Space:

http://www.space.com/scienceastronomy/090810-planet-smash.html

 I have to chuckle every time I see or hear about anything pertaining to outer space beyond our own solar system. The fact is, most of what you see in the sky is so far away, and the light takes so long to get here, that all of it might not even still be there. Can you imaging taking off on a ten year mission to reach a planet only to discover it's gone? Just think about that!

In this particular instance it took 100 years.  Not to long.

As to manned interstellar travel...because of the distance between stars it is not going to happen at sub-light speeds except for a couple of scenarios, and they aren't sexy enough to worry about now.

100 Years? Isn't gravity propegated at about the same speed as the speed of light? What this might mean is that we would neither see or feel anything that might be happening even a few hours before it happened to us. 

What I mean is, imagine that there is some gigantic apocalypse coming towards us at about the speed of light. We would have no warning outside of a few days or hours that it was approaching. We wouldn't even feel it because the speed of gravity is about the same as that of light. 

In the cosmic scale of things, just because our short human history of a few thousand years hasn't seen it happen here, doesn't mean that it doesn't happen on a regular basis to whole galaxies in ways that we have not understood. All kinds of celestial phenomenon might be pointing to this having happened throughout the universe, yet the light we receive from such hppenings could easily be misinterpreted by our scientists - until it happens here. 

Fun to think about.