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Web life: Hyperphysics


So what is the site about?

Hyperphysics is a network of cross-linked articles on topics from acceleration to the Zeeman effect — essentially an online physics encyclopedia. Unlike some sites featured in this column, Hyperphysics is far from new. In fact, by Web standards, it is positively ancient; when it was launched back in 1998 as a “hyperphysics exploration environment”, the search engine Google was still based in a California garage. Today, Google’s algorithms place Hyperphysics entries near the top of results pages for most physics-related search terms — it receives some three million hits per year — and some readers may already have stumbled across the site while searching for physics information on the Internet.

Can you describe a typical entry?

In addition to basic information, diagrams and relevant mathematical expressions, some pages also contain boxes that calculate numerical answers to questions using values typed in by the user. The main page devoted to the Schrödinger equation, for example, begins by explaining how the equation’s potential- and kinetic-energy terms differ from their classical equivalents. Further down the page is a section describing how to calculate the energy of the nth quantum state for a particle in a box — a standard “first problem” in many undergraduate quantum-mechanics courses. A link to “applications of the Schrödinger equation” brings up a map of interrelated subjects such as quantum tunnelling and the hydrogen atom. Such maps appear frequently on the site to illustrate how various subtopics can be traced back to common principles.

Who is it aimed at?

According to its creator Rod Nave, a physicist at Georgia State University in the US, Hyperphysics grew out of a summer course in “conceptual physics” for prospective science teachers. The course was originally meant to give biology and chemistry specialists a basic exposure to physics, but when Nave realized that many of them would actually be teaching physics (due to a severe shortage of physicists), he decided to build something to support them after the course was over. Now, most e-mails he gets about the site come from physics students, who use it to supplement their main course materials, or engineers, who rely on it for general background information.

How often is the site updated?

Hyperphysics is always considered to be a work in progress,” Nave tells Physics World, and it is updated “almost continuously”. One of the site’s current goals is to incorporate more topics from disciplines like chemistry and biology, so that users can explore the physical principles that underlie them. In addition to this formal programme of updates, Nave says he receives hundreds of e-mails a year containing corrections, suggestions for new topics, and queries about his approach. “The helpfulness of users has been one of the really inspiring things about the project,” he says.

Why should I visit?

Despite its unflashy graphics, Hyperphysics remains one of the Web’s finest and easiest-to-use physics resources. The main topics are listed in an index, and a dense web of links between them allows users to explore a subject in as much or as little depth as they choose. It is not difficult to start off looking for a specific piece of information — the Boltzmann constant, say — and emerge an hour later, newly knowledgeable about both the original question and about apparently distant topics like ionic bonding and the electron affinity of chlorine.

Doing science in the open

In your high-school science classes you almost certainly learned Hooke’s law, relating a spring’s length to how hard you pull on it. What your high-school science teacher probably did not tell you is that when Robert Hooke discovered his law in 1676, he published it as an anagram, “ceiiinossssttuv”, which he revealed two years later as the Latin “ut tensio, sic vis”, meaning “as the extension, so the force”. This ensured that if someone else made the same discovery, then Hooke could reveal the anagram and claim priority, thus buying time in which he alone could build upon the discovery.

Hooke’s secretiveness was not unusual. Many great scientists of the age, including Leonardo da Vinci, Galileo Galilei and Christiaan Huygens, used anagrams or ciphers for similar purposes. The Newton—Leibniz controversy over who invented calculus occurred because Isaac Newton claimed to have invented calculus in the 1660s and 1670s, but did not publish his work until 1693. In the meantime, Gottfried Leibniz developed and published his own version of calculus. Imagine modern biology if the human genome had been announced as an anagram, or if publication had been delayed 30 years.

Why were Hooke, Newton and their contemporaries so secretive? In fact, until this time discoveries were routinely kept secret. Alchemists intent on converting lead into gold or finding the secret of eternal youth would often take their discoveries with them to the grave. A secretive culture of discovery was a natural consequence of a society in which the personal gain from sharing discoveries was fraught with uncertainty.

The great scientific advances in the time of Hooke and Newton later motivated wealthy patrons, such as the government, to begin subsidizing science as a profession. Much of the motivation came from the public benefit delivered by scientific discovery, and that benefit was strongest if discoveries were shared. The result was a scientific culture that to this day rewards the sharing of discoveries with jobs and prestige for the discoverer.

This cultural transition was just beginning in the time of Hooke and Newton, but a little over a century later the great physicist Michael Faraday could advise a younger colleague to “Work. Finish. Publish”. The culture of science had changed so that a discovery not published in a scientific journal was not truly complete.

The adoption and growth of scientific journals has created a body of shared knowledge for our civilization, a collective long-term memory that is the basis for much of human progress. This system has changed surprisingly little in the last 300 years. Today, the Internet offers us the first major opportunity to improve this collective long-term memory, and to create a collective short-term working memory — a conversational commons for the rapid collaborative development of ideas.

This change will not be achieved without great effort. From the outside, scientists currently appear puzzlingly slow to adopt many online tools. As we will see, this is a consequence of some major barriers deeply embedded within the culture of science. Changing this culture will only be achieved with great effort, but I believe that the process of scientific discovery — how we do science — will change more over the next two decades than in the past 300 years.

How can the Internet improve the way we do science?

