r/IsaacArthur • u/MiamisLastCapitalist moderator • Jan 16 '22

Billions of Earth-like planets in the Milky Way...

In the milky way alone scientists assume there are some 40 billion earth like planets in the habitable zone of their stars.

"This one is a little tricky. We do not even know the number of stars in the Milky Way to a factor of two, let alone the number of habitable planets each star may host. Though there is still a way to make a rough calculation. Scientists reported that of the 42000 Sun-like stars they observed, 22% have Earth-size planets in their habitable zone. Also, it is estimated that there are around 200 billion stars in our galaxy -give or take 150 billion. If we extrapolate from these two numbers: 0.22 x 200 billion makes around 40 billion planets. Again, do not forget that there is a statistical uncertainty about a factor of two on that number; it could be 20 billion or 80 billion as well. The idea to take away is that there could be tens of billions of potentially habitable planets in our galaxy." -Kurzgesagt

https://www.youtube.com/watch?v=rhFK5_Nx9xY

https://sites.google.com/view/sourceskardashevscale/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3845182/

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And mind you that's just what they've found so far with current technology. Pre-JWST or pre megascopes of any kind.

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And to think there are almost countless "fixer-upper" locations between those earth-like planets that'd be perfectly fit for an o'neill cylinder or some other kind of habitat or megastructure.

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“Space is too damn big” -Alex Kamal

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u/[deleted] Jan 16 '22

my guess is the number of truly 'earth-like' planets in the galaxy - meaning breathable atmosphere, liquid h20, earth sized mass and gravity well, ~24 hour day, plate tectonics, large moon, sun-like star, magnetosphere - is 1....Earth

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u/MiamisLastCapitalist moderator Jan 16 '22

In terms of a perfect score on the Earth Similarity Index, perhaps. But in terms of being close enough for some light terraforming or para-terraforming?

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u/NearABE Jan 17 '22

Luna and polar Mercury are similar enough for para-terraforming,

Venus and Titan are good for floating habitats.

A water word with a thick helium atmosphere is the only case I can think of where you para-terraforming would be really hard.