For the past half-century, humanity has been listening for alien radio transmissions, but so far we appear to be the only ones broadcasting into the void. Astrobiologists now seek to narrow down the search by looking for other technological and biological signatures. In this video, I explore some of the methods by which they hope to do so, and why the great silence of the universe is such a mystery.
While reference #7 below does indeed suggest an instrument the size of the Square Kilometer Array could detect our radio leakage from a distance of "several hundred lightyears", it would require a full month of uninterrupted observation. This is unrealistic because our radio leakage isn't constant but rather fluctuates with the Earth's rotation. According to this paper, a more reasonable range estimate is approximately 50 lightyears.