On The So Called Fermi Paradox

Where are all the aliens?

That's what the physicist Enrico Fermi wanted to know when he was having lunch with some other physicists and talking about aliens. Fermi did some back of the envelope calculations of Earth-like planets and concluded that there must be many aliens and we should have seen them by now. But we don't see any. So how does that work?

Various explanations have been given, but I think that most of the reasoning is confused.

What's the argument

The argument goes something like this:

• There are many sun-like stars in the galaxy
• Because there are so many stars, there's a high chance that there are Earth like planets in the habitable zone
• Because there are so many stars, and so many of these planets, there must be many planets where life has evolved
• Among those planets, there is a high chance that there are planets where intelligent life has evolved
• If they're intelligent they must be resourceful enough to travel through space given enough time to develop
• But if that's true then we should have been visisted by extra-terristial civilisations
• But there's no evidence for that

Sometimes this is expressed in terms of Drake's equation: NumberOfAlienCivilisations = StarFormationRate x FractionWithPlanets x HabitableFraction x FractionWithLife x FractionWithIntelligentLife x FractionOfDetectableIntelligentLife x TimeItTakesToDetect.

Already I think there are significant problems with this reasoning. However, my real problem is with the claims people make to explain this

How do people explain it

I'll be explicitly describing the explanations I strongly disagree with, there are a number of explanations that I either agree with or don't think are false but also don't think really explain it.

For example, people have said that:

• Intelligent life inevitably destroys itself with the technology it creates, and we should expect the same fate.
• Intelligent alien civilisations wipe out other alien civilisations that they find. Perhaps because they find them to be threats and try to deal with it pre-emptively
• Aliens are very very weird and don't live on planets
• Aliens can't be bothered to communicate -Commication kills -Aliens are avoiding Earth. Maybe to allow us to develop naturally, or to observe us, or because they don't like us
• Reality is a simulation
• Aliens are already on Earth

These explanations have a few things in common. They all require accepting extra claims without evidence. They often require that aliens all have the same unlikely motivations, which becomes less likely the more aliens there are. These assumed universal motivations are contradicted by the only intelligent species we have evidence of.

They all assume that the galaxy is filled with technological civilisations, a conclusion they come to through a highly speculative process.

I think that the best explanation is a lot less exciting.

What's a good explanation

Let's put some numbers in the Drake equation, and introduce a few more terms.

• 300 million potentially habitable exoplanets in this galaxy.
• Let's say that 50% of them have a magnetic field that makes sure life isn't killed off by solar flares. That leaves 150 million candidates.
• Let's say that 20% of those don't have to worry about bombardment wiping out all life because they have something functionally equivalent to Jupiter or they're just lucky. That leaves 30 million candidates.
• Plate tectonics seem to be crucial for recyling chemicals and keeping life going. They also seem to be rare. Let's say a third of planets have it. That leaves 10 million candidates.
• Lets say abiogenesis occurs on 1% of those. That leaves 100000 candidates.
• Let's say multicellular life occurs in 10% of those. That leaves 10000 candidates.
• Now let's say animals evolve in 10% of those. This leaves 1000 candidates.
• Out of the the 8 million or so animal species on Earth, 1 are an intelligence technological civilisation. That would give us 0.000125 candidates in this galaxy.

You get the picture. So many proverbial stars have to align, that there's no reason to suspect that space is filled with alien life.

Whilst this assumes that things will be like Earth, since the paradox relies of life being frequent, and we only have evidence of life on Earth, I don't think that changes the analysis much.

You could say that space is really really big, and that I've just shown estimates for 1 out of 100 billion galaxies. And that's true. But because space is so vast, we shouldn't expect to be contacted by any aliens outside of the galaxy. Even if we assume advanced technology, other galaxies are just too far. We can't magic our way beyond the speed limit of the universe. We know that nothing with mass can accelerate to the speed of light. And no amount of future discoveries will change that, just like no future discoveries will show that the Earth is flat.

Even if intelligent alien life develops on these planets, most intelligent life is non-space-faring, at least on our planet. Dolphins, octopodes, and chimps aren't gong to space any time soon. They're happy where they are. Being human-like is one particular way of being, it's not the ultimate goal of evolution.

But even if you get there, space is big, really big. Intergalactic space travel will always be highly resource intensive, slow, and difficult.

Space is so big that we wouldn't know where to look in large distance. Things like radio signals suffer from inverse square laws.

To summarise, there probably is not that much advanced intelligent life, and they'd be pretty limited in their influence. There is no reason we should expect to see them. There is no paradox.

There's no reason to worry about our fate as an explanation to this so-called paradox.