# News this Week

Science  01 Jul 2005:
Vol. 309, Issue 5731, pp. 28
1. FUSION RESEARCH

# ITER Finds a Home--With a Whopping Mortgage

1. Daniel Clery,
2. Dennis Normile*
1. With reporting by Gong Yidong of China Features in Beijing and Andrey Allakhverdov in Moscow.

After a year and a half of tense diplomacy and secret discussions, an international fusion research collaboration has finally chosen a site for the world's most expensive science experiment. Meeting in Moscow this week, ministers from China, the European Union (E.U.), Japan, Russia, South Korea, and the United States announced that Cadarache, in southern France, has been chosen as the location of the International Thermonuclear Experimental Reactor (ITER).

“I'm extremely pleased,” says Jean Jacquinot, former head of the Cadarache, fusion lab and now science adviser to France's high commissioner for atomic energy, “not because it is Cadarache, but because the whole community can now get together and build something.”

Japan, after standing firm against foreign opposition, in the end may have surrendered to internal pressure to give up its desire to be ITER's host. Observers speculate that the Ministry of Finance, seeking to rein in Japan's deficit spending, may have balked at the price tag, about $2.5 billion for the host country. In return for the withdrawal of the Japanese site, companies in Japan will get substantial E.U. procurement contracts, and European money will help build a major research center in Japan. The choice of Cadarache “is disappointing,” says plasma physicist Kenro Miyamoto, a professor emeritus at the University of Tokyo, “but it's preferable to having the project fall apart.” ITER aims to recreate the sun's power on Earth. Using intense magnetic fields to hold hydrogen isotopes at enormous temperature and pressure, it would produce a flood of energy as the isotopes fuse to form larger nuclei. Originally proposed at a U.S.-Soviet summit in 1985, the ITER design was essentially complete in 2001, but when the six partners gathered in Washington, D.C., in December 2003 to pick between two candidate sites, South Korea and the United States supported Rokkasho in northern Japan, whereas Russia and China backed the E.U.'s candidate at Cadarache (Science, 2 January 2004, p. 22). Further technical studies failed to resolve the impasse. Some Europeans accused U.S. officials of favoring Japan because, unlike France, it had supported the U.S.-led invasion of Iraq. The logjam began to move in April this year when E.U. research commissioner Janez Potocnik visited Tokyo; negotiations continued during a visit by Japanese Prime Minister Junichiro Koizumi to Luxembourg in May. The two rivals for host agreed on a deal guaranteeing certain concessions to the loser (Science, 13 May, p. 934). All that remained was for one side to back down. This week, Japan graciously removed Rokkasho from the running. As expected, the E.U. will pay for 50% of ITER's$5 billion construction price tag. The other five partners will contribute 10% each as payments in kind. As a consolation to Japan, the E.U. will place some of its industrial contracts with Japanese companies so that Japan will end up building 20% of the reactor. Japanese researchers will make up 20% of the staff of the ITER organization, and the E.U. agreed to support a Japanese candidate for director general. Some headquarters functions will also be sited in Japan, and the E.U. promised to back Japan as a host for any subsequent commercial prototype reactor.

Japan will also get to host an extra research center to speed work toward commercial fusion reactors. Japan can choose from a list, drawn up by the six partners, that features a high-energy neutron source for materials testing, a fusion technology center, a computer simulation lab, and an upgrade of Japan's existing JT-60 fusion reactor. To pay for the center, the E.U. and Japan will contribute up to $800 million more than the normal ITER budget. “Japan will serve as what you could call a quasi-host country for the ITER project,” Japan's science minister, Nariaki Nakayama, told a press conference today. “Through the [extra facility], we will become a base for international research and development in fusion energy equal in importance to the E.U.” Other partners, particularly South Korea and China, are less enamored with the deal. Luo Delong, an official with China's Ministry of Science and Technology, says that “more discussion is needed on the issues of the ITER director and the additional research facility.” European fusion researchers are delighted with the result. “Everyone is very happy,” says Alex Bradshaw, scientific director of the Max Planck Institute for Plasma Physics in Garching/Greifswald, Germany, and chair of Germany's fusion research program. But some researchers are wondering whether, considering the final deal, it wouldn't have been better to be the loser—especially because France seems to be getting the whole pie, with slim pickings for other E.U. countries. There are also worries that little will be left for fusion research supporting ITER if the European research budget shrinks (Science, 24 June, p. 1848). “It is essential to keep other activities going, or no one from Europe will be around to use ITER” in 10 years' time, says Bradshaw. For now, however, there's a palpable sense of relief after 18 months of wrangling. “I will certainly be quite happy to share a glass with my European colleagues,” says France's Jacquinot. 2. SPACE SCIENCE # Solar-Sail Enthusiasts Say Mission Lost, Possibly in Space 1. Daniel Clery Cosmos 1, a privately funded spacecraft that aimed to demonstrate solar sailing for the first time, appears never to have had a chance to unfurl its sails. But staff from the Pasadena, California-based Planetary Society, the nonprofit organization running the project, say tantalizing messages ground controllers received shortly after the craft's launch on 21 June hint that it might have made it into orbit. “We're hanging in there,” says project director Louis Friedman. “But it's an increasingly dim hope.” Officials from the Russian Space Agency (RKA), which launched the spacecraft on board a converted ICBM from a submarine in the Barents Sea, believe the rocket's first stage failed, causing launcher and payload to crash into the sea. The plan was for the Volna rocket to lift Cosmos 1 into an 825-kilometer-high orbit. There researchers would have inflated booms to spread eight solar sails made of ultralight reflective Mylar, designed to show that the pressure of sunlight could slowly push Cosmos 1 into a higher orbit. The main space agencies hope to use solar sails to reach parts of the solar system inaccessible to chemical rockets (Science, 17 June, p. 1737). An earlier demonstration by the Planetary Society, also called Cosmos 1, failed on launch in 2001. Although RKA's launch telemetry suggested a booster failure, some tracking stations along the planned orbit picked up signals that seemed to come from Cosmos 1. Researchers from Russia's Space Research Institute in Moscow continue to listen for the craft and are sending commands to turn on its transmitter. Even if Cosmos 1 did reach space, Friedman says, “it would be in a very low orbit and probably decayed quickly.” Still, Friedman says, “it would be nice to know the spacecraft worked.” Friedman says the Planetary Society is talking to the mission's main sponsor, the entertainment company Cosmos Studios, and others about mounting another attempt. “We can still advance this whole thing,” he says. But after two failed attempts, “we'll never use a Volna again.” 3. U.S. BUDGET # House 'Peer Review' Kills Two NIH Grants 1. Jocelyn Kaiser For the second year in a row, the House of Representatives has voted to cancel two federally funded psychology grants. A last-minute amendment to a spending bill would bar the National Institutes of Health (NIH) from giving any money in 2006 to the projects, one a study of marriage and the other research on visual perception in pigeons. The grants total$644,000 a year and are scheduled to run until 2008 and 2009.

The amendment was offered by Representative Randy Neugebauer (R-TX), who last year won a similar victory involving two other grants, although his efforts were later rejected in a conference with the Senate. Researchers are hoping the Senate will come to the rescue again this year.

Neugebauer says that he is correcting skewed priorities at the National Institute of Mental Health (NIMH), in particular, the institute's “fail[ure] to give a high priority to research on serious mental illnesses.” But NIH officials and scientific societies say he's meddling in a grantsmaking process that is the envy of the world. In a statement before the vote, NIH Director Elias Zerhouni called the amendment “unjustified scientific censorship which undermines the historical strength of American science.”

Some House Republicans have been scrutinizing NIH's portfolio for the last few years and in 2003 almost killed several grants studying sexual behavior. Neugebauer's concerns echo the arguments of longtime NIMH critic E. Fuller Torrey, a psychiatrist who contends that the agency should spend more on diseases such as depression and schizophrenia. Last year's vote was aimed at two NIMH psychology grants that had already ended, so the effect would have been symbolic (Science, 17 September 2004, p. 1688).

This year, the vote could have a real impact, and it came as a rude shock to the two principal investigators involved. “I'm disappointed that peer review is being undermined,” says Sandra Murray of the University at Buffalo in New York, who received $345,161 from NIMH in 2005 and is expecting an equivalent amount each year through early 2009. Murray has so far enrolled 120 newlywed couples—the target is 225—in a study of factors that contribute to stable marriage and to divorce, which, she notes, “has a huge societal cost.” Her study will also look at mental illnesses, she says. Neugebauer says funds for “research on happiness” would be better spent on new treatments for depression. The second grant, to Edward Wasserman of the University of Iowa in Iowa City, continues his 14-year investigation of visual perception and cognition in pigeons. The study, slated to receive$298,688 a year through mid-2008, sheds light on “how the human brain works” and could help develop therapies for mental and developmental disorders, Wasserman says. Neugebauer, however, questions whether it “would have any value for understanding mental illnesses.”

The American Psychological Association and the Association of American Medical Colleges were part of a coalition that tried last week to quash the amendment, sending a flurry of letters to lawmakers. Several Democrats also opposed the cancellation, with Iowa Representative James Leach warning his colleagues belatedly that setting “a precedent of political 'seers' overriding scientific peers … is a slippery slope.” The Neugebauer language passed as part of a set of amendments that were not debated on the floor, and no vote count was recorded.

Observers expect this year's effort by Neugebauer to be deleted (as was the case last year) when the House and Senate meet to reconcile differences in the two bills. Still, says NIMH Director Thomas Insel, “this is really unfortunate. It adds a congressional veto to the process of peer review.” Adds lobbyist Patrick White of the Association of American Universities, “Our community has got to wake up on this. … We have a serious problem, and it's not going away.”

4. 2006 FUNDING

# Senate Squeezes NSF's Budget

1. Jeffrey Mervis,
2. Charles Seife

It's crunch time for the National Science Foundation (NSF). Last week, a Senate spending panel voted less money for the agency than even the president's stingy request. It delivered bleak news to backers of a proposed high-energy physics experiment at Brookhaven National Laboratory in Upton, New York. And, in a last-minute reversal, the panel restricted the agency's ability to strike the best deal on the icebreaking services needed to ferry scientists into the polar regions.

These developments are part of NSF's budget for the 2006 fiscal year that begins on 1 October. In February, the White House had requested a 2.5% budget boost, to $5.6 billion, and on 16 June the House of Representatives approved an increase of 3.1%. But the Senate panel voted a mere 1% bump. The two bills must be reconciled later this summer. “We live in hope that we'll end up better than we are now. But we know it's a tough year,” says NSF Director Arden Bement. The Senate panel did single out a few programs for special attention, including adding$6 million to the $94 million plant genome program and a similar amount for the Experimental Program to Stimulate Competitive Research to bolster 25 research-poor states. It also pumped up the$47 million operating budget of the National Radio Astronomy Observatories by $4 million. The Senate took a harder line than did the House on NSF's$841 million education directorate, which the president had proposed cutting by $104 million. The House added back$70 million, while the Senate panel restored only $10 million. Of that,$4 million would go to a 4-year-old program linking universities and local school districts to improve student achievement that the president and the House want to shift to the Department of Education. It's seen as a marker for the Senate to lobby for retention of NSF's program.

6. FOUNDATIONS

# Joining Forces for Brain Tumor Research

1. Jennifer Couzin

Frustrated by the sluggish pace of brain tumor research and the often dismal prognosis for those afflicted, eight brain tumor nonprofits* in the United States and Canada are pooling up to 6 million total to finance risky, innovative research projects, potentially including mathematical modeling and studies of neural development and stem cells. The effort announced this week, called the Brain Tumor Funding Collaborative, is unusual in the disease advocacy world, where organizations in the same disease area are typically rivals competing aggressively for donations. Here, however, several foundations tentatively began discussing 2 years ago how to fuel brain tumor research. Roughly 41,000 people are diagnosed with brain tumors in the United States each year, and just under half of those tumors are malignant. “We really want to break out of the traditional mold,” says Susan Weiner, whose child died of a brain tumor. A cognitive psychologist and vice president for grants at the Children's Brain Tumor Foundation, Weiner notes that each of the eight groups had “to understand that you can't do it by yourself.” Each has pledged a certain amount (they decline to say how much) which will enable the collaborative to offer much larger individual grants—up to600,000 per year—than each typically funds. They will begin accepting initial proposals in August and hope to announce the first awards in January.

Brain cancer research is notoriously difficult, in part because the blood-brain barrier prevents easy access and because there's no good rodent model, says Susan Fitzpatrick, a neuroscientist and vice president of the McDonnell Foundation, another participant. But advances in genomics have begun to clarify brain cancer biology, leaving the collaborative hopeful that its effort, exceedingly challenging to pull together, says Fitzpatrick, will pay off.

• * The American Brain Tumor Association, the Brain Tumor Foundation of Canada, the Brain Tumor Society, the Children's Brain Tumor Foundation, the Goldhirsh Foundation, the James S. McDonnell Foundation, the National Brain Tumor Foundation, and the Sontag Foundation.

