Arthur C Clarke once wrote that a trillion years from now an advanced civilization will look back at us with envy and say "They knew the Universe when it was young."
The story of the Universe according to Sasselov in is new study, The Life of Super-Earths, looks like this: generations of stars made enough iron and oxygen, silicon and carbon, and all the other elements from the original hydrogen and helium about 13 billion years ago to be able to form the Earth we live on and the planets the Kepler Mission is discovering today.
Stable environments in galaxies that were enriched enough to have planets only became available some nine billion years ago and rocky Earth-like planets and larger super-Earths, only some 7 to 8 billion years ago. And Life had to wait until that time if not later to begin its emergence throughout the Universe. Between 7 and 9 billion years ago, enough heavy elements were available for the complex chemistry needed for life to emerge were in place along with the terrestrial planets with stable environments necessary for chemical concentration.
Enrico Fermi argued that given the old age of the Universe and given the large number of stars and planetary systems and the incredibly short timescale it took humans to develop technology that other origins of life and civilizations in the Milky Way could have had a significant head start and should be significantly more advanced than we are.
Sasselov concludes that the statistical argument for Fermi's Paradox "holds true only if the timescale for the emergence of life is much shorter than the age of the universe, but not so if the two are comparable." The future for life in the Universe looks excellent, says Sasselov.
Planets may be just a tiny fraction of the Universe because of their small size, but there are so many of them that the probability of life grows exponentially. The Universe is passing through the stelliferous era --its peak of star formation--but appears to be still peaking in its formation of planets. There are more stars in the Universe than there are grains of sand on Earth and there are an equal number of planets.
There are 200 billion stars in the Milky Way and 90% are small enough and old enough to have planets in orbit. And only 10% of these stars were formed with enough heavy elements to have Earth-like planets with 2% of these --or 100 million super-Earths and Earths-- will orbit within their star's habitable zone.
Sasselov's argument in The Life of Super-Earths is compelling. One has to wonder, however, that if another planet out there in the Milky Way (and billions of galaxies beyond) is only a billion years older than Earth, how much more advanced and detectable would their technology be?
As Arthur C. Clarke famously wrote, any advanced alien technology would be indistinguishable from magic.
The Daily Galaxy via www.cfa.harvard.edu/