waterfall 225 meters [739 feet] high," according to a 1974 research paper in the journal Science. But those who have chased the salination dream have collided with technological barriers.

Brogioli has developed a new approach to salination, a prototype cell that relies on two chunks of activated carbon, a porous carbon commonly used for water and air filtration. Once he jump starts the cell with electric power, all that is required to produce electricity are sources of fresh and salty water and a pump to keep the water flowing. When the separate streams of salty and fresh water mix, energy is released.

A typical cell would require about three dollars worth of activated carbon, and, given a steady flow of water, the cell could produce enough electricity to meet the needs of a small house. It's the equivalent, in hydroelectric power, of running your appliances from a personal 100 meter (338 feet) high waterfall.

Salination would be an ideal technique for places where fresh and salty waters naturally mix, such as estuaries, according to Brogioli. He said that a coastal community of about a hundred houses could set up a plant with minimal damage to the ecosystem. "A salinity difference plant will be much smaller than a solar plant," he said. The only waste product is slightly brackish water that can be poured directly into the sea or, Brogioli suggested, into ponds that support estuary-friendly flora and fauna.

Instead of using fresh water, an increasingly scarce global resource, a salinity power plant could use water that is polluted or slightly contaminated with salt, giving new life to unusable water, Brogioli said. Seawater could also be mixed with high-salinity water, obtained by evaporating seawater—perfect for a desert community with little fresh water but sunshine to spare.

"Preliminary evaluations confirm that the setup can be scaled up to very big plants suitable for powering whole cities," said Brogioli.

Scientists agree that Brogioli's concept is sound but are cautious to declare it practical on a large scale.

"I don't see any reason why it should not work," said Yury Gogotsi, director of the A.J. Drexel Nanotechnology Institute at Drexel University in Philadelphia. "Capacitor desalination has been demonstrated and commercialized, and this can be called reverse capacitance desalination. It appears to be a logical approach. Of course the challenge is the practical implementation."

George Crabtree, a senior scientist at Argonne National Laboratory in Illinois, said he likes that the device extracts the energy as immediately usable electricity. But he sees difficulties in scaling up from a lab experiment to megawatt plants that could compete with wind turbines or other clean energy sources. Crabtree thinks the water requirements might limit the technology to large river deltas, like the mouth of the Mississippi. The energy it could potentially generate, he said, "is significant ... [but] not enough to solve everyone's problems."

Fred Schlachter, a retired staff scientist at Lawrence Berkeley National Lab in California, is more skeptical. Brogioli’s experiment, says Schlachter, “only demonstrates that it works in concept on [a small] scale." He points out that salt water is very corrosive, which is one reason that renewable energy ideas for harnessing ocean tides rarely get off the ground. "Realistically I've never seen anything involving the ocean work," he said.

Brogioli maintains that his salinity cell could be ramped up faster than other salination approaches and could be made as affordable as solar power in a decade or so. He argues that any new renewable energy source is worth looking into, even if it is only a partial solution to our energy and environmental problems.

"There is no really clean energy source, and none of them can replace fossil fuels alone," he said. "So, it's a matter of compromise: find the best resource for a given region and use many different resources together."

A paper describing Brogioli’s research is due to be published in an upcoming issue of the journal Physical Review Letters.

By Lauren Schenkman

Energy, just from mixing salty water with fresh? Yes, thanks to a fundamental truth: nature likes disorder. Your coffee always seems to go cold before you can finish it, and your just-organized desk reverts to a chaos of post-it notes, random physics toys, and those half-drunk cups of coffee at an alarming rate (if you're anything like me, at least). According to thermodynamics, increasing a system's entropy, or roughly how mixed up it is, releases energy, but the ridiculousness of trying to harness the mess in your cubicle to run your computer gives you a sense of how hard it would be to grab the stuff. But Brogioli has devised an ingenious way to reap this energy windfall and turn it into a voltage gain in a capacitor.

As the above article mentions, he key ingredient in a salt-water capacitor is "activated carbon," extremely porous carbon made from wood, coal, or coconut shells. Its Swiss-cheese structure means just a gram boasts an incredible 1000 square meters of surface area. It's commonly used in water and air filtration; you've probably drunk water that was filtered by activated carbon. The large surface area also makes it an ideal material for capacitors, because the greater a capacitor's surface area, the more charge it can store.

