> Interestingly, I was watching a documentary about Jupiter recently where
> Gene Shoemaker (I think) was claiming that without a large gas giant in
> the system to 'hoover up' comets events like the dinosaur extinction would
> be so common that sentient life could not have evolved on Earth. If true,
> this could be another reason why life seems so rare in the universe.
I don't think that explanation holds; gas giants seem to be very
common. Most solar system models seems to predict them in the outer
solar system, and the few planets we have discovered outside the
solar system are (almost by definition due to our measurement
methods) gas giants.
-----------------------------------------------------------------------
Anders Sandberg Towards Ascension!
asa@nada.kth.se http://www.nada.kth.se/~nv91-asa/main.html
GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y