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Generations of schoolchildren have memorized the names of the nine planets. Now, a discovery by Yale astrophysicist David Rabinowitz '83 and his colleagues may force a revision of the old mnemonics. At a press conference on July 29, Rabinowitz, along with Mike Brown of Caltech and Chad Trujillo of Hawaii’s Gemini Observatory, announced that they had spotted the largest object seen orbiting the sun since the 1846 discovery of Neptune.
This new object, temporarily christened 2003UB313 (it will eventually be given a more elegant name; Rabinowitz’s team has code-named it “Xena”), is estimated to be as much as 50 percent larger than Pluto. It is the most distant object known to orbit the sun. Rabinowitz and his colleagues had already expanded our concept of the solar system enormously with the discovery last year of Sedna, a smaller object more than 8 billion miles from the sun (Findings, May/June 2004). The new object is currently almost 10 billion miles away from the sun and takes about 560 years to complete one circuit. For comparison, Pluto’s average distance from the sun is about 3.5 billion miles, and it completes an orbit in 248.5 years.
Rabinowitz, Brown, and Trujillo discovered 2003UB313 in the comprehensive photographic survey of the solar system they have undertaken with Yale’s QUEST Large Area Camera, which is attached to a Palomar Observatory telescope in California. The team actually photographed the object on October 21, 2003, but missed it in their initial analyses. Last January, a routine recheck of that night’s data picked up the object, and subsequent study established its large size.
Although the work depended considerably on automated computer software yoked to the 160-megapixel camera at the telescope’s end, Rabinowitz says that didn’t diminish the thrill of discovery. “When you first get the signal, if it’s moving very slowly and it’s bright, it’s likely to be a good detection,” he says. “It’s very exciting. We had quite a lengthy e-mail exchange, exclaiming and kind of jumping around, saying, ‘What could this be?’”
That turns out to be a tough question. The sighting of 2003UB313 complicates a long-standing debate over whether diminutive Pluto, which is somewhat smaller than the Earth’s moon, merits planetary status. “You might want to call the biggest objects in their relative positions planets,” Rabinowitz suggests, which would mean he has found the tenth. But even that could be temporary. “We may find more—by the time we’re done, maybe two or three,” he cautions. (The group also has recently found two other, somewhat smaller objects.) “Then it would be tougher, if they’re all the same size, to call them all planets.” So should Pluto be demoted? “It doesn’t really matter to us,” says Rabinowitz. “That’s a cultural question.”
For the elderly, TV is harmful to mental health
Whether or not Father Knows Best, the grandfathers in sitcoms are woefully underinformed: elders on the airwaves are mostly either laughable or missing. (Think Grampa Simpson, Martin Crane on Frasier, “Where’s the beef?”) Becca Levy, a social psychologist in the department of epidemiology and public health at the School of Medicine, says this trend may explain her finding that the more time older people have spent in front of the tube, the worse are their images of aging.
It takes more than an afternoon to make people think of themselves as doddering fools. In a study in the Journal of Social Issues in June, Levy and her colleagues measured the amount of television that 76 New Englanders, ages 60 to 92, had watched over the course of their lives. “Repetitive exposure over time to the same stereotypes,” says Levy, allows the stereotypes to “reinforce and build on each other” in the mind of the viewer. Victims of frequent TV exposure tend, more than non-TV addicts, to think of elders as grumpy, senile, helpless, or sick.
These negative stereotypes of aging can have real health effects on older individuals. In other experiments, Levy found that older people randomly assigned for as little as a day to view negative age-stereotype words such as “decrepit” tend to get more forgetful, walk more slowly, and have higher blood pressure and lower will to live than those randomly assigned to view positive words such as “wisdom.”
But the researchers are working on a vaccine. About half of the participants in their TV study kept a diary of viewing impressions for one week. The diarists were more aware of television’s skewed demographics. (Prime-time TV has less than a sixth as many seniors as the general population.) “I feel like we’re non-existent,” wrote one 68-year-old. And always playing the fool got less funny to the people keeping diaries—who also reported that they planned to cut down on their TV viewing in the future. Being conscious of ageism in entertainment, Levy says, may help people “resist the influence of those stereotypes.”
The male club-winged manakin is a tiny, nondescript South American bird that has caused ornithologists to take notice in a big way. Alone among birds, Machaeropterus deliciosus can make pure, high-pitched, violin-like tones using just its feathers.
