SETI again

Thanks for sparing me the work of pouring all this data and discussion
about the Oort Cloud, Doug! I would just like to add:

On 7/28/06, Douglas May wrote:
> No Oort cloud object
> has actually been seen at the Oort cloud distance. Its existence is
> calculated by many different means.
(...)

Remembering that everything started when Oort himself, back in the
50's, saw that if the comets that we see had always occupied their
observed orbits, all comets would have become extinct billions of
years ago because they would have passed close to the Sun too many
times. So in fact comets *have* to be constantly replenished in the
Solar System, and then Oort postulated that there was a huge comet
reservoir (obviously later called Oort Cloud) enveloping the Solar
Systems. From the trajectories and frequency of comets, the Oort Cloud
diameter and number of comets was estimated.