The Fermi Paradox and fear of the Great Filter

1. Fermi Paradox solutions: There is no intelligent life out there (or isn’t anymore)

Given the sheer volume of Earth-like planets I mentioned on the previous page, surely the chances of this are pretty low? Well, maybe, but we’re basing this on what we know about Earth’s evolution. What if we’re just a quintillion-to-one shot that came good? Afterall, it’s now believed that Earth as we know it was formed by the collision of two planets 4.5 billion years ago, which is nothing if not down to chance. So there’s a possibility we’re the most intelligent lifeforms in the galaxy, and hey, if we haven’t cracked it then who can?

But that seems pretty conceited to me, especially considering the raw numbers involved (do I need to hammer my zero key again?). We know the likely numbers and plenty of those planets will have had the conditions ripe for life for far longer than Earth. We’re around 4.5 billion years old, and humans have only been around for 0.004% of that time. If other planets have been around for (say) seven billion years and followed roughly the same time scale, they’d have a whopping 2.5 billion years of evolution on us. Enough to have this whole galaxy travel thing licked.

Or would they? This is where the Great Filter theory comes into play.

The Great Filter theory

One of the theories about why we’re yet to see any aliens is that all life reaches a point where it hits a wall where it’s vanishingly unlikely that it’ll evolve any further. If you’re an optimist, you’d say that we’re special and we’ve passed this. If you’re a pessimist, you’ll say we’re yet to hit it. If you’re really pessimistic, you’ll say that we’re yet to hit it and, when we do, it’ll wipe out all of mankind.

Yep, the seriously hardcore pessimists reckon that the reason there are no aliens popping in for a chat is because any civilisation that gets advanced enough to travel through space destroys itself before it can get there. Elon Musk has his concerns about this, pointing out that we should really head to Mars in case World War III occurs and the world is wiped out by nukes.

 So if the Great Filter theory is right, we’re either virtually unique or yet to hit total catastrophe. We don’t really know what the filter is, but we can rule out a few things: it’s not moving from single-cell to multi-cell life, for example, because we know that’s happened many times on Earth, so is nowhere near rare enough. If we were to find fossilised alien life on Mars when we eventually pay it a visit, we’re in trouble because it rules out a number of potential Great Filters if two planets have managed to harbour advanced life. It would suggest the Great Filter is ahead of us, and given the sheer odds involved, you wouldn’t bet on our chances of passing the test at Ladbrokes.

Of course, it could just be that there are aliens out there, but they’re ignoring us. Why would they do that, then?

Images: Tom Hall, Alexander Kaufhold, JD Hancock, Damien Phillips, Moyan Brenn, Maxwell Hamilton and Chris Moore used under Creative Commons