Brogioli created a prototype salination cell with two chunks of this porous carbon submerged in salty water. The chunks are connected to a power supply, which forces negative charge to accumulate on the surface of one chunk, and positive charge to accumulate on the surface of the other. The charge also attracts the salt in the water. Salt water is a soup of free-floating ions, positively charged sodium and negatively charged chloride. Chloride ions huddle near the positive chunk, while a crowd of sodium gathers near the negative one. Then Brogioli flushes the cell; salty water pours out, fresh water rushes in, and a battle ensues. Electrostatic attraction tries to grip the ions near the carbon chunks near the carbon chunks, but diffusion tears them away. The work that diffusion does against the electrostatic force results in an increase in the capacitor's voltage, much as lifting a ball off the ground against gravity raises its potential energy. (If you know college physics, it's analogous to forcefully removing a dielectric from a capacitor you've charged and disconnected. The capacitance drops, but because C=Q/V the voltage goes up.) So the capacitor gains the energy that mixing the water releases. The capacitor can now be discharged in a current used to light a bulb or power a computer. Finally, Brogioli flushes the cell with salty water and charges the capacitor, beginning the cycle again.

Brogioli's laboratory cell, which squeezes out a mere 5 microjoules per cycle (better materials, he said, would get a payoff of 1.6 KJ per liter of fresh water) has to operate below 1 volt. Anything higher would cause redox reactions on the electrodes, allowing the salt ions to trade electrons with the carbon, and suddenly your dielectric is a watery conductor. Robert Norman, the author of the original Science article on saline-based energy devices, said he thinks this is a major hangup. Real river water and seawater, he said, might have an even lower tipping point.

Read the rest of the post . . .

## Wednesday, July 22, 2009

### Space fever!

July is the month for space nuts. We're in the midst of a wonderful hullaballoo surrounding the 40th anniversary of Apollo 11, giving the younger generation a taste of the original excitement. The Guardian, the New York Times, and almost every other major newspaper is providing tons of Apollo 11 anniversary coverage, although my favorite piece of media so far is a stunning collection of high-resolution photos from the mission, thanks to the Boston Globe's amazing photo essay collection, The Big Picture. There's something timeless about these gigantic photos; one of my favorites is the close-up shot of Neil Armstrong from an earlier mission, where he had to pilot Gemini VIII through the atmosphere and dock it to a vehicle in orbit. He looks wonderfully lost in thought, almost melancholy; my romantic brain thinks it's the expression only a man who's seen earth from space could wear.

But enough reminiscing. In July space nuts are spoiled for choice, because we've also got a real, live mission to ooh and aah over: the space shuttle Endeavor and its crew of seven finally took off last Wednesday for the International Space Station. The launch had been scrubbed four times since the first failed attempt over a month ago, due to hydrogen leaks and the Floridian weather (thunderstorms and space shuttles are not a winning combination). But the delays made the sixteen-day mission overlap with the anniversary of Apollo 11, launched from the same pad in Cape Canaveral forty years ago. Here's the story so far, with some help from the New York Times, other news sources, and NASA's mission news feed.

Although it's unlikely to cause a problem, the launch was not entirely free of hitches. The shuttle lifts off in tandem with a large external fuel tank, covered in insulating foam. During the launch, about a dozen pieces of foam broke off, and a few hit the shuttle's nose, resurrecting bad memories of the 2003 Columbia tragedy. A twenty-inch piece of foam had smacked the shuttle Columbia's left wing during launch, compromising the heat-insulation tiling and causing the craft to explode in the 3000-degree-fahrenheit inferno of reentry.

Luckily, an inspection with a laser scan and mirror showed nothing worse than a few scuff marks on Endeavor. After a day-long orbital chase, the shuttle performed a backflip as it docked with the International Space Station so ISS crew members could snap hundreds of high-res photos of the belly for analysis back at Mission Control; so far NASA is saying no damage has been done, and apparently the pitch maneouvre is standard procedure.

But like a dorm on move-in day, just as the shuttle and station crews were celebrating a record population in orbit (thirteen), the station's \$19-million-dollar toilet broke down. The shuttle crew are at the station to install a 4.1-ton outboard "porch" for space experiments (and its accompanying scientific equipment) onto Kibo, the 38-foot-long Japanese facility, a dramatic feat involving five spacewalks. But the mundane plumbing task stole the limelight from the installation of the porch, known officially as the Exposed Facility, on Sunday.

Inside Kibo

Artist's rendition of Kibo with its porch, for conducting experiments that are constantly exposed.

JAXA patches for the Kibo installation missions. The third shows the outboard porch.

The astronauts are still adding scientific equipment to the porch. Today NASA TV viewers were treated to a live feed of astronauts Dave Wolf and Chris Cassidy changing some of the batteries on the station's power channel and readying the new equipment for installation. We've got two space walks left to enjoy, so don't miss the action!

