Hypothetically we will get answer from aliens in 25 years

Phil Plait : blogger
"SETI is the Search for Extraterrestrial Intelligence, and its name tells you its story: it’s a group of astronomers looking for signs of intelligent life in space. They use various methods to look for advanced aliens, but the most promising one is to listen for any messages sent across the skies".
"The basic SETI assumption is that aliens are out there and want to contact us. If that’s the case, there’s a good way they can signal us: radio waves. They’re the perfect medium: they’re cheap, easy to make, easy to encode with information, they travel across the whole galaxy unimpeded, and they move at the speed of light, the fastest thing we know. So SETI scours the skies looking for radio signals from ET.
They haven’t found anything yet, but as SETI astronomer Seth Shostak points out, we’ve just started looking. There’s a lot of galaxy and a lot of radio wave frequencies to sift through. But our technology gets better all the time, allowing for more sensitive searches. According to Shostak, if they’re out there and currently sending signals our way, we should have an answer one way or another in about 25 years given the way things are going."

BBC's report "Will we ever… find life elsewhere in the universe?"