# News this Week

Science  04 Jan 2008:
Vol. 319, Issue 5859, pp. 18
1. 2008 U.S. BUDGET

# Promising Year Ends Badly After Fiscal Showdown Squeezes Science

1. Jeffrey Mervis*
1. With reporting by Eli Kintisch, Andrew Lawler, and Eliot Marshall.

The U.S. science community's reaction to the 2008 federal budget adopted last month has been uniformly bleak. “A step backwards, … a missed opportunity, … a keen disappointment” declared press releases from advocates, including AAAS (which publishes Science), about a belated, $555 billion spending package (HR 2764) that was cobbled together and approved in a 4-day rush before the holidays. Those sad words are a reaction to the last-minute rollback of substantial planned increases for science that occurred after the Democratic-controlled Congress lost a showdown with the Republican White House. The year began on a high note in February when President George W. Bush submitted his second straight request for large increases in the physical sciences at the National Science Foundation (NSF), the Department of Energy (DOE), and the National Institute of Standards and Technology (NIST), three agencies that constitute his American Competitiveness Initiative (ACI) (Science, 9 February 2007, p. 750). The good vibes continued with passage last summer of the America COMPETES Act, which contained even higher authorized spending levels for research, education and training, and innovation (Science, 10 August 2007, p. 736). Separate House and Senate spending panels working on the 2008 budget also matched or exceeded the president's request for several science agencies. But the legislation either languished in Congress or, in the case of a bill involving the National Institutes of Health (NIH), was vetoed by the president. In the end, the numbers in the so-called omnibus spending bill (HR 2764) that was signed by President Bush the day after Christmas are much smaller than science boosters had thought likely for the 2008 fiscal year that began on 1 October. Research spending at NSF, for instance, will rise by only$56 million, to $4.8 billion, rather than by the$365 million requested back in February or by the even higher amounts the House and Senate had approved separately last fall. DOE's Office of Science saw a requested 15% increase in its $3.8 billion budget, which legislators had embraced, shrink by two-thirds. Programs in high-energy physics and fusion sciences were hit especially hard (for details, see ScienceNOW, http://www.sciencenow.org/, for 18, 19, and 21 December 2007), and more than half of the growth is devoted to special projects earmarked by legislators. NIST winds up with a scant$6 million more for its core $434 million research programs instead of the$65 million boost that the president requested and legislators had approved earlier.

View this table:

The pictures at other agencies not under the ACI umbrella are no brighter. NIH's $29.1 billion budget remains essentially flat once a$300 million transfer is subtracted; that's better than the 1% cut the president had sought but much less than a 3.7% rise Congress approved in the bill he vetoed this fall. NASA managed to hold onto the president's requested increase, a 3.1% jump to $17.3 billion. But it lost a$1 billion bump that legislators had previously adopted. Within that total, its $5.57 billion science budget, up$111 million, is eroded by millions of dollars in earmarks and directed spending for specific missions the agency hadn't requested.

Why did science fall short? Despite bipartisan support for boosting research budgets, larger forces prevailed. By threatening to veto any bills that exceeded his bottom line of $932 billion for domestic programs—which includes all research spending outside the Department of Defense—President Bush succeeded in forcing Democratic leaders to abandon$22 billion in additional proposed spending. The retreat affected almost every agency.

The legislators most intimately involved in the process—the chairs of the spending panels that assembled the individual pieces of the 1400-page bill—are no happier than their constituents. “The Commerce, Justice, Science Subcommittee agrees that the bill represents inadequate funding across the departments and agencies under our jurisdiction,” says Representative Alan Mollohan (D-WV), chair of the panel that oversees NSF, NASA, the National Oceanic and Atmospheric Administration, and NIST. “The House-passed bill,” Mollohan laments, “is far more representative of the committee's priorities than is the omnibus.”

Presidential science adviser John Marburger says he's also disappointed by the terms of the omnibus bill, although he says the president was pleased with its bottom line. “The most surprising aspect to me is the absence of any visible priority for basic research in the physical sciences … after the president asked for the money,” Marburger told Science. Mollohan's comments are equally partisan. “Between the holes in President Bush's budget request and his veto threats,” he says, the committee had little choice but to make “several rounds of unpleasant cuts.”

NSF's budget reflects those last-minute changes. Only a few days before the final deal was announced on 15 December, NSF's budget was still at the president's request of $6.43 billion. It had survived a previous round of cuts imposed after Democratic leaders shaved$11 billion off their earlier total. But then the leadership ordered another $11 billion to be pared to satisfy the president's demands. That's when a$514 million overall increase for NSF, to $6.43 billion, shrunk to$150 million.

Traces of the promised largess can still be found in the report accompanying the massive bill, in language a staffer admits “was written before the cuts were taken.” The legislators urge NSF to give the biological sciences and the social, behavioral, and economic sciences “comparable growth” to what the math and physical sciences, computer sciences, and engineering directorates are receiving—although the budgets of all six research directorates are essentially flat. And two programs within those directorates receive special treatment. NSF was ordered “to provide the budget request” for operating all its ground-based telescopes, part of a strong lobbying campaign by supporters of the Arecibo radio telescope in Puerto Rico after NSF decided to reduce funding for the observatory (Science, 10 November 2006, p. 904). And legislators actually added $8 million to the$107 million requested for the Experimental Program to Stimulate Competitive Research, a long-running program to help 27 have-not states and territories.

NSF Director Arden Bement says those two directives “will pinch” other programs. As one NSF staffer notes, “those are all things that you can do with a $500 million increase. But we're only getting$56 million [more for research].”

Despite the lower ceiling, Mollohan still made an effort to accommodate agencies' wishes. NSF, for example, received all but $4 million of a$40 million requested increase in its $246 million account for salaries and operations. “I consider that to be a victory” for an overburdened merit-review system, says Bement, “and a sign that Congress realizes its importance.” Congressional aides say that Bement made clear it was a top priority. Along with their scalpel, legislators also used an administrative fiat to meet the lowered spending ceiling. NSF must return$33 million, and NASA $192 million, from funds not spent during the 2007 fiscal year. DOE's Office of Science was ordered to trim 0.9%, or a total of$33 million, from what it has received in fiscal year 2008 for current activities.

Some other legislative priorities scattered throughout the omnibus bill include:

