The Others Out There

A few weeks ago I finished reading David Waltham’s book, Lucky Planet, and I’d like to comment on it in this blog post.  This is not in the nature of a book review, although I do recommend the book if you’re into the question of life on other worlds.  (It was published by Basic Books in 2014).  Dr. Waltham’s main point is that our Earth has had a phenomenal run of luck during its 4-billion-plus lifespan, and that has allowed life not only to arise about two billion years ago, but to flourish and result in the development of us humans.  He notes that the conditions on Earth have been remarkably constant for the past two billion years in spite of asteroid impacts and mass extinctions, constant enough that although many life forms have gone extinct, at no time has life ever been totally extinguished, and other forms have been able to take the place of the extinct species.  Temperatures have certainly fluctuated on Earth, but never has the temperature gone so high or so low that life was ever wiped out once it got started.  It is an amazing set of circumstances.  I never thought of it that way until I read his book.  It is this stable climate that is at the heart of Dr. Waltham’s book.

Dr. Waltham goes into some detail about his theory that Earth has been extremely lucky over the past several billion years, and I won’t try to summarize the arguments.  I’m not sure I followed all of them, anyway.  He does state near the beginning of the book that if we take all the different facets of evolution that have led to the development and maintenance of life on this planet, such as being in the habitable zone, having a magnetic field that protects us from radiation, having an atmosphere, having a moon that stabilized Earth’s orbit, having large outer planets in our solar system that gobbled up stray asteroids to prevent them from bombarding us too often (but not so often that life wasn’t shaken up now and then), and so forth, and if we add all those up, the number of conditions would be so large that the presence of life on Earth would not only be unique in our galaxy, but perhaps in all galaxies.  With the number of planets in our galaxy alone (in the range of hundreds of billions) that probably isn’t very likely.  But it is possible that our planet has been just lucky enough to allow life to develop and thrive, perhaps lucky enough that there aren’t any other planets that have achieved the same result.

More recently, in the past few weeks, astronomers have begun to say that they are confident they will find life on another world within twenty years or so.  Seems a little like braggadocio to me, considering how long we’ve been looking for life on other worlds and not found squat.  I have no doubt that life will be found on another planet or moon sooner or later.  But I’m only saying “life of any sort.”  A few bacteria-like organisms would fulfill that prediction.  I’m not talking about intelligent life capable of traveling the galaxy.  Life is fabulously complex, and the emergence of intelligent species will take time.  Lots of time, and that requires conditions on the birthing planet to be constant and mild for a very long time.  How many other planets out there will fulfill those requirements?

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