7. PUBLIC HEALTH

# Gates Foundation Picks Winners in Grand Challenges in Global Health

1. Jon Cohen
1. * The funded projects are listed and described at http://www.grandchallengesgh.org/.

In January 2003, Microsoft billionaire Bill Gates challenged scientists to think big. He asked them to identify critical problems that stand in the way of improving the health of people in developing countries, and he announced that the Bill and Melinda Gates Foundation would bankroll novel research projects aimed at solving them. Last week, after reviewing 1517 letters of intent and then inviting 445 investigators from 75 countries to submit full proposals, the foundation announced the winners: 43 projects that will receive a total of $437 million. “We all recognize that science and technology alone will not solve the health problems of the poor in the developing world,” says Richard Klausner, who runs the foundation's global health program. “What science and technology can and must do, however, is create the possibility of new vaccines, new approaches, and new cures for diseases and health conditions that for too long have been ignored.” The 5-year grants range from$579,000 to $20 million and address 14 “Grand Challenges in Global Health” that mainly focus on R&D for drugs and vaccines, controlling mosquitoes, genetically engineering improved crops, and developing new tools to gauge the health of individuals and entire populations. Grant recipients come from 33 countries—although more than half live in the United States—and include Nobel laureates and other prominent academics as well as investigators from biotechnology companies and government research institutions.* “These projects truly are on the cutting edge of science, and many of them are taking very important risks that others have shied away from,” says Elias Zerhouni, director of the U.S. National Institutes of Health in Bethesda, Maryland, who serves on the Grand Challenges board that evaluated the ideas. Klausner, who formerly ran the National Cancer Institute (NCI), said the idea for the Grand Challenges grew out of a meeting he had with Gates in the fall of 2002. Says Klausner: “He asked me an interesting question: 'When you were running NCI, did you have a war room with the 10 most critical questions, and were you monitoring the progress?'” They also discussed German mathematician David Hilbert, who in 1900 famously spelled out 23 problems that he predicted “the leading mathematical spirits of coming generations” would strive to solve. Gates announced the Grand Challenges initiative at the World Economic Forum in Davos, Switzerland, in January 2003, committing$200 million from his foundation. More than 1000 scientists suggested ideas that led the initiative's board to select 14 grand challenges (Science, 17 October 2003, p. 398). After sifting through the letters of intent and, subsequently, the full proposals, Gates decided to up the ante: The foundation contributed another $250 million;$27 million more came in from Britain's Wellcome Trust and $4.5 from the Canadian Institutes of Health Research. Researchers applying for grants had to spell out specific milestones, and they will not receive full funding unless they meet them. “We had lots of pushback from the scientific community, saying you can't have milestones,” says Klausner. “We kept saying try it, try it, try it.” Applicants also had to develop a “global access plan” that explained how poor countries could afford whatever they developed. Nobel laureate David Baltimore, who won a$13.9 million award to engineer adult stem cells that produce HIV antibodies not found naturally, was one of the scientists who pushed back. “At first, I thought it was overly bureaucratic and unnecessary,” said Baltimore, president of the California Institute of Technology in Pasadena. “But as a discipline, to make sure we knew what we were talking about, it turned out to be interesting. In no other grant do you so precisely lay out what you expect to happen.”

Other grants went to researchers who hope to create vaccines that don't require refrigeration, modify mosquitoes so they die young, and improve bananas, rice, and cassavas. In addition to HIV/AIDS, targeted diseases include malaria, dengue, tuberculosis, pertussis, and hepatitis C. Many of the projects involve far-from-sexy science. “We had this idea we were supposed to be hit by bolts of lightning,” says Klausner. “But this is about solving problems. These things aren't often gee-whiz, they're one area applied to a new area.”

Klausner says this is not a one-shot deal. “We're not being coy with people,” he says. “If they hit all their milestones and it looks spectacular, we would expect them to come back and ask for future funding.”

8. ECOLOGY

# Flying on the Edge: Bluebirds Make Use of Habitat Corridors

In many parts of the world, landscapes are turning into isolated fragments of habitat. Conservation biologists and land managers often try to link these patches via connecting strips of habitat that, in theory, give animals better access to food and mates. But testing whether, and how, these so-called corridors work has been difficult.

On page 146, a team led by ornithologist Douglas Levey of the University of Florida, Gainesville, and ecologist Nick Haddad of North Carolina State University in Raleigh describes the largest replicated, controlled study of corridor efficacy and reports that bluebirds prefer to travel along the edges of these habitat connectors. The study also shows that small-scale observations of behavior can be used to predict how animals move through larger landscapes. Such results have conservation biologists excited. “This provides a lot more confidence that corridors are working as hypothesized,” says ecologist Reed Noss of the University of Central Florida in Orlando.

The study team created eight experimental sites in the pine forests of western South Carolina to test how corridors are used. Within each, five patches of forest were cut down to make the open habitat that eastern bluebirds (Sialia sialis) prefer. The central “source” patch, 100 meters by 100 meters, was connected to another “receiver” patch by a 150-meter-long corridor. Each site also had three patches isolated from the source, at least one of which had “wings”—dead-end corridors on either side—in order to test the idea that even unlinked corridors help organisms find patches of natural habitat. “It's a very clever experiment,” comments Stuart Pimm of Duke University in Durham, North Carolina.

The middles of the source patches were planted with wax myrtle bushes, whose fruits are a major food resource for the bluebirds. For two field seasons, Levey's postdoc Joshua Tewksbury, who is now at the University of Washington, Seattle, and others tracked single birds in the source patch as they flew from the wax myrtle bushes to other perches within patches or the surrounding forest. For each hop, until the birds flew out of sight, they noted the direction and distance traveled—usually no more than 20 meters—and the resting time at each perch. The birds' movements weren't totally random; when they encountered an edge of a patch, for example, they most often flew parallel to it.

The researchers then developed a computer model in which short bird flights mimicking the observational data were stitched together to simulate a 45-minute journey—the estimated time it takes a bird to digest fruit and excrete seeds—that took a simulated bird sometimes more than 250 meters from its starting point. After tens of thousands of runs, the model predicted that birds in a source patch were 31% more likely to end up in the connected patch than in unconnected ones.

To test the model, the researchers sprayed a fluorescent solution onto wax myrtle fruit in the source patches. Each week, they checked pole-mounted flowerpots in the four surrounding patches for any bird defecations with fluorescent seeds. Although they couldn't identify what kinds of birds had deposited the seeds, bluebirds were the most common species to perch over the pots.

After analyzing 11,000 defecations, they found that seeds were 37% more likely to occur in the connected receiver patch than in the isolated ones, backing up the model prediction. Also mirroring the model, there was no significant difference in seed number between the isolated patches that had the dead-end wings and those that did not, suggesting that the birds weren't using that type of corridor to find habitat patches.

Experts caution that it's difficult to generalize these results about corridor use to other species. But the basic point that small-scale observations can reliably inform landscape design is good news for those who can't afford to run large experiments. “It is comforting to conservation planners that one of the first attempts to scale up has proven quite successful,” says Paul Beier of Northern Arizona University in Flagstaff.

The observations also provided insight into how bluebirds use corridors. Instead of flying down the middle, the bluebirds tended to stay along their edges in the pine plantations. The trees there may offer higher perches than the shrubby opening or better protection from hawks. One implication, for bluebirds at least, is that the width of a corridor or the quality of its habitat may not matter as much as that it has edges. Levey suspects that this edge effect holds true for other animals. But Beier points out that the experimental habitat differs from most corridors, which are usually strips of forest running through urban or agricultural land.

9. SCIENCE IN IRAN

# Hard-Liner's Triumph Puts Research Plans in Doubt

1. Richard Stone

TEHRAN—Shapour Etemad was stunned by the victory of Tehran's hard-line mayor Mahmoud Ahmadinejad in last week's presidential runoff election. Like many intellectuals, Etemad, director of the National Research Institute for Science Policy in Tehran, had campaigned for a moderate government, adding his name to a public endorsement of former president Hashemi Rafsanjani. After Ahmadinejad's surprise landslide victory, Etemad was left wondering if he should resign his influential post and retreat to academia.

Many Iranians were troubled by the stark choices in this election. Ahmadinejad campaigned on a promise to breathe new life into the Islamic revolution, whereas Rafsanjani pledged to seek closer ties with the United States. Although Ahmadinejad has not aired his views on science, some researchers fear that his ascendancy could result in a curtailment of foreign collaborations, an accelerated brain drain, and a shift toward more applied projects.

That's not what Iranian scientists want to hear, given the distance they've come since 1979 when the Islamic revolution closed universities for 4 years. “We were completely isolated,” says string theorist Hessamaddin Arfaei, deputy director of research at the Institute for Studies in Theoretical Physics and Mathematics in Tehran. Stagnation deepened during the protracted Iran-Iraq war in the 1980s; afterward, U.S. economic sanctions slowed the recovery.

It's only recently that Iranian science has enjoyed a widespread renaissance. The number of foreign collaborations has risen threefold in the past 4 years, says Iran's deputy minister of science, research, and technology, Reza Mansouri. “Scientific output has skyrocketed since 1993,” boasts Mohammad Javad Rasaee, dean of medical sciences at Tarbiat Modares University. Iran's share of global scientific output rose from 0.0003% in 1970 to 0.29% in 2003, with much of the growth occurring since the early 1990s, according to a study earlier this year in the journal Scientometrics. The analysis, led by immunologist Mostafa Moin of Children's Medical Center in Tehran, was based on publications tracked by the Institute for Scientific Information in Philadelphia, Pennsylvania. (Moin, a former science minister, ran as the sole reform candidate for president, placing fifth in the election's first round.)

But momentum is in danger of being lost, some observers warn. After Moin was eliminated from the race, Etemad and a few dozen colleagues wrote an editorial in East newspaper on 20 June, urging “all cultivated people” to vote for Rafsanjani and arguing that “a total catastrophe is pending and immediate.”

Others caution against rushing to judgment. Mansouri anticipates only “minor fluctuations” for Iranian scientists. The situation will become clearer, he says, when the new government, including a science minister, is appointed in early August. And some found hope in last week's offer by the board of the American Institute of Aeronautics and Astronautics to suspend a controversial ban on publications from Iran and three other countries (Science, 17 June, p. 1722); AIAA stated it will “formally reconsider” the policy on 1 September.

Ahmadinejad's predilections may become apparent when a high council for science and technology, chaired by the president, meets this fall. The council, created earlier this year, controls most of Iran's science budget. Others argue that the country's scientific community has weathered previous changes of government well. “My thinking is that we will be affected very little, if at all,” says Yousef Sobouti, director of the Institute for Advanced Studies in Basic Sciences in Zanjan. But even if some fears have been exaggerated, Etemad predicts, “we're in for a long, hard time.”

10. NANOTECHNOLOGY

# EPA Ponders Voluntary Nanotechnology Regulations

1. Robert F. Service*
1. With reporting by Amitabh Avasthi.

Last week, the U.S. Environmental Protection Agency (EPA) held its first public meeting to gauge sentiments about a proposed voluntary pilot program to collect information on new nanomaterials that companies are making. The agency got an earful.

More than 200 people gathered here at the Washington Plaza hotel to weigh in on the program, a possible precursor to guidelines that would mark the agency's first attempt to regulate nanotechnology. In a document released before the meeting, a coalition of 18 environmental and health-advocacy groups charged that a voluntary program would be inadequate to protect people from new chemical hazards. But most makers of nanomaterials applauded EPA's initial move as appropriate, because so little is known about the possible hazards of nanosized particles.

“The meeting was like the blind man feeling the elephant,” says David Rejeski. He heads a new 2-year project at the Woodrow Wilson International Center for Scholars in Washington, D.C., on managing health and environmental impacts of nanotechnology. EPA and other agencies are still sorting out the scale of the challenge they face, Rejeski says.

Nanomaterials put regulators in an unfamiliar bind. With traditional chemical toxins, any two molecules with the same chemical formula look and behave alike. Two nano-particles made of the same elements but of different sizes, however, may have drastically different chemical properties. Even particles of the same size and elemental composition can have very different properties, due to differences in their chemical architecture—for example, diamond nanocrystals and buckyballs shaped like soccer balls, both made of pure carbon. That diversity makes it a daunting task to sort out just which particles are hazardous to people and the environment and to control their production and release.

As a first step, EPA is thinking about asking nanomaterials makers to submit information on just what they are producing, how much is made, and possible worker exposure. “That's a good first step,” says Sean Murdoch, executive director of the NanoBusiness Alliance in Chicago, Illinois. But Jennifer Sass of the Natural Resources Defense Council in Washington, D.C., argues that asking companies to participate voluntarily doesn't go far enough. “It's going to be tough getting these companies to be good corporate citizens without the threat of regulation hanging over their heads,” Sass notes.

