“And that’s the way it is.”

When Walter Cronkite ended “CBS Evening News” with that signoff, millions of people believed him. The major networks and newspapers exposed Americans to a diversity of viewpoints – at least in theory.

But in the digital world, we each live in our own bubble, according to Kelly McBride of the Poynter Institute’s Sense-making Project.

She says Facebook and Twitter are increasingly referring people to their news.

“It can create a bubble where you only receive a certain political viewpoint because you are friends with people who tend to share your values,” she said.

“It tends to make the free exchange of ideas less likely to happen.”

But how do we know what we don’t know? There’s a new app for that: Rbutr.

It’s a tool to add to your browser to help provide contrary points of views.

McBride says Rbutr has a lot of potential. For example, the Poynter staff used Rbutr to find different points of view to an Andrew Sullivan article about Mormons, “Did Jesus Foresee the Constitution.”

Other users submitted an article that rebut Sullivan’s story, such as, “Conservative Mormons Will Be Crazy Politicians; Moderates Won’t.”

“As a user, I had a completely different understanding of Andrew Sullivan’s original article because other users submitted different points of view that I would have never stumbled upon, had I not had the Rbutr toolbar,” she said.

Call Me Maybe?

Internet bubbles are not just about ideology. It’s possible to be totally clueless about cultural trends, too.

McBride brought up the example of “Call Me Maybe.” The song by Carly Rae Jepsen has become a hit through the Internet, but it’s a lot bigger than that.

Hundreds of people have re-made the song on You Tube (check out this lip sync by the Harvard Baseball team.) Jimmy Fallon and the Roots invited Jepsen to do this low-tech version with them.

There’s also the auto-tuned version that edits President Obama’s speeches so he appears to sing the song.

And NPR had to get in on the act in their own low-key way.

I had no idea of this trend, whereas McBride says people inside her bubble of mothers with teenagers knew all about it.

“The fact that I am immersed in these, and you didn’t know anything about them, is a perfect illustration that we live in completely different internet bubbles,” she said. “In my world, everybody knows about these memes.”

http://www.youtube.com/watch?v=hX1YVzdnpEc