There are two useful ways to answer this question. The first is to view online tools as a way of expanding the range of scientific knowledge that can be shared with the world. Many online tools do just this, and some have had a major impact on how scientists work. Two successful examples are the physics preprint server arXiv, which lets physicists share preprints of their papers without the months-long delay typical of a conventional journal, and GenBank, an online database where biologists can deposit and search for DNA sequences. But most online tools of this type remain niche applications, often despite the fact that many scientists believe broad adoption would be valuable. Two examples are Journal of Visualized Experiments, which lets scientists upload videos that show how their experiments work, and “Open Notebook Science”, as practised by scientists like Jean-Claude Bradley and Garrett Lisi, who expose their working notes to the world. In the coming years we will see a proliferation of tools of this type, each geared to sharing different types of knowledge.

There is a second and more radical way of thinking about how the Internet can change science, and that is through a change to the process and scale of creative collaboration itself, enabled by social software such as wikis, online forums and their descendants.

There are already many well known but still striking instances of this change in parts of culture outside of science (well documented in Clay Shirky’s excellent book Here Comes Everybody). For example, in 1991 an unknown Finnish student named Linus Torvalds posted a short note in an online forum, asking for help extending a toy operating system he had programmed in his spare time; a volunteer army responded by assembling Linux, one of the most complex engineering artefacts ever constructed. In 2001 another young unknown named Larry Sanger posted a short note asking for help building an online encyclopedia; a volunteer army responded by assembling Wikipedia, the world’s most comprehensive encyclopedia.

Another example of the power of online collaboration comes from chess. In 1999, Garry Kasparov, the greatest chess player of all time, played against the “World Team” — a single team consisting of thousands of chess players, many rank amateurs, which decided on their moves by vote. Kasparov won, but instead of the easy victory he expected, he got the most challenging game of his career, which he called “the greatest game in the history of chess”.

These examples are not curiosities or special cases; they are the leading edge of a great change in the creative process. Science is an example par excellence of creative collaboration, yet scientific collaboration still takes place mainly via small scale face-to-face meetings. With the exception of e-mail, few of the new social tools have been broadly adopted by scientists, even though it is these tools that have the greatest potential to speed up the rate of scientific discovery.

Why have scientists been so slow to adopt these remarkable tools? Is it simply that they are too conservative in their habits, or that the new tools are no better than what we already have? Both these glib answers are wrong. We can resolve this puzzle by looking in detail at two examples where excellent online tools have failed to be adopted by scientists. It turns out that there are major cultural barriers preventing scientists from getting involved, thereby slowing down the progress of science.

A failure of science online: online comment sites

Like many people, when I am considering buying a book or electronic gadget, I often first browse the reviews at Amazon. Inspired by the success of Amazon, several organizations have created comment sites where scientists can share their opinions of scientific papers. Perhaps the best known was Nature’s 2006 trial of open commentary on papers undergoing peer review at the journal (see Physics World January 2007 pp29—30). The trial was not a success, as Nature’s final report explained: “There was a significant level of expressed interest in open peer review. A small majority of those authors who did participate received comments, but typically very few, despite significant Web traffic. Most comments were not technically substantive. Feedback suggests that there is a marked reluctance among researchers to offer open comments.”

The Nature trial is just one of many attempts at comment sites for scientists. The earliest example I am aware of is the Quick Reviews site, which was launched in 1997 and discontinued in 1998. Physics Comments was developed a few years later, and discontinued in 2006. A more recent site, Science Advisor, is still active, but has more members (1139) than reviews (1008). It seems that people want to read reviews of scientific papers, but not write them. An ongoing experiment that incorporates online commentary and many other innovative features is PLoS ONE, but it is too early to tell how successful its commentary will be.

The problem that all these sites have is that while thoughtful commentary on scientific papers is certainly useful for other scientists, there are few incentives for people to write such comments. Why write a comment when you could be doing something more “useful”, like writing a paper or a grant proposal? Furthermore, if you publicly criticize someone’s paper, then there is a chance that the person may be an anonymous referee in a position to scuttle your next paper or grant application.

To grasp the mindset here, you need to understand the monklike intensity that ambitious young scientists bring to the pursuit of scientific publications and grants. To get a position at a major university the most important thing is an impressive record of scientific papers. These papers will bring in the research grants and letters of recommendation necessary to get hired. Competition for positions is so fierce that 70—80 hour working weeks are common. The pace relaxes after tenure, but continued grant support still requires a strong work ethic. It is no wonder people have little inclination to contribute to online comment sites.

The contrast between the science comment sites and the success of the reviews at Amazon is stark. To pick just one example, you will find approximately 1500 Pokemon products on Amazon, more than the total number of reviews on all the scientific comment sites I described above. The disincentives facing scientists have led to a ludicrous situation where popular culture is open enough that people feel comfortable writing Pokemon reviews, yet scientific culture is so closed that people will not publicly share their opinions of scientific papers. Some people find this contrast curious or amusing; I believe it signifies something seriously amiss with science, something we need to understand and change.

A failure of science online: Wikipedia

Wikipedia is a second example where scientists have missed an opportunity to innovate online. Wikipedia has a vision statement to warm a scientist’s heart: “Imagine a world in which every single human being can freely share in the sum of all knowledge. That’s our commitment.” You might guess Wikipedia was started by scientists eager to collect all of human knowledge into a single source. In fact, Wikipedia’s founder, Jimmy Wales, had a background in finance and as a Web developer for an “erotic search engine”, not in science. Co-founder Larry Sanger was a philosopher who had left academia. In the early days, few established scientists were involved. Just as for the scientific comment sites, to contribute aroused suspicion from colleagues that you were wasting time that could be better spent writing papers and grants.

