Size isn't the only problem. Time is the bigger issue. The likelihood of there being something else out there is one thing. The chance that they've been acti

Size isn't the only problem. Time is the bigger issue. The likelihood of there being something else out there is one thing. The chance that they've been active enough during a time in which we're looking for them is vanishingly small. Look at it this way, what if they died out just before the first telescopes were created here on earth? Or what if they're active right now? We won't see any signs of them for hundreds of years. Space is big, sure, but time is even more vast. Whoops, missed them by that much...