Recently the news announced the discovery of a planet with characteristics similar in size to earth with the possibility for liquid water, 4.2 light years away.
Now, if there was a civilisation of human beings, pretty much identical to our own civilisation, with the same population, radio output, distribution, etc then, could we detect them now?
If not, assuming the progression of radio/telescope technology here on earth continues at the same pace, how long would it be before we were aware something artificial was happening on that planet ( disregarding communications, language, etc etc )
If it helps, assume the planet is an identical clone of earth in every way. I'm more interested in if our civilisation was on our closest star would we know?