The blogosphere measures popularity by the number of people who read your posts and link back to you. And social media tools have evolved in a way that reflects this. Blogging tools, Facebook, Digg, Twitter, and most other tools allow you to measure and in some cases display your popularity. I can very easily track how many people have read my blog and with Feedburner I know how many have subscribed to it. There are also trackback functions that let me know how many others have linked to my blog. And of course, we can all see how many people have commented on my posts. All of these factors come together to define my popularity within the blogosphere.

But this system was not invented in the age of social media. Not by a long shot.

This is the same methodology used to measure the “impact” of a scientific paper. Each article cites the work previously done in the field as the basis of the new data being presented. So a quick glance at the papers with the highest number of referring articles, is likely the one describing a ground-breaking discovery. 2916 subsequent papers have cited Watson & Crick’s seminal paper describing the structure of DNA (and that’s only through February 15, 2006).

Journals are ranked this way by ISI Thompson Scientific, so authors can more easily wade through the hundreds (or thousands) of journals that are published each month. ISI also ranks authors by the number of times their papers have been cited, conferring something like a popularity ranking on individuals.

Clay Shirky describes that fame is a real concept, going beyond just popularity. When someone is famous they can’t possibly (and therefore really don’t want to try to) respond to everyone that contacts them. So it is with highly cited authors; they do not cite back to all papers that have cited them. They can’t possibly do that, and in fact, many of them are irrelevant to their subsequent work. This is less true of authors with lower impact factors, whose work is cited less and often only by individuals doing similar work to their own. In my mind, this is similar to a group of friends who comment and linkback to each others’ blogs.

Tracking all of these connections in science is much easier now because of the need for similar tools for social media. I can’t imagine trying to track this before!