The club-wing is the bird world’s answer to the cricket, says Rick Prum, the Yale ornithologist who became captivated by these weird “singers” on a research trip to Ecua-dor in 1987. Prum is an expert in the biology of feathers, but he couldn’t figure out how the manakins created their “tick … tick … wheeer!” mating call. (For a video, go to dsc.discovery.com/news/media/birdwings.html.)
In 1997, Kimberly Bostwick, then Prum’s graduate student, began filming manakins, and it was soon clear that the first two notes were the result of the wings smacking together like drumsticks. But the source of the “wheer” was revealed only recently, when Bostwick, now a Cornell biologist, was able to film with a high-speed digital camera that captures 1,000 frames a second. The scientists finally saw the secret: when the manakin raised its wings, it was actually rubbing together specialized feathers that work like fingers rubbed on a comb. Their “violin bird” study appeared in the July 29 issue of Science.
The secret history of CO2
No one knows precisely what’s going to happen to Earth’s climate if factories and tailpipes keep churning out carbon dioxide. Geologist Mark Pagani has taken a historian’s approach to filling this information gap, looking to the climatic past for clues about the future. His research, published in the July 22 edition of Science, provides a comprehensive look at how atmospheric carbon dioxide levels have changed between 45 million and 5 million years ago—and what happened to the climate when they did.
To assess how much of the greenhouse gas was present long ago, Pagani and his team analyzed carbon isotopes of organic molecules derived from fossil algae that were present in cores drilled from ocean-floor sediments. About 45 million years ago, carbon dioxide levels were sky-high—up to five times greater than they are today. At that time, the Earth remained largely ice-free, even in now-frigid locales such as the Arctic and Antarctica.
Over the next 15 million years or so, greenhouse gas levels gradually began to drop. In the middle of this decline phase, Earth’s climate abruptly went from hot and moist to what Pagani calls “an icehouse world.” As a result, large ice sheets formed in the Antarctic region, and there were major changes in the diversity and abundance of plants and animals. Pagani views this as evidence that extreme climatic events can be triggered even when shifts in carbon dioxide levels are less than drastic. “This was a very steady CO2 decline, not a sharp drop,” he says. “Certain thresholds may need to be crossed in order for Earth to go from one climate phase to another.”
Pagani thinks we may soon inhabit a hotter planet than we’ve seen in ages. “Carbon dioxide levels are higher now than they’ve been for 25 million years,” he says. “During other times like this, we lived in a very warm world.” Disturbances in the climatic status quo may also alter regional precipitation cycles on Earth, affecting how high sea levels rise and how much rain falls on farmers' fields. “We’re performing an experiment,” he says. “We may have to deal with unpredictable results.”
Monkeys in the marketplace
The cash economy is a relatively recent event in human history, but when a team of Yale researchers introduced capuchin monkeys to the concept, they discovered some surprising behavior. Monkeys, it turns out, can be just as irrational about money as we are.
For a study being revised for the Journal of Political Economy, management professor Keith Chen, psychology professor Laurie Santos, and research assistant Venkat Lakshminarayanan taught tufted capuchins (a South American species commonly used in behavioral experiments) how to trade tokens—in this case, metal disks—for favors or goods. Chen and Santos are the first to show that capuchins can grasp the concept of fungibility.
“The monkeys understood, kind of like humans, that a token doesn’t just represent an apple or an orange or a Jell-O cube,” says Chen, “but in fact an opportunity to consume possibly any of those things.” When the researchers introduced sticker shock into the monkeys' economy—suddenly doubling the cost of apples, for instance—they discovered that the animals changed their buying patterns quite logically, showing that humans aren’t the only ones with a knack for managing budgets.
More interesting was how the monkeys reacted to a game designed to measure whether they share the human trait of loss aversion. “Loss aversion is this basic observation that people feel losses more poignantly than they feel gains,” Chen explains. The pain of losing $5, for example, tends to be disproportionately higher than the happiness brought by winning the same amount.
“Economists hate this about humans,” Santos observes, “because it doesn’t fit their mathematical models of predicting humans based on rationality. To an economist, $5 is $5—it buys the same amount of things—so why should $5 feel less good just because yesterday you had $10?”
But experimental evidence and marketplace behavior consistently show that humans are loss-averse to an irrational degree. So are capuchins, Chen and Santos found. Given a choice between two statistically identical gambles—one in which a single apple slice brought a bonus slice half the time, and one in which two slices (for the price of one) were reduced to one half the time—the monkeys markedly preferred the former.
