Galaxy Has Billions of Earths?
From an article on BBC News:
There could be one hundred billion Earth-like planets in our galaxy, a US conference has heard.
Dr Alan Boss of the Carnegie Institution of Science said many of these worlds could be inhabited by simple lifeforms.
He was speaking at the annual meeting of the American Association for the Advancement of Science in Chicago.
So far, telescopes have been able to detect just over 300 planets outside our Solar System.
Very few of these would be capable of supporting life, however. Most are gas giants like our Jupiter; and many orbit so close to their parent stars that any microbes would have to survive roasting temperatures.
But, based on the limited numbers of planets found so far, Dr Boss has estimated that each Sun-like star has on average one "Earth-like" planet. This simple calculation means there would be huge numbers capable of supporting life.
"Not only are they probably habitable but they probably are also going to be inhabited," Dr Boss told BBC News. "But I think that most likely the nearby 'Earths' are going to be inhabited with things which are perhaps more common to what Earth was like three or four billion years ago." That means bacterial lifeforms.
Dr Boss estimates that Nasa's Kepler mission, due for launch in March, should begin finding some of these Earth-like planets within the next few years.
Recent work at Edinburgh University tried to quantify how many intelligent civilisations might be out there. The research suggested there could be thousands of them.
Although this would in many ways be extraordinarily cool, I can't help but think Dr. Ross is pulling his numbers out of the air, or somewhere less pleasant. This question has been tossed around for decades now, and there really doesn't seem to be that much more information on which to base these guesses - and guesses is what they are. I'm not an astronomer, but I try to keep up, and near as I can tell there is exactly one earth-like world that has been detected. In addition, Earth is special in more ways than just having the right composition and being at the right distance from its star. Current theory has the tide-producing moon being formed by a rather unlikely collision, while the presence of Jupiter helps buffer the inner solar system from impacts.
Any guesstimate that ndicates there are many civilizations in the galaxy runs smack into the Fermi Paradox. (The Fermi Paradox, simplified, raises the question that - if complex life is common - where the heck is it? If star travel is possible, even slowly, the galaxy should have been colonized millions of years ago. At the very least, we should be finding buried starships or Brontosaurus bones with bullet holes in them. If it's not possible to bridge the gap between the stars, then signs of an advanced civilization should still be observable over galactic distances.
The fact that we don't see them is a pretty good indication that they aren't there - either technological civilizations are extremely rare, or they have a very short shelf-life in cosmicterms. Other explanations make for good science-fiction stories, but aren't very convincing.
Theologically, intelligent extraterrestrial life would raise all sorts of interesting questions for a Christian. Is Jesus unique to Earth, making us the lone universal source forthe Gospel? It sounds conceited on our part, but the Savior would have had to be born somewhere, and Earth is as good as anywhere else. Or are the Incarnation and Atonement events that are re-presented throughout space and time in a manner symbolized by the way Christ's Incarnation and Atonement are re-presented in the Mass? I.e. are Christ's birth, death, and resurrection recapitulated wherever they are necessary? Are all these other beings fallen in the first place? If so, would they even be willing to talk with the likes of us? Or, rather horrifically, might some be fallen beyond hope of redemption?
With no data whatsoever, this is a subject best suited for late-night dorm room discussions among stoned undergraduates. The only thing I know for sure is that - should a saucer land on the White House lawn - the foreign missions assessment is going to go through the roof.