Nearly everyone agrees that far more information is needed. To get it, some groups are starting to call for increased funding for toxicity and health studies on nanoparticles. In a commentary in the 14 June Wall Street Journal, Fred Krupp, president of Environmental Defense, and Chad Holliday, chair and CEO of DuPont, argued that funding for environmental health and safety studies of nanotechnology should rise from its current level of 4% to 10% of the $1.2 billion budget of the National Nanotechnology Initiative. Rejeski argues that before a set dollar figure is agreed upon, policymakers need to decide what information they need in order to draw up nano regulations. Then, he says, they can determine how much money is needed to fill those holes. Rejeski adds that his team is currently drawing up just such an analysis and plans to release it later this summer. 11. 2006 BUDGET # Can Congress Save NASA Science? 1. Andrew Lawler In a remarkable show of bipartisan concern, U.S. lawmakers have ordered NASA not to sacrifice research programs to pay for President George W. Bush's vision of humans on the moon and eventually Mars. But at the same time, they may have compounded NASA's problems by giving a tentative green light to Bush's plans while providing little relief for an impending budget crunch in science. Last week, a Senate funding panel told NASA to spend an additional$400 million in its 2006 budget to fix the Hubble Space Telescope and bolster the flagging earth sciences effort. But the panel added only $134 million to NASA's$4 billion science budget to do so. Likewise, the House version of the spending bill, passed 2 weeks ago, is sympathetic to science but provides a relatively paltry $40 million increase over the president's request, most of which would go to saving the Glory earth science project. Reconciling the two pieces of legislation, one NASA manager says, “is sure to be difficult and confusing.” Compounding the problem are a spate of cost overruns in research projects and growing pressure to divert money to efforts like a new human space launcher to replace the space shuttle, which is due to return to flight later this month. NASA's new boss Michael Griffin has added another wrinkle: He's likely to rescue several science projects that the agency planned to cancel to save money. He recently ordered continued operation of the Tropical Rainfall Measurement Mission, which NASA sought to turn off last year in a decision that triggered a congressional outcry (Science, 13 August 2004, p. 927). NASA's efforts to win funding from the National Oceanic and Atmospheric Administration failed, so the space agency must shoulder the entire$16 million needed to keep it functioning through 2009, says NASA spokesperson Delores Beasley. Griffin is also under pressure not to turn off a host of other spacecraft, including Voyager 1 and 2, now under review for termination. Each has staunch supporters in Congress.

Griffin also recently promised senators a mission to Jupiter's moon Europa in the middle of the next decade, an effort sure to cost upward of $1 billion even with help from the European Space Agency. Congress likes the idea, and the House funding panel urged the agency to include Europa as a new start in 2007. But how that mission will fit into an increasingly strained long-term budget remains a mystery. This week, Griffin told Congress that it would be “rather dumb” to turn off Voyager 1 and 2, a cost-saving move in NASA's 2006 budget request. A team of agency officials and outside researchers, meanwhile, is working on ways to cope with a$1 billion cost overrun for the James Webb Space Telescope. That report is due later this summer. Cost increases in the Solar Dynamic Observatory and other missions that are already well into development are worrying agency managers.

The fate of space station science also hangs in the balance. A sweeping internal NASA study laying out a revamped construction schedule for the international space station is due in July. NASA officials say that they must decrease the 28 flights now planned to meet the president's 2010 deadline for halting shuttle flights. That change, they add, is certain to reduce the number of missions devoted to orbiting research equipment and experiments.

One likely victim, Griffin told Congress, is the centrifuge, once the central facility for station research. Life scientists will need to “go elsewhere,” he says. “I cannot put microbiology and fundamental life sciences higher than” the need for a new launch vehicle for astronauts.