Some scientists will object that contributing to Wikipedia is not really science. And, of course, it is not if you take a narrow view of what science is, and take it for granted that science is only about publishing in specialized scientific journals. But if you take a broader view, if you believe science is about not only discovering how the world works, but also about sharing that understanding with the rest of humanity, then the lack of early scientific support for Wikipedia looks like an opportunity lost. Nowadays, Wikipedia’s success has to some extent legitimized contribution within the scientific community. But how strange that the modern day Library of Alexandria had to come from outside academia.

The challenge: achieving extreme openness in science

These failures of science online are all examples where scientists show a surprising reluctance to share knowledge that could be useful to others. This is ironic, for the value of cultural openness was understood centuries ago by many of the founders of modern science; indeed, the journal system is perhaps the most open system for the transmission of knowledge that could be built with 17th-century media. The adoption of the journal system was achieved by subsidizing scientists who published their discoveries in journals. This same subsidy now inhibits the adoption of more effective technologies, because it continues to incentivize scientists to share their work in conventional journals and not in more modern media.

We should aim to create an open scientific culture where as much information as possible is moved out of people’s heads and labs, onto the network and into tools that can help us structure and filter the information. This means everything — data, scientific opinions, questions, ideas, folk knowledge, workflows and everything else. Information not on the network cannot do any good.

Ideally, we will achieve a kind of extreme openness: making many more types of content available than just scientific papers; allowing creative reuse and modification of existing work through more open licensing and community norms; making all information not just human readable but also machine readable; providing open interfaces to enable the building of additional services on top of the scientific literature, and possibly even multiple layers of increasingly powerful services. Such extreme openness is the ultimate expression of the idea that others may build upon and extend the work of individual scientists in ways that they themselves would never have conceived.

To create an open scientific culture that embraces new online tools, two challenging tasks must be achieved: first, build superb online tools; and second, cause the cultural changes necessary for those tools to be accepted. The necessity of accomplishing both these tasks is obvious, yet projects in online science often focus mostly on building tools, with cultural change an afterthought. This is a mistake, for the tools are only part of the overall picture. It took just a few years for the first scientific journals (a tool) to be developed, but many decades of cultural change before journal publication was accepted as the gold standard for judging scientific contributions.

None of this is to discount the challenge of building superb online tools. To develop such tools requires a rare combination of strong design and technical skills, and a deep understanding of how science works. The difficulty is compounded because the people who best understand how science works are scientists themselves, yet building such tools is not something scientists are typically encouraged or well suited to do. Scientific institutions reward scientists for making discoveries within the existing system of discovery; there is little space for people working to change that system. A technologically challenged head of department is unlikely to look kindly on a scientist who suggests that instead of writing papers they would like to spend their research time developing general-purpose tools to improve how science is done.

What about the second task, achieving cultural change? As any revolutionary can attest, that is a tall order. Let me describe two strategies that have been successful in the past, and that offer a template for future success. The first is a top-down strategy that has been successfully used by the open-access (OA) movement. The goal of the OA movement is to make scientific research freely available online to everyone in the world. It is an inspiring goal, and the OA movement has achieved some amazing successes. Perhaps most notably, in April 2008 the US National Institutes of Health (NIH) mandated that every paper written with the support of their grants must eventually be made open access. The NIH is the world’s largest grant agency; this decision is the scientific equivalent of successfully storming the Bastille.

The second strategy is bottom-up. It is for the people building the new online tools to also develop and boldly evangelize ways of measuring the contributions made with the tools. To understand what this means, imagine you are a scientist sitting on a committee that is deciding whether or not to hire a scientist. Their curriculum vitae reports that they have helped build an open-science wiki, and also that they write a blog. Unfortunately, the committee has no easy way of understanding the significance of these contributions, since as yet there are no broadly accepted metrics for assessing such contributions. The natural consequence is that such contributions are typically undervalued.

To make the challenge concrete, ask yourself what it would take for a description of the contribution made through blogging to be reported by a scientist on their curriculum vitae. How could you measure the different sorts of contributions a scientist can make on a blog — outreach, education and research? These are not easy questions to answer. Yet they must be answered before scientific blogging is accepted as a valuable professional scientific contribution.

A success story: arXiv and SPIRES

One example illustrating the bottom-up strategy in action is the well-known physics preprint server arXiv. Since 1991 physicists have been uploading their papers to arXiv, often at about the same time as they submit the material to a journal. The papers are made freely available within hours for anyone to read. arXiv is not refereed, although a quick check is done by moderators to remove crank submissions. arXiv is an excellent and widely used tool, with more than half of all new papers in physics appearing there first. Many physicists start their day by seeing what has appeared on the site overnight. Thus, arXiv exemplifies the first step towards achieving a more open culture: it is a superb tool.

Not long after arXiv began, a citation-tracking service called SPIRES decided it would extend its service to include both arXiv papers and conventional journal articles. SPIRES specializes in particle physics, and as a result it is now possible to search on a particle physicist’s name and see how frequently all their papers, including arXiv preprints, have been cited by other physicists.

