The Rock Test

I propose a simple test for evaluating the resilience, technology and overall "usefulness" of a given civilization.  I call it the Rock Test.

The test is as follows:

Imagine a rock falling from space on your position.  How big does the rock need to be to wipe out all your stuff?

If you are an advanced spacefaring civilization and can quickly evacuate a planet where your citizens live, it needs to be a pretty darn big rock - assuming you don't just blow it up.  A passing planet would probably doom the people of a particular world, but not the whole civilization.  On the other hand, even a fair-sized meteorite means the end of the world for early 21st century Earth.