Tom Marshburn on his first spacewalk

I like to keep NASA TV on in the background and watch the intermittent space noises confuse my coworkers, but if you're looking for a way to keep up with the mission while at work that's a bit more discreet and convenient, follow mission commander Mark Polansky on Twitter. @Astro_127 has over 37,000 followers and counting.

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## Tuesday, July 21, 2009

### NASA followers gather for tweetup

With the Smithsonian (@ReliveApollo11) tweeting the 40th anniversary of the Apollo11 mission and current space shuttle mission commander Mark Polansky (@Astro_127) tweeting the crew's work on the International Space Station, no space nut these days can operate without a twitter account. Today NASA took the experiment one step further and held a tweetup. Part of the growing twitter lexicon this term refers to a real-life meetup for tweople (people on twitter, I'm led to believe). Usually this means a dozen or so people in a bar, but in the case of NASA followers, which broke 100,000 today, the auditorium at NASA headquarters did the trick today. A lucky 150 or so people flew in from as far away as Arizona, Vancouver, and even (wow!) Spain, crowded in, turned on their iPhones and laptops, and were treated to a good two hours with the crew of the STS-125 shuttle mission to make repairs to rejuvenate the Hubble space telescope.

We've come a long way since the first TV transmission from space, just 40 years ago yesterday; the entire STS-125 mission was webcast on NASA TV. Viewers watched on tenterhooks as the astronauts, equipped with cameras on their helmets, removed tiny screws from the telescope's housing and replaced batteries the size of a baby grand piano. And during it all, astronaut Mike Massimino was tweeting. The public loved it; Massimino, or @Astro_Mike as he's known on twitter, has 692,564 followers and counting. His tweets were 140-character haikus from earth orbit—funny, thoughtful, and quietly profound:

Night pass over Australia, the city lights give stunning signs of life on our planet within the darkness of nighttime
Hard to sleep last night after my spacewalk, images of the work and the views still vivid in my mind.
Eating chocolates in space, floating then in front of me then floating and eating them like I am a fish.

When the seven astronauts walked on stage in their identical blue polos, one woman shouted, "We love you, Mike!" The astronauts talked about the grueling back-to-back spacewalks they underwent to complete the repairs and how they felt when the mission was delayed in October. They played clips from the mission video and gave a sort of live "director's commentary" on scenes such as a tour of the shuttle toilet and the extra days they spent in microgravity waiting "doing astronaut tricks," as mission specialist Megan McArthur put it, while waiting for permission to head home. And they fielded questions about everything from how stars look without the atmosphere in the way (brighter, more colorful, and not twinkling, apparently) to what the crew members were like in middle school.

"My favorite subject was physical education," said mission pilot Greg Johnson. The crowd laughed. "I was always interested in math and science but I was very interested in fun."

My personal favorite question was about why fizzy drinks don't make it into space. Besides the fact that soda easily becomes foamy mass in free-fall, the simple act of burping can have a disastrous outcome, we were told.

"One of the most dangerous things to do in space is the burp reflex," said commander Scott "Scooter" Altman. "Here on earth gravity makes the liquid stay at the bottom and gas go to the top. In space, well, you have to watch out."

All in all, the astronauts were "very, very down to earth, warm, friendly, and really funny," said Kathleen Forden, a technology project manager at the University of Phoenix who'd flown in with a co-worker for the event. ("I'm an uber-geek," she explained.) "They seem like they could be their own comedy club based on a space theme."

"I feel like I'd always thought of them as being some strange remote aliens," admitted twerson Andria Schwortz (@aschwortz)with a laugh. "It was hard to think of them as humans, and then i see them up there on the stage not only as humans, but humorous. They're funny, they've got a sense of humor, they're cracking jokes at us."

Throughout the tweetup, a screen behind them showed the constant stream of tweets from the audience. (You can look through them by checking out the #Nasatweetup trending topic.)

"The experience of watching everybody tweeting and interacting with each other is also interesting, getting to see what everybody thought was cool rather just than what I thought was cool," said Schwortz, who teaches physics and astronomy at a community college in Massachusetts. She added that she'll be using twitter in the fall with her online and face-to-face classes for discussions, questions, and to facilitate study groups. She said she's part of a growing number of teachers who are using social networking tools to add an extra dimension to learning.

"One of the main uses I've heard of is people with really large lecture classrooms," Schwortz said. "They tell people to bring their laptops and follow along with the conversation. These people who couldn't ask questions in a huge lecture group can still interact with each other through twitter."