SPIRES has been run since 1974 by one of the most respected and highly visible institutions in particle physics, the SLAC National Accelerator Laboratory. The effort that SLAC has put into developing SPIRES means that its metrics of citation impact are both credible and widely used by the particle-physics community. It is now possible for a particle physicist to convincingly demonstrate that their work is having a high impact, even if it has only been submitted to arXiv and has not yet been published in a conventional scientific journal. When hiring committees meet to evaluate candidates in particle physics, people often have their laptops out, examining and comparing the SPIRES citation records of candidates.

SPIRES and arXiv have not stopped particle physicists from publishing in peer-reviewed journals. When you are applying for jobs, or up for tenure, every ounce of ammunition helps, especially when the evaluating committee may contain someone from another field who is reluctant to take the SPIRES citation data seriously. Still, some physicists have become more relaxed about publication, and it is not uncommon to see CVs including preprints that have not been published in conventional journals.

The problem of collaboration

Even Albert Einstein needed help occasionally. In 1912, when Einstein first realized that a new kind of geometry was needed to describe space and time, he had little idea of how to proceed. Fortunately, he shared his difficulties with a mathematician friend, Marcel Grossman, who knew just what Einstein needed and introduced him to the work of the mathematician Bernhard Riemann. It took Einstein three more years to work out the full theory, but Grossman was right, and this was a critical point in the development of general relativity.

Einstein’s conundrum is familiar to any scientist. When doing research, subproblems constantly arise in unexpected areas. No-one can be expert in all those areas. Most of us instead stumble along, picking up the skills necessary to make progress towards our larger goals, grateful when the zeitgeist of our research occasionally throws up a subproblem in which we are already truly expert. Like Einstein, we have a small group of trusted collaborators with whom we exchange questions and ideas when we are stuck. Unfortunately, most of the time even our collaborators are not that much help. They may point us in the right direction, but rarely do they have exactly the expertise we need. Is it possible to scale up this conversational model, and build an online collaboration market to exchange questions and ideas, a sort of collective working memory for the scientific community?

It is natural to be sceptical of this idea, but an extremely demanding creative culture already exists that shows that such a collaboration market is feasible — the culture of free and open-source software. Scientists browsing for the first time through the development forums of open-source programming projects are often shocked at the high level of the discussion. They expect amateur hour at the local karaoke bar; instead, they find professional programmers routinely sharing their questions and ideas, helping solve each other’s problems, often exerting great intellectual effort and ingenuity. Rather than hoarding their questions and ideas, as scientists do for fear of being scooped, the programmers revel in swapping them. Some of the world’s best programmers hang out in these forums, swapping tips, answering questions and participating in the conversation.

I will now describe two embryonic examples that suggest that online collaboration markets for science may be valuable. The first is InnoCentive, which allows companies like Eli Lilly and Proctor and Gamble to pose “challenges” over the Internet: scientific research problems with associated prizes for their solution, often many thousands of dollars. For example, one of the challenges currently on InnoCentive asks participants to find a biomarker for motor neuron disease, with a $1m prize. If you register for the site, it is possible to obtain a detailed description of the challenge requirements, and attempt to win the prize. More than 140 000 people from 175 countries have registered, and prizes for more than 100 challenges have been awarded.

InnoCentive is an example of how a market in scientific problems and solutions can be established. Of course, it has shortcomings as a model for collaboration in basic research. Only a small number of companies are able to pose challenges, and they may do so only after a lengthy vetting process. InnoCentive’s business model is aimed firmly at industrial rather than basic research, and so the incentives revolve around money and intellectual property, rather than reputation and citation. It is certainly not a rapid-fire conversational tool like the programming forums; one does not wake up in the morning with a problem in mind and post it to InnoCentive, hoping for help with a quick solution.

FriendFeed is a much more fluid tool that is being used by scientists as a conversational medium to discuss research problems. What FriendFeed allows users to do is set up what is called a lifestream. As an example, my lifestream is set up to automatically aggregate pretty much everything I put on the Web, including my blog posts, del.icio.us links, YouTube videos and several other types of content.

I also subscribe to a list of about 100 or so “friends” whose lifestreams I can see aggregated into one giant river of information — all their Flickr photos, blog posts and so on. These people are not necessarily real friends — I am not personally acquainted with my “friend” Barack Obama — but it is a fantastic way of tracking a high volume of activity from a large number of people.

As part of the lifestream, FriendFeed allows messages to be passed back and forth in a lightweight way, so communities can form around common interests and shared friendships. In April 2008 Cameron Neylon, a chemist from the University of Southampton, used FriendFeed messaging to post a request for assistance in building molecular models. Pretty quickly Pawel Szczesny, a biologist at the Max Planck Institute for Developmental Biology in Tübingen, Germany, replied, and said he could help. A scientific collaboration was now under way.

FriendFeed is a great service, but it suffers from many of the same problems that afflict the comment sites and Wikipedia. Lacking widely accepted metrics to measure contribution, scientists are unlikely to adopt FriendFeed en masse as a medium for scientific collaboration. And without widespread adoption, the utility of FriendFeed for scientific collaboration will remain relatively low.

The economics of collaboration

How much is lost due to inefficiencies in the current system of collaboration? To answer this question, imagine a scientist named Alice. Like most scientists, many of Alice’s research projects spontaneously give rise to problems in areas in which she is not an expert. She juggles hundreds or thousands of such problems, re-examining each occasionally and looking to make progress, but knowing that only rarely is she the person best suited to solve any given problem.

