TUESDAY, AUGUST 24, 2010


KLMNO SCIENCE NEWS THE GREEN LANTERN Can you save a tree electronically? by Brian Palmer BIGSTOCK


A mouse in its own house is not the same as a mouse on the move


The living conditions of lab mice affect their behavior,


their brains and, ultimately, the results of experiments in- volving them, according to a report from the University of Colorado Medical School published in the June issue of PLoS ONE, a journal of the Public Library of Science. “Mice communicate with each other through smell,” said Diego Restrepo, a contributing author of the report and a neuroscience professor at the medical school. When mice smell the familiar scents of their cagemates’ urine and body odors, Restrepo explained, they know they are home. Mice, according to this report, can smell the difference


between a “low-ventilated cage” that passively exchanges air and a “high-ventilated cage” that mechanically ex- changes fresh air for stale, and this scent change affects mice behaviors and neuroanatomy. Past studies had demonstrated that the degree of a


mouse’s sense of smell strongly correlates with aggressive- ness, so the Colorado researchers examined how the be- havior of their mice differed. Those in high-ventilated cag- es were more aggressive than those in low-ventilated cag- es. Stress hormone levels, sound and temperature did not vary significantly with differences in cage environment. As a final test, researchers interfered with the animals’ sense of smell. By plugging one nostril in each mouse, their neuroanatomical and behavioral disparities dis- appeared. The mice apparently could not smell the differ- ence between the high- and low-ventilated cages. Based on all this, the scientists concluded that cage scent may influence mice in ways that affect the reliability of lab-test results.


Restrepo and co-author Ernesto Salcedo developed their study after they moved their mice to a facility that supplied only high-ventilated cages. A student who had spent years collecting consistent data in the previous lab could not replicate his results in the new lab. “We can now say it was the cages,” said Salcedo. As scientists continue to use mice for research, Restrepo and Salcedo hope that others recognize that under- standing lab animals’ “ground-zero behaviors” is vital to collecting reproducible results. “Before you change the gene, before you change the be-


havior,” Salcedo said, you need to know: “How does the mouse behave in a lab cage?”


— Leslie Tamura Waning but not waxing


The moon is shrinking, scientists from Center for Earth and Planetary Studies at the Smithsonian’s National Air and Space Museum reported last week. Geological faults observed on the lunar surface indicate


that the moon’s interior has cooled and shrunk, reducing its diameter by about 330 feet over the past billion years. But given that the moon is about 2,160 miles across, it’s not the kind of change that will make moonlit nights any less romantic.


— Associated Press SCIENCE SCAN


E-readers are everywhere, even at my local library. But what about the trees? You told us about reading the newspaper online vs. getting the print edition, so now tell us about e-books. Does reading on my Kindle represent a win for the envi- ronment? Environmental analysis can be an endless balancing of this vs. that. Do you care more about con- serving water or avoiding toxic chemical usage? Minimizing car- bon dioxide emissions or radioac- tive nuclear waste? But today the Lantern has good news: There will be no Sophie’s Choice when it comes to e-books. As long as you consume a healthy number of ti- tles, you read at a normal pace and you don’t trade in your gadget every year, perusing elec- tronically will lighten your envi- ronmental impact. If the Lantern has taught you


anything, it’s that most consumer products make their biggest scar on the Earth during manufacture and transport, before they ever get into your greedy little hands. Accordingly, green-minded con- sumers are usually — although not always — better off buying fewer things when possible. Reus- able cloth diapers, for example, are better than disposables, be- cause the environmental costs of manufacture and transport out- weigh those of washing. Think of an e-reader as the cloth diaper of books. Sure, pro- ducing one Kindle is tougher on the environment than printing a single paperback copy of “Pride and Prejudice.” But every time you download and read an elec- tronic book, rather than purchas- ing a new pile of paper, you’re paying back a little bit of the car- bon dioxide and water deficit from the Kindle production proc- ess. The actual operation of an e- reader represents a small per- centage of its total environmental impact, so if you run your device into the ground, you’ll end up paying back that debt many times over. (Unless, of course, reading “Pride and Prejudice” over and over again is enough for you. Then, by all means, buy it in print and enjoy.) Let’s talk numbers. According to the environmental consulting firm Cleantech, which aggregated a series of studies, a single book generates about 7.5 kilograms (al- most 17 pounds) of carbon diox- ide equivalents. (That’s the value of all its greenhouse gas emis- sions expressed in terms of the impact of carbon dioxide.) This figure includes production, trans- port and either recycling or dis- posal.


Apple’s iPad generates 130 ki- IAN DODDS


Amy Hardie, left, with Nell Kravitz, her daughter, in Hardie’s documentary about interpreting nightmares.


