Source: http://popsci.com/article/science/al...

In the search for extraterrestrial intelligence (SETI), people typically seek messages, not send them. Think Jodie Foster in the movie Contact as an alien signal pulses in her headphones. The inspiration for Foster’s character, astrophysicist Jill Tarter, wants to help make future humans the kind of talkative interstellar society she has spent the past 38 years trying to find. 

Popular Science: Why search for alien broadcasts if we’re not sending them ourselves?

Jill Tarter: Given the history of the galaxy, statistically, any civilization that we could communicate with is going to be much older. And since transmitting is harder than listening, we put the onus on them.

PS: What about the messages we sent on Voyager 1 and 2?

JT: Those are like messages in a bottle. If you’re serious about sending a transmission that has any chance of being received, you want to send out a billion bottles. You need to transmit continuously—not just for a year or a decade. Right now we’re not very good at making 10,000-year plans, but I definitely think transmitting is in our long-term future.