• The National Children's Study to track the health of 100,000 infants from birth to age 21 will get an increase of $42 million, to$111 million. NIH officials had said the $3 billion study is too expensive to continue (Science, 9 February 2007, p. 751). Congress also required “all investigators funded by the NIH” to submit final peer-reviewed manuscripts of papers accepted for publication to NIH's PubMed Central for release on the Internet “no later than 12 months after the official date of publication.” • NASA was given$40 million for future earth science missions, $60 million for the Space Interferometry Mission—$38.4 million more than it had requested—and $5 million to determine the next outer-planet destination. It will have$42 million to develop a robotic lunar lander, a mission that NASA had dropped to accommodate construction of its new rocket. Legislators also allocated $13.5 million more for microgravity life and physical sciences. • Applied energy research at DOE may be the biggest winner. The department's Energy Efficiency and Renewable Energy budget will rise by$282 million in 2008, to $1.7 billion, although$180 million of the increase will go to research and demonstration projects earmarked by legislators. The added program money will launch a $55 million project at the National Renewable Energy Laboratory in Golden, Colorado, to connect renewable energy systems such as intermittent wind power or plug-in hybrid cars to the U.S. electrical grid system. Legislators also added$40 million to the president's $79 million request for research on carbon sequestration. DOE's Advanced Scientific Computing Research program will get$354 million, $14 million more than requested. 2. GENETICS # The Elusive ALS Genes 1. Ken Garber* 1. Ken Garber is a freelance writer in Ann Arbor, Michigan. The disease that killed baseball legend Lou Gehrig has largely refused to reveal its secrets. In amyotrophic lateral sclerosis (ALS), motor neuron death causes irreversible wasting of skeletal muscles, but the underpinnings of this lethal condition remain elusive, particularly to geneticists. In 1993, researchers identified mutations in the copper-zinc superoxide dismutase gene responsible for about 20% to 25% of the rare familial form of the disease, and other genes contributing to familial ALS have since been found. Yet the sporadic, or noninherited, form of ALS, making up at least 90% of cases, resists efforts to isolate genetic risk factors. In the past few years, ALS researchers intensified their hunt. After screening about 35 genes that could affect motor neurons, they tentatively linked several to sporadic ALS, including one that encodes a detoxifying enzyme. But the hottest new tool in genetics, the whole-genome association (WGA) study, has added nothing but confusion to the gene hunt. Since August, three ALS teams have unveiled results from WGA studies. None of them has highlighted genes already under suspicion. Adding to the mystery, each WGA study tabs a different ALS gene. “Each time these things aren't replicating, we have to ask ourselves why,” says Ammar Al-Chalabi, an ALS researcher at King's College London. WGA studies have soared in popularity as they've found genes associated with diseases such as type 2 diabetes and multiple sclerosis (Science, 11 May 2007, p. 820). Researchers scan patients' DNA for variants called single-nucleotide polymorphisms (SNPs) and then compare the results to those from a healthy control group. SNPs appearing more frequently in patients will often point to a nearby gene that confers risk. The ALS gene hunts using this method may be struggling because the disease is actually a spectrum of conditions. Many rare mutations could predispose to different ALS subtypes, making genes difficult to find in a WGA study lumping everyone together. And the sheer thoroughness of whole-genome scans may be producing false leads for ALS scientists. Geneticists test a patient's DNA for half a million or more SNPs, and these enormous numbers magnify the possibility of getting an association at random. “When you roll the dice 555,000 times, … by sheer chance alone, SNPs are going to show up with a significant P value,” says ALS researcher Bryan Traynor of the National Institute of Mental Health in Bethesda, Maryland. “They're not genuinely associated with ALS, but they've shown up because of luck.” Statistical methods can correct for this, but they can obscure real associations and false positives alike. The first WGA study for ALS, by Traynor's group, actually found no SNPs significantly associated with the disease, although its power was limited by having fewer than 300 cases. Still, it “showed that there was no major gene that had a huge effect within ALS,” says Traynor. Now three positive WGA studies have been published and at least two more have been submitted to journals, each of them finding different ALS genes. In the 23 August 2007 issue of the New England Journal of Medicine, a group from the nonprofit Translational Genomics Research Institute in Phoenix, Arizona, flagged a SNP near the obscure gene FLJ10986. In this study of 1152 patients, the odds of carriers of the SNP having ALS were, compared to noncarriers, 1.35 to 1, suggesting a minor contribution to the disease. In the October 2007 issue of The Lancet Neurology, a Dutch group reported that the inositol 1,4, 5-triphosphate receptor 2 (ITPR2) gene was associated with ALS in three European populations. But when the same Dutch team expanded its analysis by including the patients whom Traynor surveyed and using a different methodology, ITPR2 did not make the cutoff for significance. Instead, the Dutch team reported online 16 December in Nature Genetics an association for the dipeptidyl-peptidase 6 (DPP6) gene. In each case, the identified genes only subtly increased the odds of developing ALS. View this table: The ITPR2 finding was plausible because ITPR2 triggers release of calcium within neurons, and excess calcium can cause motor neuron death. A DPP6 role in ALS is harder to fathom, but finding the association across four separate countries makes the Dutch researchers confident it's genuine. Still, the group has already embarked on studies to validate ITPR2 and DPP6 as ALS susceptibility genes. In the meantime, say others, these genes and others should be viewed with skepticism. “I would like to have at least one or two additional replications,” says Guy Rouleau, a neurologist at the University of Montreal in Canada. “And then I'll think it's possible.” Before the WGA studies started to roll out, a promising ALS gene candidate was the one encoding the enzyme paraoxonase 1 (PON1). Last year, Polish and American groups reported that PON1 was associated with sporadic ALS, and this year Australian and Irish groups also found a link. “It's only a weak signal, but it is seen every time it's looked for,” says Al-Chalabi. PON1 belongs to a family of enzymes that detoxify a wide variety of chemicals, including many insecticides and herbicides. If the ALS connection holds up, analyzing the effect of PON1 mutations on the enzyme's targets could point to specific toxins or environmental exposures causing the disease. “That's the dream,” says ALS researcher Robert Brown of Harvard Medical School in Boston. But, frustratingly, PON1 did not emerge in any of the WGA studies. Brown suspects that only very large WGA efforts are likely to work for ALS, in which many genes probably interact with the environment. The ALS Association is now organizing a study combining WGA data; most of the ALS groups have signed on. “In the end, it's going to require a concerted effort by the whole ALS community … coming up with hopefully a credible answer that everyone believes,” says Al-Chalabi. 3. PLANETARY SCIENCE # Saturn's Rings Look Ancient Again 1. Richard A. Kerr SAN FRANCISCO, CALIFORNIA— Saturn's rings, like any aging beauty, are keeping their age mysterious. Before the first spacecraft reached Saturn, planetary scientists assumed its rings formed along with the planet 4.5 billion years ago. But the Voyager spacecraft flying by in the early 1980s sent back evidence that the rings could be just a few hundred million years old. Now, the still-orbiting Cassini spacecraft is getting a longer look and finding signs of old age. “Right now, we still don't know whether it's old or new,” concludes ring specialist Joseph Burns of Cornell University. But if the rings are indeed old, some researchers think they see ways that the rings make themselves look forever young. The latest sign of the rings' antiquity is a tendency to put on weight—at least in the eyes of planetary scientists. Last month at the fall meeting of the American Geophysical Union here, Larry W. Esposito of the University of Colorado (UC), Boulder, and colleagues discussed results from Cassini's Ultraviolet Imaging Spectrograph (UVIS). In one mode of operation, UVIS can precisely and quickly record the brightness of a star as it appears to pass behind the rings, twinkling as the metersize particles that make up the rings block varying amounts of starlight. Voyager recorded a single such stellar occultation, which Esposito used to estimate the mass of the rings. But in the dense B ring, Cassini's occultation results have yielded at least three times the mass of Voyager's. “I hit myself on the head,” said Esposito. “‘I must have made a mistake with Voyager,’ I thought.” Once Cassini observed a number of occultations, the reason for the discrepancy became clear: Mass in the rings is clumped, not spread uniformly. As a result, starlight passes through the rings mostly by way of nearly empty gaps, and some angles offer clearer passage than others. Esposito compares it to a car's headlights viewed through a picket fence, shining brightly viewed head-on but dimly when viewed at a steep angle. Because Voyager was looking through the rings at a higher angle, it caught more starlight and underestimated the mass. Given the new big ring mass, planetary scientists Glen Stewart, Stuart Robbins, and Joshua Colwell, all of UC, argue that the B ring, at least, could not have formed in recent eons. A moon massive enough to form the ring is unlikely to have broken up during the past 4 billion years, they argue; collisions able to do that kind of damage were much more common during the solar system's early days, when lots of big lingering debris was still winging around. Even if Saturn's rings formed long ago, Esposito sees reasons they might appear young. The ice in the rings' particles seems too pure to have spent eons accumulating dark, dirty meteoritic material, and moonlets in the rings are too small to have survived that much time under cometary bombardment. But a larger mass of ring ice could have diluted the pollution, Esposito argues, and the moonlets might be recycling themselves—breaking up and reassembling by agglomeration. Researchers are comfortable with a heftier B ring but not necessarily with Esposito's take on the implications. “There's a bunch of caveats in all of this,” says ring dynamicist and Cassini camera principal investigator Carolyn Porco of the Space Science Institute in Boulder, Colorado. “Very little in this area is definite. Each part of the rings may have a different age.” The rings—like scientists' understanding of them—may be a work in progress. 4. SCIENCE POLICY # Science and the Next U.S. President 1. Jeffrey Mervis How do the candidates view science? Sometimes it's hard to tell from the campaign trail, but they have offered opinions on topics from evolution to global warming Many factors can make or break a U.S. presidential candidate in the 2008 race for his or her party's nomination. The ability to raise millions of dollars is key, as are positions on megaissues such as the Iraq war, immigration, and taxes. Voters also want to know if a candidate can be trusted to do the right thing in a crunch. Science and scientific issues? So far, with the exception of global warming, they are not getting much play. “It's pretty hard to find a candidate from either party who is gung ho for science,” laments Representative Vernon Ehlers (R-MI), one of two Ph.D. physicists in Congress and an indefatigable promoter of science and technology. (As a supporter of Mitt Romney, whose father was governor of Ehlers's home state of Michigan back in the 1960s, Ehlers will be trying to pump science and technology into his campaign.) Read about the science positions of: But just because science isn't on the front burner in this year's seemingly interminable election campaign, that doesn't mean the community should tune out. The candidates are addressing issues, from climate change to how the next Administration should manage science, that will affect researchers next year—and for decades to come. Differences have emerged on embryonic stem cell research, on the urgency of combating climate change, and even on the teaching of evolution. What are they saying on the stump, and how would they govern? This special report tries to answer those questions by examining the leading contenders among the Democrats and the Republicans, in alphabetical order, based on recent polls identifying those with a plausible shot at their respective nominations. (We've also provided basic information on the rest of the field.) Although none of the campaigns afforded us direct access to the candidates themselves—a telling indicator of the importance of science in the campaign, perhaps—we've talked to some of their advisers, as well as to colleagues, friends and foes alike, who are familiar with their careers. By the time you read this, some of the candidates may have surged, and others may have slumped. However, the issues seem likely to remain relevant no matter who becomes the 44th president of the United States. 5. DEMOCRAT # Hillary Clinton 1. Eli Kintisch Hillary Clinton's Speech at the Carnegie Institution of Washington on 4 October, the 50th anniversary of the launch of Sputnik, was the most detailed examination of science policy that any presidential candidate has offered to date. That's not surprising, however, given the extensive network of former advisers to her husband that the Democratic front-runner has tapped. Their voices could be heard in Clinton's emphasis on innovation to drive economic growth, a bottom line that is as much a creature of the 1990s as grunge music. And the senator from New York linked her call for Americans to better “compete and innovate” in science to a post- Sputnik plea by President Dwight Eisenhower for “heroism, sacrifice, and accomplishment when the chips are down.” But campaign adviser Thomas Kalil, formerly a technology official in the Clinton Administration and now an administrator at the University of California, Berkeley, insists that the candidate's science platform is not stuck in the past. “2008 is not 1992,” he says. “There are a new set of challenges.” Those new challenges include reducing the country's dependence on foreign oil, responding to climate change, and reversing what Clinton calls the Bush Administration's “assault on science.” To address the first two, Clinton has proposed a$50 billion research and deployment fund for green energy that she'd pay for by increasing federal taxes and royalties on oil companies. She would also establish a national energy council to oversee federal climate and greentech research and deployment programs. Both steps, she says, would help achieve the goal of an 80% reduction in carbon emissions from 1990 levels by 2050 and use tax credits, regulations, and carbon caps to create “5 million new jobs in clean energy over the next decade.” Last month, as a member of the Senate Environment and Public Works Committee, she voted for a bill almost as aggressive that passed along party lines, although the panel failed to adopt several amendments she offered (Science, 14 December, p. 1708).