Suppose that for a particular problem, Alice estimates that it would take her 4—5 weeks to acquire the required expertise and solve the problem. That is a long time, and so the problem is out on the back burner. Unbeknown to Alice, though, there is another scientist in another part of the world, Bob, who has just the skills required to solve the problem in less than a day. This is not at all uncommon. Quite the contrary; my experience is that this is the usual situation. Consider the example of Grossman, who saved Einstein what might otherwise have been years of extra work.

Do Alice and Bob exchange questions and ideas, and start collaborating towards a solution to Alice’s problem? Unfortunately, nine times out of 10 they never even meet, or if they do, they just exchange small talk. It is an opportunity lost for a mutually beneficial trade, a loss that may cost weeks of work for Alice. It is also a great loss for the society that bears the cost of doing science. Expert attention, the ultimate scarce resource in science, is very inefficiently allocated under existing practices for collaboration.

An efficient collaboration market would enable Alice and Bob to find this common interest, and exchange their know-how, in much the same way as eBay and craigslist enable people to exchange goods and services. However, in order for this to be possible, a great deal of mutual trust is required. Without such trust, there is no way that Alice will be willing to advertise her questions to the entire community. The danger of free riders who will take advantage for their own benefit (and to Alice’s detriment) is just too high.

In science, we are so used to this situation that we take it for granted. But let us compare it to the apparently very different problem of buying shoes. Alice walks into a shoe shop with some money. Alice wants shoes more than she wants to keep her money, while Bob the shop owner wants the money more than he wants the shoes. As a result, Bob hands over the shoes, Alice hands over the money, and everyone walks away happier after just 10 minutes. This rapid transaction takes place because there is a trust infrastructure of laws and enforcement in place that ensures that if either party cheats, then they are likely to be caught and punished.

If shoe shops operated like scientists trading ideas, first Alice and Bob would need to get to know one another, maybe go for a few beers in a nearby bar. Only then would Alice finally say “You know, I am looking for some shoes”. After a pause, and a few more beers, Bob would say “You know what, I just happen to have some shoes I am looking to sell”. Every working scientist recognizes this dance; I know scientists who worry less about selling their house than they do about exchanging scientific information.

In economics, it has been understood for hundreds of years that wealth is created when we lower barriers to trade, provided there is a trust infrastructure of laws and enforcement to prevent cheating and ensure trade is uncoerced. The basic idea, which goes back to economist David Ricardo in 1817, is to concentrate on areas where we have a comparative advantage, and to avoid areas where we have a comparative disadvantage.

Although Ricardo’s work was in economics, his analysis works equally well for the trade in ideas. Indeed, even were Alice to be far more competent than Bob, Ricardo’s analysis shows that both Alice and Bob benefit if Alice concentrates on areas where she has the greatest comparative advantage, and Bob on areas where he has a comparative disadvantage. Unfortunately, science currently lacks the trust infrastructure and incentives necessary for such free, unrestricted trade of questions and ideas.

An ideal collaboration market will enable just such an exchange of questions and ideas. It will include metrics of contribution so that participants can demonstrate the impact that their work is having. Contributions will be archived, time-stamped and signed, so it is clear who said what, and when. Combined with high-quality filtering and search tools, the result will be an open culture of trust that gives scientists a real incentive to outsource problems, and contribute in areas where they have a great comparative advantage. This will change science.

At a Glance: Open science

• The Internet provides an opportunity to create a conversational platform for scientists to develop ideas rapidly and collaboratively
• Scientists, however, have been relatively slow to adopt online tools such as comment sites and Wikipedia
• The Internet can improve the way we do science in two ways. First, online tools are a way of expanding the range of scientific knowledge that can be shared with the world. Second, the Internet can change the process and scale of creative collaboration itself, using social software such as wikis, online forums and their descendents
• Great online applications will not be sufficient to change scientific collaboration. We still require a cultural change that embraces an open scientific culture. This will include new metrics that acknowledge online collaboration as a genuine scientific contribution — something that will act as an incentive for scientists to share their problems online

More about: Open science
Open-access blogs
Author’s blog: michaelnielsen.org/blog
Cameron Neylon’s blog: blog.openwetware.org/scienceintheopen/2008/04/16/the-science-exchange
Open-access news: www.earlham.edu/~peters/fos/fosblog.html
Online communities
Science 2.0: friendfeed.com/rooms/science-2-0
Science commons: sciencecommons.org
Articles
Bill Hooker’s essays: 3quarksdaily.blogs.com/3quarksdaily/2006/10/the_future_of_s_1.html
M Waldrop 2008 Science 2.0: great new tool or great risk? Scientific American May pp68—73

Supersolids seen in new light

It’s a solid that’s not a solid — it can flow effortlessly through normal matter as if it were not there. This is a supersolid in principle, but for at least five years the true origin of this state of matter, if it is indeed real, has challenged the both minds and experimental prowess of physicists.

Now two studies by researchers in the US are giving new perspectives on the mystery, although it is far from being solved.

In the first study, Nobel laureate Philip Anderson of Princeton University addresses supersolids theoretically. Contrary to present computer models, he claims that supersolidity can be explained as superfluid of atom vacancies in a solid lattice. Moreover, he says that all “bosonic” solids — those that contain atoms with integer values of spin — should be a supersolid in their quantum ground state.