In contrast, preserving science aboard the station is one of the goals of a bill introduced last week to reauthorize NASA programs. “Such a restriction on the range of research disciplines aboard the [space station] is not in the best interest of the nation or of our partners,” says its sponsor, Senator Kay Bailey Hutchison (R-TX). The bill calls for NASA to spend an additional $100 million on station research in the next 5 years and come up with a revamped research plan. 12. CONDENSED-MATTER PHYSICS # Flowing Crystals Flummox Physicists 1. Adrian Cho Solidified helium appears to flow without any resistance. How that happens is anything but crystal clear UNIVERSITY PARK, PENNSYLVANIA—The gizmo could be mistaken for an artifact from a science museum or a custom-made part for your old VW Beetle. An aluminum cylinder 13 millimeters wide and 5 millimeters tall sits atop a slender post of beryllium copper. From its sides, two flaps protrude like large ears on a small boy's head, and fine wires festoon the top of the can. As Eunseong Kim, a postdoc here at Pennsylvania State University (Penn State), cradles it in his palm, the device hardly looks like the heart of a breakthrough physics experiment. Yet it produced perhaps the weirdest stuff ever made. Last year, while Kim was a graduate student, he and physicist Moses Chan used the can to squeeze ultracold helium into a crystalline solid that appears to flow without resistance—like a liquid with no viscosity. For decades physicists had mused about such a bizarre “supersolid,” and others had searched for and failed to find it. So Kim and Chan's results have touched off a flurry of activity among experimenters and a debate among theorists as to whether it's even possible for a perfect crystal to flow. They are rejuvenating helium physics, a small field that has played a large role in shaping modern physics (see sidebar, p. 39). Kim and Chan had previously seen signs of such “superfluid” flow in solid helium crammed into the pores of a spongelike glass. But on 3 January 2004 they saw the first clear evidence that it could occur in a pure crystal. “That was an exciting moment,” the soft-spoken Kim recalls as he sits at his desk in the subbasement of Osmond Hall. “That morning Moses came into my lab and I said to him, 'Maybe you'll get the Nobel Prize.'” Many others agree. “If verified, the discovery of supersolid helium will be one of the most important results in solid state physics—period,” says Jason Ho, a theorist at Ohio State University in Columbus, who has come to Penn State to discuss his theory of the phenomenon. Anthony Leggett, a theorist at the University of Illinois, Urbana-Champaign, says the observations challenge the widely held belief that a well-ordered crystal cannot enter a free-flowing supersolid “phase.” “I would have bet quite strongly against such a phase,” says Leggett in a phone interview from his office. “It looks like the experiments will make me rethink that.” Kim and Chan's results must still be confirmed, however. And physicists must deduce whether the helium crystal itself is flowing, or whether the effect arises from the superfluid flow of liquid helium in cracks and crevices in the crystal—a less mind-bending alternative that wouldn't count as supersolidity. To make the call, researchers are tackling new experiments that should challenge even helium physicists, who enjoy a reputation as expert tinkerers who can squeeze every drop of information out of a thimbleful of helium. ## Letting go Prone to burst into effusive laughter, Moses Chan talks fast and forcefully. But when discussing solid helium, he chooses his words carefully. “I think it's safe to say we've done all the possible control experiments,” he says. “And though it sounds weird, I think the simplest explanation is that we see superfluidity in a solid.” It's a big claim. Chan is saying that a material structurally similar to rock salt oozes through itself unimpeded. Yet other physicists agree with his assessment of the situation. Of course, they're used to the perversity of helium. Since it was first liquefied nearly a century ago, physicists have puzzled over ultracold helium. Every other element freezes at some temperature, but unpressurized helium remains a liquid all the way down to absolute zero. Below 2.17 kelvin, however, the most common helium isotope, helium-4, undergoes a stranger transformation: It becomes a superfluid that flows without any resistance. That happens because, compared with other atoms, light and lively helium atoms act a bit less like billiard balls and a bit more like quantum waves. At low enough temperatures, many collapse into a single quantum wave that resists disturbances, in a process known as Bose-Einstein condensation. Theorists have long speculated that something similar might happen in solid helium-4, which can be made by squeezing the liquid to 25 times atmospheric pressure. In 1969, Russian theorists A. F. Andreev and I. M. Lifshitz proposed that missing atoms, or vacancies, within the helium crystal could condense to form a free-flowing fluid of their own, which would mimic the flow of atoms through the liquid. But no one had seen any sign of a flowing solid until now. To spot the stuff, Kim and Chan set their little can twisting back and forth on its shaft. The frequency of oscillation depends on the stiffness of the shaft and the inertia of the can, which in turn depends on the amount of helium stuck to it. At pressures ranging up to 145 times atmospheric pressure, the frequency began to rise suddenly as the temperature sank below about 0.2 kelvin. Those upswings indicated that as much as 1% of the helium was letting go of the oscillator and standing stock-still while the rest of the crystal twisted back and forth, as Kim and Chan reported online on 2 September 2004 in Science. That strange behavior implies that some of the helium glided through the crystal without resistance. In principle, the experiment is simple. In practice, it's a challenge, as a glimpse of the guts of one of Chan's refrigerators, or “cryostats,” suggests. The assemblage of tubes, wires, coils, and myriad handmade gadgets hangs like a mechanical stalactite from a platform supported by four great wooden legs. The whole thing stands inside a metal box the size of a small room, which Chan installed to block out radio interference from a nearby campus police station. From the tip of the stalactite hangs the oscillating can; when the can is twisting, its flaps move as little as a single atom's width. Kim and Chan measure changes in the oscillator's frequency to part-in-a-million precision. Kim and Chan performed a series of experiments that slowly built the case for supersolid helium. For example, they replaced the helium-4 with the isotope helium-3, the atoms of which cannot crowd into a single quantum state because of the way they spin. That implies solid helium-3 should not flow, which is what the experimenters observed. “Moses was very careful and asked all the questions that he could ask with the kind of apparatus he had,” says experimenter Richard Packard, from his office at the University of California, Berkeley. “And all the answers indicate that something lets go” in helium-4. But although researchers agree that the experiments are sound, they disagree on how to explain them. And no one knows whether a crystal really can flow. ## Exchange, grains, and defects Ohio State's Ho has no doubt that it can. He has come to Penn State to discuss the theory he is developing, which assumes that supersolid flow occurs and attempts to explain how swirls resembling smoke rings reduce the flow as the temperature increases. In a conference room on the third floor of Davey Hall, Ho stands beside a viewgraph projector and gestures at the screen with a length of half-inch threaded steel rod. “If it gets too complicated, then I apologize,” he says. He's been talking for 90 minutes and will go on for another hour. He's covered blackboards on two walls with equations. It seems supersolidity has no easy explanation. Theorists have already advanced several ideas, but most run afoul of the data in one way or another. For example, Andreev and Lifshitz's notion of a quantum wave of vacancies jibed nicely with the results of Kim and Chan's experiments with helium in porous glass, reported in January 2004 in Nature. It seemed plausible that, cramped by the nanometer-sized pores, the crystals would be riddled with vacancies. But this scheme appears less likely in the “bulk” crystal, as experimental evidence suggests that pure solid helium has very few vacancies. And if the vacancies are mobile, then they should quickly wander to the edge of the crystal and vanish, anyway. If vacancies don't explain the flow, then perhaps some of the helium atoms themselves undergo Bose-Einstein condensation within the crystal. Leggett and others explored that idea in the 1970s. At first it sounds absurd: In a crystal, each atom is ordinarily confined to a specific site in the three-dimensional “crystal lattice,” whereas in the quantum wave of a Bose-Einstein condensate it's impossible to say precisely where any particular atom is. But thanks to their quantum-wave nature, neighboring helium atoms have a tendency to swap places spontaneously in a process called “exchange.” If they trade places often enough, then in principle some of them may be able to collapse into a single wave and flow in a way that leaves the pristine crystal structure unsullied. In actuality, that scenario may be unlikely, however. Leggett originally calculated that the amount of free-flowing helium would be tiny. And computer simulations suggest that a perfectly orderly helium crystal does not undergo Bose-Einstein condensation, as theorists David Ceperley of the University of Illinois, Urbana-Champaign, and Bernard Bernu of Pierre and Marie Curie University in Paris, France, reported in October 2004 in Physical Review Letters. “There's been a lot of speculation that somehow you can get a flow of atoms in a solid,” Ceperley says in a phone interview. “I just don't think that's possible.” Some theorists have suggested that supersolid helium is really superslushy helium, with the flow occurring in liquid seeping between tiny bits of solid. Boris Svistunov and Nikolay Prokof'ev of the University of Massachusetts (UMass), Amherst, note that solid helium undoubtedly consists not of a single large crystal but of many smaller interlocking crystalline grains. They calculate that more conventional superfluid liquid flowing between the grains might account for Kim and Chan's data, as they reported this April in Physical Review Letters. But that explanation would require a multitude of micrometer-sized grains, whereas data indicate that helium tends to form fewer, larger grains. The secret to supersolidity could lie in the conceptual middle ground between a flowing crystal and liquid flowing between crystal grains, says theorist Burkhard Militzer from his office at the Carnegie Institution of Washington, D.C. The flow could occur within the crystal, he speculates, but along elongated, immobile defects called “stacking faults,” which resemble missed stitches in a piece of fabric. Simulations show that atoms swap places easily along the faults, Militzer says, but they do not yet prove that such faults account for Chan's observations. ## More data, please To sort things out, physicists are planning a variety of experiments designed to confirm the observation—and to explain why others had failed to spot the effect before. In 1981, researchers from Cornell University in Ithaca, New York, and Bell Telephone Laboratories in Murray Hill, New Jersey, saw no evidence for supersolidity in torsional oscillator experiments similar to Chan's. But the researchers may have been foiled by bad luck and a bit of helium-3. The experiment most comparable to Chan's was contaminated with several parts per million of helium-3, says Cornell's John Reppy in a phone interview. “That would have been enough to wipe out the signal, according to Moses's [data],” he says. “I'm willing to believe it.” Reppy and colleagues at Cornell are running yet another torsional oscillator experiment to try to reproduce the effect. Others have searched for supersolidity by trying to squeeze solid helium through tiny holes. If the crystal is free-flowing then it might seep through, just as superfluid liquid helium will flow through openings so small they stop ordinary liquid helium dead. But the fact that solid helium cannot perform this trick may mean only that supersolid and superfluid helium respond to pressure differently, says John Beamish, an experimenter at the University of Alberta in Edmonton, Canada: “If it is a supersolid—and we're not saying it isn't—it doesn't flow as you would naively expect.” Curiously, over the past decade, experimenters studying the propagation of sound and heat in solid helium did see signs of a “phase transition.” But they interpreted them very differently. John Goodkind and colleagues at the University of California, San Diego, found that the speed of sound in solid helium increases suddenly as the temperature drops below 0.2 kelvin, and the rate at which the waves die away peaks at that temperature. Goodkind interpreted these and other signs as evidence that some sort of defect proliferates as the temperature of the crystal increases and that these “defectons” undergo Bose-Einstein condensation above a critical temperature. Goodkind hopes to resume his experiments, and Haruo Kojima, a physicist at Rutgers University in Piscataway, New Jersey, has begun sound experiments of his own. If supersolidity exists, then it should be possible to generate a sound wave in which only the free-flowing helium moves, explains Kojima, who has come to Penn State to discuss the experiments with Chan. But the experiments may be tricky, he warns, because researchers aren't sure precisely what signals they should expect to see. For his part, Chan is devising an elaborate experiment to determine just how many vacancies, grain boundaries, and defects exist in a helium crystal. He plans to run a torsional oscillator in the beamline of a synchrotron x-ray source and to alternately shake the crystal and shine x-rays through it. The sloshing of the oscillator will tell how many atoms are in the crystal, while the scattered x-rays will reveal how many lattice sites there are in it. Only if the crystal is perfect will the two numbers be equal. The experiment may be the key to cutting through the confusion, says UMass's Svistunov in a phone interview: “To answer, how perfect is the crystal? In my opinion, that is the most important question in the field.” Meanwhile, in the sunless subbasement of Osmond Hall, Chan's young colleagues continue their work. Kim is taking data with a bigger oscillator that twists at lower frequencies. Graduate student Anthony Clark is studying solid hydrogen. In March, at the American Physical Society meeting in Los Angeles, California, Clark presented preliminary data that suggest hydrogen may also become a supersolid (Science, 8 April, p. 190). “I want to be completely confident,” Clark says, “and we've been doing a lot of control experiments.” Both Kim and Clark say they feel intense pressure working on such potentially groundbreaking experiments. Chan takes the hubbub in stride, however. “Nobel Prize or no Nobel Prize, that doesn't matter. What's really nice is that [our work] has attracted so much attention” from other researchers, he says. “We have already had more fun than we deserve.” He smiles wryly, like a magician who has pulled off a particularly clever trick. Only this time, not even the conjurer knows precisely how the trick works. 13. CONDENSED-MATTER PHYSICS # The Quirks and Culture of Helium 1. Adrian Cho Ordinarily an inert gas so light it floats off into space, helium might seem to hold little interest for condensed-matter physicists. But since it was liquefied by Dutch physicist Heike Kamerlingh Onnes in 1908, the odd stuff has revealed much about the physics of liquids and solids. “Throughout history, it has provided a variety of new paradigms,” says Jason Ho, a theorist at Ohio State University in Columbus. Since 1938, physicists have known that below 2.17 kelvin the most common isotope of helium, helium-4, becomes a “superfluid” that flows without resistance, as about 9% of the atoms crowd into a single quantum wave. In 1972, physicists discovered that helium-3 also becomes a superfluid at just a few thousandths of a kelvin. Because of the way they spin, helium-3 atoms cannot pile into a single quantum wave. Instead, they form pairs that glide without resistance, as electrons do in superconductors. Experiments with helium-3 validated much of the “Fermi liquid theory” that also describes electrons in metals. The superfluid transition in helium-4 provided the primary test bed for the theory of “second-order phase transitions,” which describes, for example, the onset of magnetism in materials. While helium has helped theorists develop key concepts, experimenters working with ultracold helium have developed a reputation for old-fashioned ingenuity. Their experimental devices are usually mechanical contraptions that shake, spin, and squeeze helium to produce subtle but telling signals. By tradition, “you don't buy your instrumentation; you invent it,” says John Goodkind, an experimenter at the University of California, San Diego. “You make it, you leak-check it, and you fix it.” Helium physicists are also known for seat-of-the-pants problem solving, slathering their refrigerators with soap and glycerin to plug elusive leaks so small only superfluid helium squeezes through, or using a condom to regulate the flow of gas. Never very big, the field of helium physics has contracted since its heyday in the 1970s. But researchers trained in helium physics have become leaders in high-temperature superconductivity, nanomechanical devices, two-dimensional electron systems, and other areas. “The people in the field are willing to take risks,” says Richard Packard, an experimenter at the University of California, Berkeley. “They aren't afraid of making new devices, and when they go out into other fields, that same state of mind goes with them.” 14. CLIMATE CHANGE # Atlantic Climate Pacemaker for Millennia Past, Decades Hence? 1. Richard A. Kerr An unsteady ocean conveyor delivering heat to the far North Atlantic has been abetting everything from rising temperatures to surging hurricanes, but look for a turnaround soon Benjamin Franklin knew about the warm Gulf Stream that flows north and east off the North American coast, ferrying more than a petawatt of heating power to the chilly far North Atlantic. But he could have had little inkling of the role that this ponderous ocean circulation has had in the climatic vicissitudes of the greater Atlantic region and even the globe. With a longer view of climate history and long-running climate models, today's researchers are tying decades-long oscillations in the Gulf Stream and the rest of the ocean conveyor to long-recognized fluctuations in Atlantic sea-surface temperatures. These fluctuations, in turn, seem to have helped drive the recent revival of Atlantic hurricanes, the drying of the Sahel in the 1970s and '80s, and the global warming of the past few decades, among other climate trends. The ocean conveyor “is an important source of climate variability,” says meteorologist James Hurrell of the National Center for Atmospheric Research in Boulder, Colorado. “There's increasing evidence of the important role oceans have played in climate change.” And there are growing signs that the conveyor may well begin to slow on its own within a decade or two, temporarily cooling the Atlantic and possibly reversing many recent climate effects. Greenhouse warming will prevail globally in both the short and long terms, but sorting out just what the coming decades of climate change will be like in your neighborhood could be a daunting challenge. Researchers agree that the North Atlantic climate machine has been revving up and down lately (Science, 16 June 2000, p. 1984). From recorded temperatures and climate proxies such as tree rings, researchers could see that temperatures around the North Atlantic had risen and fallen in a roughly 60- to 80-year cycle over the past few centuries. This climate variability was dubbed the Atlantic Multidecadal Oscillation (AMO). Ocean observations suggested that a weakening of the ocean conveyor could have cooled the Atlantic region and even the entire Northern Hemisphere in the 1950s and '60s, and a subsequent strengthening could have helped warm it in the 1980s and '90s. But the records were too short to prove that the AMO is a permanent fixture of the climate system or that variations in the conveyor drive the AMO. Taking the long view, climate modeler Jeff Knight of the Hadley Centre for Climate Prediction and Research in Exeter, U.K., and colleagues analyzed a 1400-year-long simulation on the Hadley Centre's HadCM3 model, one of the world's leading climate models. The simulations included no changes in climate drivers such as greenhouse gases that could force climate change. Any changes that appeared had to represent natural variations of the model's climate system. At April's meeting of the European Geosciences Union in Vienna, Austria, Knight and colleagues reported that the Hadley Centre model produces a rather realistic AMO with a period of 70 to 120 years. And the model AMO persists throughout the 1400-year run, they note, suggesting that the real-world AMO goes back much further than the past century of observations does. The model AMO also tends to be in step with oscillations in the strength of the model's conveyor flow, implying that real-world conveyor variability does indeed drive the AMO. Such strong similarities between a model and reality “suggest to me it's quite likely” that the actual Atlantic Ocean works much the same way as the model's does, says climate modeler Peter Stott of the Hadley Centre unit in Reading, who did not participate in the analysis. Hadley model simulations also support the AMO's involvement in prominent regional climate events, such as recurrent drought in North East Brazil and in the Sahel region of northern Africa, as well as variations in the formation of tropical Atlantic hurricanes, including the resurgence of such hurricanes in the 1990s. On page 115, climate modelers Rowan Sutton and Daniel Hodson of the University of Reading, U.K., report that they could simulate the way relatively warm, dry summers in the central United States in the 1930s through the 1960s became cooler and wetter in the 1960s through 1980s. All that was needed was to insert the AMO pattern of sea-surface temperature into the Hadley atmospheric model. That implies that the AMO contributed to the multidecadal seesawing of summertime climate in the region. If the Hadley model's AMO works as well as it seems to, Knight and his colleagues argue, it should serve as some guide to the future. For example, if North Atlantic temperatures track the conveyor's flow as well in the real world as they do in the model, then the conveyor has been accelerating during the past 35 years—not beginning to slow, as some signs had hinted (Science, 16 April 2004, p. 371). That acceleration could account for about 10% to 25% of the global warming seen since the mid-1970s, they calculate, meaning that rising greenhouse gases haven't been warming the world quite as fast as was thought. Judging by the 1400-year simulation's AMO, Knight and colleagues predict that the conveyor will begin to slow within a decade or so. Subsequent slowing would offset—although only temporarily—a “fairly small fraction” of the greenhouse warming expected in the Northern Hemisphere in the next 30 years. Likewise, Sutton and Hodson predict more drought-prone summers in the central United States in the next few decades. But don't bet on any of this just yet. The AMO “is not as regular as clockwork,” says Knight; it's quasi-periodic, not strictly periodic. And no one knows what effect the strengthening greenhouse might have on the AMO, adds Sutton. Most helpful would be an understanding of the AMO's ultimate pacemaker. In the Hadley Centre model, report modelers Michael Vellinga and Peili Wu of the Hadley Centre in Exeter in the December Journal of Climate, the pulsations of the conveyor are timed by the slow wheeling of water around the North Atlantic. It takes about 50 years for fresher-than-normal water created in the tropics by the strengthened conveyor to reach the far north. There, the fresher waters, being less dense, are less inclined to sink and slide back south. The sinking—and therefore the conveyor—slows down, cooling the North Atlantic and reversing the cycle. That may be how the Hadley AMO works, says oceanographer Jochem Marotzke of the Max Planck Institute for Meteorology in Hamburg, Germany, but it doesn't settle the mechanism question. How a model generates multidecadal Atlantic variability “seems to be dependent on the model you choose,” he says. Before even tentative forecasts of future AMO behavior are taken seriously, other leading models will have to weigh in, too. 15. ASTRONOMY # Suitcase-Sized Space Telescope Fills a Big Stellar Niche 1. Andrew Fazekas* 1. Andrew Fazekas is a freelance writer in Montreal, Quebec. Small but single-minded, Canada's MOST microsatellite is revealing the inner clockwork of stars and characterizing exoplanetary systems MONTREAL, CANADA—To astronomers, bigger telescopes usually mean better telescopes. But a Canadian space-based instrument is bucking that trend. Just 2 years into monitoring subtle periodic dips in starlight, the suitcase-sized MOST (Microvariability and Oscillations of Stars) telescope is probing the hidden internal structures of sunlike stars and pinning their ages down to a greater precision than ever before. At a meeting here,* astronomers announced that MOST has also begun to provide information about the planets that orbit some of those stars, even hinting at their weather patterns. “Not bad for a space telescope with a mirror the size of a pie plate and a price tag of$10 million Canadian, eh?” says astronomer Jaymie Matthews of the University of British Columbia.

MOST blasted into space aboard a converted Russian intercontinental ballistic missile on 30 June 2003. Nicknamed “the Humble Space Telescope,” Canada's first space observatory is also the world's smallest, weighing in at only 60 kg and sporting a modest 15-cm mirror. Designed and built for less than 1/20 of the projected cost of any upcoming competing mission, the single-purpose satellite does without most of the instruments found on its larger space-based cousins but still conducts science no other orbiting observatory is equipped to do.

Above the blurring effect of our atmosphere, MOST's ultraprecise photometer can detect fluctuations in stellar brightness as small as one part in a million—10 times better than ground-based telescopes can achieve. Thanks to a specially designed gyroscope, the Canadian Space Agency-run microsatellite can stare at a star around the clock for up to 2 months. The Hubble Space Telescope, by contrast, can look at a given object for only about 6 days. “MOST is pushing frontiers in stellar astronomy in terms of time sampling and light-measuring precision,” Matthews says. “While this may seem more abstract than what Hubble can do, it is just as revolutionary in terms of what this tiny telescope allows us to see in stars and their planets.”

Using methods of asteroseismology—the study of starquakes—MOST monitors optical pulsations caused by vibrations of sound waves coursing through a stars' deep interior. Just as geologists can map Earth's interior from earthquake signals, astronomers can probe a star's hidden structure by tracking minute oscillations in its luminosity. As the star contracts, its internal pressure increases, heating its gases and temporarily increasing its brightness. The MOST team hopes the technique will lead to better theories about how stars evolve with age.

“Most of the research is being done on sunlike stars, because we know how to interpret the data using our sun as a model,” says starquake hunter Jørgen Christensen-Dalsgaard of the University of Aarhus in Denmark. According to astrophysical models, stars between 80% and 170% as massive as the sun pass through the same basic life cycles as the sun does and should show similar upper atmosphere turbulence and micro-magnitude oscillations. But whereas short, subtle changes in brightness are relatively easy to detect on the sun, they are much trickier to spot in more-distant sunlike stars.

Not until 2000 did ground-based telescopes become sensitive enough to confirm them in a few dozen solar-type stars. Those observations used spectroscopes to detect shifts in the color of light, from which astronomers could calculate the radial velocity of the stellar surface as it moves up and down. Now MOST—which makes it possible to draw similar inferences from much smaller changes in brightness—is opening a new chapter in the field, says astronomer Travis Metcalfe of the High Altitude Observatory in Boulder, Colorado: “This modest instrument is bound to have a great impact on our understanding of stellar evolution.”

