The Internet has enabled the public to participate in science in a way that was never possible before. Starting with SETI@home and a growing number of other projects that use the BOINC infrastructure, home computer users could contribute processing time to actual science projects and, in return, get a glimpse of some of the analysis that was being performed on their computers. But these projects left the public as passive participants, watching as their computers did all the heavy lifting. There are many problems where humans are actually better than computers, and a new set of projects is using the Internet to harness the abilities of non-scientists to contribute towards a scientific goal.

The best known project of this sort may be the highly successful FoldIt project, which turned protein energy minimizations into a game, enabling home users to help solve protein structures that could sometimes trip up a computer. But a number of other citizen science projects are being hosted on the Zooniverse site, named after one of its most successful projects, the Galaxy Zoo. Robert Simpson, a post-doc at Oxford, described the Galaxy Zoo experience at a recent Science Online meeting, and generously shared the slides from his talk.

Galaxy Zoo has been an attempt to get citizen science to classify all the galaxies present in various data sets, such as the Sloan and Hubble surveys, as elliptical, spiral, etc. in order to give astronomers a better sense of just what's out there. In the process, however, the citizens have also proven adept at identifying some unusual things that appear in these images and, in doing so, have contributed to the publication of at least five astronomy papers.

Galaxy Zoo started off with a very simple premise: computers are lousy at doing many types of image recognition, but humans are generally quite good at it. And, with the advent of full sky survey telescopes, astronomers had a lot of images to classify on their hands. So, why not turn some of the work over to the public, which might have an interest in some of the pictures?

The Galaxy Zoo Web interface easily guides even a casual user through the process of characterizing a galaxy's shape and properties; more sophisticated decision trees have been added in newer iterations of the effort, but the process remains simple from the user perspective. That's critical, because most of the people who have contributed have only characterized somewhere between five and 25 galaxies (although a few users have gone through the whole set of 900,000).

The project makes up for this with volume. Even though most people don't contribute that much, enough have been interested to actually cause the server to fail on launch day (they now use Amazon Web Services). A user also created an iPhone app that, in two months of availability, has produced over 300,000 classifications. This high level of interest relative to the size of the data set is critical, as it ensures that each galaxy can have multiple independent classifications, which provides a degree of statistical certainty in the results, and protects against vandalism.

Citizens do actual science

Simpson laid out what he called the ground rules for citizen science: be open about research goals, treat participants as partners, and don't waste their time. To foster this open partnership, Galaxy Zoo created a user forum that let participants discuss what they are doing and ask questions of the astronomers. This actually turned out to be essential for some of the science, since it was on these forums that the astronomers actually spotted the users discussing some of the oddities they had seen.

One of these objects is now known as Hanny's Voorwerp, named for Dutch schoolteacher Hanny van Arkel, and shown above. Van Arkel spotted this strange green mass next to a normal looking spiral galaxy, and commented on it in the forums. For her efforts, she now appears as an author on three scientific papers that argue over what exactly the green blob represents (one favors a reflection of a quasar, the other two that it's a gaseous cloud being lit up by an active galactic nucleus in the nearby galaxy).

Van Arkel isn't the only citizen success story. In response to an initial post, Galaxy Zoo users created an entire photo gallery of what became known as "green peas," small structures that were often near normal galaxies and appeared green in the survey images. Two papers came out of the green peas, which turned out to be extremely compact galaxies with unusually high rates of star formation. That combination actually gave them spectral qualities that were distinct from typical galaxies.

Leaving the heavens behind

The "don't waste the participant's time" dictum that Simpson described has caused Zooniverse to be very selective about the projects it hosts—scientists, after all, would love to have strangers take care of the most tedious work for them. Most of the work there involves astronomy, which tends to attract high levels of public interest and involve photographs of sometimes stunning beauty.

So, additional projects have involved searches for merging galaxies and supernovae (amateur astronomers have a long history of being the first to spot exploding stars). Closer to home, researchers are crowdsourcing watching the Sun for signs of solar storms and the classifications of features on the surface of the Moon. Galaxy Zoo continues to move forward with new sources of survey data, like Galaxy Zoo: Hubble.

But if most of the projects have appealed to astronomy buffs, its latest may draw in some amateur historians. Old Weather is an attempt to fill out the sparse data we have on the global climate from early last century. Its appeal to the history fan is its source of new data: ships' logs from the British Royal Navy from the World War I era. As part of their daily logs, the ships' captains provided position and weather data, including temperature, but it was all written by hand, which makes it difficult for computers to decipher. People have fewer problems, so the project shows them images of the log entries and asks them to enter the data.

As an enticement, the project sometimes lets them see a bit of history, such as the entry Simpson showed, which included the order to commence hostilities against German vessels.

Another project will attempt to get users to assemble fragmentary scrolls that contain bits of Coptic text. If there are enough Coptic speakers online, they'll crowdsource translating them, as well.

Simpson said there are other, unspecified projects in the works, and Zooniverse isn't the only group that's working on getting participants involved. So it appears that citizen science may be a permanent part of the research landscapes.

Listing image by NASA