One measure of loss aversion is how much more strongly losses affect a person’s choices than comparable gains. When researchers look at humans who are investing their retirement stock portfolios, that number is about 2.3. For experiments in which people trade goods such as coffee mugs or pens, the number is about 2.8. When Chen and his colleagues calculated the number for capuchins, it came in at about 2.7.
“In capuchin monkeys, loss aversion is statistically indistinguishable from the loss aversion of a human stock market investor,” Chen says.
The findings suggest that some human economic behaviors may have deep evolutionary roots. In fact, primates may be hardwired to make certain types of irrational decisions: from an evolutionary perspective, loss aversion could be an adaptive trait.
In a world where survival was difficult and animals often found themselves on the brink of starvation, a small loss might have had life-or-death implications. But a small gain may simply have meant living to face the same grim calculus another day.
How to become a cactus
Pereskia is a leafy, thin-limbed tropical shrub that looks nothing like a cactus. But “looks are definitely deceiving,” says Erika J. Edwards, a graduate student in ecology and evolutionary biology. Edwards has confirmed what many researchers suspected: that distant relatives of modern-day Pereskia species represent the ancestral stock from which today’s 1,800 species of cactus evolved.
Fossil cacti are unknown, so Edwards and her colleagues compared five different DNA sequences in more than three dozen species of cacti and cactus relatives; they found many similarities to the same DNA regions in Pereskia. In the July issue of the American Journal of Botany, the team provides a cactus family tree, as well as hints about when and where the transformations that enable cacti to thrive may have taken place.
Scientists suspect that about 25 million years ago, a group of Pereskia species now found in the Caribbean and the northern part of South America branched off the evolutionary pathway that would, in time, lead to cacti. Later, a second branching took place, yielding a different line of Pereskia. Edwards’s team traced the origin of this second group to the area in South America that would become the Andes.
The Andean Pereskia species display some crucial cactus traits, the most important of which involve tiny openings called stomates. Stomates take in carbon dioxide and expel oxygen and water vapor during photosynthesis. They are typically found in the leaves, and they open during the day and close at night. Adult cacti have no leaves; photosynthesis takes place in their stems, and, to conserve water, their stomates may open only at night.
The Andean Pereskia have stomates in both leaves and stems, says Edwards: “the southern Pereskia have the beginnings of the right cactus machinery, but they’re not using it.” However, about 20 million years ago in the same Andean region, the third branch of this plant family evolved into plants recognizable as cacti.
While the Earth’s surface temperatures have shown a steady increase over the past 30 years, the lower-atmosphere temperatures measured by weather balloons have remained either steady or in slight decline. This discrepancy has buoyed global warming doubters. But geologist Steven Sherwood has a new explanation: bad data. In the August 11 online edition of Science, Sherwood and colleagues showed that when the proper correction factor was applied to daytime weather balloon readings, the temperature of the lower atmosphere also showed the signature of global warming.
Even a perfect suicide-bomber detection system may not reduce casualties. A mathematical model developed by SOM professor Edward H. Kaplan and colleagues showed that because of the “grisly physics” of a detonation, a warning followed by a sudden blast could actually result in more injuries than if no warning had taken place. In the July 19 Proceedings of the National Academy of Science, Kaplan suggested that “investment in intelligence-gathering to prevent suicide bombers before they attack seems a wiser strategy.”
Deep sea animals can’t see red. Or can they? In the July 8 Science, graduate student Casey Dunn and his colleagues upset a biological truism when they reported that jellyfish-like invertebrates called siphonophores attract prey a mile below the ocean’s surface using red fluorescent lights.
Didn’t get that job? In the June issue of Psychological Science, psychology professor Geoffrey Cohen and colleagues showed that even people who saw themselves as “objective and principled” shifted their hiring criteria to reflect “the idiosyncratic credentials of the [individual] they wanted to hire.” This kind of subtle discrimination disappeared when the interviewing process was conducted using previously established criteria.
There’s never a good time to have a heart attack, but you’ll get faster life-saving treatment in a hospital if you arrive during regular hours. In the August 17 Journal of the American Medical Association, medical school professor Harlan Krumholz and colleagues reported that at night and on weekends, patients waited on average more than 20 minutes longer for balloon angioplasties than people who arrived between 7 a.m. and 5 p.m. (There was little difference in the wait for drug therapy.) The delay was associated with a seven percent mortality-risk increase.
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