In July 2004—a year into its observations—MOST's science team, led by Matthews, generated their own waves in the asteroseismology community when they published their observations on the well-studied star Procyon. To the shock of everyone, the satellite found that Procyon showed none of the oscillations that ground-based measurements had seen and theoretical models had predicted for nearly 20 years. “We had 32 continuous days of data representing over a quarter of a million individual measurements and saw nothing,” says Matthews.

Asteroseismologists around the world are still puzzling over those observations. Christensen-Dalsgaard, a member of one of the first teams to detect Procyon's oscillations from the ground and biggest critic of MOST's Procyon results, suspects that either light scattered back from Earth into the telescope washed out the data, or “noisier”-than-expected convection in the star's atmosphere made the oscillations unreadable. The possibility of using MOST to study stars' atmospheric churning “is, of course, itself interesting,” he adds. The MOST team revisited Procyon this year and plans to publish an analysis of the new measurements within a few months.

Things went more smoothly this year, when MOST fixed its gaze on Eta Bootis. This time the data matched both stellar models and earlier ground-based observations. By comparing the data against a library of over 300,000 theoretical stellar models, Matthews and his team have pegged the star's age at 2.4 billion years, plus or minus 30 million years—about 10 times the precision of previous estimates. Studying a variety of sunlike stars with differences in mass, age, and composition will lead to better models, Christensen-Dalsgaard says.

As a bonus, MOST's ability to measure exquisitely small variations in starlight enables it to double as an exoplanet explorer. At the meeting, the MOST team announced that the telescope had staked out an alien world around a far-off star and turned up subtle hints of an atmosphere and possible cloud cover. NASA's Spitzer Space Telescope had detected the infrared glow from exoplanet HD209458b in March. MOST tracked the subtle dip in optical brightness as the planet slipped behind its parent star during its orbit.

By following the frequencies and amplitudes of the changes in stellar brightness, the team concluded that the planet is a gas giant 1.2 times as massive as Jupiter, parked less than 1/20 as far from its star as Earth is from the sun. Astronomers think HD209458b's low reflectance (less than 40%, compared with 50% for Jupiter) sets limits on the planet's atmosphere, in which the Hubble Space Telescope saw signs of carbon and oxygen in 2004. MOST will conduct a 45-day survey of the system later this summer with the hope of getting a clearer picture of the exoplanet's atmosphere and even its weather: temperature, pressure, and cloud cover.

MOST's asteroseismological monopoly is destined to be short-lived. Similar satellites on the horizon include the European COROT (Convection, Rotation, and planetary Transits) mission, slated for launch in June 2006, and NASA's own planet seeker, Kepler, due in 2007. Unlike MOST, both satellites will be technologically capable of detecting Earth-size worlds. COROT's more sensitive detector will also be able to look at many stars simultaneously, rather than one at a time, as MOST does. But COROT and Kepler will focus on fainter stars than MOST observes, and their vision will be limited to smaller sections of the sky, Metcalfe says. As a result, he argues, during the tail end of its 5-year life span, MOST will complement the other missions and will not become obsolete when they come on line.

Christensen-Dalsgaard agrees. “MOST is giving us the experience that we need to learn how stars behave photometrically and helps us learn how to choose targets for these later missions,” he says. “So in the next couple of years, we need to make the most out of MOST.”

• * CASCA 2005, Montreal, Quebec, 15-17 May.

16. CENTRAL ASIA

# Combating Radioactive Risks and Isolation in Tajikistan

1. Richard Stone

The science academy of this war-weary country is reaching out for help in tracking down lost radioactive sources—and restoring scientific vitality

FAIZABAD, TAJIKISTAN—In the early 1990s, as civil war raged in this mountainous land, a terrorist's prize was here for the taking. Powerful radioactive sources lay buried in an open-air, gravel-covered pit on a compound ringed by a dilapidated concrete wall and chain-link fence. During the 5-year war, villagers and fighters pillaged nearby apple orchards and industrial sites. But the makings of dirty bombs—including radioisotopes such as cesium, cobalt, and americium in old Soviet gauges and other devices—remained untouched. “We were lucky,” says Gennady Krivopuskov, manager of the 6-hectare waste storage facility 50 kilometers northeast of the capital, Dushanbe. “Maybe the radiation hazard signs kept looters away.”

How long the rad cops' luck will last is an open question. One or two derelict radioactive generators, which produce electricity from the heat harnessed from the decay of strontium-90, were never moved to this storage facility and remain unaccounted for, experts say. Each radioisotope thermoelectric generator (RTG) packs a whopping 40,000 curies—equivalent to the radioactivity from strontium-90 released during the 1986 Chornobyl explosion and fire. “How serious is it that they aren't secured? Well, that depends on who has them,” says a Western diplomat. Last month, a U.S. Department of Energy (DOE) team was in Dushanbe to train specialists at the Nuclear and Radiation Safety Agency of the Academy of Sciences of the Republic of Tajikistan (AST) on how to detect abandoned sources. Search efforts are about to get under way.

Concern about RTGs as a serious proliferation threat first got attention 3 years ago, when the International Atomic Energy Agency (IAEA) in Vienna helped secure a pair of abandoned generators in the Republic of Georgia (Science, 1 February 2002, p. 777). IAEA has since learned that more than 1000 such generators were produced in the Soviet Union; the vast majority stayed in Russia, where they were used primarily to power Arctic lighthouses. But in recent years scores have gone astray or been vandalized for scrap metal. In Tajikistan, where the generators were used to power remote weather stations, four RTGs have been recovered and are awaiting transfer to Russia for disposal, says Ulmas Mirsaidov, director of the radiation safety agency. Although Mirsaidov told Science that all RTGs in Tajikistan are now secured, DOE officials and a Western diplomat in Dushanbe say that units are missing; one or two is the best estimate based on present information.

Tajikistan's radiation agency is now working with IAEA to compile an inventory of radiological sources. “We're helping them make sense of their records and develop a search plan,” says Carolyn MacKenzie, a radiation source specialist with IAEA. There's no indication that any RTGs have fallen into the wrong hands. Still, there's a disconcerting lack of knowledge about where precisely to look. “When the Soviets left, the records weren't passed on,” MacKenzie says. “We don't have definite information,” adds Roman Khan, a health physicist at Argonne National Laboratory in Illinois. DOE's Search and Secure Program, Khan says, has provided Mirsaidov's agency with a suite of instruments—including a portable radiometer capable of detecting alpha and beta particles and gamma rays, a hand-held gamma ray spectrometer, and a broad energy germanium detector—for tracking down orphan sources.

The hope is that the loose RTGs can be located and stored as soon as possible at the Faizabad facility, a hilly territory alive with discus-sized tortoises, a cacophony of sparrows, and a riot of bright-red poppies. A short walk up the road, through an inner fence patrolled by a machine gun-toting guard, is a whitewashed building with a massive gray steel door. Buried here, 9 meters beneath the dirt floor, are a variety of radioactive sources, including x-ray fluorescence instruments containing americium-241 that were used for geological surveys, radiotherapy canisters filled with cobalt-60, and four RTGs recovered so far.

31. # How and Where Did Life on Earth Arise?

1. Carl Zimmer*
1. Carl Zimmer is the author of Soul Made Flesh: The Discovery of the Brain—and How it Changed the World.

For the past 50 years, scientists have attacked the question of how life began in a pincer movement. Some approach it from the present, moving backward in time from life today to its simpler ancestors. Others march forward from the formation of Earth 4.55 billion years ago, exploring how lifeless chemicals might have become organized into living matter.

Working backward, paleontologists have found fossils of microbes dating back at least 3.4 billion years. Chemical analysis of even older rocks suggests that photosynthetic organisms were already well established on Earth by 3.7 billion years ago. Researchers suspect that the organisms that left these traces shared the same basic traits found in all life today. All free-living organisms encode genetic information in DNA and catalyze chemical reactions using proteins. Because DNA and proteins depend so intimately on each other for their survival, it's hard to imagine one of them having evolved first. But it's just as implausible for them to have emerged simultaneously out of a prebiotic soup.

Experiments now suggest that earlier forms of life could have been based on a third kind of molecule found in today's organisms: RNA. Once considered nothing more than a cellular courier, RNA turns out to be astonishingly versatile, not only encoding genetic information but also acting like a protein. Some RNA molecules switch genes on and off, for example, whereas others bind to proteins and other molecules. Laboratory experiments suggest that RNA could have replicated itself and carried out the other functions required to keep a primitive cell alive.

Only after life passed through this “RNA world,” many scientists now agree, did it take on a more familiar cast. Proteins are thousands of times more efficient as a catalyst than RNA is, and so once they emerged they would have been favored by natural selection. Likewise, genetic information can be replicated from DNA with far fewer errors than it can from RNA.

Other scientists have focused their efforts on figuring out how the lifeless chemistry of a prebiotic Earth could have given rise to an RNA world. In 1953, working at the University of Chicago, Stanley Miller and Harold Urey demonstrated that experiments could shed light on this question. They ran an electric current through a mix of ammonia, methane, and other gases believed at the time to have been present on early Earth. They found that they could produce amino acids and other important building blocks of life.

Today, many scientists argue that the early atmosphere was dominated by other gases, such as carbon dioxide. But experiments in recent years have shown that under these conditions, many building blocks of life can be formed. In addition, comets and meteorites may have delivered organic compounds from space.

Just where on Earth these building blocks came together as primitive life forms is a subject of debate. Starting in the 1980s, many scientists argued that life got its start in the scalding, mineral-rich waters streaming out of deep-sea hydrothermal vents. Evidence for a hot start included studies on the tree of life, which suggested that the most primitive species of microbes alive today thrive in hot water. But the hot-start hypothesis has cooled off a bit. Recent studies suggest that heat-loving microbes are not living fossils. Instead, they may have descended from less hardy species and evolved new defenses against heat. Some skeptics also wonder how delicate RNA molecules could have survived in boiling water. No single strong hypothesis has taken the hot start's place, however, although suggestions include tidal pools or oceans covered by glaciers.

Research projects now under way may shed more light on how life began. Scientists are running experiments in which RNA-based cells may be able to reproduce and evolve. NASA and the European Space Agency have launched probes that will visit comets, narrowing down the possible ingredients that might have been showered on early Earth.

Most exciting of all is the possibility of finding signs of life on Mars. Recent missions to Mars have provided strong evidence that shallow seas of liquid water once existed on the Red Planet—suggesting that Mars might once have been hospitable to life. Future Mars missions will look for signs of life hiding in under-ground refuges, or fossils of extinct creatures. If life does turn up, the discovery could mean that life arose independently on both planets—suggesting that it is common in the universe—or that it arose on one planet and spread to the other. Perhaps martian microbes were carried to Earth on a meteorite 4 billion years ago, infecting our sterile planet.

32. # What Determines Species Diversity?

1. Elizabeth Pennisi

Countless species of plants, animals, and microbes fill every crack and crevice on land and in the sea. They make the world go 'round, converting sunlight to energy that fuels the rest of life, cycling carbon and nitrogen between inorganic and organic forms, and modifying the landscape.

In some places and some groups, hundreds of species exist, whereas in others, very few have evolved; the tropics, for example, are a complex paradise compared to higher latitudes. Biologists are striving to understand why. The interplay between environment and living organisms and between the organisms themselves play key roles in encouraging or discouraging diversity, as do human disturbances, predator-prey relationships, and other food web connections. But exactly how these and other forces work together to shape diversity is largely a mystery.

The challenge is daunting. Baseline data are poor, for example: We don't yet know how many plant and animal species there are on Earth, and researchers can't even begin to predict the numbers and kinds of organisms that make up the microbial world. Researchers probing the evolution of, and limits to, diversity also lack a standardized time scale because evolution takes place over periods lasting from days to millions of years. Moreover, there can be almost as much variation within a species as between two closely related ones. Nor is it clear what genetic changes will result in a new species and what their true influence on speciation is.

Understanding what shapes diversity will require a major interdisciplinary effort, involving paleontological interpretation, field studies, laboratory experimentation, genomic comparisons, and effective statistical analyses. A few exhaustive inventories, such as the United Nations' Millennium Project and an around-the-world assessment of genes from marine microbes, should improve baseline data, but they will barely scratch the surface. Models that predict when one species will split into two will help. And an emerging discipline called evo-devo is probing how genes involved in development contribute to evolution. Together, these efforts will go a long way toward clarifying the history of life.

Paleontologists have already made headway in tracking the expansion and contraction of the ranges of various organisms over the millennia. They are finding that geographic distribution plays a key role in speciation. Future studies should continue to reveal large-scale patterns of distribution and perhaps shed more light on the origins of mass extinctions and the effects of these catastrophes on the evolution of new species.

From field studies of plants and animals, researchers have learned that habitat can influence morphology and behavior—particularly sexual selection—in ways that hasten or slow down speciation. Evolutionary biologists have also discovered that speciation can stall out, for example, as separated populations become reconnected, homogenizing genomes that would otherwise diverge. Molecular forces, such as low mutation rates or meiotic drive—in which certain alleles have an increased likelihood of being passed from one generation to the next—influence the rate of speciation.

And in some cases, differences in diversity can vary within an ecosystem: Edges of ecosystems sometimes support fewer species than the interior.

