3 was partly answered in https://www.reddit.com/r/IAmA/comments/45g8qu/we_are_the_ligo_scientific_collaboration_and_we/czxqa71 https://www.reddit.com/r/IAmA/com

3 was partly answered in https://www.reddit.com/r/IAmA/comments/45g8qu/we_are_the_ligo_scientific_collaboration_and_we/czxqa71 https://www.reddit.com/r/IAmA/comments/45g8qu/we_are_the_lig... >How many signals we see has to do both with how sensitive our detectors are and how often events that can cause waves strong enough happen; because we observed one of these events in 18 days of observation, we can tell that there are between 2 and 400 of these events per year per gigaparsec cubed events like this in the space around us.