Quote:
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Originally Posted by mr1drfl
My grade school science teacher stated that there are more solar systems in the universe than there are grains of sand in the world!
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She -- or he -- certainly left you with an impression!
Stars are uncountable. Stars are being made and self-destructing even as I write.
Entire galaxies are colliding with one another.
But
solar systems (like our Sun and planets) are not as common -- and may be comparatively rare.
Most of the few planets in other solar systems studied are made of superheated gases (like our Jupiter) and not rocky-solid (like Earth and Mars).
Life on Earth has been a testiment to Serendipity.
Early life on Earth was struck by repeated large meteor impacts. More than three major impacts led to massive die-offs of Life. Sometimes it was the simple forms like algae, sometimes just marine life. Then it was the dinosaurs' turn.
The impact 65 million years ago killed off the dinosaurs. That was good news for us mammals, none of whom were bigger than a possum back then. Mammal evolution, the fossil record of which is still being pieced together, eventually lead to
Homo sapiens.
More good news was that our Solar System has the massive planet of Jupiter, whose huge gravitational pull "vacuumed" stray meteors and comets from striking Earth, stopping the progress of Life -- again. Our one Moon affects Life's progress in both positive -- and mysterious -- ways.
Life "out there" could happen. It could also "have already" happened -- and been extinguished. (And the reason our decades-long efforts to detect other Life in the Cosmos have had futile results).
UFOs are
Unidentified
Flying
Objects.
IFOs are (
Identified
Flying
Objects),
and never make the news.
Homo sapiens enjoys one very lucky collection of Life in the Universe.
http://www.newscientist.com/news/news.jsp?id=ns99996236