To end what she calls President George W. Bush's “open season on open inquiry,” the 60-year-old lawyer and former first lady says that her science adviser would report directly to her rather than be “filtered through political advisers.” Government advisory committees must not be hamstrung by political considerations, she adds, which she insists has happened repeatedly since Bush took office. In her Carnegie speech, she also promised an executive order that would “ban political appointees from altering or removing scientific conclusions in government publications without any legitimate basis … and prohibit unwarranted suppression of public statements by government scientists.”

But science policy expert Roger Pielke Jr. of the University of Colorado, Boulder, says her efforts to stop political meddling are poorly defined and won't work. “What is ‘legitimate’ and ‘unwarranted’?” he asks. “As written, [the proposal] is a political Rorschach test.”

Clinton Administration-era official Ellis Mottur helped the campaign prepare her package of proposals, and Kalil and former White House science officials Neal Lane and Henry Kelly, who is now head of the Federation of American Scientists, were among a crew of unpaid advisers who offered input. Mottur says that he expects “the science-technology issues will come more to the fore in the general election.”

In the meantime, Clinton has called for another doubling of the $30-billion-a-year National Institutes of Health budget during the next decade, the preservation of the NASA team involved in the shuttle program even as the agency shifts to new exploration missions, and the augmentation of NASA's earth science and aeronautics programs. But finding the money won't be any easier than mustering the political will to tax energy companies, Pielke predicts. “Good luck finding room in the R&D budget for all of that,” he says. However, supporting good research isn't just about money, says physicist David Moncton, director of the Nuclear Reactor Laboratory at the Massachusetts Institute of Technology and a former administrator at two national laboratories. Just as important as any budget, says Moncton, who is not advising the campaign, are “competent individuals managing [science policy].” And Moncton thinks “that might be more likely to happen with a Hillary Clinton [presidency]. 6. DEMOCRAT # John Edwards 1. Jocelyn Kaiser, 2. Eliot Marshall John Edwards made a fortune as a personal-injury lawyer in the 1980s and was John Kerry's vice president on the unsuccessful Democratic presidential ticket in 2004. But this year, he is campaigning as a populist and a Washington outsider. The son of mill workers, Edwards pounds away at the “big, powerful interests,” the “corrupt,” and the “very greedy” in his standard stump speech. The 54-year-old former North Carolina senator (1998–2004) wants to make sweeping changes, some of which would affect research. He would end what he calls the “antiscience” practices of George W. Bush's Administration—such as “censoring research and slanting policy on climate change, on air pollution, on stem cell research.” And he would increase science funding. Despite such promises, however, biomedical researchers who remember the malpractice lawsuits that Edwards championed 2 decades ago—some of which were based on questionable science—are wary. If Edwards actually does move into the White House, he says his own presidential science adviser would have more clout than the current one and would play “a central role as an assistant to the president.” To protect scientific integrity, Edwards would “eliminate political litmus tests for government scientists” and forbid political appointees “from overriding agencies' scientific findings unless the chief White House science adviser concludes they are erroneous.” Edwards's agenda for improving the U.S. economy includes a mixture of very specific projects and broad promises. For example, he advocates a low-cost “universal Internet” for rural communities and more research on autism and fragile X syndrome, a genetic cause of mental impairment. He favors federal funding of human embryonic stem cell research, including nuclear DNA transfer. He wants to create a universal, federally backed health system. And his spokesperson, Audrey Waters, says he supports budget increases “substantially better than the pace of inflation” for the National Institutes of Health (NIH) and the National Science Foundation. On environmental policy, Edwards has won the “enthusiastic endorsement” of Friends of the Earth Action, the nonprofit group's political arm. That support is based in part on his proposal to cut greenhouse gas emissions by 80% by 2050, using a cap-and-trade system to auction off permits as a regulatory incentive. Edwards says he would take at least$10 billion a year from that auction and another $3 billion from other sources to invest in a trust fund for new technologies. It would develop solar, wind, and “cellulose-based biofuel” projects. The environmentalists are also pleased with what Edwards would not do. He opposes any expansion of nuclear power, the candidate explained in a recent debate, because it is “extremely costly … and we don't have a safe way to dispose of the nuclear waste.” Liquefied coal is out, too, he says, because “the last thing we need is another carbon-based fuel.” Yet among scientists, Edwards “carries some baggage,” says Peter Agre, a Nobel Prize-winning biochemist now at Johns Hopkins University in Baltimore, Maryland. Although Edwards is a “good man,” says Agre, “I know people who would never vote for him” because of the way he and other lawyers pursued and won multi-million-dollar medical malpractice awards representing children born with cerebral palsy. In a 1985 case, for example, Edwards addressed the jury in the voice of a brain-damaged child, describing from within the womb how she waited for a doctor to perform a cesarean section as a fetal heart monitor signaled her distress. The doctor was accused of waiting too long; the jury awarded$6.5 million. Many such suits were “fueled by bad science,” says neurologist Karin Nelson of NIH, who concedes she has not reviewed the specific cases that Edwards handled. She says that the same type of cerebral palsy litigation has now spread to Europe—to the detriment of children's health, she believes. Nelson sat on a panel of the American College of Obstetricians and Gynecologists that in 2003 found that most cases of cerebral palsy are not caused at birth.

