Search All NYTimes.com Advertise on NYTimes.com GRAY MATTER It’s Science, but Not Necessarily Right Guy Billout By CARL ZIMMER Published: June 25, 2011 ONE of the great strengths of science is that it can fix its own mistakes. “There are many hypotheses in science which are wrong,” the astrophysicist Carl Sagan once said. “That’s perfectly all right: it’s the aperture to finding out what’s right. Science is a self-correcting process.” If only it were that simple. Scientists can certainly point with pride to many self-corrections, but science is not like an iPhone; it does not instantly auto-correct. As a series of controversies over the past few months have demonstrated, science fixes its mistakes more slowly, more fitfully and with more difficulty than Sagan’s words would suggest. Science runs forward better than it does backward. Why? One simple answer is that it takes a lot of time to look back over other scientists’ work and replicate their experiments. Scientists are busy people, scrambling to get grants and tenure. As a result, papers that attract harsh criticism may nonetheless escape the careful scrutiny required if they are to be refuted. In May, for instance, the journal Science published eight critiques of a controversial paper that it had run in December. In the paper, a team of scientists described a species of bacteria that seemed to defy the known rules of biology by using arsenic instead of phosphorus to build its DNA. Chemists and microbiologists roundly condemned the paper; in the eight critiques, researchers attacked the study for using sloppy techniques and failing to rule out more plausible alternatives. But none of those critics had actually tried to replicate the initial results. That would take months of research: getting the bacteria from the original team of scientists, rearing them, setting up the experiment, gathering results and interpreting them. Many scientists are A Banker Speaks, With Regret A Decade of Progress on AIDS Log In With Facebook MOST E-MAILED MOST VIEWED Log in to see what your friends are sharing on nytimes.com. Privacy Policy | What’s This? What’s Popular Now Sign up for a roundup of the day's top stories, sent every morning. Today's Headlines Daily E-Mail 1. WELL How Exercise Benefits the Brain 2. PERSONAL HEALTH It Could Be Old Age, or It Could Be Low B12 3. OP-ED COLUMNIST My Man Newt 4. HOLIDAY GIFT GUIDE The 10 Best Books of 2011 5. STATE OF THE ART A Thermostat That’s Clever, Not Clunky 6. OP-ED COLUMNIST A Banker Speaks, With Regret 7. Judy Lewis, Secret Daughter of Hollywood, Dies at 7 6 Subscribe: Home Delivery / Digital Log In Register Now Help HOME PAGE TODAY'S PAPER VIDEO MOST POPULAR TIMES TOPICS WORLD U.S. N.Y. / REGION BUSINESS TECHNOLOGY SCIENCE HEALTH SPORTS OPINION ARTS STYLE TRAVEL JOBS REAL ESTATE AUTOS RECOMMEND TWITTER LINKEDIN SIGN IN TO E-MAIL PRINT REPRINTS SHARE converted by Web2PDFConvert.com