In the second study, Seamus Davis of Cornell University and colleagues find evidence that supersolid signatures observed in other experiments actually suggest more of a glassy, rather than a crystalline, behaviour. In other words, the supersolids reported might be termed more accurately “superglasses”.

Strange signals

The first good evidence for supersolidity came in 2004, when Moses Chan and his graduate student Eun–Seong Kim of Pennsylvania State University studied samples of helium–4 inside a torsion oscillator. They found a spike in the frequency of oscillations below a temperature of about 200 mK, which implied some of the helium had become a supersolid and detached from the rest of the sample. Since then at least five other groups have reproduced Chan’s supersolid signals, although results from other studies have confused any understanding of the phenomenon’s origin.

The original theory of supersolids — given 40 years ago by Russian theorists Alexander Andreev and Ilya Liftshitz — said the strange behaviour would be caused at low temperatures when vacancies in a lattice of bosons “condense” into the same quantum ground state, and thus behave as a single, coherent entity. But recently computer simulations have shown that near absolute zero there should be few, if any, vacancies left. Experiments have also shown that disordered helium crystals seem to give stronger supersolid signals, which implies the phenomenon may not be an intrinsic property of bulk helium but rather a property of defects in the lattice.

Anderson’s theoretical study, in his own words, addresses these issues “from a different point of view.” He thinks today’s computer simulations do not have the capability to rule out vacancies. On the basis that vacancies exist, he investigates how their phase can change using the “Gross-Pitaevskii equation”, which is commonly used for studying atomic condensation in cold gases. He makes arguments for choosing various parameters based on experimental results, and predicts that vacancies would condense below 50 to 70 mK. More importantly, however, he predicts defects should attract vacancies and therefore magnify the supersolid signal, as experiments indicate.

Glassy dynamics

Davis’s group, on the other hand, has investigated what the dynamics of a torsion oscillator can say about supersolids. They came up with a theory that predicts the relationship between the energy-dissipation response and frequency response for any material inside a torsion oscillator at different times and temperatures. They then reproduced the torsion oscillator experiments with samples of helium–4 warmed abruptly from 50 mK to different temperatures up to about 300 mK.

They found that, given their predictions, the dynamics were more indicative of a glassy rather than the crystalline state. But because of the large size of the frequency shift, they say the state seemed also to have a “super” component. This means a likely explanation for the reported supersolid signatures is therefore a superglass — an amorphous solid that exhibits some superfluidity.

Chan says he is pleased Davis’s group has confirmed his group’s previous findings, and says it is “interesting and instructive” to examine the result in terms of glassy dynamics. He also thinks Anderson’s paper is significant, because it shows, as experiments indicate, that supersolidity can exist in both disordered and “perfect” helium crystals. Nevertheless he says many mysteries remain, such as the fact that the supersolid signature has been shown to vary by up to three orders of magnitude.

What is the ground state?

Boris Svistunov, a theorist at the University of Massachusetts who in 2006 helped predict the existence of a superglass state for helium–4, thinks the conclusions of Davis’s group are “remarkable”.

The most intriguing direction is cold atoms in a lattice, and people are doing that Philip Anderson, Princeton University

However, he has less praise for Anderson’s work. He thinks Anderson is mistaken when he says simulations are not powerful enough to rule-out vacancies, because all the simulations need to do is calculate the gap required to create just one of them. In addition, he claims Anderson’s assertion that every bosonic solid is a supersolid in its ground state is “wrong”. He points to research he published in 2005 in which he calculates that finite gaps for vacancy and defect sites cause non-supersolid, insulating ground states.

Anderson told physicsworld.com he expected his work to be controversial, and admits no-one yet has the experimental capabilities to examine other bosonic solids in their ground state and so lend weight to his assertion. “The most intriguing direction is cold atoms in a lattice, and people are doing that,” he says.

The research is published in Science.

New camera 1000 times faster than competitors

A revolutionary new type of camera that can take photos more than 1000 times faster than conventional cameras has been revealed this week. Its creators at the University of California, Los Angeles (UCLA) say the device is set to become an indispensable tool for studying dynamic processes like shockwaves, communication between living cells, and laser surgery.

The key to this new camera is its ability to produce high-quality images using just a single-pixel light detector. This is made possible with a new imaging technique that both captures and amplifies light within the same unified process. The UCLA team showcased the camera by taking snapshots of a surgical laser technique at a significantly faster rate than is possible with the best digital camera on the market.

“Our camera overcomes the fundamental trade-off between sensitivity and speed without resorting to high-intensity illumination that can damage the sample being imaged,” said Keisuke Goda, on of the UCLA researchers.

Picture this

In conventional digital imaging such as CCD and CMOS cameras, the rate at which images are produced is restricted by the time it takes to read data from an array of millions of sensors. Also, as you increase the shutter speed, you are reducing the amount of light that reaches the sensors resulting in images of limited quality. “To put it simply, when you are taking a picture, you can’t collect enough light from an object if the exposure time is short,” Goda told physicsworld.com.

To get around this compromise, the UCLA researchers have developed a new technology which they refer to as STEAM — “serial time-encoded amplified microscopy”. STEAM works by freezing images using an optical rather than an electronic process. At its heart, a single-pixel photodiode and oscilloscope capture a stream of one dimensional time-varying data then convert this into high-quality two dimensional images.