Asked today about Edwards's courtroom tactics, his staff points to statements from his vice presidential campaign. Speaking then about his legal team, Edwards claimed that “we would take months investigating” any brain-injury case before deciding whether to accept it. And he said he only litigated those that “were merited.”

7. REPUBLICAN

# Rudolph Giuliani

1. Eliot Marshall

Speaking “In the most humble way possible,” Rudy Giuliani disclosed on the campaign stump in Iowa last summer that “I'm very good at doing the impossible. I am.” Indeed, he's made a career of slaying dragons, including winning the convictions of prominent Wall Street and organized crime figures as a federal prosecutor in the 1980s and overseeing a huge drop in New York City's crime rate as its mayor from 1993 to 2001.

So what does this 63-year-old dragon slayer make of science? That's hard to determine because his campaign successfully discouraged key advisers from speaking to Science about specific issues. But his public career suggests that Giuliani is a pragmatist with a quick grasp of issues, a lover of statistics, and a firm believer that most tasks can be done better by private institutions than by government.

On social issues, Giuliani stands out among the Republicans for what he has said about abortion: With reservations, he would let the woman decide what to do. On a linked topic, research on human embryonic stem cells, he said in May that “as long as we're not creating life in order to destroy it—as long as we're not having human cloning … I would support [federal funding].” David Carmel, a biotech executive and member of the board of the New York Stem Cell Foundation, made the case for embryonic stem cell research in a private debate last fall that the candidate staged to explore both sides of the issue. Based on Giuliani's questions, Carmel says he believes Giuliani, if elected, would reduce federal restrictions.

Giuliani's record as mayor and author add few clues about his outlook on science. Rodney Nichols, former president of the New York Academy of Sciences (NYAS), gives him high marks for his interest in two city-backed projects involving science and somewhat lower marks for follow-through. Nichols recalls how the mayor agreed to host an NYAS award to honor scientific excellence, even though it “would not win [him] votes.” At the same time, Nichols says that “not much came” of a panel on how to bring biotech companies into the city, as the mayor lost interest once local medical institutions began to jockey for concessions.

In his 2002 book Leadership, Giuliani wrote, “I loved learning biology” as a premedical student at Manhattan College. But in the end, he says that he chose law school and politics because “I liked ideas better than science.” New York City invested heavily in crime statistics—a system called CompStat—to help command a burgeoning police force. The model has been copied in many cities, and Giuliani has proposed clones for other tasks, which he calls JobStat, SchoolStat, EnergyStat, and HealthStat.

The technical issue that proved most controversial for Giuliani this fall, in fact, involved his use of health data. An ad in New Hampshire claimed that people diagnosed with prostate cancer (as he was in 2000) in the United Kingdom are more likely to die of their disease because of its system of “socialized medicine” than their U.S. counterparts. The ad cited survival rates of 82% for the United States and 44% for Britain. This provoked a flurry of criticism. A spokesperson for Giuliani revealed that the candidate found the data in the journal of the Manhattan Institute for Policy Research, a conservative think tank to which he has close ties.

Experts say it's easy to misread the numbers. Recent data from the U.S. National Cancer Institute and an international survey called Eurocare indicate that the 5-year survival rates are about 77% for Britain and 98% for the United States. What this shows, according to biostatistician Donald Berry of the M. D. Anderson Cancer Center in Houston, Texas, is that U.S. doctors screen and diagnose more patients, finding prostate cancer in people not at risk of dying from it, and that “there is no credible evidence that screening decreases prostate cancer mortality.” The Giuliani campaign has said it won't stop using the original ad data.

Giuliani's campaign has skated lightly over most issues with scientific and technological components. On energy, for example, he would boost all domestic energy sources, emphasizing coal, nuclear power, ethanol (with a goal of 20% more output), and renewable sources such as windmills, but he has not spelled out how this would work. Likewise, his pledges to “promote science and mathematics through technical certification or an associate degree” and “expand the number of H-1B visas for skilled foreign workers” come with few details. The League of Conservation Voters reports that Giuliani has “no articulated position” on most of the environmental issues it tracks. Giuliani has said, “I do believe there's global warming,” but he has not spelled out his response to the problem.

8. REPUBLICAN

# Mike Huckabee

1. Jennifer Couzin

The first time Mike Huckabee was asked in a national candidates' debate if he believed in evolution, he raised his hand to say that he didn't accept the theory. The second time, Huckabee initially ducked the question and instead replied, “I'm not planning on writing the curriculum for an 8th grade science book.”

Scientists in Arkansas who know Huckabee from his decade as governor say the response is consistent with his approach to many social issues: Take a strong stance but don't impose your views on others. The former president of the Arkansas Baptist State Convention holds many staunchly conservative positions, including support for displaying the Ten Commandments in public schools and opposition to the use of embryonic stem cells for research. But when it comes time to act, Huckabee has often veered toward the center of the political road.

As chief executive of this largely rural state from 1996 to January 2007, Huckabee persuaded a Democratic-led legislature to expand health coverage for poor children and raise taxes to improve schools and roads and unsuccessfully campaigned for teenage immigrants who did not have proof of citizenship to receive college vouchers after graduating from high school. Those positions were anathema to many of his constituents and a pleasant surprise to others. “He really was much less radical and ideological than we all expected,” says Rita Sklar, executive director of the ACLU of Arkansas in Little Rock. He also supported a bond program to help improve infrastructure at universities.

That centrism is being tested now that Huckabee is on a national stage. Seeking to expand his base among evangelicals, for example, he has promised to fight for constitutional amendments that would ban abortion and gay marriage.

One issue dear to his heart has been the promotion of healthy living. When the Arkansas legislature rejected his proposal to use millions of dollars in tobacco-settlement funds for health care and medical research, he exercised his right as chief executive to call for a referendum, which passed handily. That effort only intensified after he was diagnosed with type 2 diabetes and shed 110 pounds.

“He would certainly be a friend” of the National Institutes of Health as president, says G. Richard Smith, who helped with the referendum and now directs the psychiatric research institute at the University of Arkansas for Medical Sciences. On the campaign trail, Huckabee has talked about funding disease-prevention efforts along the lines of the indoor smoking ban he signed into law while governor.

In a presidential debate and in a television interview, Huckabee sidestepped questions about whether human actions are behind climate change, but he supported a 2006 statement by the National Governors Association calling for more climate change research. “Our responsibility to God means that we have to be good stewards of this Earth,” he said in a May debate. That attitude, say environmental advocates, is a marked shift for someone who, as governor, declined to take sides in a court battle with Oklahoma about pollution in the shared Illinois River and once referred to environmentalists as “wackos.”

Although he won four statewide races, Huckabee never created the reservoir of political goodwill enjoyed by his predecessor once removed, Bill Clinton, especially among members of his own party. (The two men hail from the same small town of Hope, Arkansas.) Jeremy Hutchinson, a Republican and former assistant minority leader in the legislature, notes that Huckabee rarely socialized with or lobbied state lawmakers, unlike the famously charismatic former president. “With Clinton, even if you didn't agree with him, you liked him,” says Hutchinson. Huckabee also has a short fuse, say several Arkansans inside and outside politics. “He was very thin-skinned and could be pretty vindictive,” says Ernest Dumas, a newspaper columnist from Little Rock who was subjected to a 5-minute televised tirade from the governor for his past criticism of Huckabee's highway program.