NIGHTMARE SCENARIOS


Delving into the mind “THE EDGE OF DREAMING”


Scottish filmmaker Amy Hardie turns the camera on herself in the documentary “The Edge of Dreaming,” about her quest to interpret her nightmares. In one dream, her horse George tells her he’s about to fall to his left. She wakes up, goes outside and finds George lying on his left side, dead from a heart attack. “It was sort of spooky, George dying as I dreamt it, but I believe coinci- dences are random, just two things happening at the same time,” Hardie says. Then her deceased partner, Arthur, tells her in a dream that she’s going to die when she’s 48 . . . just before her 48th birthday. Hardie taps into her back- ground as a science filmmaker to explore the idea of whether our dreams are real and why we have them in the first place. Will she live to see 49? Find out Tuesday, when “The Edge of Dreaming” airs on PBS.


MATHEMATICS


A trying odyssey “THE PYTHAGOREAN THEOREM” (PROMETHEUS BOOKS, $27) The Pythagorean theorem, a2


lograms of carbon dioxide equiv- alents during its lifetime, accord- ing to company estimates. Ama- zon has not released numbers for the Kindle, but Cleantech and other analysts put it at 168 ki- lograms. Those analyses do not indicate how much additional carbon is generated per book read (as a result of the energy required to host the e-bookstore’s servers and power the screen while you read), but they do include the full cost of manufacture, which likely accounts for the lion’s share of emissions. (The iPad uses just three watts of electricity while you’re reading, far less than most light bulbs.) If we can trust those numbers, then, the iPad pays for its CO2


emissions about one-third


of the way through your 18th book. You’d need to get halfway into your 23rd book on Kindle to get out of the environmental red. So far, electronic readers — not the machines, in this case, but their owners — seem to be in a hurry to get out of that red zone. Forrester Research estimates that the average user purchases three books per month. At that rate, you could earn back your iPad’s carbon dioxide in just six months. Water is also a major consider-


+ b2 = c2 ,


is one of the best-known equations in ge- ometry and all of mathematics. Discov- ered about 2,500 years ago, it provides the foundation for trigonometry and even worms its way into architecture,


music and pop culture, such as when the scarecrow in “The Wizard of Oz” spouts an incorrect version to show that he has a brain. Alfred S. Posamentier has written more than 45 books about mathematics, such as “The Fab- ulous Fibonacci Numbers” and a “biography” of the num- ber pi. His new book promises to be “a fascinating journey through some truly amazing mathematics,” but only those with a real passion for geometry — or who hope to ignite one — should join Posamentier on his voyage. —Rachel Saslow


ation. The U.S. newspaper and book publishing industries to- gether consume 153 billion gal- lons of water annually, according to figures by the nonprofit group Green Press Initiative included in the Cleantech analysis. It takes about seven gallons to produce the average printed book, while e- publishing companies can create a digital book with less than two cups of water. (Like any other company, e-book publishers con- sume water through the paper they use and other office activ- ities.) Researchers estimate that 79 gallons of water are needed to make an e-reader. So you come out on top, water-wise, after read- ing about a dozen books. E-readers also have books beat on toxic chemicals. The produc- tion of ink for printing releases a number of volatile organic com- pounds into the atmosphere, in- cluding hexane, toluene and xy- lene, which contribute to smog


Science


E3


MICHAEL SLOAN FOR THE WASHINGTON POST The Green Lantern is a weekly


environmental column from Slate. Read previous columns at www.slate.com/greenlantern.


and asthma. Some of them may also cause cancer or birth defects. Computer production is not free of hard-to-pronounce chemicals, to be sure, but both the iPad and the Kindle comply with Europe’s RoHS standards, which ban some of the scarier chemicals that have been involved in electronics pro- duction. E-readers do, however, require the mining of nonrenew- able minerals, such as columbite- tantalite, which sometimes come from politically unstable regions.


And experts can’t seem to agree on whether we’re at risk of ex- hausting the world’s supply of lithium, the lifeblood of the e- reader’s battery. If you’re not ready to plunk down $139 for a Kindle or $499 for an iPad, or if you just love the feel of dead tree between your fin- gers, there’s one thing you can do to significantly ease the environ- mental impact of your reading: Buy your books online. Brick- and-mortar bookstores are very inefficient because they stock way more books than they can sell. Be- tween a quarter and a third of a bookstore’s volumes will ulti- mately be shipped back to the publisher and on to recycling cen- ters or landfills. An even better option is to walk to your local library, which can


spread the environmental impact of a single book over an entire community. Unfortunately, li- braries are underutilized. Studies suggest that fewer than a third of Americans visit their local library at least once a month, and fewer than half went in the last year. Li- braries report that the average community member checks out 7.4 books per year — far less than the three per month consumed on e-readers — and more than a third of those items were chil- dren’s books.


Of course, you could also stop reading altogether. But then how would you know how much car- bon you saved?


Is there an environmental quandary that’s been keeping you up at night? Send it to ask.the.lantern@gmail.com.


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