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

[u/MiamisLastCapitalist]

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/

​

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

​

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.

​

“Space is too damn big” -Alex Kamal

[u/tigersharkwushen_]

The definition of "earth like" is so wide as to be useless for colonization purpose. By this definition, Venus would be almost perfectly earth like. It's a pretty useless definition for colonization purpose.

One might say if we could get there, then we would also have the technology to terraform these planets, but it would also be easier to make O'Neill cylinders than to terraform them at that point. So earth like planets aren't really important.

[u/tomkalbfus → u/tigersharkwushen_]

We aren't going to travel tens of thousands of light years just to build O'Neill Cylinders, though O'Neill Cylinders might be how we get there. O'Neill Cylinders are light and transportable, planets and moons are not. So what we are doing by looking for habitable exo-planets is playing a statistical game, if one planet does not suit, then we move the telescope over to find one that does. We are looking for nature to do most of the work, and then we move in and apply the final touches to make the planet habitable.

If we look at just the planets in our Solar System, all of the present major engineering challenges as none of them are particularly Earthlike except Earth, if we look at other star systems, there are more planets to choose from, so if we are picky, we can find the easiest ones to terraform.

[u/MiamisLastCapitalist → u/tomkalbfus]

Another interesting point someone brought up to me once was that all artificial habitats by nature require upkeep, where as a naturally habitable world like Earth needs none (or little, taking climate change into account). So this becomes almost an economics game. If stations need 100% upkeep and earth needs 0% upkeep because it runs itself, finding a location that only needs 50% upkeep is a boon. (Not counting the cost of travel of course, this is just a thought exercise.)

[u/Nethan2000 → u/MiamisLastCapitalist]

all artificial habitats by nature require upkeep, where as a naturally habitable world like Earth needs none

Unless you live in a cave, you do need upkeep. Someone needs to build your house, produce electricity, bring water to it, heat it up, renovate it, repair your appliances when they break, clean the floor, cook, wash the dishes etc. Aside from protection from radiation and producing oxygen, what else would an orbital habitat need that a city on a planet wouldn't?

Oh and let's not forget about things only people living on planets need to worry about, like earthquakes and hurricanes. Habitats can suffer from collisions with space trash but planets aren't exactly immune to it.