Jay Barth, a political scientist at Hendrix College in Conway who has written about Huckabee's career, says Huckabee owes his success to a conservative ideology, a winning personality, and media savvy. Huckabee is “very talented [and] never made a lot of political mistakes,” says Barth. “Arkansans never loved him the way they loved other politicians, [but] they never hated him,” either.

9. REPUBLICAN

# John McCain

1. Constance Holden

John McCain doesn't have any scientific training or expertise. But he trusts the experts. They've told him that global warming is the most urgent issue facing the world, and that makes climate change one of the three issues—along with immigration and the Iraq war—that he's emphasizing in his presidential campaign.

The 71-year-old retired Navy pilot turned Arizona politician discovered the issue during his previous, unsuccessful run for the White House in 2000, says his economic adviser, Douglas Holtz-Eakin, a former director of the Congressional Budget Office. It's popular lore that the candidate woke up to the issue when confronted by a Dartmouth College student dressed as a penguin at an event that year in New Hampshire. In fact, says Holtz-Eakin, McCain got the message “again and again” during the campaign.

McCain used his position on the Senate Commerce Committee, which he chaired from 2003 to 2005, to focus attention on the subject and has led congressional delegations to both poles to witness its impact. “He's probably more knowledgeable [about it] than all the other candidates,” says Timothy Profeta, a former staffer for Senator Joseph Lieberman (I-CT) who now runs Duke University's Nicholas Institute for Environmental Policy Solutions.

McCain equates environmentalism with national security. And although he has been a staunch supporter of President George W. Bush's stance on the Iraq war, his views on climate change have triggered some sharp exchanges with Bush Administration officials. In 2002, he declared that White House science adviser John Marburger's comments on global warming, which many scientists saw as overly cautious, had “no credibility” in light of the growing severity of the problem. In a 2005 hearing, he accused Vice Admiral Conrad Lautenbacher, head of the National Oceanic and Atmospheric Administration, of having a “complete lack of concern about future generations of Americans who are affected by climate change.” He has also called the president's approach to global warming “disgraceful.” Last month, McCain tasted his first legislative victory on the issue, as Democrats on the Senate Environment and Public Works Committee approved a bill designed to reduce greenhouse gas emissions using a system that caps and trades emissions allowances that he and Lieberman first proposed in 2003.

John Raidt, a former Commerce Committee staffer and now one of McCain's closest advisers, says McCain “understands the limits of his own understanding; … he trusts the experts.” One of these is R. James Woolsey, former chief of the CIA under President Bill Clinton, who has briefed McCain on issues relating to energy independence. Woolsey teasingly calls McCain a “very quick learner in spite of his record at the Naval Academy”—where he ranked fifth from the bottom of his class.

McCain, who has served 26 years in Congress, also listened to the scientific experts in the stem cell debate. Although he opposes abortion, he voted for a bill to expand President George W. Bush's policy on research with human embryonic stem cells. However, he draws the line at human nuclear transfer, or research cloning, arguing that there is no ethical difference between cloning for research and cloning for reproduction.

Most nonclimate science issues are far down on McCain's list of priorities. A free-trade advocate, he has sponsored a bill to restrict taxes on Internet use. He also wants to make better use of cyberspace to advance the cause of freedom in the tradition of Radio Free Europe. In keeping with his stance on immigration, he has also been involved in expanding H-1B visas for foreign science graduate students studying in the United States.

Sometimes the interests of science take a back seat to those of his constituents. He's supported an amendment to the Native American Graves Protection and Repatriation Act that could make it easier to turn over ancient human remains that are unrelated to existing American Indians to tribal representatives, a step that researchers worry will make the remains off limits. And McCain has waffled on the teaching of evolution. In 2005, he told the Arizona Daily Star that “there's nothing wrong with teaching different schools of thought [on] … how the world was created.” But the next year, he opined that creationism should “probably not” be taught in science classes.

10. SCIENCE POLICY

11. DEMOCRAT

# Barack Obama

1. Yudhijit Bhattacharjee

Speaking last summer to a convention of bloggers in Chicago, Barack Obama accused the Bush Administration of ignoring or distorting data to shape its decisions on sciencerelated issues. He promised the audience that his policies would be based on “evidence and facts.” Political rhetoric? Perhaps. But some scientists who have seen the first-term U.S. Democratic senator in action say that's how he operated as a community activist in Chicago and as an Illinois state legislator.

Eric Whitaker, a research administrator at the University of Chicago and former director of the Illinois Department of Public Health, points to a 2004 proposal before the state legislature to offer free flu shots to everyone without health insurance during a shortage of the vaccine. Obama, then chair of the Health and Human Services Committee in the state senate, pressed Whitaker and others on their advice that the shots be limited to high-risk groups. “He pushes you to defend your data,” says Whitaker. In the end, Obama was convinced by their argument that vaccinating everybody would be economically unwise and bucked the majority in voting against the proposal.

Deborah Burnet, a pediatrician at the University of Chicago who studies the connection between obesity and diabetes, says Obama displayed the same evidence-based philosophy whenever she invited the Harvard Law School grad and community organizer to lecture her class on racial disparities in health. The 30-something Obama would urge her students to think about “how to use scientific inquiry to make intelligent public policy,” says Burnet. She says she was so inspired by his message that students should apply “insights from scientifically collected evidence” to real-world problems that she began a program to help low-income residents make better nutritional choices.

Obama's campaign sets out a number of lofty science policy goals that might be difficult to achieve in that real world, however. He'd like to double federal spending on basic research and help more Americans get on the Web by broadening Internet access. He also wants to spend $18 billion on education initiatives covering everything from early childhood learning and precollege math and science instruction to attracting more minority students into science and engineering. Ironically, he'd pay for it in part by delaying NASA's program to return to the moon and explore Mars—a project that would employ thousands of scientists and engineers. Like the other Democratic contenders, Obama has made global warming an important part of his campaign. He supports a market-based carbon-trading system to cut carbon emissions to 80% below 1990 levels by 2050 and wants to invest$150 billion to develop biofuels. But he's also suffered some political bumps and scrapes along the way to that position.

Last year, for example, Obama introduced a bill to subsidize the conversion of coal to liquid fuel, arguing that it would make the United States less dependent on foreign oil. But environmentalists saw it as a sop to the multi-billion-dollar coal industry in his home state. Obama then backtracked, saying he would support liquefying coal only if the net carbon dioxide emissions from producing and burning the fuel were 20% lower than levels generated by petroleum-based fuels.

Observers say the awkward shuffle reflects Obama's relative inexperience in national politics. “It was naïve of him to think that he could side with the coal industry to please voters in his home state and not land in a frying pan on the national stage,” says Frank O'Donnell of Clean Air Watch, a Washington, D.C.-based nonprofit. Nonetheless, O'Donnell says, the senator's green credentials are still pretty solid.

Since winning his U.S. Senate seat in 2004, Obama has continued to track health policy issues. He has proposed or supported legislation to promote embryonic stem cell research, increase research on avian influenza, and develop microbicides to protect women from HIV/AIDS. The measures suggest that Obama has retained his strong interest in applying science to public health challenges. For academic health centers, says Burnet, that means “getting the translational component going.”

12. DEMOCRAT

# Bill Richardson

1. Jeffrey Mervis

As New Mexico's New Governor, Bill Richardson enlisted experts from in-state Los Alamos National Laboratory to help him with technical issues. Barely a year later, however, they had been fired, Donald Trump-style. Richardson felt that the Department of Energy's (DOE's) weapons lab was dragging its feet on cleaning up long-standing environmental problems, and when a top lab official suggested one day that budget cuts might force the lab to recall its environmental adviser, it was the last straw. “We weren't going to be blackmailed,” recalls Ned Farquhar, a former staffer now serving as senior adviser to the campaign on energy and climate.

A year later, a new set of advisers from Los Alamos was in place, and Richardson had reached a deal with the lab on a cleanup schedule. “It was pretty rigorous. I don't think the state budged very much,” notes physicist Dennis Erickson, on detail as science adviser, who remembers being given 24 hours to clean out his desk. Despite having a year's work go down the drain, Erickson doesn't disagree with what the governor did. “I have nothing but good feelings toward him,” says Erickson, now retired and a contributor to Richardson's presidential campaign.

