Are we alone ?
by Anthony Francis Cernosek 11/12/2003
The simulation doesn't answer this question directly , but focuses on
the search for potentially life-suitable worlds. If millions of such worlds exist, then intelligent life
may have evolved on a few of them. Why only a few?
Primitive life has existed on Earth for 4 billion years, and diversified into millions of living species, yet true intelligence evolved only once - within the last few million years. The respected biologist Steven J. Gould knew that countless small steps were involved - all of them driven by random mutations - and believed that the odds for human intelligence evolving on Earth were 1 in 100 million. If these odds are typical of other worlds, then evolution might require millions of life-filled worlds to produce intelligent aliens only once.
By our best rough estimate, our galaxy could contain 12 billion planetary systems, 48 billion individual planets, and 480 million Earth-sized planets - which should have liquid surface water and other requirements for life. Many of these worlds are old enough to have evolved complex lifeforms. This sounds promising for intelligent life, but....
How often will life actually begin on a suitable planet, and how often will life evolve to a highly complex or intelligent form? Here on Earth, life evolved for 4 billion years and produced truly human intelligence only once.
Let's assume that intelligent life did evolve 5 times at different locations among our 480 million Earth-sized worlds - and at different times in the past. Let's assume that the earliest of these intelligent species evolved somewhere in our galaxy 9 billion years ago, and that the youngest species (humans) evolved less than 1 million years ago ( .001 billion ). So we have 2 intelligent species, born 9 billion years apart. Now let's assume that the other 3 intelligent species evolved at random times in between - roughly 2 billion years apart.
How long does a typical species survive? Earth's fossil record says 1 million years - so it's unlikely that any two of these 5 intelligent species will be alive at the same time. Even if 2 civilizations co-exist, they're likely to be separated by tens of thousands of light years - which will make contact difficult. Perhaps one of our assumptions is too pessimistic. I hope so.
Even if we are alone, there must be a very large number of worlds with strange, beautiful lifeforms . Worlds waiting for us to explore or colonize. And some of them may not be far away. Are you ready to go find them?
Start simulation now!
© 2003 by Anthony Francis Cernosek