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Stepping outside at night and looking up at the stars is one of my favourite things to do. It seems to put everything into perspective. We can only see a tiny fraction of the stars that are out there, but even that is enough to remind us how important our mundane worries are in the grand scheme of things. Not very.

If you’re Enrico Fermi (1901-54), the Italian-American physicist responsible for the first nuclear reactor, when you look at the stars you might see more than crippling nihilism. Quite the opposite: you might be puzzled that we really do seem to be so special.

“You’d like to think that at least some of these intelligent civilisations might have thought about interstellar travel”

There are billions of stars in the galaxy which are just like the Sun. It’s incredibly likely that many of them are orbited by Earth-like planets, of similar mass, size, and atmosphere. If the Earth is typical, it’s likely that many of these planets have developed intelligent life. You’d like to think that at least some of these intelligent civilisations might have thought about interstellar travel, like we are right now. An industrious civilisation could traverse the whole Milky Way in just a few million years. This is nothing compared to the age of the universe, which sits at around 13.6 to 14 billion years, depending on who you ask.

So why haven’t we been visited by aliens yet?

The question seems a little ridiculous at first, but in 1975 Michael H. Hart, an American astrophysicist (and sadly an active white separatist) became the first to publish a rigorous analysis of Fermi’s question. His work showed that the question really did need some attention, and became so foundational that Fermi’s question is now often known as the Fermi-Hart paradox.

Hart’s explanation was the Rare Earth hypothesis: only a very small set of conditions are viable for life, and Earth really is astonishingly special. This is perhaps an unsurprising argument for a white separatist to make. It doesn’t hold much water for me, though. Throughout history, humans have always thought that Earth is more special than it actually is. Only 400 years ago, the Catholic church condemned Galileo for arguing that the Earth was not the centre of the universe. Only 250 years ago did Thomas Wright suggest that the sun was not the centre of the universe either. We probably have a long way to go before we truly overturn our natural intuition that the Earth is somehow important.

Instead, another idea appeals to me: that of a ‘Great Filter’. In this model, any embryonic civilisation must pass through some sort of test which has a high likelihood of causing mass extinction. With any luck, that test is behind us. Maybe it’s really hard to have sex for the first time. Maybe it’s hard for single-cell life to evolve into multi-cell life. Maybe it’s tough to pick up a tool, or pick up a language.

But maybe the test is in front of us. This would not be good news. If the Great Filter is still to come, it’s probably imminent (on a geological scale). Even with current space technology, we could traverse the Milky Way in about two to 50 million years, so the Great Filter would have to kill us off before then. The Great Filter could be anything: perhaps sufficiently intelligent life is very likely to annihilate itself via nuclear war, or climate change, or hyper-intelligent AI, or…

Next time you’re out at night, take a look at the stars. What do you think?