Supporters say the incident demonstrates that the 60-year-old Hispanic politician is a principled manager, a tough negotiator, and someone who doesn't see a conflict between national security and the environment. But some wonder if it is also the portrait of someone who acts precipitously, punishing critics and putting principles above results.

Reelected easily in 2006, Richardson has promised voters that he will shake up the Washington establishment. But he's hardly a fresh face. After earning a bachelor's and a master's degree (in public policy) from Tufts University, Richardson spent nearly 30 years working for the federal government, first as a Democratic staffer, then as a seven-term congressman, and finally, as U.N. ambassador and energy secretary in the second Clinton Administration.

The most striking part of his résumé is his extensive, hands-on negotiations with regimes in North Korea, Iraq, and Sudan for the release of U.S. prisoners and other human-rights issues. Richardson has also taken a very aggressive stance on climate change, including calls for a 90% reduction in U.S. greenhouse gas emissions by 2050 through a cap-and-trade system, a 50% cut in oil consumption by 2020, greater reliance on renewable energy sources by utility companies, and federal subsidies to promote plug-in hybrid cars. “There is no free market when it comes to greenhouse gas emissions,” says Farquhar. “We need rules and boundaries.”

To help meet those goals, Richardson has proposed a $10 billion to$15 billion trust fund to support new energy technologies, replenished by the fruits of successful investments. But Farquhar says it's not a honey pot for academic researchers, as the fund would pursue a more product-oriented approach than the Advanced Research Projects Agency-Energy created last summer. Farquhar says Richardson also plans to “reconfigure” DOE to deal with the twin challenges of energy independence and global warming, possibly shifting DOE's ethanol program to the agriculture department and giving the Environmental Protection Agency a bigger role in climate change.

The lack of specifics is characteristic of someone who, in the words of one former aide, “has more ideas than time to implement them.” That's equally true for his education platform. His response to the president's signature No Child Left Behind program to improve elementary and secondary schools is characteristically blunt: “Scrap it.” But when asked what would replace the annual testing regimen and penalties for schools that don't make the grade, his answer is a call for a national summit to work out the details. His promise to “hire 100,000 new science and math teachers [and] create 250 math, science, and innovation academies” likewise ignores the fact that state and local authorities, not the federal government, hire teachers and run schools.

Despite repeated campaign statements about the importance of innovation, Richardson isn't above embracing his own scientific illiteracy as a way to identify with the average voter. In his new book on energy, Leading by Example, Richardson asserts that more people would use energy-saving technologies, including light-emitting diodes, if they were given simpler names. “Does anyone on Earth know what a diode is?” he writes. “Probably someone at the two national labs in New Mexico, but not me! And probably not you.”

13. SCIENCE POLICY

14. REPUBLICAN

# Mitt Romney

1. Andrew Lawler

Last month, as Mitt Romney campaigned in Iowa, he laced his stump speeches with references to his opposition to embryonic stem (ES) cell research and abortion and his doubts about the role of humans in global warming. All those positions, plus a declaration that his Mormon faith would not dictate any decisions he might make as president, were aimed at wooing conservative Christian voters in the state.

That focus is a far cry from 5 years ago, when the 60-year-old businessman campaigned successfully to become governor of the high-tech state of Massachusetts. The new chief executive wowed biotechnology leaders and university administrators with his aggressive and no-nonsense talk about unleashing the power of research. “We were impressed by his willingness to talk about the importance of research universities in the state and national economies,” says Paul Parravano, co-director of government and community relations at the Massachusetts Institute of Technology (MIT) in Cambridge. “For a lot of people here, this was fresh and important.” As a venture capitalist with an MBA from Harvard University, Romney “understands the role of places like MIT and was very supportive,” says another university official.

During his first years as governor, researchers say, Romney talked the talk, co-chairing a national summit on innovation and telling the Massachusetts Biotechnology Council that “we want to make sure we are at absolutely the front edge” of stem cell research. He promised he would work to provide “the same kind of opportunities that you would find in any other state in America.” And he walked the walk. He launched an effort to lure more high-tech talent into the state and joined with seven other Northeastern states on a regional plan to reduce carbon dioxide emissions at power plants—the first collective U.S. effort to control greenhouse gases. He also consistently opposed efforts to introduce the teaching of intelligent design in the classroom.

His 2-year honeymoon with the research community ended abruptly in 2005, however, just as Romney's presidential campaign was getting started. The governor abruptly backed out of the regional emissions plan, citing its cost to consumers. He vetoed a bill passed by the Massachusetts legislature to allow ES cell research, citing his ethical concerns. Research advocates say that they never were able to sit down with the governor to discuss the bill, which was a major concern for many industry and university biologists in the state. “We were never able to engage,” says one supporter who requested anonymity. “This was an eye opener; he was changing his stripes.”

Even so, one of the strongest advocates for science in Congress, Representative Vernon Ehlers (R-MI), calls Romney “the best choice for any scientist or engineer.” The former physicist and longtime member of the House Science Committee praises the candidate as bright and unburdened by ideology, noting that “he appreciates the benefits of science.” Ehlers, who knew Romney's late father, a former governor of Michigan, says that he is heading up a science advisory committee for the candidate.

Ehlers told Science that he expects Romney's list of priorities to include, in particular, increased funding for math and science education and, more generally, higher spending on research of all kinds. But he speculates that Romney “may choose not to be vocal” on global warming, although Ehlers himself supports sharp reductions in carbon dioxide emissions. In a July 2007 issue of Foreign Affairs, Romney calls for “a bold, far-reaching research initiative—an energy revolution—that will be our generation's equivalent of the Manhattan Project or the mission to the moon.” But he adds that “scientists still debate how much human activity impacts the environment.”

Romney can speak knowledgeably about some science issues on the campaign trail. He supports raising the cap on the number of H-1B visas so that more foreigners with high-tech skills can work in the United States. And this fall, he pledged to “substantially increase funding” for basic research related to energy efficiency and production. But as the primaries kick into high gear, expect Romney to put his focus more on hot-button social issues than the cooler high-tech matters that occupied him as governor of the Bay State.

15. REPUBLICAN

# Fred Thompson

1. Eli Kintisch,
2. Benjamin Lester

In 2000, when House Republicans wanted to pull the plug on the \$1.4 billion Spallation Neutron Source (SNS) being built at the Department of Energy's Oak Ridge National Laboratory in Tennessee, the state's congressional delegation went to bat for the project. Fred Thompson, then one of the two Republican senators from Tennessee, was “extremely helpful” in assigning staff to work the issue, recalls physicist David Moncton, then head of the SNS project.

But Moncton, now a professor at the Massachusetts Institute of Technology, remembers something else about his interaction with the senator on SNS, which staved off the threat and opened last year. “The issue [for Thompson] was this billion-dollar project was happening in Tennessee,” says Moncton. “There was no discussion of how intrinsically interested he was in science.” Rick Borchelt, a longtime Democratic aide and former spokesperson for the Department of Energy lab, concurs. “He's pretty much a cipher on science and technology,” says Borchelt.

The 65-year-old Tennessee native has played the president—as well as a military officer and a hard-nosed district attorney—during a long television and film career. He's also been a lawyer, lobbyist, and talk-show host after coming to Washington in 1973 as a Republican staffer during the Watergate hearings. Since jumping into the race for president last summer, he has rarely addressed science issues. But Norman J. Ornstein of the American Enterprise Institute in Washington, D.C., who worked with Thompson when he chaired what was then called the Government Affairs Committee, credits him with being “knowledgeable and insightful” on the often thorny issues that came before the panel. “I found him to be quite engaged on issues he cared about,” says Ornstein. “But he was not a guy who stuck around if he didn't need to.”

