Nature magazine: Wikipedia's scientific accuracy comes close to Britannica's, 1 in 10 Nature authors are wikipedians.

Wales: More expert wikipedians still needed; some articles will eventually have both static and dynamic versions.

The exercise revealed numerous errors in both encyclopaedias, but among 42 entries tested, the difference in accuracy was not particularly great: the average science entry in Wikipedia contained around four inaccuracies; Britannica, about three.

Considering how Wikipedia articles are written, that result might seem surprising. A solar physicist could, for example, work on the entry on the Sun, but would have the same status as a contributor without an academic background. Disputes about content are usually resolved by discussion among users.

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Only eight serious errors, such as misinterpretations of important concepts, were detected in the pairs of articles reviewed, four from each encyclopaedia. But reviewers also found many factual errors, omissions or misleading statements: 162 and 123 in Wikipedia and Britannica, respectively.

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Several Nature reviewers agreed with Panelas' point on readability, commenting that the Wikipedia article they reviewed was poorly structured and confusing. This criticism is common among information scientists, who also point to other problems with article quality, such as undue prominence given to controversial scientific theories. But Michael Twidale, an information scientist at the University of Illinois at Urbana-Champaign, says that Wikipedia's strongest suit is the speed at which it can updated, a factor not considered by Nature's reviewers.

"People will find it shocking to see how many errors there are in Britannica," Twidale adds. "Print encyclopaedias are often set up as the gold standards of information quality against which the failings of faster or cheaper resources can be compared. These findings remind us that we have an 18-carat standard, not a 24-carat one."

The most error-strewn article, that on Dmitry Mendeleev, co-creator of the periodic table, illustrates this. Michael Gordin, a science historian at Princeton University who wrote a 2004 book on Mendeleev, identified 19 errors in Wikipedia and 8 in Britannica. These range from minor mistakes, such as describing Mendeleev as the 14th child in his family when he was the 13th, to more significant inaccuracies. Wikipedia, for example, incorrectly describes how Mendeleev's work relates to that of British chemist John Dalton. "Who wrote this stuff?" asked another reviewer. "Do they bother to check with experts?"

But to improve Wikipedia, Wales is not so much interested in checking articles with experts as getting them to write the articles in the first place.

As well as comparing the two encyclopaedias, Nature surveyed more than 1,000 Nature authors and found that although more than 70% had heard of Wikipedia and 17% of those consulted it on a weekly basis, less than 10% help to update it. The steady trickle of scientists who have contributed to articles describe the experience as rewarding, if occasionally frustrating (see 'Challenges of being a Wikipedian').

Greater involvement by scientists would lead to a "multiplier effect", says Wales. Most entries are edited by enthusiasts, and the addition of a researcher can boost article quality hugely. "Experts can help write specifics in a nuanced way," he says.

Wales also plans to introduce a 'stable' version of each entry. Once an article reaches a specific quality threshold it will be tagged as stable. Further edits will be made to a separate 'live' version that would replace the stable version when deemed to be a significant improvement. One method for determining that threshold, where users rate article quality, will be trialled early next year.