Presenting their findings in Nature, the scientists used their camera to record laser ablation — a technique used in surgery to remove targeted areas without damaging near-by tissue. The ablation was performed with a mid-infrared pulse laser focused on a silicon substrate coated with aluminium foil. The camera, normally incident to the substrate surface, was able to capture the particle ejection at a frame rate of 6.1 MHz, where high-end digital cameras can manage only 1kHz.

Snapshot of the future

Goda told physicsworld.com that despite this success there is still much room for development. Even though the camera uses a state-of-the-art ADC, the quality of images is still restricted somewhat by the conversion of analogue to digital signals. However, whereas conventional digital cameras will never overcome this problem, STEAM could be adapted to segment an optical image into several channels and then detect these using an array of detectors.

“This work is interesting and exciting… it will be fascinating to see the upper limit on the amplification they can achieve,” said Changhui Yang, a biophotonics researcher at Caltech.

Ala L Hijazi, an optics researcher at Hashemite University in Japan told physicsworld.com that he is similarly impressed but warned that STEAM technology may find itself limited to high speed applications. “There would be concern about using such a device for obtaining quantitative 2D mapping such as PIV or spray analysis,” he said.

Something from nothing

By Hamish Johnston

The BBC’s resident polymath Melvyn Bragg was talking physics again. This morning he was exploring the physics of nothing with Frank Close, Jocelyn Bell Burnell and Ruth Gregory. Bell Burnell, by the way, is president of the Institute of Physics.

The programme is called the Vacuum of Space and you can listen to it here.

The team began with a philosophical discussion of a vacuum — apparently it was heresy in the Middle Ages to suggest that nothing could exist — and moved swiftly on to Torricelli’s studies involving atmospheric pressure.

The three physicists then discussed aether, the Michelson-Morley experiment and concluded that “Einstein got rid of Reading Station”.

Then it was time to delve into the weird world of quantum mechanics and the virtual particles that appear to bubble out of nothing. The physicists were keen on using banking analogies to explain all this — I suppose we are all familiar with virtual money these days — but Melvyn banned any mention of banks.

I had to switch off early as I got to work, but the team seemed to be coming round to the conclusion that in the quantum world “the uncertainty principle abhors a vacuum” — a new twist on a very old concept.

Can gravitational waves be detected in 'Millikan oil drops'?

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LIGO in Hanford, Washington: Could two drops of helium beat it in the race to detect gravitational waves?

By Hamish Johnston

Experiments that search for gravitational waves tend to be very large. The LIGO detectors in the US, for example, have arms that are 4 km long.

This is because the gravitational interaction is much weaker than the electromagnetic forces that govern the detectors. As a result humongous masses and long distances are needed to produce the tiniest signal — indeed, gravitational waves have yet to be detected directly.

However, Raymond Chiao believes that gravitational waves can be detected in tiny drops of superfluid helium that are coated with a specific number of electrons.

The drops would be suspended in a strong magnetic field — a setup that conjures up the famous oil drop experiment that allowed Robert Millikan to measure the charge of the electron.

Chiao describes his experiment in a book entitled Visions of Discovery: New Light on Physics, Cosmology and Consciousness, to be published by Cambridge University Press in 2010. The book is edited by Chiao — who has a long and distinguished career in quantum optics — and includes contributions from Nobel laureates Anthony Leggett and William Phillips.

As far as I can tell, the trick in Chiao’s proposed experiment is to set the charge-to-mass ratio of the drops such that each electron corresponds to a ‘Planck mass’ quantity of helium. Objects lighter than the Planck mass tend to be governed by quantum mechanics rather than general relativity.

“Now the force of gravity is approximately 137 times stronger than the force of electricity”, he writes.

Furthermore, two such drops separated by a centimetre or so would act as a “quantum transducer” that could convert an incoming gravitational wave into an outgoing electromagnetic wave — which Chiao believes could be used to detect gravitational waves.

So what do other physicists think?

The chapter is prefaced with an editor’s note, which begins “The following chapter has been the subject of considerable controversy during the review process”.

It goes on to say that one reviewer thought Chiao’s proposal was “reasonable”, while the others “found this claim to be highly questionable”.

Apparently the problem is that “some statements in the paper may be inconsistent with the current theory of superfluids. However that theory may be wrong…” — I believe this refers to Chiao’s proposed mechanism that couples gravitational and electromagnetic waves on the surface of the drops.

One way or another, Chiao’s chapter makes for a fascinating read.

Fledgling graphene circuit performs basic logic

Researchers in Italy have created the first integrated circuit to combine two transistors made from the “wonder material” graphene. By adapting a technique used to fabricate silicon transistors the team created the device and then showed that it was capable of performing basic computational tasks. The innovation represents an important step in the pursuit of carbon-based electronics, say the researchers.

“This opens a way for the fabrication of more complex integrated circuits on graphene, which may replace silicon chips once silicon technology reaches its limits,” said Roman Sordan, one of the researchers at the Politecnico di Milano.

To push the boundaries of computing power further, we will need microscale electronics that performs simple logic tasks at ever faster speeds. With conventional silicon chips, the limiting factor is the carrier mobility, which is a measure of ease at which its electrons travel through the material.

Roadmap to high speed electronics

Graphene — the one-atom-thick sheet of carbon discovered in 2004 — may overcome this problem with the help of its unique electronic properties. Unsurpassed mobility and carrier velocities mean that graphene should be able to operate at much higher frequencies than conventional electronics.