@Astro_Mike and @PhysicsCentral: Guess who's the astronaut?

Mike Massimino, who calls himself NASA's twitter "guinea pig," said putting life in space into 140 characters was "a great way to share" his experience.

"It's the greatest job in the world, but we can't take all of our friends and family with us, they just can't fit in there!" he said. "So it's nice to be able to try to share it."

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## Monday, July 20, 2009

### Where were you when we landed on the moon?

I think I'll always regret not being alive during the moon landing, forty years ago today. If the Beatles form Exhibit A in the case for me being born in the wrong decade, Apollo 11 is exhibit B. I can't remember it, so what I remember is my dad describing the moon landing as a near-psychedelic experience, forever bound to the bad classic rock song he happened to be listening to at the same time. Figures. It was 1969, and he was 21 years old, living in his parents' basement in Queens, which was lined with those slender, acid-yellow paperbacks that formed the Old and New Testaments of his childhood: Heinlein, Kornbluth, Verne, Asimov.

"I was jumping up and down in that basement cave with all the science fiction books that I'd grown up with, and it was actually happening," he recalls.

A ghostly Neil Armstrong stepping off a ladder 240,000 thousand miles away flickered on the old black-and-white, while WBAI FM simulcast Lothar and the Hand People's "Walking on the Moon." The song may not have stuck around in the collective memory, but in my dad's mind it became inextricably linked to big leaps forward.

"The first thing I did on the internet was track down that song," he says.

My mom has an entirely different take.

"I didn't see it, but I did hear it," she says. Fresh from nursing school, she on duty at a rural hospital in central America, far from Cape Canaveral, NASA, and psychedelic rock. There were no televisions in the hospital, but she and her colleagues noticed that a very strange report was coming in on the patients' radios.

"Everyone was listening and the doctor was saying, 'You know, they put a guy on the moon.' And everyone was like, 'No way, there's no way that we've done that,'" she remembers. "Everybody was skeptical that it had actually happened, until we went home, and then we saw it on TV."

But if, like me, you lack these rich memories of the original moon landing, don't miss out on the many ways you can build them. The Smithsonian National Air and Space Museum is tweeting a nearly minute-by-minute reenactment of the Apollo 11 mission, which you can follow at @ReliveApollo11; their last tweet, as of 5:03 pm EDT, was:

Armstrong: "we could not see any stars out the window" but "I'm looking at the Earth. It's big and bright and beautiful."
Just clicking on the Apollo 11 trending topic brings up a constant stream of Apollo 11-related news, facts, and musings—"'The moon's an arrant thief, And her pale fire she snatches from the sun.' -Will Shakespeare," tweets @janeaustenworld—from around the globe.

For something a bit more substantial, visit http://www.wechoosethemoon.org/, which provides a continuos audio stream of the mission, beeps and space noises included. Or visit http://kottke.org/apollo-11/ for a "live" stream of the memorable CBS coverage, cleverly framed by an old-fashioned TV set that would probably do my grandparents' basement proud. If you've missed the great "the Eagle has landed" moment less than an hour ago, when Walter Cronkite memorably took off his glasses, wiped his nose, and said, "Whew, boy," tune in tonight around 10 pm for the moon walk. (Whether you decide to listen to Lothar and the Hand People at the same time is entirely optional.)

If you're one of the hundreds of millions of people who watched the first moon walk live, please tell us about it. If you're too young, ask a parent, grandparent, or teacher to tell you their Apollo 11 story, then post it here!

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## Friday, July 17, 2009

### Crazy (in a good way)

After a month of cramming for finals and living off raw ramen noodles, there's nothing more appealing to a college student at the end of May than a long summer doing nothing, punctuated, if you're feeling really ambitious, by an occasional camping trip or jaunt to the beach.Unless you're Laurie Stephey or Brad Dinardo. In that case you might feel more up to nine weeks of performing cutting-edge scientific research.

Laurie and Brad are two of this summer's Society of Physics Students interns, a group of motivated, physics-lovin' college students who spend nine weeks every summer working on projects ranging from from locating ice under the Martian soil to developing fun hands-on science curriculum. The interns worked at NASA Goddard Space Flight Center, the University of Maryland's Materials Research Science and Engineering Center, the American Institute of Physics, and the American Physical Society. Laurie and Brad worked at the National Institutes of Standards and Technology laboratory in Gaithersburg, Maryland, exploring bendable electronics and spray-on solar cells.

