The March
2012 issue of Scientific American
magazine has a fascinating article by Donald Goldsmith, an astronomer who once
served as consultant on Carl Sagan’s 1980s Cosmos
television series on PBS. In his article titled “The Far, Far Future of Stars,”
Goldsmith points out that, while the glorious period of star and galaxy
formation in our universe is largely behind us, the universe has a very, very long time yet to go, before
it becomes a doddering, failing entity. In fact, this grand cosmos we inhabit
is just getting started. It is yet in its infancy, at 13.7 billion years of age,
according to the latest scientific understanding. Many exciting events are yet
to come, and one of those, Goldsmith says, is that the universe will become
increasingly conducive to life, as it ages further.
That, to me, is a remarkable fact, given the rapidly changing
understanding in the scientific community, that the presence of life in places
other than Earth is far more likely than we previously thought. Humanity has historically
tended to believe that, in this entire universe, the solitary location of life has
been our tiny planet. We are most special, according to this line of
thinking, and are divinely delegated to be the single island of life and
consciousness in this immense cosmos.
That self-centered perception is wrong, I believe. We still have a very limited understanding of the universe, and we are finding new facts every day. The more humanity has opened up to another-centered
perspective, the more we have come to comprehend the reality of this incredible
cosmos. Forms of life recently discovered in unlikely places on our planet are
indicating that life can thrive in far more inhospitable locations than we once
believed. There is an increasing understanding that life may well exist “out
there” somewhere and we will soon prove it to be true.
Returning to Goldsmith’s message: There is a lot more history
to come, in our fantastic universe. It is now a little shy of 14 billion years
of age. In its very beginning, hydrogen and helium were the only elements
existing in the nascent cosmos. The first stars were formed from these gaseous elements
(99% hydrogen and 1% helium). When they quickly burned out (over just a few million years), they collapsed and the high internal pressures formed a few
heavier elements—such as carbon, nitrogen, and oxygen. As subsequent stars
formed over the next few billion years, more and more heavier elements were
forged.
Eventually, there were enough heavy elements (maybe then 1%
of the total matter in the universe) that when a star formed, there was enough solid material present
to form planets. When our cosmos was about eight billion years old, our sun
materialized out of the existing local stardust, with enough solid material left over
to form eight planets (nine, if you are old fashioned and wish to include
Pluto). It required another five or so billion years to bring about complex life
on this planet.
So what is the prognosis for our five billion year-old solar
system? In another five billion years our sun will use up most of its nuclear
fuel and will swell up to a red giant star. That process will toast the inner
four planets, after which the sun will collapse into a white dwarf and slowly
recede into oblivion. Any life aboard planet Earth will have long before been
incinerated.
Meanwhile, in the rest of the universe, events will slowly,
slowly wind down. The emphasis here is slowly…
really slowly. After the Earth will
be long gone, the universe will be just coming into its stride. The
stars that form after our sun dies will have even more heavy elements and will
last much longer than our sun. These cooler stars will harbor many more planets
than our current cosmos holds and they will live for far longer—trillions of
years, rather than billions. Life will have many more opportunities to arise
and flower, in this far distant future. That forthcoming cosmos may be teeming
with life.
More on the aging universe next time…
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