Evolutionary biologists are just beginning to sort out how all these factors are intertwined in different ways for different groups of organisms. The task is urgent: Figuring out what shapes diversity could be important for understanding the nature of the wave of extinctions the world is experiencing and for determining strategies to mitigate it.

33. # What Genetic Changes Made Us Uniquely Human?

1. Elizabeth Culotta

Every generation of anthropologists sets out to explore what it is that makes us human. Famed paleoanthropologist Louis Leakey thought tools made the man, and so when he uncovered hominid bones near stone tools in Tanzania in the 1960s, he labeled the putative toolmaker Homo habilis, the earliest member of the human genus. But then primatologist Jane Goodall demonstrated that chimps also use tools of a sort, and today researchers debate whether H. habilis truly belongs in Homo. Later studies have honed in on traits such as bipedality, culture, language, humor, and, of course, a big brain as the unique birthright of our species. Yet many of these traits can also be found, at least to some degree, in other creatures: Chimps have rudimentary culture, parrots speak, and some rats seem to giggle when tickled.

What is beyond doubt is that humans, like every other species, have a unique genome shaped by our evolutionary history. Now, for the first time, scientists can address anthropology's fundamental question at a new level: What are the genetic changes that make us human?

With the human genome in hand and primate genome data beginning to pour in, we are entering an era in which it may become possible to pinpoint the genetic changes that help separate us from our closest relatives. A rough draft of the chimp sequence has already been released, and a more detailed version is expected soon. The genome of the macaque is nearly complete, the orangutan is under way, and the marmoset was recently approved. All these will help reveal the ancestral genotype at key places on the primate tree.

The genetic differences revealed between humans and chimps are likely to be profound, despite the oft-repeated statistic that only about 1.2% of our DNA differs from that of chimps. A change in every 100th base could affect thousands of genes, and the percentage difference becomes much larger if you count insertions and deletions. Even if we document all of the perhaps 40 million sequence differences between humans and chimps, what do they mean? Many are probably simply the consequence of 6 million years of genetic drift, with little effect on body or behavior, whereas other small changes—perhaps in regulatory, noncoding sequences—may have dramatic consequences.

Half of the differences might define a chimp rather than a human. How can we sort them all out?

One way is to zero in on the genes that have been favored by natural selection in humans. Studies seeking subtle signs of selection in the DNA of humans and other primates have identified dozens of genes, in particular those involved in host-pathogen interactions, reproduction, sensory systems such as olfaction and taste, and more.

But not all of these genes helped set us apart from our ape cousins originally. Our genomes reveal that we have evolved in response to malaria, but malaria defense didn't make us human. So some researchers have started with clinical mutations that impair key traits, then traced the genes' evolution, an approach that has identified a handful of tantalizing genes. For example, MCPH1 and ASPM cause microcephaly when mutated, FOXP2 causes speech defects, and all three show signs of selection pressure during human, but not chimp, evolution. Thus they may have played roles in the evolution of humans' large brains and speech.

But even with genes like these, it is often difficult to be completely sure of what they do. Knockout experiments, the classic way to reveal function, can't be done in humans and apes for ethical reasons. Much of the work will therefore demand comparative analyses of the genomes and phenotypes of large numbers of humans and apes. Already, some researchers are pushing for a “great ape 'phenome' project” to match the incoming tide of genomic data with more phenotypic information on apes. Other researchers argue that clues to function can best be gleaned by mining natural human variability, matching mutations in living people to subtle differences in biology and behavior. Both strategies face logistical and ethical problems, but some progress seems likely.

A complete understanding of uniquely human traits will, however, include more than DNA. Scientists may eventually circle back to those long-debated traits of sophisticated language, culture, and technology, in which nurture as well as nature plays a leading role. We're in the age of the genome, but we can still recognize that it takes much more than genes to make the human.

34. # How Are Memories Stored and Retrieved?

1. Greg Miller

Packed into the kilogram or so of neural wetware between the ears is everything we know: a compendium of useful and trivial facts about the world, the history of our lives, plus every skill we've ever learned, from riding a bike to persuading a loved one to take out the trash. Memories make each of us unique, and they give continuity to our lives. Understanding how memories are stored in the brain is an essential step toward understanding ourselves.

Neuroscientists have already made great strides, identifying key brain regions and potential molecular mechanisms. Still, many important questions remain unanswered, and a chasm gapes between the molecular and whole-brain research.

The birth of the modern era of memory research is often pegged to the publication, in 1957, of an account of the neurological patient H.M. At age 27, H.M. had large chunks of the temporal lobes of his brain surgically removed in a last-ditch effort to relieve chronic epilepsy. The surgery worked, but it left H.M. unable to remember anything that happened—or anyone he met—after his surgery. The case showed that the medial temporal lobes (MTL), which include the hippocampus, are crucial for making new memories. H.M.'s case also revealed, on closer examination, that memory is not a monolith: Given a tricky mirror drawing task, H.M.'s performance improved steadily over 3 days even though he had no memory of his previous practice. Remembering how is not the same as remembering what, as far as the brain is concerned.

Thanks to experiments on animals and the advent of human brain imaging, scientists now have a working knowledge of the various kinds of memory as well as which parts of the brain are involved in each. But persistent gaps remain. Although the MTL has indeed proved critical for declarative memory—the recollection of facts and events—the region remains something of a black box. How its various components interact during memory encoding and retrieval is unresolved. Moreover, the MTL is not the final repository of declarative memories. Such memories are apparently filed to the cerebral cortex for long-term storage, but how this happens, and how memories are represented in the cortex, remains unclear.

More than a century ago, the great Spanish neuro-anatomist Santiago Ramòn y Cajal proposed that making memories must require neurons to strengthen their connections with one another. Dogma at the time held that no new neurons are born in the adult brain, so Ramòn y Cajal made the reasonable assumption that the key changes must occur between existing neurons. Until recently, scientists had few clues about how this might happen.

Since the 1970s, however, work on isolated chunks of nervous-system tissue has identified a host of molecular players in memory formation. Many of the same molecules have been implicated in both declarative and nondeclarative memory and in species as varied as sea slugs, fruit flies, and rodents, suggesting that the molecular machinery for memory has been widely conserved. A key insight from this work has been that short-term memory (lasting minutes) involves chemical modifications that strengthen existing connections, called synapses, between neurons, whereas long-term memory (lasting days or weeks) requires protein synthesis and probably the construction of new synapses.

Tying this work to the whole-brain research is a major challenge. A potential bridge is a process called long-term potentiation (LTP), a type of synaptic strengthening that has been scrutinized in slices of rodent hippocampus and is widely considered a likely physiological basis for memory. A conclusive demonstration that LTP really does underlie memory formation in vivo would be a big breakthrough.

Meanwhile, more questions keep popping up. Recent studies have found that patterns of neural activity seen when an animal is learning a new task are replayed later during sleep. Could this play a role in solidifying memories? Other work shows that our memories are not as trustworthy as we generally assume. Why is memory so labile? A hint may come from recent studies that revive the controversial notion that memories are briefly vulnerable to manipulation each time they're recalled. Finally, the no-new-neurons dogma went down in flames in the 1990s, with the demonstration that the hippocampus, of all places, is a virtual neuron nursery throughout life. The extent to which these newborn cells support learning and memory remains to be seen.

35. # How Did Cooperative Behavior Evolve?

1. Elizabeth Pennisi

When Charles Darwin was working out his grand theory on the origin of species, he was perplexed by the fact that animals from ants to people form social groups in which most individuals work for the common good. This seemed to run counter to his proposal that individual fitness was key to surviving over the long term.

By the time he wrote The Descent of Man, however, he had come up with a few explanations. He suggested that natural selection could encourage altruistic behavior among kin so as to improve the reproductive potential of the “family.” He also introduced the idea of reciprocity: that unrelated but familiar individuals would help each other out if both were altruistic. A century of work with dozens of social species has borne out his ideas to some degree, but the details of how and why cooperation evolved remain to be worked out. The answers could help explain human behaviors that seem to make little sense from a strict evolutionary perspective, such as risking one's life to save a drowning stranger.

Animals help each other out in many ways. In social species from honeybees to naked mole rats, kinship fosters cooperation: Females forgo reproduction and instead help the dominant female with her young. And common agendas help unrelated individuals work together. Male chimpanzees, for example, gang up against predators, protecting each other at a potential cost to themselves.

Generosity is pervasive among humans. Indeed, some anthropologists argue that the evolution of the tendency to trust one's relatives and neighbors helped humans become Earth's dominant vertebrate: The ability to work together provided our early ancestors more food, better protection, and better childcare, which in turn improved reproductive success.

However, the degree of cooperation varies. “Cheaters” can gain a leg up on the rest of humankind, at least in the short term. But cooperation prevails among many species, suggesting that this behavior is a better survival strategy, over the long run, despite all the strife among ethnic, political, religious, even family groups now rampant within our species.

Evolutionary biologists and animal behavior researchers are searching out the genetic basis and molecular drivers of cooperative behaviors, as well as the physiological, environmental, and behavioral impetus for sociality. Neuroscientists studying mammals from voles to hyenas are discovering key correlations between brain chemicals and social strategies.

Others with a more mathematical bent are applying evolutionary game theory, a modeling approach developed for economics, to quantify cooperation and predict behavioral outcomes under different circumstances. Game theory has helped reveal a seemingly innate desire for fairness: Game players will spend time and energy to punish unfair actions, even though there's nothing to be gained by these actions for themselves. Similar studies have shown that even when two people meet just once, they tend to be fair to each other. Those actions are hard to explain, as they don't seem to follow the basic tenet that cooperation is really based on self-interest.

The models developed through these games are still imperfect. They do not adequately consider, for example, the effect of emotions on cooperation. Nonetheless, with game theory's increasing sophistication, researchers hope to gain a clearer sense of the rules that govern complex societies.

Together, these efforts are helping social scientists and others build on Darwin's observations about cooperation. As Darwin predicted, reciprocity is a powerful fitness tactic. But it is not a pervasive one.

Modern researchers have discovered that a good memory is a prerequisite: It seems reciprocity is practiced only by organisms that can keep track of those who are helpful and those who are not. Humans have a great memory for faces and thus can maintain lifelong good—or hard—feelings toward people they don't see for years. Most other species exhibit reciprocity only over very short time scales, if at all.

Limited to his personal observations, Darwin was able to come up with only general rationales for cooperative behavior. Now, with new insights from game theory and other promising experimental approaches, biologists are refining Darwin's ideas and, bit by bit, hope that one day they will understand just what it takes to bring out our cooperative spirit.

36. # How Will Big Pictures Emerge From a Sea of Biological Data?

1. Elizabeth Pennisi

Biology is rich in descriptive data—and getting richer all the time. Large-scale methods of probing samples, such as DNA sequencing, microarrays, and automated gene-function studies, are filling new databases to the brim. Many subfields from biomechanics to ecology have gone digital, and as a result, observations are more precise and more plentiful. A central question now confronting virtually all fields of biology is whether scientists can deduce from this torrent of molecular data how systems and whole organisms work. All this information needs to be sifted, organized, compiled, and—most importantly—connected in a way that enables researchers to make predictions based on general principles.

Enter systems biology. Loosely defined and still struggling to find its way, this newly emerging approach aims to connect the dots that have emerged from decades of molecular, cellular, organismal, and even environmental observations. Its proponents seek to make biology more quantitative by relying on mathematics, engineering, and computer science to build a more rigid framework for linking disparate findings. They argue that it is the only way the field can move forward. And they suggest that biomedicine, particularly deciphering risk factors for disease, will benefit greatly.

The field got a big boost from the completion of the human genome sequence. The product of a massive, trip-to-the-moon logistical effort, the sequence is now a hard and fast fact. The biochemistry of human inheritance has been defined and measured. And that has inspired researchers to try to make other aspects of life equally knowable.

Molecular geneticists dream of having a similarly comprehensive view of networks that control genes: For example, they would like to identify rules explaining how a single DNA sequence can express different proteins, or varying amounts of protein, in different circumstances (see p. 80). Cell biologists would like to reduce the complex communication patterns traced by molecules that regulate the health of the cell to a set of signaling rules. Developmental biologists would like a comprehensive picture of how the embryo manages to direct a handful of cells into a myriad of specialized functions in bone, blood, and skin tissue. These hard puzzles can only be solved by systems biology, proponents say. The same can be said for neuroscientists trying to work out the emergent properties—higher thought, for example—hidden in complex brain circuits. To understand ecosystem changes, including global warming, ecologists need ways to incorporate physical as well as biological data into their thinking.

Today, systems biologists have only begun to tackle relatively simple networks. They have worked out the metabolic pathway in yeast for breaking down galactose, a carbohydrate. Others have tracked the first few hours of the embryonic development of sea urchins and other organisms with the goal of seeing how various transcription factors alter gene expression over time. Researchers are also developing rudimentary models of signaling networks in cells and simple brain circuits.

Progress is limited by the difficulty of translating biological patterns into computer models. Network computer programs themselves are relatively simple, and the methods of portraying the results in ways that researchers can understand and interpret need improving. New institutions around the world are gathering interdisciplinary teams of biologists, mathematicians, and computer specialists to help promote systems biology approaches. But it is still in its early days.

No one yet knows whether intensive interdisciplinary work and improved computational power will enable researchers to create a comprehensive, highly structured picture of how life works.

37. # How Far Can We Push Chemical Self-Assembly?

