Other commenters (rightly) pointed out this is a stretch to the term "habitable".
What's becoming clear though is the only thing stopping us from lots of Earth-mass planets is the abilities of our detectors to detect ever-smaller gravitational wobbles and ever-smaller transits. Bear in mind we only tend to find planets around stars where we're on their ecliptic planes.
So planets seem to be really common. If they weren't the odds of finding planetary systems on our nearest stellar neighbour would be quite low.
But the distances are still so vast that the energy expenditure and timelines are completely impractical (if you assume the speed of light of a hard cosmic limit, which I do).
So if planets are common and interstellar travel is impractical, the only way to expand really is around your own star. This is the Dyson Swarm. This would actually solve the energy issue of interstellar travel (ie"stellar highways") so it's almost a prerequisite. Thing is, Dyson Swarms are likely detectable from vast distances due to their IR emissions (ie the only way to get rid of heat is to radiate it into space and that has a specific frequency depending on the temperature of the radiating object).
But if planets are really common and we don't see any Dyson Swarms it seems that spacefaring life is extremely rare and the most likely number of such civilizations in the Milky Way is 1 including us.
What's becoming clear though is the only thing stopping us from lots of Earth-mass planets is the abilities of our detectors to detect ever-smaller gravitational wobbles and ever-smaller transits. Bear in mind we only tend to find planets around stars where we're on their ecliptic planes.
So planets seem to be really common. If they weren't the odds of finding planetary systems on our nearest stellar neighbour would be quite low.
But the distances are still so vast that the energy expenditure and timelines are completely impractical (if you assume the speed of light of a hard cosmic limit, which I do).
So if planets are common and interstellar travel is impractical, the only way to expand really is around your own star. This is the Dyson Swarm. This would actually solve the energy issue of interstellar travel (ie"stellar highways") so it's almost a prerequisite. Thing is, Dyson Swarms are likely detectable from vast distances due to their IR emissions (ie the only way to get rid of heat is to radiate it into space and that has a specific frequency depending on the temperature of the radiating object).
But if planets are really common and we don't see any Dyson Swarms it seems that spacefaring life is extremely rare and the most likely number of such civilizations in the Milky Way is 1 including us.