&gt;&gt; that shortly after the detector came online we just happened to observe the exact moment a billion years ago that two black holes collided?<p>Counterintuitive, but yes.  Because it happened billions of years ago, it happened a long long way away.  The sphere of objects billions of years away&#x2F;ago is far larger than those closer to us.  So such a detector should be detecting exponentially more very old objects than new ones.  Given the rarity, I would expect nearly all detected events to have happened long long ago in galaxies far far away.<p>Also, models point to such events being more common in the distant past where there were more black holes (primordials) floating around than there are now.