The final tally of injured people from the overhead cometary airburst in Russia last February 15th stands at 1,500. It's a miracle no one was killed. But will we be so lucky next time? The explosion above the city of Chelyabinsk was the largest since the 1908 Tunguska airburst, also in Siberia. What are we to make of the fact that this recent blast happened 12 hours before another asteroid about twice as large was scheduled to pass Earth by in 'the closest fly-by ever'? This week hosts Joe...