For this week’s post, I want to return to a favorite topic of mine, the presence of life in the rest of our galaxy: where is it?

On the one hand, with around fifty billion stars in the Milky Way galaxy (of which we are a member) and an average of eight or perhaps ten planets orbiting each of those stars, plain ordinary common sense should tell us that at least one and probably hundreds if not thousands or millions of them should harbor intelligent life.  (I’m talking intelligent life here, not just jellyfishes swimming in a primordial sea.)  By intelligent life I mean a civilization capable of understanding that there must be other life besides them in this galaxy, and capable of reacting to a signal sent their way.  That is, someone just about as scientifically literate as we are on Earth.  That’s not unlikely.

So, where are they?

SETI people have been listening for signals from outer space for as long as I’ve been alive (almost), and haven’t heard anything that could even remotely be called a definite signal.  Every few years or so they remind us that it’s only a short time, they believe, before they will hear a legitimate signal that will prove someone out there is trying to reach us, long distance.  But nothing has happened and no signal has arrived.

Some physicists tell us that time-travel is possible, though no one really knows how to do it.  Going faster that light is one way, but Einstein’s theories absolutely reject the possibility of faster-than-light travel and Einstein’s theories have held up to scrutiny time after time.  Other ways to travel in time may be possible, though, but if time-travel is possible, however unlikely, then where are the time travelers?  No one has ever convincingly demonstrated he/she has ever met a time traveler, fans of Dr. Who notwithstanding.  Several possibilities exist.  Either the time travelers have decided–for one reason or another–not to come to this region of our timeline, or, if they have, they’ve been damn good at not making themselves known.  It’s more likely, I believe, that time travel is not and never will be possible, except in fiction.

Then there’s the search for earth-like planets surrounding other nearby stars.  The latest attempts to identify planets around other stars has been remarkably successful, identifying over a thousand candidate planets in just the past few years.  This in itself is a fantastic scientific achievement, and I consider myself lucky to be living in the dawning age of extra-terrestrial planetary discovery.  (So should you.)  The number of planets discovered, scaled up to the size of the galaxy itself, implies a huge number of planets total, as I mentioned above.  And a few of the planets discovered have been found in the “habitable zone,” where liquid water could exist on the planet’s surface, essential for carbon-based life.  Yet, none of them, for one reason or another, are really likely.  Earth-like planets just haven’t been found.  Will they ever?  Perhaps.

In short, we seem to be alone in this arm of the galaxy.  At least so far, we haven’t demonstrated the presence of even a planet that could hold extra-terrestrial life, and we may never.  I’m willing to believe the latter, though it doesn’t bother me as much as it does some.  If we’re alone, then so be it.

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