i've heard that the james webb telescope can see the atmosphere of a planet and using that data determine if a planet might have life. eg increased oxygen increased methane. so riddle me this. earth has had a biosignature for what 3 billion years? that means if a civilization was at our tech level for around 3 billion years now it could spot that earth has life on it. so would an alien civilization be able to see the life on earth, and if they did how would they get here and what would they do if they did. like leave a marker for a future potential civ. or perhaps colonize?