"It's huge," Laurie says of NIST. "It took me six weeks to figure out they had a nuclear reactor and particle accelerator." Laurie gushes that she recently toured the lab's cleanroom—after donning a hairnet, clean suit, and booties, of course. "It was so awesome."

NIST is a smorgasbord of physics, chemistry, materials science, and astronomy research. It also boasts a team of full-time mathematicians (what? mathematicians do things?), a laboratory for analyzing pieces of the fallen World Trade Center, and a building out in a far corner of the campus with a small sign reading, "Special Projects."

"I felt like a little kid at Christmas," Laurie says of her first day. "There is just so much cool stuff."

Brad, a physics and math major, has spent the last 9 weeks exploring how you can make a photovoltaic solar cell by spraying organic molecules onto a surface. He said that that diving right into the world of organic photovoltaics was a baptism by fire...or by organic ink, as it were. "The first two weeks I was swamped and just read and read and read all the time," he says. But soon enough, he was mixing solutions in a glove box, airbrushing with semiconductor ink, and learning the mantra of the physicist: "Uh, it's not working."

"It takes forever to get things to work and when they finally do it's such a relief," says Brad, who presented his results—his spray-on solar cells did work—to a room full of Goddard and NIST researchers today. Results (with the capital R) are usually the product of months or years of research; SPS interns have just nine weeks to make a meaningful contribution to a project.

Laurie, who studied how bendable "memristors" switch states, recently graduated from college and was daunted by the huge commitments scientists make to their research. But her summer at NIST, she said, has her hooked. She wants to study oceanography, and plans to apply to the astronaut program as soon as she get's her master's degree. "When I use the glove box, I pretend I'm in space," she confides.

Working with everyone from graduate students to post-docs to salted veterans, Laurie and Brad saw first hand the dedication it takes to be a scientist, and admit it's not for everyone.

"I think all scientists have a little insanity in them, they all have that drive," said Brad, who wants to teach and do research one day as a professor. "They're all crazy—in a good way."

"The kind of crazy it takes to be in science," Laurie explained.
And the SPS interns, it seems, already have that spark of "awesome crazy," as Brad puts it. first night out among new acquaintances usually includes a trip to a bar, but rarely does it end in a heated discussion of wave functions.

"From the very first night when we went out to eat, we were talking about quantum and Schrödinger's cat," Brad recalls, laughing. "You won't get that anywhere else."

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## Thursday, July 16, 2009

### 'Invisible' Building Design Could Reduce Earthquake Damage

Engineers have been developing earthquake-resistant buildings for years, but a group of physicists now believe it's possible to make an entire building effectively disappear from an earthquake's destructive path, avoiding serious damage. Inspired by the recent development of novel materials that precisely control the flow of light waves around objects, they've shown that the same ideas can work whether the waves make up light, sound or earthquakes.

Earthquakes are some of the most destructive forces in nature. The waves they produce ripple across the earth's surface, much as water waves travel across the ocean. The waves from earthquakes crumple buildings, bridges, and other structures, causing millions of dollars in damage and often death. Despite efforts to understand earthquakes and reinforce buildings against them, damage from the shaking ground is nearly impossible to avoid. But that may not be the case for long, say a team of physicists in France and the United Kingdom.

Recently, physicists have been developing better and better invisibility cloaks, which hide an object from sight by causing incoming light waves to bend around the object, and come together behind the object. Physicists Mohamed Farhat and Stefan Enoch of the Fresnel Institute in Marseille, France, and Sebastien Guenneau of Liverpool University in England wondered if they could use the same principles to hide an object from the destructive waves produced during an earthquake. In a paper to be published this week in the journal Physical Review Letters, the three physicists show that the answer may be "yes."

Guenneau said that it's possible to shield an object, even a building, so that an incoming earthquake wave behaves as if the object weren't there. The building in the path of the wave is like a rock in a fast-flowing river, he said.

"It's the same picture, the wave pattern, as for a water wave that is propagating in a river, and it's bent smoothly around the rock and will be reconstructed around the rock." The object, or building, is "invisible" to the mechanical waves.

A series of concrete rings would surround a building or other structure, forming the shield. The shield would redirect the vibration around the object inside. "Each ring is going to wobble in such a way that the wave will bend around (the object)," Guenneau said.

Earthquake waves come in varying lengths, with many peaks and troughs in a given distance, or just a few. To effectively shield a building from short and long waves that earthquakes generate, several rings could be built around a structure, each "tuned" to a different wavelength.

