Q&A: Black Holes

Q:
Could some catastrophic event such as a black hole tearing a star apart or the universe exploding be headed our way - without our knowledge?

A:
It's possible that some catastrophic event could have occurred in the universe and be headed our way, but we're safe from cataclysmic events in other galaxies because they're so far away. An event like a supernova or a gamma ray burst that occurred in our galaxy might eventually have an effect on the Earth, but luckily these events are very rare, and the fact that life has survived for so long on this planet means that we're not in any immediate danger. Events like meteorite impacts might be more important, and may have resulted in the extinction of the dinosaurs, but again, cataclysmic events are very rare.

Information on Tidal Disruption in the Milky Way:
http://chandra.harvard.edu/photo/2004/rxj1242/tidal_disruption_in_milky_way.html

Useful information on Cosmic Look-back time:
http://chandra.harvard.edu/photo/cosmic_lookback.html