I find it so easy to get lost in human affairs and completely forget about our growing knowledge of space. It really shows the full range of issues we have in life. I found this quote from an article on the search for Earth-like planets in the December 2009 edition of National Geographic:
“While grappling with the daunting technological challenge of performing a chemical analysis of planets they cannot even see, scientists searching for extraterrestrial life must keep in mind that it may be very different from life here at home. The lack of the red edge, for instance, might not mean a terrestrial exoplanet is life-less: Life thrived on Earth for billions of years before land plants appeared and populated the continents. Biological evolution is so inherently unpredictable that even if life originated on a planet identical to Earth at the same time it did here, life on that planet today would amost certainly be very different from terrestrial life.
As the biologist Jacques Monod once put it, life evolves not only through necessity – the inversal workings of natural law – but also through chance, the unpredictable intervention of countless accidents. Chance has reared its head many times in our planet’s history, dramatically so in the many mass extinctions that wiped out millions of species and, in doing so, created room for new life-forms to evolve. Some of these baleful accidents appear to have been caused by comets or asteroids colliding with Earth – most recently the impact, 65 million years ago, that killed off the dinosaurs and opened up opportunities for the distant ancestors of human beings. Therfore scientists look not just for exoplanets [planets outside our galaxy that orbit stars] identical to the modern Earth, but for planets resembling the Earth as it used to be or might have been. ‘The modern Earth may be the worst template we could use in searching for life elsewhere,’ notes Caleb Scharf, head of Columbia University’s Astrobiology Center.”
