A story in the New York Times about dark matter and dark energy published last October referred to me as “a physicist and blogger at the California Institute of Technology”. This is a perfectly accurate description of course – as would have been “physicist and poker player” or “physicist and jazz buff”, although I doubt that newspapers would ever refer to me in that way. Why should my blogging be singled out?

For me, blogging is not part of my job. Although it is a hobby that takes up maybe half an hour on average each day, blogging is a public activity through which one’s words become part of a larger discourse. Once you start blogging, and people begin reading your blog, “blogger” is part of your identity.

I started blogging in 2003 via Preposterous Universe (preposterousuniverse.blogspot.com). It was a spur-of-the-moment decision, but on my first day I received about 100 visits, which was both surprising and thrilling. Then in 2005 I joined forces with four other theoretical physicists to launch a group blog, Cosmic Variance (cosmicvariance.com). Among blogs with some sort of physics focus, we are the largest on the Internet – and by various measures we are about the 1000th largest blog of any sort. On a typical day the site gets about 3000 visits, which is a tiny number compared to the 100,000 or more hits of the largest political and technology blogs but still much greater than the number of people who attend a public talk or read my cosmology papers in Phys. Rev. D.

So who reads my blog? Many readers are physicists themselves (every time I visit another university to give a talk, several people will mention the blog), while an even larger number are students who are interested in what it is like to be a working physicist. There are also journalists looking for feedback on their news stories from active researchers. But a sizable majority seem to be people who simply have a strong amateur fascination in cosmology, gravitation, particle physics and the other subjects we touch upon.

Blogs are an enormously flexible medium, as easily deployed in the service of technical disquisitions as for gossiping about Paris Hilton or posting the family’s holiday photos. Some science bloggers use their blogs as research tools, bringing together experts for high-level discussions. At Cosmic Variance we concentrate more on building bridges between the worlds of specialists and interested outsiders. Blogs offer both immediacy and unfettered access to the inner workings of mysterious vocations of all sorts, which is hard to get from more formal journalism.

But blogs enhance rather than replace traditional media, for instance when a discussion on our site about the representation of women in physics was quoted in the New York Times. We have been interviewed by journalists, invited to conferences and taken part in discussions on the radio – no doubt due to our natural charm, but the visibility provided by blogging certainly has not hurt. Best of all, blogs provide a novel mechanism for interacting with the media. We have also invited experts on some breaking news story to comment on our blog, or even to contribute guest-postings. We have blogged about articles that we have read in newspapers and magazines, and been pleased to have the authors of the original articles show up in our comment sections to amplify or defend their work.

Informal communication

Along with immediacy, blogs are characterized by informality. At Cosmic Variance we freely mix scientific pedagogy and news analysis with personal anecdotes, opinions about art and politics, and even paeans to our favourite cocktail recipes. We do not think of ourselves a “physics blog”, which would imply some specific statement of purpose. Rather, ours is a blog written by people who happen to be physicists.

The mixture of informality and expertise is one of the key strengths of blogging because it lowers the barriers between scientists and the public. But it also contributes to the suspicions of those who simply do not “get it”. Distracted by the tendency of many bloggers to post pictures of their cats or to indulge in occasional invective, some physicists think of blogs as little more than 21st-century personal diaries. They miss the greater potential for a uniquely interactive and cross- or even extra-disciplinary discussion.

There are plenty of things that scientists care deeply about yet would never write about in technical journals. At Cosmic Variance, we have undertaken intense discussions about the relationship between science and religion, the purported hegemony of string theory within fundamental physics, the nature of successful science journalism, and how to choose the best graduate school. Without blogs, these conversations would never have extended beyond our own lunch tables. My fellow physicists have expressed surprise when I explain to them how effectively blogs are used by academics in the humanities and social sciences. Within economics, for example, there are Nobel laureates with blogs (Gary Becker) and within law the entire University of Chicago Law School faculty shares a group blog. Meanwhile, physicists, who are quick to claim credit for inventing the Web, have been relatively slow to embrace its latest and most dynamic manifestation.

Perhaps it is not so hard to guess why. In contrast to other fields like politics, economics and law, our work relates only indirectly to the concerns of most non-experts. The expertise of a professor working in contemporary Middle Eastern politics, say, is of direct interest to a typical informed citizen in a way that the expertise of a theoretical cosmologist simply is not. So compared with our colleagues elsewhere on campus, scientists have been reluctant to embrace the close contact with a general audience that blogging provides. Even for those of us interested in public-outreach activities, the traditional formats of popular books and talks stick closely to the standard lecturer–audience dynamic: we talk, you listen. Blogs are different because the audience can talk back.

We all know people who long resisted using e-mail or mobile phones only to eventually become enthusiastic converts. Similarly, physicists will eventually become more comfortable with the blogosphere. Blogging is certainly not for everyone, and some people are happiest being left alone with their work. But physicists, I predict, will ultimately embrace blogs wholeheartedly, as an amazingly effective way to share our enthusiasm for science and to put our work in a wider context.