Astronomers Detect a Possible Signature of Life on a Distant Planet

This is your daily reminder that if we do indeed discover life so close (~120 LY) to Earth, it's an incredibly bad sign for us. This is an exercise in Bayesian reasoning.

Imagine there are 2 planets in the Milky Way where life has developed. The odds are incredibly low they're next to each other, assuming a random distribution. So it's way more likely that there are more than 2. Imagine a sphere of radius 60 LY (120/2). Our Earth is the center of one. This planet is another. That's a volume of 10^6 LY^3. The Milky Way volume (from Google) is ~17T LY^3 so there'd be roughly 170M such spheres in our galaxy.

Now imagine if the odds of simple life becoming intelligent life that we could detect and could become spacefaring is 1 in 1 million. There'd be ~170 such civilization in the Milk Way.

We have absolutely no evidence of this So simple life is a lot less common, intelligent life is a lot less likely or, and this is the scary part, something tends to wipe out sentient civilizations and that's likely in our future.

In Fermi Paradox terms, we call this a Great Filter.

If you assume life is very likely then the Great Filter has to be an almost perfect filter to explain the Fermi Paradox. With fewer civilisations in the galaxy (<50) you might be able to assume that if 95% of them destroy themselves it would be unlikely we'd ever find life. If we assume 170 civilisations then the great filter would have to be something akin to a natural law.

My gut says that the Great Filter is real but probably doesn't filter more than 99% of civilisations. Were I to guess complex life is uncommon, and intelligent life very uncommon. The majority of planets which do develop intelligent life destroy themselves fairly quickly.

There's only the fact that we probably just CANNOT perceive extremely advanced civilizations.

An insect crawling around a 75 year old brick house that is covered in ivy and moss will have NO idea that the object it is walking upon is NOT part of it's natural environment. That brick house seems as natural to the environment as the grass, and trees, and rocks, and streams nearby it -- to the bug at least.

Similarly we take our telescope out and see what looks like a natural organic universe with organic galaxies and normal looking stars etc...

Because we don't have solar system sized brains and billion year life spans we are absolutely hopeless to realize that theres' a lot of massive artificial structures in this universe. We're too bug-like to even be able to perceive them from our natural environment.

*we do know of massive cosmic structures like filaments, voids, and the great wall. So it is possible we as humans are starting to notice the "house" in the woods since our theories of physics cannot really explain why these structures exist at these massive scales (we would expect uniformity at those scales). See [here](https://en.wikipedia.org/wiki/List_of_largest_cosmic_structu...)