Some of Thompson's recent positions have not endeared him to researchers. Within a few hours of reading about a method of genetically reprogramming skin cells into what appear to be embryoniclike stem cells, he rushed out a statement lauding the discovery. “Today's announcement is just one more indication that our current policy in relying only on adult cells is working,” he said on 20 November. Thompson ranked the achievement as the latest addition in “73 breakthroughs for adult and cord blood research” that he said have paved the way for new treatments for several diseases.

That tally comes from the Family Research Council, a conservative advocacy group in Washington, D.C. Many scientists regard the analysis, by the council's David Prentice, as seriously flawed, and even Prentice says the list did not imply that those breakthroughs had led to available treatments. “[The list] not only misrepresents existing adult stem cell treatments, but also frequently distorts the nature and content of the references he cites,” wrote Steven Teitelbaum, former president of the Federation of American Societies for Experimental Biology in Bethesda, Maryland, in a letter published in Science (28 July 2006, p. 439). “Fred Thompson is misinformed,” Teitelbaum says about the candidate's latest pronouncement.

Thompson has also climbed out on a limb in discussing climate change. “While we don't know for certain how or why climate change is occurring, it makes sense to take reasonable steps to reduce CO2 emissions without harming our economy,” notes an issues statement from the campaign. In March, Thompson jokingly told a radio audience that “quite a few planets in our solar system seem to be heating up a bit. This has led some people, not necessarily scientists, to wonder if Mars and Jupiter, nonsignatories to the Kyoto Treaty, are actually inhabited by alien SUV-driving industrialists.”

Gavin Schmidt, a climate modeler at NASA's Goddard Institute for Space Studies in New York City, calls the statement “ridiculous” and says it's based on the faulty idea of a recent warming of the sun. “We've been measuring the sun['s temperature] for 30 years—it's not doing anything,” Schmidt notes.

Campaign staffers declined repeated requests from Science to detail Thompson's views on science and technology issues. And last month, at an Iowa debate in which each Republican candidate was asked whether climate change was real and caused by human activities, Thompson chose to go for a punch line rather than inform his audience. First he declined to give a yes-or-no answer. Then, after one long-shot candidate gave a rambling response that seemed to ignore the question, Thompson passed again. “I agree with Alan Keyes's position on climate change,” he cracked to wide laughter from the audience.

16. NEWS

# Untangling the Celestial Strings

In an effort that weaves together astronomy, astrophysics, and cosmology, scientists are mapping the filamentary framework that gives shape to the cosmos

CHICAGO, ILLINOIS— All the universe is a tangled web, and all the stars and galaxies its captives. Fans of the Bard may groan, but that doggerel nicely sums up scientists' understanding of the cosmos. Unraveling that “cosmic web” presents astronomers, astrophysicists, and cosmologists with their next great challenge.

The web is the framework on which the universe is built. It consists primarily of “dark matter,” mysterious stuff that makes up 85% of the matter in the universe but has revealed itself only through its gravity. Enormous filaments and blobs of the stuff condensed as the universe matured. Within them nestle the galaxies and their stars, creating streams of light stretching between inky voids. Even-stranger dark energy pervades everything, stretching space and affecting the evolution of the web.

That's the big picture. Now, scientists are turning to the details. What are the properties of dark matter and dark energy? Precisely how is the web organized? Exactly how do galaxies form in it? The web spans size scales from individual galaxies to the breadth of the observable universe. In its evolution, it traces the complexity we see today back through time to the big bang. And it bridges the conceptual divide between the reductive theories of cosmology and the rich and varied astrophysics of galaxies and clusters.

“To me, the really exciting part of astronomy and astrophysics in the next 15 years is how to interpret the light that we see in terms of the web of dark matter,” says Howard Yee, an astronomer at the University of Toronto in Canada and one of 106 researchers who met here last month* to discuss efforts largely aimed at mapping out the cosmic web. “We don't know how to say, ‘Here [in the web], a galaxy will show up at a certain time and with a certain size.’”

The drive to trace the cosmic web is changing the practice of astronomy. Researchers are turning to the galaxies with renewed interest, says Michael Gladders, an astronomer at the University of Chicago. Only now, they are analyzing them en masse. “We're going to see a resurgence of what you might consider classical astronomy—looking at distinct objects at optical and infrared wavelengths—except millions of them at a time,” Gladders says.

## A recipe for the universe

Ten years ago, most theorists agreed that dark matter had to exist, as its gravity appears to hold the galaxies together. Then three observations in quick succession helped cosmologists nail down a precise list of ingredients for the cosmos.

In 1998, two teams used the light from exploding stars called type Ia supernovae to measure the expansion of the universe. To their surprise, they found that instead of slowing as expected, it's speeding up as though driven by dark energy (Science, 27 February 1998, p. 1298).

Meanwhile, astronomers were beginning huge surveys of the galaxies. Scientists used the 3.9-meter Anglo-Australian Telescope on Mount Worrat in New South Wales, Australia, to measure the three-dimensional (3D) positions of 221,000 galaxies as part of the 2dF Galaxy Redshift Survey, which ran from 1997 to 2002. Others with the Sloan Digital Sky Survey, which began in 1998, have used a 2.5-meter telescope at Apache Point, New Mexico, to pinpoint 800,000 galaxies. The results of the surveys can help theorists probe the interplay between dark matter, whose gravity pulls galaxies together, and dark energy, which pushes them apart.

Then in 2003, NASA's Wilkinson Microwave Anisotropy Probe (WMAP) spacecraft mapped the afterglow of the big bang, the cosmic microwave background (CMB), to produce, in essence, the universe's baby picture. The universe supposedly sprang into existence infinitely dense and hot and immediately doubled its size 100 times over. After about 10−32 seconds of such “inflation,” the expansion slowed, and 400,000 years later, the universe cooled enough to allow free-flying protons and electrons to form hydrogen atoms. That transformation freed light trapped by the particles, which has since stretched into microwaves and cooled to 2.725 kelvin.

(As light travels through the expanding universe, it is stretched, or “redshifted,” to longer wavelengths. Scientist use redshift to mark cosmic history. Light whose wavelength has increased 200% has a redshift of 2 and was emitted when the universe was one-third its current size—about 10 billion years ago.)

The CMB is not exactly uniform. Inflation magnified infinitesimal quantum fluctuations in the newborn universe, which eventually seeded the filaments in the cosmic web. The fluctuations also caused the temperature of the CMB to vary across the sky by about 0.001%. Analyzing the temperature ripples, and throwing in supernova and galaxy-cluster data, WMAP researchers found that, bizarrely, the universe consists of 73% dark energy, 23% dark matter, and 4% ordinary matter and is precisely 13.7 billion years old (Science, 19 December 2003, p. 2038).

“The CMB is a great gift because the fluctuations are big enough to measure but small enough to be easily understood,” says Gary Hinshaw, a cosmologist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. “You can read the parameters right off the spectrum” of ripples. But plenty of questions remain, says cosmologist Edward “Rocky” Kolb of the University of Chicago. “The rough picture works,” he says, “but the details of how galaxies form, how they interact, and whether mergers and acquisitions [of galaxies] are important still need to be worked out.”

## Filling in the fishbowl

Scientists hope to trace the web from near to far, from the present into the past. Humans have glimpsed the oldest light, the CMB, which appears to emanate from near the periphery of the observable universe 46.5 billion light-years away. (Everything farther away is rushing away so fast that its light will never reach us.) We've also started to explore the nearby cosmic web. So we're a bit like fish in a murky bowl that see the smudgy glass and the castle next to them. What's in between remains to be discovered.

Primarily, researchers are charting the galaxies, which lie within the dark-matter strands. In 2005, they forged a link between the ripples in the distribution of the galaxies and those in the CMB. Before atoms formed and as matter settled into the primordial fluctuations, protons pushed against light, sending tsunami-like sound waves zipping through space. Leaving their imprint on the CMB, the waves traveled about 100 kiloparsecs—326,000 light-years—before atoms formed.