A 1,000 square foot house, for example, would need a circular shield with a 33-foot radius, which could be built with commercially available concrete. Guenneau suggested that the method might be used to protect a large building like a stadium, where people could seek shelter after an earthquake and be protected by the rings from possible aftershocks.

Guenneau warned that there are some limits to what the cloak can accomplish. He and his colleagues could not find a way to shield a structure from the types of earthquake waves that travel below the earth’s surface. He noted that surface waves are typically the most destructive in an earthquake.

Jim Beck, an earthquake engineering expert at the California Institute of Technology in Pasadena, wondered if the ring would be worth building if it couldn't protect a structure from different types of shaking, not just different wavelengths. The cloak might only work perfectly in special circumstances, he said.

"It sounds like an interesting idea, but I think there's a long way to go before they get to what they would like to see done," he said.

Guenneau said he hopes that others will take the idea and explore its promising applications. Last year, Guenneau and his colleagues made headlines by building a prototype tsunami invisibility cloak that uses ring-shaped channels to redirect water waves around an object. Now they're probing that idea further in a large-scale experiment.

The reality of making buildings seem invisible to the destructive forces of nature, be they the waves from earthquakes or tsunamis, "seems a bit crazy, but it's not science fiction," Guenneau said. "We gave the people the concept, now people can try to improve it to make it more tractable."

By Lauren Schenkman
for Inside Science News Service

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## Wednesday, July 15, 2009

### "Sixty Symbols"

Whether µ, h, and l make perfect sense or are (literally) Greek to you, don't miss "Sixty Symbols", the latest in science video yumminess from the hilarious, kooky, and frequently brilliant media team at the University of Nottingham. Now that they've completed their quest to capture the essence of every element in the periodic table in a five minute video, they've decided to take on the mysterious and meaningful language of scientific symbols.

Each video is an intimate desk-side chat with a scientist, taking on concepts ranging from the fundamental, such as vectors, to the erudite, such as chaos theory's Feigenbaum constant. The style is a cocktail of home video and scientific portrait. I love that director Brady Haran keeps them short and sweet and gets interesting angles on even drier-sounding symbols like "magnetic susceptibility" (the above video features levitating beer!) Think of the series as a meandering, nonlinear journey through the world of physics. Each arcane-looking symbol is like a different door, so choose your adventure and enter!

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## Tuesday, July 14, 2009

### USA! USA! USA!

Hey there sports fans there's an international showdown going on that you might not even know about! Right now some of the brightest high school physics minds in the United States are down in Mexico matching wits against some of the brightest high school physics minds of the rest of the world. It’s the annual International Physics Olympiad! Go team go!

Ok, I got that out of my system, but the IPHO, being held this year in Merida Mexico, really is an incredible event. Each year over 65 teams representing countries from around the world vie for the gold. Instead of incredible feats of strength the participants must perform incredible feats of intellect. Through three physics problems and a lab held over the course of eight days from July 12th to the 19th, the teams will duke it out to see who goes home with the gold!

I had the privilege of meeting some of the team members and coaches in May when they were training at the University of Maryland. I was really blown away when I met them; I have never seen a big group of kids who got such a big kick out of science and discovery.

"It's really fun. It's really exciting. You're challenged a lot more than you would be in high school," said Anand Natarajan, who was selected to travel to Mexico.

Getting to the finals was no easy task for the team members. About four thousand students took the first round "F=MA" exam. From there two more tests followed, each getting tougher as they go. I've looked through some of old exams and the actual IPHO questions and they are not simple matters by any stretch.

What struck me most about the team when I visited was even though many of them had only met each other a few days earlier, how close a bond they all seemed to have. Not only were they a team, but they all really seemed like a big group of friends. When everyone ate lunch together they were relaxed and joked around like they had known each other for years and did this every day.

"They can be who they are without being self conscious about being the only kid in the room who likes physics," said Paul Stanley, their head coach.

Even though there were only five who would travel to Mexico and nineteen kids hoping to go, there was no rivalry between them for the coveted slots. Everyone was there doing what they loved to do, physics.

“I never felt that the camp was about fostering competition over the five traveling team spots,” said Marianna Mao who is currently down in Mexico, “Physics is our idea of a good time.”

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## Monday, July 13, 2009

### Manhattan's grid is a modern-day Stonehenge

{creator and copyright holderManicMaurice, image available on Flickr}

Yesterday evening, the citizens of New York City enjoyed an awesome spectacle of the sun setting exactly in line with the east-west streets of the Manhattan grid. Known as Manhattanhenge, a term coined by Hayden Planetarium's director, Neil deGrasse Tyson, the phenomenon is just like what you see at Stonehenge at the summer and winter solstices. But in New York City, the special days are May 30 and July 12. This is due to the fact that the grid, made up of streets running east to west and avenues running north-south, isn't exactly in line with the compass. It's offset 28.9 degrees east from geographic north.