In 2007 physicists in the US created the world’s first prototype graphene transistor by fabricating nanoscale electrodes next to the surface of graphene to create a p-n junction. Since then researchers have continued to seek ways in which to increase the speed of graphene transistors. This latest development represents the next step towards an operational graphene circuit — combining multiple transistors.

The researchers first isolated an amount of graphene from a sheet of carbon using mechanical exfoliation — basically, “sticky tape” — before depositing these onto a silicon substrate. Then, using high resolution electron beam lithography, the researchers fabricated two p-type transistors on the same flake on graphene.

It’s all logical

The next step was to create an “inverter” by joining up a type p transistor with a type n. They passed an electric current through one of the transistors and used the heating effect to remove contaminants — this converted one of type p transistors to type n.

To demonstrate that they had created a very simple computing device the researchers used the “circuit” to perform the simple logic task of Boolean inversion.

“It is good that someone has finally taken the initiative to build basic circuits with graphene,” said Tomas Palacios, an electrical engineering researcher at Massachusetts Institute for Technology (MIT).

Other researchers are not so impressed by the latest development. Yu-Ming Lin, a nano-scale applications researcher at the IBM T.J. Watson Research Center in New York feels that this fledgling graphene circuit needs substantial development before it can serve any practical purpose.

“While inverter is the critical component in any digital circuits, one important aspect of an inverter is the gain, which must be larger than unity to be of useful,” he said. The research was published on the arXiv preprint server.

The perfect pizza toss revealed!

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How can chefs improve their technique?

By James Dacey

A trio of scientists at Monash University have studied footage of a professional chef to calculate the mechanics of the perfect pizza toss. This knowledge, they say, can now be used by engineers to improve the efficiency of micro-machines.

Kuang-Chen Liu and his team say this problem was a variation on the famous bouncing ball on vibrating platform problem. They report that for single dough-tosses, helical motion is best because it maximizes energy efficiency and the dough’s airborne rotational speed. For multiple tosses, they say a semi-elliptical motion is preferred because it is easier to maintain high-speed dough rotation.

Publishing their findings in Europhysics Letters, the researchers say this knowledge could now be used to optimize the design of standing wave ultrasonic motors (SWUM), applications of which include autofocus camera lenses.

“The only difference is that a chef tosses dough about once a second, a few tens of centimetres into the air. A SWUM tosses the rotor a few million times a second into the air,” said James Friend, one of dough-physics experts at Monash.

A strong contender for this year’s Ig Nobel prizes

Accelerator lab targets medical isotopes

Canada’s TRIUMF accelerator lab is teaming up with the medical isotope supplier MDS Nordion to study the feasibility of making molybdenum–99 in a linear accelerator — rather than in nuclear reactors as is done today.

TRIUMF, which is in Vancouver, and Ottawa-based MDS Nordion, also announced today that they will create a plan to commercialize the accelerator-based production of the isotope – which is used in around 80% of all diagnostic nuclear medicine tests worldwide.

The announcement comes amidst growing concern about the age, safety and reliability of reactors that produce molybdenum–99 following a series of well publicized technical problems and unscheduled plant shutdowns. New reactors are urgently needed to prevent future shortages of molybdenum–99 — but gaining consent, funding and political support for such plans is proving to be far from easy.

Intense photon beam

In November 2008, however, TRIUMF — along with the University of British Columbia, and the firm Advanced Applied Physics Solutions (AAPS) — released a report suggesting that a reactor may not be needed. Researchers instead proposed firing a highly intense photon beam — generated by a linear electron accelerator — at a uranium target to create molybdenum–99.

Although accelerator-based processing would need much more electrical power to run than a reactor-based facility, the advantage is that it would be possible to stop and re-start isotope production according to demand, which cannot be achieved with a nuclear reactor.

Another benefit of the new technique is that natural uranium targets can be used — whereas the reactor method requires highly enriched uranium targets that are difficult to transport and handle.

Building to start next year

Construction of such a facility at TRIUMF is scheduled to start in 2010 with tests slated for 2013.

MDS Nordion and TRIUMF already collaborate on the production of other medical isotopes using cyclotron accelerators.

Tweet your preprints

By Michael Banks

The Twitter bandwagon keeps on rolling.

Earlier this month Physics World joined the likes of Barack Obama, 10 Downing Street and the US rapper Snoop Dogg on Twitter — a website where people can post an answer to the question “what are you doing?” in under 140 words.

While some people actually do write — or “tweet” — what they are doing in every detail, most use it to post interesting links to stories that appear on the web. For example, Physics World tweets links to stories and blog entries that appear on our website.

Now, Robert Simpson, a PhD student from Cardiff University in the UK, has created a website that ranks papers appearing on the arXiv preprint server according to their popularity on Twitter.

His website searches Twitter for tweets that mention an arXiv url or posts that are tagged “#arxiv” and include the paper’s unique identifier.

The website retrieves and lists all the tweets and produces a table of the most popular papers, authors and arXiv categories ranked by how many tweets they have received.

The website has only been active since 16 April, but already there have been 75 tweets quoting arXiv papers.

This week’s top three papers include an introduction to machine learning, a 3D study of the photosphere of HD99563 and power-law distributions in empirical data.

The paper ranked fourth in the table, however, as far as I could tell was an April fool’s joke, which proclaimed that pi has changed since 1900 BC. So maybe think twice before taking such a ranking seriously.

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