Checking the skies

While asteroids, comets, meteors and other objects in space have been around forever as far as we know, it is only relatively recently (basically the start of the 21st century) that we have begun to discover just how many objects there are out there.  Scientists estimate that we have discovered less than 10% of all the near-Earth objects.  And, we've focused more money and attention on the Northern Hemisphere.  So, the estimates may be way off.  Of the objects discovered it is estimated that more than two dozen asteroids have a chance of being the black swan relative to objects from space crashing into earth.  The last one that did so was in 1908 when it leveled all the trees in 825 square miles in Russia.  It is also thought that the dinosaurs vanished because of a collision with an object from space.