1. Robert F. Service

Most physical scientists nowadays focus on uncovering nature's mysteries; chemists build things. There is no synthetic astronomy or synthetic physics, at least for now. But chemists thrive on finding creative new ways to assemble molecules. For the last 100 years, they have done that mostly by making and breaking the strong covalent bonds that form when atoms share electrons. Using that trick, they have learned to combine as many as 1000 atoms into essentially any molecular configuration they please.

Impressive as it is, this level of complexity pales in comparison to what nature flaunts all around us. Everything from cells to cedar trees is knit together using a myriad of weaker links between small molecules. These weak interactions, such as hydrogen bonds, van der Waals forces, and π-π interactions, govern the assembly of everything from DNA in its famous double helix to the bonding of H2O molecules in liquid water. More than just riding herd on molecules, such subtle forces make it possible for structures to assemble themselves into an ever more complex hierarchy. Lipids coalesce to form cell membranes. Cells organize to form tissues. Tissues combine to create organisms. Today, chemists can't approach the complexity of what nature makes look routine. Will they ever learn to make complex structures that self-assemble?

Well, they've made a start. Over the past 3 decades, chemists have made key strides in learning the fundamental rules of noncovalent bonding. Among these rules: Like prefers like. We see this in hydrophobic and hydrophilic interactions that propel lipid molecules in water to corral together to form the two-layer membranes that serve as the coatings surrounding cells. They bunch their oily tails together to avoid any interaction with water and leave their more polar head groups facing out into the liquid. Another rule: Self-assembly is governed by energetically favorable reactions. Leave the right component molecules alone, and they will assemble themselves into complex ordered structures.

Chemists have learned to take advantage of these and other rules to design selfassembling systems with a modest degree of complexity. Drug-carrying liposomes, made with lipid bilayers resembling those in cells, are used commercially to ferry drugs to cancerous tissues in patients. And selfassembled molecules called rotaxanes, which can act as molecular switches that oscillate back and forth between two stable states, hold promise as switches in future molecular-based computers.

But the need for increased complexity is growing, driven by the miniaturization of computer circuitry and the rise of nanotechnology. As features on computer chips continue to shrink, the cost of manufacturing these ever-smaller components is skyrocketing. Right now, companies make them by whittling materials down to the desired size. At some point, however, it will become cheaper to design and build them chemically from the bottom up.

Self-assembly is also the only practical approach for building a wide variety of nanostructures. Making sure the components assemble themselves correctly, however, is not an easy task. Because the forces at work are so small, self-assembling molecules can get trapped in undesirable conformations, making defects all but impossible to avoid. Any new system that relies on self-assembly must be able either to tolerate those defects or repair them. Again, biology offers an example in DNA. When enzymes copy DNA strands during cell division, they invariably make mistakes—occasionally inserting an A when they should have inserted a T, for example. Some of those mistakes get by, but most are caught by DNA-repair enzymes that scan the newly synthesized strands and correct copying errors.

Strategies like that won't be easy for chemists to emulate. But if they want to make complex, ordered structures from the ground up, they'll have to get used to thinking a bit more like nature.

38. # What Are the Limits of Conventional Computing?

1. Charles Seife

At first glance, the ultimate limit of computation seems to be an engineering issue. How much energy can you put in a chip without melting it? How fast can you flip a bit in your silicon memory? How big can you make your computer and still fit it in a room? These questions don't seem terribly profound.

In fact, computation is more abstract and fundamental than figuring out the best way to build a computer. This realization came in the mid-1930s, when Princeton mathematicians Alonzo Church and Alan Turing showed—roughly speaking—that any calculation involving bits and bytes can be done on an idealized computer known as a Turing machine. By showing that all classical computers are essentially alike, this discovery enabled scientists and mathematicians to ask fundamental questions about computation without getting bogged down in the minutiae of computer architecture.

For example, theorists can now classify computational problems into broad categories. P problems are those, broadly speaking, that can be solved quickly, such as alphabetizing a list of names. NP problems are much tougher to solve but relatively easy to check once you've reached an answer. An example is the traveling salesman problem, finding the shortest possible route through a series of locations. All known algorithms for getting an answer take lots of computing power, and even relatively small versions might be out of reach of any classical computer.

Mathematicians have shown that if you could come up with a quick and easy shortcut to solving any one of the hardest type of NP problems, you'd be able to crack them all. In effect, the NP problems would turn into P problems. But it's uncertain whether such a shortcut exists—whether P = NP. Scientists think not, but proving this is one of the great unanswered questions in mathematics.

In the 1940s, Bell Labs scientist Claude Shannon showed that bits are not just for computers; they are the fundamental units of describing the information that flows from one object to another. There are physical laws that govern how fast a bit can move from place to place, how much information can be transferred back and forth over a given communications channel, and how much energy it takes to erase a bit from memory. All classical information-processing machines are subject to these laws—and because information seems to be rattling back and forth in our brains, do the laws of information mean that our thoughts are reducible to bits and bytes? Are we merely computers? It's an unsettling thought.

But there is a realm beyond the classical computer: the quantum. The probabilistic nature of quantum theory allows atoms and other quantum objects to store information that's not restricted to only the binary 0 or 1 of information theory, but can also be 0 and 1 at the same time. Physicists around the world are building rudimentary quantum computers that exploit this and other quantum effects to do things that are provably impossible for ordinary computers, such as finding a target record in a database with too few queries. But scientists are still trying to figure out what quantum-mechanical properties make quantum computers so powerful and to engineer quantum computers big enough to do something useful.

By learning the strange logic of the quantum world and using it to do computing, scientists are delving deep into the laws of the subatomic world. Perhaps something as seemingly mundane as the quest for computing power might lead to a newfound understanding of the quantum realm.

39. # Can We Selectively Shut Off Immune Responses?

1. Jon Cohen

In the past few decades, organ transplantation has gone from experimental to routine. In the United States alone, more than 20,000 heart, liver, and kidney transplants are performed every year. But for transplant recipients, one prospect has remained unchanged: a lifetime of taking powerful drugs to suppress the immune system, a treatment that can have serious side effects. Researchers have long sought ways to induce the immune system to tolerate a transplant without blunting the body's entire defenses, but so far, they have had limited success.

They face formidable challenges. Although immune tolerance can occur—in rare cases, transplant recipients who stop taking immunosuppressants have not rejected their foreign organs—researchers don't have a clear picture of what is happening at the molecular and cellular levels to allow this to happen. Tinkering with the immune system is also a bit like tinkering with a mechanical watch: Fiddle with one part, and you may disrupt the whole mechanism. And there is a big roadblock to testing drugs designed to induce tolerance: It is hard to know if they work unless immunosuppressant drugs are withdrawn, and that would risk rejection of the transplant. But if researchers can figure out how to train the immune system to tolerate transplants, the knowledge could have implications for the treatment of autoimmune diseases, which also result from unwanted immune attack—in these cases on some of the body's own tissues.

A report in Science 60 years ago fired the starting gun in the race to induce transplant tolerance—a race that has turned into a marathon. Ray Owen of the University of Wisconsin, Madison, reported that fraternal twin cattle sometimes share a placenta and are born with each other's red blood cells, a state referred to as mixed chimerism. The cattle tolerated the foreign cells with no apparent problems.

A few years later, Peter Medawar and his team at the University of Birmingham, U.K., showed that fraternal twin cattle with mixed chimerism readily accept skin grafts from each other. Medawar did not immediately appreciate the link to Owen's work, but when he saw the connection, he decided to inject fetal mice in utero with tissue from mice of a different strain. In a publication in Nature in 1953, the researchers showed that, after birth, some of these mice tolerated skin grafts from different strains. This influential experiment led many to devote their careers to transplantation and also raised hopes that the work would lead to cures for autoimmune diseases.

Immunologists, many of them working with mice, have since spelled out several detailed mechanisms behind tolerance. The immune system can, for example, dispatch “regulatory” cells that suppress immune attacks against self. Or the system can force harmful immune cells to commit suicide or to go into a dysfunctional stupor called anergy. Researchers indeed now know fine details about the genes, receptors, and cell-to-cell communications that drive these processes.

Yet it's one matter to unravel how the immune system works and another to figure out safe ways to manipulate it. Transplant researchers are pursuing three main strategies to induce tolerance. One builds on Medawar's experiments by trying to exploit chimerism. Researchers infuse the patient with the organ donor's bone marrow in hopes that the donor's immune cells will teach the host to tolerate the transplant; donor immune cells that come along with the transplanted organ also, some contend, can teach tolerance. A second strategy uses drugs to train T cells to become anergic or commit suicide when they see the foreign antigens on the transplanted tissue. The third approach turns up production of T regulatory cells, which prevent specific immune cells from copying themselves and can also suppress rejection by secreting biochemicals called cytokines that direct the immune orchestra to change its tune.

All these strategies face a common problem: It is maddeningly diff icult to judge whether the approach has failed or succeeded because there are no reliable “biomarkers” that indicate whether a person has become tolerant to a transplant. So the only way to assess tolerance is to stop drug treatment, which puts the patient at risk of rejecting the organ. Similarly, ethical concerns often require researchers to test drugs aimed at inducing tolerance in concert with immunosuppressive therapy. This, in turn, can undermine the drugs' effectiveness because they need a fully functioning immune system to do their job.

If researchers can complete their 50-year quest to induce immune tolerance safely and selectively, the prospects for hundreds of thousands of transplant recipients would be greatly improved, and so, too, might the prospects for controlling autoimmune diseases.

40. # Do Deeper Principles Underlie Quantum Uncertainty and Nonlocality?

1. Charles Seife

“Quantum mechanics is very impressive,” Albert Einstein wrote in 1926. “But an inner voice tells me that it is not yet the real thing.” As quantum theory matured over the years, that voice has gotten quieter—but it has not been silenced. There is a relentless murmur of confusion underneath the chorus of praise for quantum theory.

Quantum theory was born at the very end of the 19th century and soon became one of the pillars of modern physics. It describes, with incredible precision, the bizarre and counterintuitive behavior of the very small: atoms and electrons and other wee beasties of the submicroscopic world. But that success came with the price of discomfort. The equations of quantum mechanics work very well; they just don't seem to make sense.

No matter how you look at the equations of quantum theory, they allow a tiny object to behave in ways that defy intuition. For example, such an object can be in “superposition”: It can have two mutually exclusive properties at the same time. The mathematics of quantum theory says that an atom, for example, can be on the left side of a box and the right side of the box at the very same instant, as long as the atom is undisturbed and unobserved. But as soon as an observer opens the box and tries to spot where the atom is, the superposition collapses and the atom instantly “chooses” whether to be on the right or the left.

This idea is almost as unsettling today as it was 80 years ago, when Erwin Schrödinger ridiculed superposition by describing a half living, half-dead cat. That is because quantum theory changes what the meaning of “is” is. In the classical world, an object has a solid reality: Even a cloud of gas is well described by hard little billiard ball-like pieces, each of which has a well-defined position and velocity. Quantum theory seems to undermine that solid reality. Indeed, the famous Uncertainty Principle, which arises directly from the mathematics of quantum theory, says that objects' positions and moment a are smeary and ill defined, and gaining knowledge about one implies losing knowledge about the other.

The early quantum physicists dealt with this unreality by saying that the “is”—the fundamental objects handled by the equations of quantum theory—were not actually particles that had an extrinsic reality but “probability waves” that merely had the capability of becoming “real” when an observer makes a measurement. This so-called Copenhagen Interpretation makes sense, if you're willing to accept that reality is probability waves and not solid objects. Even so, it still doesn't sufficiently explain another weirdness of quantum theory: nonlocality.

In 1935, Einstein came up with a scenario that still defies common sense. In his thought experiment, two particles fly away from each other and wind up at opposite ends of the galaxy. But the two particles happen to be “entangled”—linked in a quantum-mechanical sense—so that one particle instantly “feels” what happens to its twin. Measure one, and the other is instantly transformed by that measurement as well; it's as if the twins mystically communicate, instantly, over vast regions of space. This “nonlocality” is a mathematical consequence of quantum theory and has been measured in the lab. The spooky action apparently ignores distance and the flow of time; in theory, particles can be entangled after their entanglement has already been measured.

On one level, the weirdness of quantum theory isn't a problem at all. The mathematical framework is sound and describes all these bizarre phenomena well. If we humans can't imagine a physical reality that corresponds to our equations, so what? That attitude has been called the “shut up and calculate” interpretation of quantum mechanics. But to others, our difficulties in wrapping our heads around quantum theory hint at greater truths yet to be understood.

Some physicists in the second group are busy trying to design experiments that can get to the heart of the weirdness of quantum theory. They are slowly testing what causes quantum superpositions to “collapse”—research that may gain insight into the role of measurement in quantum theory as well as into why big objects behave so differently from small ones. Others are looking for ways to test various explanations for the weirdnesses of quantum theory, such as the “many worlds” interpretation, which explains superposition, entanglement, and other quantum phenomena by positing the existence of parallel universes. Through such efforts, scientists might hope to get beyond the discomfort that led Einstein to declare that “[God] does not play dice.”

41. # Is an Effective HIV Vaccine Feasible?

1. Jon Cohen

In the 2 decades since researchers identified HIV as the cause of AIDS, more money has been spent on the search for a vaccine against the virus than on any vaccine effort in history. The U.S. National Institutes of Health alone invests nearly \$500 million each year, and more than 50 different preparations have entered clinical trials. Yet an effective AIDS vaccine, which potentially could thwart millions of new HIV infections each year, remains a distant dream.

