[maaku]

Great filter theory is nonsense. The period between intelligent life evolving and it taking over the universe at near the speed of light is so short, in cosmic time, that any civilization anywhere should expect to see an empty universe (in their light cone).

[Lost_BiomedE]

Before reading Power, Sex, and Suicide, I may have agreed.

http://en.wikipedia.org/wiki/Power,_Sex,_Suicide

It is a possibility that there is a relatively small window where single celled life has the opportunity to become multicellular life. As one amazon review summed it:

'After the origin of life, the next big step on the way to us was the origin of eukaryotes. These are all the organisms - including people, trees, mushrooms, and slime molds - who package most of our DNA into chromosomes in cell nuclei. Mitochondria, the "powerhouses" of eukaryotes, are descended from bacteria which took to living in a very close relationship with another type of one-celled organism; in fact they came to live inside the other. Nick Lane argues that this merger must have preceded the formation of the nuclear membrane.' *

The great filter is stronger and weaker in argument depending on where you place the filter, but the idea in general remains the same.

*more info here but less than the book, via an article in new scientist by the author: http://ronbarak.tumblr.com/post/25996121029/life-is-it-inevi...

[maaku]

I'm not sure what aspect of my post you are arguing against? I guess there could be different definitions at play here, but I was talking about a hypothetical developmental stage where most civilizations destroy themselves. E.g. nuclear war, climate change, etc.

Regarding how common life is in the universe, I wasn't talking about non-intelligent life. I fully expect that we will find signs of such life elsewhere in the cosmos in the next hundred years, either on Mars, Europa, Titan, Enceladus, or perhaps in the atmospheric spectra of some extra-solar planet.

No, I was talking about intelligent life, which if iot exists has a very short gestational period before transforming into lasting intelligence(s) expanding into the universe at close to physical limits. In particular the window between development of technology detectable from distant observation (e.g. radio) and a runaway singularity pushing that civilization's expansion rate to light speed limits is so small that regardless of the prevalence of intelligent life in the universe, we should expect to see an empty sky. Why? Because for most of the history of the cosmos we see an empty sky in our light cone. Then suddenly the most distant stars start to go dim with strangely shifted spectra, in an expanding wave that flows through visible star systems at >0.9c until it hits us, and ... well who knows what happens then.

The Fermi paradox is: "if there are so many intelligences, why can't we see them?" The transhumanist response is: "if we could see them, we'd be dead." By the anthropic principle we can only expect to exist in the time period where we are alive, not dead, so we should expect with very high probability to see an empty sky, and with very low probability the coming onslaught of darkness.

[lumpypua]

I agree with your overall statistical/singularity argument, but that's not reason enough to call a great filter nonsense. The biology of a great filter is at play along with the overall cosmological context.

"Power, Sex, and Suicide" argues that eukaryotic (and thus multicellular) life is basically a fluke—it is the great filter. The tumblr link Lost_BiomedE gave takes a while to get to that punchline but it's worth a read.

[maaku]

I should have said "the great filter explanation of the Fermi paradox is nonsense." There may be one or more great filters. There may be an early filter, or a late filter, or both. But that issue is orthogonal to why we see an empty sky. We see an empty sky because the amount of time between observing an extraterrestrial intelligence and being absorbed by it is so short that we should expect to exist in an empty-sky universe, regardless of how common life is.

One might then argue about the prevalence of extraterrestrial intelligence based on the age of the universe and the fact that our light cone apparently does not contain any other intelligent life. IMHO a sample size of 1 isn't that interesting however.

[lumpypua]

Power, Sex, and Suicide is one of the best books that has ever been written for the educated lay audience on biology. Great topics—the origin of life, sex, maad biochemistry. Seriously, if you're interested in biology and you have a decent background, read this fucking book.