Galap comments on The Octopus, the Dolphin and Us: a Great Filter tale - Less Wrong

48 Post author: Stuart_Armstrong 03 September 2014 09:37PM

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Comment author: chaosmage 31 August 2014 12:30:24PM *  42 points [-]

I don't think filters have to be sequential - some could be alternatives to each other, and they might interact. Consider the following.

Each supernova sterilizes everything for several lightyears around them. This galaxy has three supernovas per century, and it used to have more. Earth has gone unsterilized for 3.6 billion years, i.e. each of the last (very roughly) 100 million supernovas was far enough away to not kill it.

That's easy to do for a planet somewhere on the outer rim, but the ones out there seem to lack heavy elements. If single-celled, mullti-celled, even intelligent life was easy given a couple billion years of evolution, you still couldn't go to space on a periodic table that didn't contain any metals.

So planets in areas with lots of supernova activity (i.e. high density of stars) could simply never have enough time between sterilizations to achieve spacefaring civilization, while planets in areas with low density of stars/supernovas haven't accumulated enough heavy elements to build industry and spaceships. Neither effect prohibits everything, but together they're a great filter.

There could be other combinations of prohibitive factors, where passing one makes passing the other more difficult. Maybe you need to be a carnivore in order to evolve theory of mind, but you also need to be a herbivore in order to evolve agriculture and exponential food surplus. Or maybe you need tectonic plates to avoid stratification of elements, but you also need a very stable orbit around your star, and those two conditions usually rule our each other. I don't know. It just seems that a practically linear model of sequential filters, where filters basically don't interact with each other, is entirely too simplistic to merit confidence.

In a few years, we'll have a much clearer picture of the chemical makeup of the closest few hundred exoplanets, and that'll cut down the number of possible explanations of Fermi's Paradox to a maybe sort of manageable size. Until then, this discussion is unlikely to lead anywhere.

Comment author: Galap 19 September 2014 04:14:35AM 3 points [-]

I don't agree that metals and heavy elements are necessary for industry and spaceships: you can do quite a lot with light elements, particularly carbon (for example plastics, carbon fiber, etc.). Also, biology makes all of its structure through lighter elements.

That being said, I think you're very much on the money with the general idea: I also thought something similar while reading the artifcle (that the filters are likely multivariate and interdependent), but not in as well thought out a way.

Comment author: AnthonyC 17 August 2015 10:36:13AM 0 points [-]

We can do quite a lot with light elements now, after we spent millennia figuring out metals. We still use a lot of metal equipment and catalysts in the manufacturing of polymers and carbon fiber. I'm sure there are processes for making them without metals, but getting civilization going in the first place would be much harder without elements heavier than iron.