Quote Originally Posted by Papewaio View Post
Wouldn't all our radio and tv broadcasts have a more significant signal.

After all by their thinking aliens would have to investigate every Venusian planet... Might explain their preference for probing :)
I'm not sure. Those signals diminish quite rapidly, while you can detect the components of the atmosphere quite far away (it's the next (or two) generation(s) technique of detecting planets with oxygen atmospheres iirc). I'm guessing that the light signal doesn't scatter as much.

Anyway, unless they use bioweapons, wiping out humanity is probably going to do massive ecological damage and the nuclear arsenal is still nasty enough to do it by itself, so I think the odds are quite low.