As Tyson suggests, I can just imagine the archaeologists of the future trying to piece together why Manhattan's streets are aligned just the way they are. What's so important about 28.9 degrees? Were May 30 and July 12 the holy days of this lost civilization?

To save archaeologists the trouble, I decided to do my own digging, and called Joyce Gold, Manhattan history maven and NYC tour guide. Gold told me there's a really simple reason for why Manhattan's grid was drawn the way it was in the 1811 plan. The 28.9-degree tilt means the east-west streets run the shortest route across town from the Hudson River to the East River. However, Gold said, "There is at least one street laid out by a compass." That's Stuyvesant Street, which runs due east from 9th St. and 3rd Ave. to 10th St. and 2nd ave.

"A lot of people think of that as the crooked street in the East Village, but in fact it's the only straight one," Gold said.

Manhattanhenge is one of the phenomena that reminds you just how dramatically the sun's apparent journey through the sky changes over the course of the year, thanks to the 23-degree tilt to the earth's axis. But there's another way, if you're patient, to see this in action.

Photographer Justin Quinnell made this solargraph using a pinhole camera strapped to a telephone mast. The film inside the camera was exposed for six months, creating this ghostly record of half a year. With little more than a soda can, some photographic paper, and a decent helping of patience,you can create your own solargraph. (The developing process even uses a scanner and Photoshop instead of dark room chemicals, so really, no fancy photo knowledge or tools required.)

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## Friday, July 10, 2009

### The numbers are in: people like science

Yesterday the Pew Research Center for the People and the Press released an extensive study exploring how the public feels about scientists and how scientists feels about the public. (It occurs to me that the way I phrased that makes it sound like they recently went through a bad breakup.) Here are the results, in a nutshell:
Public: "Oh look, scientists! Hey, I'm a big fan. I mean, thanks for the internet and medication and stuff."
Scientists: "Um, you're welcome?"
Public: "But you know what, to be honest, I don't really understand you very well."
Scientists: "Maybe you're short-selling yourself."
Public: "No, seriously. Ask me a question."
Scientists: "Okay. Let's see...hey, here's an easy one. Which are smaller, atoms or electrons?"
Public: "Um..."
Scientists: "Sigh...Well, I suppose it's not your fault, considering the abysmal state of science education and science media in this country."
The report covers a broad range of topics, including how the public rates science's usefulness and importance, the opinions of scientists versus the general public on important science-related issues like global warming and animal testing, and how informed the public is about science. You can participate in the last bit by taking Pew's Science Knowledge Quiz. The report itself is extremely interesting and multifaceted, and definitely worth reading. On the whole, things look good for scientists; most people admire scientists, think that science benefits society, and value research as a worthy item on which to spend their taxes. Scientists, on the other hand, have a pretty low opinion of the media's science coverage—63% rate newspaper coverage of science as only fair or poor--and think the public's lack of scientific knowledge is a major problem for science. Which makes a bit of sense if you look at the results from Pew's science quiz. More than half of people answered the aforementioned atoms versus electrons question incorrectly.

Personally, I was really excited to see that the public had such a high opinion of science. I might have guessed as much from my experience working at a Department of Energy physics lab; when the lab opened its doors for a public lecture, hundreds of people turned up, oftentimes standing for an hour just to hear about black holes. Pew reports that even the majority of people who see the Bible as their textbook on evolutionary biology think science is good for humanity. But depending on what news source you read, you'll see a different slant on the results.

The Christian Science Monitor, USA Today, and the New York Times claim a "widening gap" between the opinions of scientists and the public on science:

...while almost all of the scientists surveyed accept that human beings evolved by natural processes and that human activity, chiefly the burning of fossil fuels, is causing global warming, general public is far less sure.

Almost a third of ordinary Americans say human beings have existed in their current form since the beginning of time, a view held by only 2 percent of the scientists. Only about half of the public agrees that people are behind climate change, and 11 percent does not believe there is any warming at all.

MSNBC Science Editor Alan Boyle handles the report deftly, moving on from the numbers to ask what can be done to get Scientists and the Public talking again, given that the Public really does actually like Science after all.

