Thinking About: Life in the Galaxy
If you have been reading this Blog for any length of time you’ll know that I periodically post articles about Extraterrestrial life. You will no doubt have realised that I am of the opinion that the probability of such life existing is high (if not actually certain) and that it is only a matter of time before we stumble over it or it stumbles upon us. After all, our Galaxy is certainly old enough for life to have emerged in it – we even have a confirmed example of it: Earth. Our Galaxy (one of many, many Galaxies) contains billions of stars around which probably orbit billions of planets. Any one (or any one other) could be the home of life so the odds against such a thing occurring elsewhere are literally astronomical. So the question remains: Where is everyone (else)? It’s a very good question and is usually referred to as the Fermi Paradox. If the Galaxy is really old enough, diverse enough and capable of producing life in multiple locations why haven’t we found it yet? Let me consider some of the facts and some speculations to try to answer that.
The first thing we need to consider is the size of the Galaxy. It’s big, really big. The distances between the stars are vast. Light from even our nearest star takes a little over 4 years to get here and light, as you may know, moves at a fairly decent speed. To send a probe there using present technology would take thousands of years. If the speed of light is indeed the universal speed limit – putting all of the various SF propulsion systems to one side – it’s hardly surprising that no one has come calling. But what about sending signals? After all radio waves move at the speed of light, right? So why haven’t we received any signals either? There was a comment from the head of NASA in one of those asteroid movies when he tried to explain why no one had seen it coming until it was almost upon us. He said that they only scanned a small percentage of the sky and it was a big-ass sky. We’ve only been listening for signals for about 50 years (though we’ve been leaking signals for somewhat longer) and it’s certainly a big-ass sky. Presumably the discovery of planets around a host of ‘nearby’ stars can narrow the search a bit but there’s still an enormous amount of ground to cover. It’s possible that a signal is one its way right now from a star 100 or 200 light years away which will get to us in 50 or 100 years. It may simply be a case that we haven’t listened long enough or we’re searching in the wrong places rather than the sky being empty of life.
We know for a fact that life exists on one world: Earth. We also know that our star isn’t particularly unique. We suspect that the same forces that produced our solar system are likely to operate universally which means that planetary systems just like ours exist orbiting stars just like ours – and that some of those planets will be in the so-called ‘Goldilocks zone’ where conditions allow liquid water on the surface and are suitable for the emergence and evolution of life. I have long contended that where conditions are conducive to the emergence of life that it will indeed emerge. After that has occurred evolution will kick in and things will start getting interesting. But it should be remembered that for the vast majority of life on Earth it was the domain of single or simple multi-cellular animals. It’s quite possible that even if life is prolific in the Galaxy that it’s at this simple level. Of course intelligent life has only existed on Earth for about a million years or so (depending on your definition of intelligent). It’s only in the last 100 years or so that we’ve begun broadcasting signals into space. It’s possible that we are the first species to do so in this part of the Galaxy so there’s no on to listen to (or to listen to us) yet. Likewise intelligent life could have flourished within 100 light years of us but may have died out 500 years ago either due to a natural or home-made catastrophe. Intelligence that can build radio transmitters and receivers capable of interstellar communication may also, inevitably maybe, create atomic bombs and bio-weapons and be stupid enough to use them. We certainly are. Maybe what intelligent life emerges in the Galaxy quickly snuffs itself out before anyone else is around to hear them? Or maybe they are snuffed out by wandering fleets of machines bent on the destruction of all organic life? It’s just as possible that one (or more) of the emergent civilisations destroyed itself by creating intelligent machines that see all organic life as a threat and have spent the last 100 million years hunting down radio signals are whipping out their producers. With a Galaxy this big, this diverse and this old such an idea might not just belong between the covers of science-fiction novels or in summer blockbusters at the multiplex.
Of course it’s quite possible that the Galaxy is indeed as empty as it appears to be. We might be the first intelligent (and I use this word advisedly) species to have evolved or simply the only one to be around at this time – others having become extinct or not evolved far enough yet. But I think the odds are against this. If intelligent life is a fairly late product of evolution, which seems likely given its obvious advantages, it’s likely that intelligent life will have evolved many times in this Galaxy. Maybe those that do exist are far above is in evolutionary terms and simply don’t regard us as worthy of communicating with. Would you spend too much time trying to speak to ants? I think not. Maybe any nearby alien life is simply too different from us and can’t see the point in dropping by to say hello. Maybe they’ve tried and failed – thereby proving that we’re not worth communicating with?
We could certainly speculate all day about why ET isn’t calling us. Presently we just have too little data to work with. My gut feeling is that it isn’t because intelligent life simply does not exist anywhere else but here (with the usual caveat). My best guess on the subject is that the vast distances involved make communication very difficult. Together with the fact that we really haven’t been listening for that long and until very recently really didn’t know exactly where to look it’s hardly surprising that we haven’t heard any alien chatter. We may be receiving messages within days of me posting this or we might have to wait hundreds of years. I really have no idea. After all…. it’s a big-ass sky.