- 100b stars in milky way
- 100b galaxies in observable universe
- 10^22 stars available
- sun-like stars 5-20% (est 1%)
- possible earth-like planets 22-50% (est 10%)
- estimate 1% of earth-like planets develop life
- estimate 1% of those planets generate a civilization
- universe 13.6b years old
- earth 4.5b years old
- life on earth
- simple life 4b
- eukaryotes 2.5b
- complex life 1.5b
- land animals 500m
- human 2.5m
- neanderthals 500k
- homo sapiens 200k
- type 1 civ - harness its planets resources, nuclear energy
- type 2 - harness its host stars energy
- type 3 - harness galaxy's energy
wall that vast majority of attempts at life hit that they can't get past en route to type 3 civ, which means no one's hit a type 2 or 3 civ bc we would have heard about it, bc those civs would have colonized the galaxy by now (4m years with replicating bots)
depending on where filter is, either we're rare, first, or fucked.
rare - we've passed the great filter.
- life occurring in the first place?
- simple prokaryote to complex eukaryote? (wtf)
- chimps to humans?
first - universe hasn't been hospitable to life forming until now, and we might be first.
fucked - great filter ahead, and we probably won't pass it by definition.
- sufficiently advanced technology almost certainly destroys civilization
- eventual gamma ray burst becomes increasingly likely as t goes to infinity
- already visited earth (only 50k years of human civ)
- galaxy's been colonized, we're just in some remote part
- type 2/3 civs might not need to take over the physical universe (singularity)
- everyone's smart enough not to broadcast that they exist
- one super civ that eliminates others
- our tech too primitize to pick up signals
- the government
- zoo hypothesis
- too primitive to perceive them (ants and a super highway)
- interstellar travel might not be possible
- life can exist orders of magnitude faster/slower than human life, consequently communications, etc
The Drake equation is:
N = R * fp * ne * fl * fi * fc * L
where:
N = the number of civilizations in our galaxy with which communication might be possible (i.e. which are on our current past light cone);
and
- R* = the average rate of star formation in our galaxy (10 stars/year)
- fp = the fraction of those stars that have planets (0.5)
- ne = the average number of planets that can potentially support life per star that has planets (2.0)
- fl = the fraction of planets that could support life that actually develop life at some point (1.0)
- fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations) (0.01)
- fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space (0.01)
- L = the length of time for which such civilizations release detectable signals into space (10k y)
- first radio waves emitted from earth - 150 light year sphere? (due to signal degradation, only a few light-years relevant for earth to be broadcasting, unless there was some focused/amplified beam)
- if so, average distance to neighboring stars? what would even distribution look like?
- how long has SETI been listening? (50 years)
- percentages and how conservative should we be?
- explain radio waves, inverse square law, why it wouldn't work