On reading an article in The Daily Galaxy today, I was interested by what the author had to say. In a nutshell, the article pointed out that it is a big mistake to believe we are the only intelligent life in the Milky Way.
Why is that?
The only reason given was that there are billions of stars, it is therefore foolish to think we are the only example of an advanced species. Unfortunately, there is no evidence to suggest that we aren’t the only intelligent life form in our galaxy. Just because there are hundreds of billions of stars possibly with billions of habitable planets does not constitute evidence that we’re not alone. That’s what science is all about, formulating a theory and then gathering the evidence. Simply saying, “There’s lots of stars, therefore there must be an intelligent species out there,” doesn’t cut it.
Dr Frank Drake toiled with this idea to eventually arrive at the famous Drake Equation, a concept I have never felt at ease with:
At first glance, we could say that the Drake equation really is nonsense (after all, how can any equation predict more than one intelligent civilization in our galaxy, when we only have experience of one: us), and that we are the only kids on the Milky Way block. — from If There’s an Alien Race Living on our Doorstep, Why Can’t We Hear Them?
How can you arrive at the conclusion that we are not the only intelligent life in the galaxy simply because there are a lot of stars?
It is true that the Milky Way contains billions of stars, of which a high percentage probably have exoplanets not dissimilar to Earth orbiting them. There’s every chance that a smaller percentage of those Earth-like terrestrial exoplanets have some kind of basic life form slivering around (or indeed swimming, flying, walking or ‘talking’). Also, there’s the chance that some of these exoplanets have nurtured something that we’d consider to be ‘intelligent.’
Now this is where things start to get a bit tricky.
There are massive international efforts under way to find any kind of extraterrestrial life. We’re toasting soil samples on Mars in the hope of finding the biological signature, and we’re using full-blown antennae scouring the skies for any organized signal from an intelligent alien species. However, whether we are looking for microbial life in the Solar System or something a little more sophisticated beyond, our search for extraterrestrial life is based on only one model: Earth.
It’s all very well saying that we should be looking for other possible forms of life, but if we have no experience of it, how do we know what to look for?
It’s a similar question to, “What is beyond a black hole’s event horizon?” We have no idea, because we cannot experience it, the physics of our Universe simply do not apply beyond an event horizon.
There are a lot of ideas, theories and conjecture but at the end of the day, we have to assume ET will have some trait we are familiar with.
When looking for intelligent extraterrestrials we make the assumption that these civilizations have progressed in a similar way to us, eventually transmitting radio signals (perhaps even laser beacons) to communicate on their home world, between planets with their own kind, or even reaching out into the cosmos, signalling their presence to other life forms capable of receiving interstellar signals.
We’ve been leaking radio signals into space for the last century and we are constantly communicating with our planetary probes. There’s every chance that if there’s an intelligent alien (with a radio receiver) within 100 light years, we may have already been detected. We are also being a bit more proactive these days, using programs such as Messaging Extraterrestrial Intelligence (METI) to make our presence known. (But what should we be saying?)
SETI, METI, SETA… SETT?
Unfortunately, apart from one isolated case, the Search for Extraterrestrial Intelligence (SETI) has drawn up blanks, we don’t think we’ve heard anything in the cosmos that’s originated from an alien.
On this single null result, we could jump to the conclusion that there is no other form of ‘intelligent’ life in our galaxy. Say if the ‘Rare Earth‘ theory is correct, and we are indeed the only form of intelligent life in our galaxy? But there are other explanations. What if ET is signalling via another method? What if there is some interstellar mechanism that is hindering (or even blocking) the transmission of electromagnetic communications? All these questions are valid as there is no scientific evidence to support otherwise. It’s very quiet out there, a fact that is bugging scientists quite a bit, and this problem been dubbed the Fermi Paradox.
The Milky Way is very old, in fact, the oldest star in our galaxy has been burning for 13.2 billion years (compare that with the age of the Universe at 13.74 billion years); you’d logically think that something resembling an intelligent civilization would have popped into existence in that time. If they did, surely we’d have detected them by now, wouldn’t we?
Actually, this spawns yet another debate: Have ancient interstellar alien civilizations come and gone? Was there a frenzy of intelligent life popping up all over the galaxy in the billions of years that our Sun was a proto-star surrounded by a proto-planetary disk? If old alien intelligence has since become extinct, our few thousand years as an evolving civilization is a mere spark in universal time scales. Could it be that we’ll have to wait until we can actually visit interstellar destinations first-hand to do the SETI equivalent of an archaeological dig, looking for alien artefacts? Perhaps SETI should be changed to the Search for Extraterrestrial Artefacts (SETA), where we’d have to look for evidence of alien civilizations past.
There’s another factor to consider. What if an advanced extraterrestrial civilization simply isn’t transmitting? If this is the case, perhaps we should consider a Search for Extraterrestrial Technology (SETT). In this case we could look for alien megastructures, searching for the stuff of science fiction. These structures could include examples of Dyson Spheres, huge alien-made hollow spheres containing a star; a means to harvest all the stellar energy for a vastly advanced civilization.
These are all options, and we shouldn’t close any possibility, no matter how extreme they may be.
There’s a reason why we haven’t received a signal via SETI, but we have no idea about what it could be. We really could be alone in the Milky Way. But then again, there’s a huge number of reasons why we might not be receiving a message from an intelligent species.
SETI may not be an interstellar switchboard, but the reasons for this are far from obvious. The theory that we are alone is just as valid as the theory that we are actually a part of a vast interstellar ecosystem. Until we have scientific evidence, we can’t say either way.