Rather than merely complaining about the sorry state of scientific literacy, scientists should value the communicators in their ranks - such as the late astronomer Carl Sagan, who was as comfortable in front of a camera as he was in a lab.
Meanwhile, the Knight Science Journalism Tracker (which keeps up with the biggest stories of the day, and media coverage of them. A really great resource if you see a lot of conflicting reports of the same thing) rounds up the articles and blogs, adding:
One notes that bylines tend to belong to science writers. Science writers can hope to cover science itself with a semblance of objective dispassion. But they have an inbuilt conflict of interest when the topic is the standing and penetration of science as a way to reach conclusions.
As for me, I was interested by the complaint among scientist that a lack of scientific education was really hurting society. It is a shame when a lack of resources in schools mean kids miss out on getting excited about science and acquiring at least some sense for what science does. But does having a lot of formal science education really help you understand the latest scientific research? Even people with a bachelor's degree in a subject like physics, biology, or chemistry lack the background knowledge to really understand what's being published in peer-review journals in those subjects, not to mention if you go across subjects. Scientists famously complain about coverage of their own fields, but I bet Ph.D.s in physics are glad that the latest medical news isn't written only for doctors. And in science journalism, you can only be so precise before you begin to lose your reader. It's easy to tear apart most lay versions of science research as "not quite right," but every science article can't be a crash course in physics.
So what do you think? Are you a scientist? A high school student? How much formal science education do you have? Take Pew's quiz and tell us how you did (anonymous posting is fine). Why do you think you got some questions wrong? How do you feel about science coverage in the media?

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## Thursday, July 09, 2009

### Putting old particle physics experiments out to pasture

Somewhere in the quintessentially Californian golden hills above Stanford University, a giant physics experiment is quietly rotting. "In" is the operative word here; the behemoth sits in a three-story-deep, concrete-lined hole in the ground, sheltered in a warehouse-sized structure in one of the more deserted reaches of SLAC National Accelerator Laboratory's sprawling campus. Cars and trucks still park in the lot outside, bearing scientists, construction workers, and engineers to the lab's current big project, accessible via two entrances nearby. But this particular piece of physics junk is closed for business.

A hulking steel beast seemingly overgrown with wires, this detector, known as Mark II, was once a microscope that could peer into the most fundamental building blocks of our universe. And it's only a small piece of the much larger experiment that made it happen. Although you can't see them, the two halves of a 2.2-km circular tunnel come together here. If you could turn the clock back about twenty-five years, electrons and positrons would be flying toward the Mark II from either side of the dank tunnel, coming together in a shower of exotic particles and radiation. The intricate family of detectors within Mark II watched and listened, sending data via its millions of wires to physicists who would then meticulously comb through the piles of numbers for some new clue to the universe's puzzle—the lifetime of the tau lepton? The whisper of "I'm here" from a passing selectron?

I was reminded of the Mark II moldering spectacularly in its grave when I saw today's Wired Science photo essay about the death of another old and much-beloved big physics experiment in the Bay Area, Berkeley Lab's once-futuristic Bevatron. It reminded me of how much SLAC, Berkeley, CERN and other labs are massive, physical palimpsests, continuously reinventing themselves. Although perhaps most famous as the proving ground of an incredibly audacious plan to build a two-mile-long accelerator in the early sixties, SLAC's been home to a venerable family tree of acronymic experiments, each building on the infrastructure (tunnels, buildings, technology) and innovations of the previous generation.

Mark-II enjoyed 13 years of use, though it wasn't always here in this underground lair. It started life in the Stanford Positron Electron Accelerating Ring, or SPEAR, in the heart of SLAC's campus, before it was moved* out to the suburbs. SPEAR hasn't just sat there either. It's now a synchrotron, a factory for high-intensity X-rays. It's a hive of activity where a constantly changing cast of biologists, chemists, earth scientists, physicists, and even archaeologists probe the unseen in their fields. And while SLAC's linear accelerator is no longer a powerhouse of particle physics, its new incarnation as an X-ray free-electron laser (or "Giant Laser," as I like to call it, though it's official moniker is the Linac Coherent Light Source), soon to be capable of molecular movies, shows SLAC scientists are still as daring and ambitious as they were in '61.

*"I mean MOVED, seriously," says Brad Plummer, who for the last three years has written about, snapped photos of, and filmed just about every corner of SLAC. "T
hat's a big, delicate piece of hardware to be moving around. The trailer they put it on had 180 wheels." Thanks, Brad for these gorgeous photos of the Mark II and the hilariously retro control room for the SLAC Large Detector. For more of Brad's stuff, including technolust-inspiring snaps of the Giant Laser, er, LCLS, check out his website.

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