The Fermi Paradox and fear of the Great Filter

What is the Fermi Paradox?

Sometimes it’s easy to forget how massive the universe is. I don’t mean purely in terms of the distances involved (although this seven-mile scale model of the solar system in the Black Rock Desert demonstrates that point quite well), but in terms of the scale. There are around 100-400 billion stars in our galaxy and around the same number of galaxies in the universe, meaning we’re possibly looking at upwards of 1,000,000,000,000,000,000,000 stars. Try and imagine every grain of sand on Earth. Done it? Right, well there’s more than 100 stars out there for every one of those grains.

Of course, not all of those will be similar to our sun, but even if you go with scientists’ conservative estimates, you’re looking at around 500 quintillion (that’s a five with 20 zeroes) suns that are a bit like ours. Some of these will have planets orbiting them, and some of these will be in their own “Goldilocks zone” – the sweet spot where it’s warm enough for liquid water not to freeze, but cold enough for it not to evaporate.

Naturally, this is speculation because most of these we can’t even see (even what we know about Kepler 452-b is inferred through its shadow), but it could be as high as 50% of these. Halve that, and call it 25%, and you still come up with 125 quintillion Earth-like planets. Hell, call it 1.5%, and there’s still enough Earth-like planets for every human on Earth to adopt one billion Earth 2.0s each, with around 400 billion spares.

These planets are of different ages, and not all of them would have the perfect blend of herbs and spices that has resulted in intelligent life to evolve, but if even 0.1% of them did, that would be around 7,500,000,000,000,000 planets with intelligent life.

Which leads to the puzzling question that physicist Enrico Fermi is said to have asked: where is everybody?

There are a bunch of possible solutions to the Fermi Paradox, but no definitive answer. In broad terms, they come in three flavours:

1. There is no life out there (or isn’t anymore)

2. There is life out there and they haven’t made contact

3. There is life out there and they have made contact. We just didn’t notice

For each of the theories, there are plenty of subsets – some creepier than others. Strap in.

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