Universities generally say their faculty have three major responsibilities: teaching, research, and service. That's the usual listing order, though in our time it would be perhaps more accurate to reverse that. Service comes first, in the form first and foremost of grants and fund-raising, and secondly, time-eating bureaucracy. Research, meaning raising funds (again!) and lots of publication comes second. Research is worshipped as a public good, but arcane research counts in many fields (like the humanities or very micro-focused science). Teaching, well, only if you can't find a way to get out of it.
Actually, we're being cynical (just a bit). 'Service' isn't only about hawking for money. Public education is also part of that. And again we're not being wholly cynical about that. The universities want to write about your work in their PR magazines sent to alumni and in press releases (of course, this is also largely about money). But educating the general public about what we're doing in research and scholarship is, in fact, an important role even if part of that is self-serving. Popular science books, for example, draw attention but also can provide the non-specialist citizenry a way to get a general understanding or even a fascination with scholarly and scientific discoveries.
Science can be very technical, specialized, and arcane. Much of what we ask about is quite remote from direct application or things the non-scientific public care about much less know anything about. That means that if you don't have the detailed background or time to continue keeping up to date in a professional sense, as most people clearly don't, having a professional explain the gist of the issues can be quite valuable and also quite interesting.
The idea of 'popular' science has changed over time, of course, because in the past only a small segment of the public was involved, perhaps only the aristocracy. This was true of much of music, philosophy, literature and so on. But there has also long been at least somewhat of a tradition of specialists explaining things to the public.
Probably among the most common instances would be religious leaders explaining the technicalities of scripture. Travelers have long told tales of what they saw in far-away places. Even ancient itinerant speakers--Homer, perhaps, in ancient Greece--came around and did this, 'performing' in a sense. Maybe most of this was for the upper classes to witness, but how restrictive that would have been probably varied.
The physician Galen was a performer of this sort. He did dissections (or, worse, vivisections) to show off anatomy and attract attention to his medical knowledge and services. I don't know about Marco Polo, but would expect he regaled many with his tales. Boyle, Thomas Edison, and others here and in Europe regularly put on demonstration shows for the public, or at least those whose support they might want. Probably phrenologists and alchemists did the same.
In the 18th and 19th centuries in Europe, travelers certainly entertained audiences with their tales, often for fund-raising purposes. A major exploratory expedition to the South Pole was funded in this way (not by government grants). Thomas Huxley, Darwin's famous 'bulldog' (outspoken, aggressive advocate) loved to give public lectures, and was especially dedicated to educating the working man. In the mid-1800s, Michael Faraday gave public lectures about phenomena related to electricity and magnetism. Not all of these were university faculty by any means, and perhaps most of the latter stayed within their classrooms. But there were several leading academics who became quite popular among the reading and museum/lecture-attending public. Tales of fossil exploration in the American west were given, back east, and public intellectuals in the major coastal universities were well-known.
Popular science and popularizing scientists: only the formats are new
The tradition has proliferated as faculty have more and more been expected to do 'service', including public education. For much of the 20th century and even more into the present, the public scientist has been a TV stable, and one widely seen in magazines and newspaper science sections. Indeed, many now are not really scientists any longer but drop-outs who became journalists or documentary makers. But a few famous ones, like Steven Jay Gould, Ed Wilson, Richard Feynman, Neal deGrasse Tyson, Sean Carroll, Carl Sagan, Richard Dawkins, and others essentially kept their academic groundings. Often one could argue they lost much of their rigorous credentials in the process, but not always.
As media changed, so did the means by which scientists, professional and once-were, could convey the gist of technical science to the public. Among other things, funding has become media-driven and so organizations like NIH, NASA, and universities (and their counterparts in other countries) have major PR departments of their own, to spin as well as educate.
We now have at least two relatively new medium: the blogosphere and open-source publishing. The latter is largely still arcanely professional, but is opening up to unmonitored commentary. Popular science magazines online allow commentary and discussion. Q and A sites, like Quora in physics, Reddit, and many others, provide interactions among scientists, students, and public freely and without being restricted to classrooms.
Blogs, such as this one, are increasingly being used as regular outlets for faculty, to communicate to the web-addicted public. Here, we can write technical or popular or tweener posts. We can Tweet a post to reach a desired audience. We can mix technical, whimsical, speculative and specific commentaries.
Universities need to get on board faster
Universities are themselves now waking up to the value of these media as part of faculty members' 'service' responsibilities. But universities, which should pioneer what's new, are often stodgy and fearsomely conservative. Deans and chairs tend to stick to what's known, the traditional, even if most research, in the sciences as well as humanities, mainly collects dust in library archive annexes. Students go to the library to work on computers, online data bases, and the like.
It's not just that most research will quickly be dust-collecting. The idea of peer review is way over-rated as a way to purge the bad and only publish the good and important. Peer review is creaking under the weight of its hoary insider tradition, and because reviewers are so overloaded that they rarely can give proper scrutiny. Overloaded 'supplemental information' doesn't help, nor does the need to review grant proposals (or write them). Time is short.
It's true that traditional publishing of research in peer-reviewed journals, even burnished with online (pay as you go) open-access routes, still has first priority in administrators' eyes. But things are changing, as they should, must, and will. Online publishing also has online open reviewing, and comments by readers. There may be far too many journals, but weird ideas do have a chance to be seen, and online searching makes them available. Much is junk, of course, but at least you, not a panel of insider reviewers, get to judge.
It's a different kind of arena, and recalcitrant institutions will have to modernize. Some faculty we know (including our own, fantastic Holly Dunsworth) have successfully, and deservedly achieved tenure with public media being a substantial part of their records. As they age into administrative roles, the changing landscape will be built into their world-views. That, too, will mature and perhaps become stodgy, to be replaced or supplemented by whatever the future holds. But it's likely to be much more dynamic and flexible than the legacy of the past that we have too much still to live with today.
As open-source and online media increase their fraction of publication, we will likely become a more widely integrated and aware society. The local classroom is opening up to a global forum, where anyone, not just the elite few, can gather round, and hear whichever oracle or orator they choose.
Homer would probably recognize the phenomenon.