Ian O'Neill tells us, “Milky way stuffed with 50 billion alien worlds” Discover (Feb 19, 2011)
Making estimates may sound trivial, but it does put the search for ET into perspective. There's at least 50 billion worlds, which have fostered the development of basic lifeforms? How many have allowed advanced civilizations to evolve?
If there are any space-faring alien races out there, "the next question is why haven't they visited us?" Borucki asked.
He responded with: "I don't know." I wonder if we'll ever know.
One problem I have with statistics that start with a current sample of one is that it strikes me as difficult to compute the odds that there are two, no matter what the sample size is. If we find a donut-shaped planet, does that mean there must be another one out there?
Possibly, but if very specific and unusual conditions were required to produce it, those conditions may never have been repeated anywhere.
Very specific conditions produced life on Earth. Whether these conditions were unusual cannot be established on the magic of large numbers alone. Still, it’s all good fun and great sound bites.
Denyse O'Leary is co-author of The Spiritual Brain.