Although AIDS researchers have turned the virus inside-out and carefully detailed how it destroys the immune system, they have yet to unravel which immune responses can fend off an infection. That means, as one AIDS vaccine researcher famously put it more than a decade ago, the field is “flying without a compass.”

Some skeptics contend that no vaccine will ever stop HIV. They argue that the virus replicates so quickly and makes so many mistakes during the process that vaccines can't possibly fend off all the types of HIV that exist. HIV also has developed sophisticated mechanisms to dodge immune attack, shrouding its surface protein in sugars to hide vulnerable sites from antibodies and producing proteins that thwart production of other immune warriors. And the skeptics point out that vaccine developers have had little success against pathogens like HIV that routinely outwit the immune system—the malaria parasite, hepatitis C virus, and the tuberculosis bacillus are prime examples.

Yet AIDS vaccine researchers have solid reasons to believe they can succeed. Monkey experiments have shown that vaccines can protect animals from SIV, a simian relative of HIV. Several studies have identified people who repeatedly expose themselves to HIV but remain uninfected, suggesting that something is stopping the virus. A small percentage of people who do become infected never seem to suffer any harm, and others hold the virus at bay for a decade or more before showing damage to their immune systems. Scientists also have found that some rare antibodies do work powerfully against the virus in test tube experiments.

At the start, researchers pinned their hopes on vaccines designed to trigger production of antibodies against HIV's surface protein. The approach seemed promising because HIV uses the surface protein to latch onto white blood cells and establish an infection. But vaccines that only contained HIV's surface protein looked lackluster in animal and test tube studies, and then proved worthless in large-scale clinical trials.

Now, researchers are intensely investigating other approaches. When HIV manages to thwart antibodies and establish an infection, a second line of defense, cellular immunity, specifically targets and eliminates HIV-infected cells. Several vaccines which are now being tested aim to stimulate production of killer cells, the storm troopers of the cellular immune system. But cellular immunity involves other players—such as macrophages, the network of chemical messengers called cytokines, and so-called natural killer cells—that have received scant attention.

The hunt for an antibody-based vaccine also is going through something of a renaissance, although it's requiring researchers to think backward. Vaccine researchers typically start with antigens—in this case, pieces of HIV—and then evaluate the antibodies they elicit. But now researchers have isolated more than a dozen antibodies from infected people that have blocked HIV infection in test tube experiments. The trick will be to figure out which specific antigens triggered their production.

It could well be that a successful AIDS vaccine will need to stimulate both the production of antibodies and cellular immunity, a strategy many are attempting to exploit. Perhaps the key will be stimulating immunity at mucosal surfaces, where HIV typically enters. It's even possible that researchers will discover an immune response that no one knows about today. Or perhaps the answer lies in the interplay between the immune system and human genetic variability: Studies have highlighted genes that strongly influence who is most susceptible—and who is most resistant—to HIV infection and disease.

Wherever the answer lies, the insights could help in the development of vaccines against other diseases that, like HIV, don't easily succumb to immune attack and that kill millions of people. Vaccine developers for these diseases will probably also have to look in unusual places for answers. The maps created by AIDS vaccine researchers currently exploring uncharted immunologic terrain could prove invaluable.

42. # How Hot Will the Greenhouse World Be?

1. Richard A. Kerr

Scientists know that the world has warmed lately, and they believe humankind is behind most of that warming. But how far might we push the planet in coming decades and centuries? That depends on just how sensitively the climate system—air, oceans, ice, land, and life—responds to the greenhouse gases we're pumping into the atmosphere. For a quarter-century, expert opinion was vague about climate sensitivity. Experts allowed that climate might be quite touchy, warming sharply when shoved by one climate driver or another, such as the carbon dioxide from fossil fuel burning, volcanic debris, or dimming of the sun. On the other hand, the same experts conceded that climate might be relatively unresponsive, warming only modestly despite a hard push toward the warm side.

The problem with climate sensitivity is that you can't just go out and directly measure it. Sooner or later a climate model must enter the picture. Every model has its own sensitivity, but each is subject to all the uncertainties inherent in building a hugely simplified facsimile of the real-world climate system. As a result, climate scientists have long quoted the same vague range for sensitivity: A doubling of the greenhouse gas carbon dioxide, which is expected to occur this century, would eventually warm the world between a modest 1.5°C and a whopping 4.5°C. This range—based on just two early climate models—first appeared in 1979 and has been quoted by every major climate assessment since.

Researchers are finally beginning to tighten up the range of possible sensitivities, at least at one end. For one, the sensitivities of the available models (5% to 95% confidence range) are now falling within the canonical range of 1.5°C to 4.5°C; some had gone considerably beyond the high end. And the first try at a new approach—running a single model while varying a number of model parameters such as cloud behavior—has produced a sensitivity range of 2.4°C to 5.4°Cwith a most probable value of 3.2°C.

Models are only models, however. How much better if nature ran the experiment? Enter paleoclimatologists, who sort out how climate drivers such as greenhouse gases have varied naturally in the distant past and how the climate system of the time responded. Nature, of course, has never run the perfect analog for the coming greenhouse warming. And estimating how much carbon dioxide concentrations fell during the depths of the last ice age or how much sunlight debris from the eruption of Mount Pinatubo in the Philippines blocked will always have lingering uncertainties. But paleoclimate estimates of climate sensitivity generally fall in the canonical range, with a best estimate in the region of 3°C.

The lower end at least of likely climate sensitivity does seem to be firming up; it's not likely below 1.5°C, say researchers. That would rule out the negligible warmings proposed by some greenhouse contrarians. But climate sensitivity calculations still put a fuzzy boundary on the high end. Studies drawing on the past century's observed climate change plus estimates of natural and anthropogenic climate drivers yield up to 30% probabilities of sensitivities above 4.5°C, ranging as high as 9°C. The latest study that varies model parameters allows sensitivities up to 11°C, with the authors contending that they can't yet say what the chances of such extremes are. Others are pointing to times of extreme warmth in the geologic past that climate models fail to replicate, suggesting that there's a dangerous element to the climate system that the models do not yet contain.

Climate researchers have their work cut out for them. They must inject a better understanding of clouds and aerosols—the biggest sources of uncertainty—into their modeling. Ten or 15 years ago, scientists said that would take 10 or 15 years; there's no sign of it happening anytime soon. They must increase the fidelity of models, a realistic goal given the continued acceleration of affordable computing power. And they must retrieve more and better records of past climate changes and their drivers. Meanwhile, unless a rapid shift away from fossil fuel use occurs worldwide, a doubling of carbon dioxide—and more—will be inevitable.

43. # What Can Replace Cheap Oil--and When?

1. Richard A. Kerr,
2. Robert F. Service

The road from old to new energy sources can be bumpy, but the transitions have gone pretty smoothly in the past. After millennia of dependence on wood, society added coal and gravitydriven water to the energy mix. Industrialization took off. Oil arrived, and transportation by land and air soared, with hardly a worry about where the next log or lump of coal was coming from, or what the explosive growth in energy production might be doing to the world.

Times have changed. The price of oil has been climbing, and ice is melting around both poles as the mercury in the global thermometer rises. Whether the next big energy transition will be as smooth as past ones will depend in large part on three sets of questions: When will world oil production peak? How sensitive is Earth's climate to the carbon dioxide we are pouring into the atmosphere by burning fossil fuels? And will alternative energy sources be available at reasonable costs? The answers rest on science and technology, but how society responds will be firmly in the realm of politics.

There is little disagreement that the world will soon be running short of oil. The debate is over how soon. Global demand for oil has been rising at 1% or 2% each year, and we are now sucking almost 1000 barrels of oil from the ground every second. Pessimists—mostly former oil company geologists—expect oil production to peak very soon. They point to American geologist M. King Hubbert's successful 1956 prediction of the 1970 peak in U.S. production. Using the same method involving records of past production and discoveries, they predict a world oil peak by the end of the decade. Optimists—mostly resource economists—argue that oil production depends more on economics and politics than on how much happens to be in the ground. Technological innovation will intervene, and production will continue to rise, they say. Even so, midcentury is about as far as anyone is willing to push the peak. That's still “soon” considering that the United States, for one, will need to begin replacing oil's 40% contribution to its energy consumption by then. And as concerns about climate change intensify, the transition to nonfossil fuels could become even more urgent (see p. 100).

If oil supplies do peak soon or climate concerns prompt a major shift away from fossil fuels, plenty of alternative energy supplies are waiting in the wings. The sun bathes Earth's surface with 86,000 trillion watts, or terawatts, of energy at all times, about 6600 times the amount used by all humans on the planet each year. Wind, biomass, and nuclear power are also plentiful. And there is no shortage of opportunities for using energy more efficiently.

Of course, alternative energy sources have their issues. Nuclear fission supporters have never found a noncontroversial solution for disposing of long-lived radioactive wastes, and concerns over liability and capital costs are scaring utility companies off. Renewable energy sources are diffuse, making it difficult and expensive to corral enough power from them at cheap prices. So far, wind is leading the way with a global installed capacity of more than 40 billion watts, or gigawatts, providing electricity for about 4.5 cents per kilowatt hour.

That sounds good, but the scale of renewable energy is still very small when compared to fossil fuel use. In the United States, renewables account for just 6% of overall energy production. And, with global energy demand expected to grow from approximately 13 terawatts a year now to somewhere between 30 and 60 terawatts by the middle of this century, use of renewables will have to expand enormously to displace current sources and have a significant impact on the world's future energy needs.

What needs to happen for that to take place? Using energy more efficiently is likely to be the sine qua non of energy planning—not least to buy time for efficiency improvements in alternative energy. The cost of solar electric power modules has already dropped two orders of magnitude over the last 30 years. And most experts figure the price needs to drop 100-fold again before solar energy systems will be widely adopted. Advances in nanotechnology may help by providing novel semiconductor systems to boost the efficiency of solar energy collectors and perhaps produce chemical fuels directly from sunlight, CO2, and water.

But whether these will come in time to avoid an energy crunch depends in part on how high a priority we give energy research and development. And it will require a global political consensus on what the science is telling us.

44. # Will Malthus Continue to Be Wrong?

In 1798, a 32-year-old curate at a small parish church in Albury, England, published a sobering pamphlet entitled An Essay on the Principle of Population. As a grim rebuttal of the utopian philosophers of his day, Thomas Malthus argued that human populations will always tend to grow and, eventually, they will always be checked—either by foresight, such as birth control, or as a result of famine, war, or disease. Those speculations have inspired many a dire warning from environmentalists.

Since Malthus's time, world population has risen sixfold to more than 6 billion. Yet happily, apocalyptic collapses have mostly been prevented by the advent of cheap energy, the rise of science and technology, and the green revolution. Most demographers predict that by 2100, global population will level off at about 10 billion.

The urgent question is whether current standards of living can be sustained while improving the plight of those in need. Consumption of resources—not just food but also water, fossil fuels, timber, and other essentials—has grown enormously in the developed world. In addition, humans have compounded the direct threats to those resources in many ways, including by changing climate (see p. 100), polluting land and water, and spreading invasive species.

How can humans live sustainably on the planet and do so in a way that manages to preserve some biodiversity? Tackling that question involves a broad range of research for natural and social scientists. It's abundantly clear, for example, that humans are degrading many ecosystems and hindering their ability to provide clean water and other “goods and services” (Science, 1 April, p. 41). But exactly how bad is the situation? Researchers need better information on the status and trends of wetlands, forests, and other areas. To set priorities, they'd also like a better understanding of what makes ecosystems more resistant or vulnerable and whether stressed ecosystems, such as marine fisheries, have a threshold at which they won't recover.

Agronomists face the task of feeding 4 billion more mouths. Yields may be maxing out in the developed world, but much can still be done in the developing world, particularly sub-Saharan Africa, which desperately needs more nitrogen. Although agricultural biotechnology clearly has potential to boost yields and lessen the environmental impact of farming, it has its own risks, and winning over skeptics has proven difficult.

There's no shortage of work for social scientists either. Perverse subsidies that encourage overuse of resources—tax loopholes for luxury Hummers and other inefficient vehicles, for example—remain a chronic problem. A new area of activity is the attempt to place values on ecosystems' services, so that the price of clear-cut lumber, for instance, covers the loss of a forest's ability to provide clean water. Incorporating those “externalities” into pricing is a daunting challenge that demands much more knowledge of ecosystems. In addition, economic decisions often consider only net present value and discount the future value of resources—soil erosion, slash-and-burn agriculture, and the mining of groundwater for cities and farming are prime examples. All this complicates the process of transforming industries so that they provide jobs, goods, and services while damaging the environment less.

Researchers must also grapple with the changing demographics of housing and how it will impact human well-being: In the next 35 to 50 years, the number of people living in cities will double. Much of the growth will likely happen in the developing world in cities that currently have 30,000 to 3 million residents. Coping with that huge urban influx will require everything from energy efficient ways to make concrete to simple ways to purify drinking water.

And in an age of global television and relentless advertising, what will happen to patterns of consumption? The world clearly can't support 10 billion people living like Americans do today. Whether science—both the natural and social sciences—and technology can crank up efficiency and solve the problems we've created is perhaps the most critical question the world faces. Mustering the political will to make hard choices is, however, likely to be an even bigger challenge.