Do you believe in aliens?
This is a really vague question. If a “believer” asks you, they want you to say “no” so they can follow up with “how can you believe we’re the only life in the universe?!11one”. But of course – that wasn’t what the question was. The question really means “do you believe we are being visited by aliens?”
I maintain that the same logic that makes alien life so overwhelmingly likely is the same logic that makes me thoroughly disbelieve in alien visitors. In short, aliens DO exist – but you shouldn’t give the matter a second thought.
Why do I believe that aliens exist but that we are most definitely not being visited? It’s quite simple and brief to be honest:
Evolution: if you understand it in any reasonable detail, you’ll appreciate that it’s not luck-based at all. Given the right conditions, and time – evolution is bound to happen. Of course, there are no guarantees over what form that life will take.
Probability: It doesn’t matter if earth-type worlds are rare or common in the universe. Earth is certainly unique of all the planets we’ve charted so far and the solar systems we’ve scanned to date. I think it’s fair to presume that earth-type worlds are rare – but however rare you want to make them you have to appreciate the vastness of the universe. It is a statistical certainty that somewhere out there, amidst the quadrillions upon quadrillions of stars, that an earth-type planet orbits a star like our own. (To be honest, quite a variety of star-to-planet distances/compositions would probably be acceptable.)
So vast is the universe it would actually be a statistical impossibility to not have any other life out there! And if you have life, and time, and enough planets – at least one of them should produce intelligent life – perhaps even rational.
But, this is where the alien fun ends. Remember how vast the universe is. In order for us to make contact with alien life, you not only need another species to be alive, be intelligent, develop space-travel, but do so within observable range of the earth.
Light travels at 186,000 miles per second. Try to appreciate just how quick that is. It would still take 100,000 years travelling at that speed to cross our galaxy. Beyond that, at the same speed, the next closest galaxy is 2,540,000 years off. In fact, even the closest star to us would take over 4 years to reach at this speed.
Humans have only been sending out EM transmissions into space for a century. The very earliest transmissions which are nowhere near as powerful as those we send now are only 100 light years away. That’s one 1/1000th the diameter of the galaxy. In order for aliens to even be aware of our existence they’d have to be within 100 light years of earth. As we know, it’s an inconceivably-gigantic universe, and the odds of that life out there being within such a ridiculously tiny radius of earth don’t bear thinking about.
But the real killer, and for me the totally unassailable argument against alien contact (let alone visitation) is time: the universe in its current state of existence is about 15 billion years old. The earth is over 4 billion years old. Life has only been on earth for a few million years. Humans have only been on earth for a couple of hundred thousand. We have only been using electricity for just over a century. We’ve been sending out EM waves for a shorter time than that. We only achieved space-flight 50 years ago. We have only been actively looking for other worlds by scanning a tiny fraction of the heavens for a few decades. Now, even if another intelligent space-faring species actively looking for life existed, or will exist – you need them to be at least at our level of technology, give or take 50 years for either of us, and within 100 light years of earth (at a stretch). And, however we communicate with each other, that signal cannot travel faster than light.
To put this in illustrative terms, let’s use what I’ll call the time-overlap thought experiment: pick a number between 1 and 4 billion: that number is how many years back in time you will travel to a random place on earth. Another person does the same. What are the odds that the two of you will now meet up? And even if luck be damned, and incredibly you both picked the same number, and live at the same time on earth – you need to make contact before you die of old age – but let’s say you’re both different ages, both or either of you could be very young or very old. Where do you look? Which direction do you start out in? What do you look for?
It’s the same with aliens. Maybe they existed but died out ages ago? Maybe they are only now discovering the internal combustion engine? Maybe somewhere out there a CO2-laced volcanic world orbits a yellow star that will evolve intelligent life in many eons to come? Or maybe they are just like us typing blogs on their internet right now, but are just too far away. Who knows?
It’s fascinating to consider, but it’s speculation without resolution. Ultimately, the notion of alien visitors (especially given the total lack of proof) should be dismissed out of hand. The existence of alien life, either good or evil, is totally irrelevant to us. So although it’s overwhelmingly likely they are out there, by the same principle it’s overwhelmingly certain we will never ever know about each other.