Stretched 1000-fold by the expansion of the universe, that length scale should show up in the galaxies, too. Given one galaxy, there should be an increased chance of finding another that distance away, precisely what researchers with the Sloan survey found when they compared the distances between galaxies, says Ravi Sheth, a cosmologist at the University of Pennsylvania. More-precise measurements of such “baryon acoustic oscillations” could give researchers another way to study the expansion of the universe and might help reveal whether dark energy is part of space itself or is something flowing through it.

Scientists are also probing the web by counting clusters of galaxies, which form when individual galaxies fall into gargantuan clumps of dark matter. The size and number of the swarms reveal the distribution of dark matter. At the same time, the stretching effects of dark energy slow the formation of jumbo agglomerations. So simply tallying the abundance of clusters of different sizes at different redshifts promises to reveal properties of both weird substances, says Toronto's Yee.

Moreover, clusters are relatively easy to spot with optical and infrared telescopes, he says. That's because the galaxies in them tend to be old and filled with red giant stars, all of which emit light of essentially the same color. So by looking at the colors of the galaxies, astronomers can immediately tell which ones belong to the same cluster and what the cluster's redshift is. Using this technique, Yee and colleagues with the Red-Sequence Cluster Survey, which uses the Canada-France-Hawaii Telescope atop Mauna Kea in Hawaii, have been scanning 1000 square degrees of sky and have cataloged 20,000 clusters.

Researchers are striving to “see” the darkmatter filaments by observing how their gravity bends light from more distant galaxies and skews their images. Known as weak gravitational lensing, the technique allows scientists to detect dark-matter blobs directly, without looking at the stars or galaxies in them, says Gary Bernstein, a cosmologist at the University of Pennsylvania.

Because of weak lensing, the galaxies everso-slightly tend to line up, like fish in a school. Researchers first observed the effect in 2000, and last year, Richard Massey, an astronomer at the California Institute of Technology in Pasadena, and colleagues took a big step further. Using images of half a million galaxies from NASA's Hubble Space Telescope, they compared the lensing of galaxies at three different distances to crudely map a bit of the 3D web, as they reported in the 18 January 2007 issue of Nature. Ultimately, researchers hope to perform such 3D studies over huge swaths of the sky, Bernstein says.

## Looking with other eyes

Staring at galaxies with optical and infrared telescopes is not the only way to study the cosmic web. For example, radio astronomers can join the hunt for galaxy clusters by looking for pimple-like spots in the CMB. Those spots arise because of a bit of physics called the Sunyaev-Zel'dovich effect. Microwave photons from the CMB crash into the electrons in hot, ionized gas within galaxy clusters, explains Matt Dobbs, an astrophysicist at McGill University in Montreal, Canada. The collisions change the microwaves' energy, creating the telltale distortion. Because the effect does not depend on the cluster's own light, it should help to reveal fainter, more distant clusters, Dobbs says.

So far, most studies have probed the Sunyaev-Zel'dovich effect in clusters already found some other way. But the Sunyaev-Zel'dovich Array, a collection of eight 3.5-meter radio dishes in Owens Valley, California, is scanning 6 square degrees of sky in a blind search for new clusters. And the 6-meter Atacama Cosmology Telescope in Chile and the 10-meter South Pole Telescope will scan 200 and 4000 square degrees of sky, respectively, which should reveal thousands of clusters.

Researchers needn't look only at galaxies. Most ordinary matter resides not in stars and galaxies but in huge clouds of neutral and ionized gas. Astronomers can detect neutral hydrogen by looking toward celestial beacons called quasars. Whenever a quasar's light passes through atomic hydrogen, some of it will be absorbed, creating a dip, or absorption line, in its spectrum. The wavelength of the dip reveals the cloud's redshift, the width of the dip reveals its temperature, and the depth of the dip reveals the amount of gas in the cloud, explains astronomer Michael Rauch of the Observatories of the Carnegie Institution of Washington in Pasadena, California. By studying many quasars, researchers hope to map out the distribution of gas in the web.

Scientists might be able to go even a step further in time. Atomic hydrogen emits radio waves of a distinct wavelength, 21 centimeters, when the proton in the atom flips. Researchers hope to exploit that radiation to detect the distribution of hydrogen back when the universe was less than a billion years old, when the first stars were forming. To do that, however, they'll need an observatory such as the proposed Square Kilometer Array, a collection of hundreds of radio dishes that astronomers propose to build in South Africa or Australia sometime in the next decade.

## Our lumpy neighborhood

Galaxies form in the web's smaller knots, and scientists are striving to determine how they swirl into existence. That's important because in galaxies, the dark-matter-dominated picture blurs. “It seems to work well on the large scales,” says Kathryn Johnston, an astrophysicist at Columbia University. “Where there seem to be some problems is on the small scales.” For example, simulations predict that the Milky Way should be surrounded by many more small satellite galaxies than astronomers have seen (Science, 3 August, p. 594).

Theorists know so little about galaxy formation that in their cosmological simulations, they let the dark matter evolve by itself and “paint” the galaxies onto the clumps and strands at the end. To fill the voids in their understanding, scientists are studying our own galaxy. “The Milky Way is the only galaxy for which we can hope to get threedimensional data about the positions and velocities” of individual stars, says Heidi Newberg, an astrophysicist at Rensselaer Polytechnic University in Troy, New York.

Most of the Milky Way's stars lie in its thin disk. But that disk resides in a fatter blob of dark matter known as a halo. Scientists once thought that the halo was smooth and that the stars in it were evenly distributed. In the past decade, that picture has changed thanks largely to star studies made by the Sloan survey. “As we keep looking deeper at the data, we keep seeing more and more lumps and things,” Newberg says. “There are big lumps, little lumps, smeared-across-the-sky lumps. It's just lumps everywhere.”

The halo seems to have been produced exclusively through the mergers of smaller galaxies, Newberg says. As the smaller galaxies fall in, the Milky Way's gravity tears them into sinuous “tidal streams,” such as the Sagittarius stream, which arches over the disk. By measuring the positions and velocities of stars, researchers can determine, statistically, which ones belong to which stream. And they may be able to make clearer connections by comparing the stars' chemical content, Johnston said at the meeting.

## Mapped out?

Ultimately, the cosmic web may bridge the divide between cosmology on one hand and astronomy and astrophysics on the other. Cosmologists seek to reduce the universe to its most basic ingredients and rules. Astronomers and astrophysicists study the myriad objects in the heavens and try to explain how they work and whether they are related to one another. In principle, the cosmic web ties the two types of work together. Whether it will in practice remains to be seen, says Chicago's Kolb. “Ten or 20 years from now, we may look back and say it had that unifying effect,” he says. “But we're too close to it now” to know if that will be the case.

Nevertheless, interest in the web is helping to change the craft of astronomy, fueling the drive to ever-larger surveys. For example, even as the Sloan survey continues, researchers with the Dark Energy Survey plan to use the 4-meter Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile to observe 5000 square degrees of sky and pinpoint 200 million galaxies. The first Pan-STARRS telescope on Mauna Kea will survey 3/4 of the sky—30,000 square degress—starting this year. And researchers have proposed an 8.4-meter behemoth known as the Large Synoptic Survey Telescope that would use a 3-gigapixel camera to image 10 square degrees of the sky at a time and fix the positions and redshift of 3 billion galaxies starting in 2014.

Many embrace the bigger-is-better approach. “You're compelled to do this by the science,” says Steven Myers, an astronomer at the National Radio Astronomy Observatory in Socorro, New Mexico. “I'm very enthusiastic for the new age of great survey projects.”

Surveys are growing so large that some researchers are beginning to talk of spotting all the 100 billion bright galaxies in the observable universe. The cosmos will always provide new mysteries, says Timothy McKay, an astrophysicist at the University of Michigan, Ann Arbor, who works on both the Sloan survey and the Dark Energy Survey, but researchers should eventually chart all of its large features. “We should look forward to a future in which the universe we can observe will be observed,” he says. “This cosmos incognita will be mapped out in our lifetimes.”

Researchers won't run out of galaxies to observe for a while, however. In the meantime, they've got plenty to do as they try to weave a deeper understanding of the cosmos one conceptual thread at a time.