"That's all we can really say at this point," Barnes says. "We don't have any clue if they actually are habitable, let alone if they are inhabited."
Quoteing from the article, the above just about sums it up for me. Are some "earth like" planets out there somewhere? Very possibly so, but right now we don't really have a clue.
When they say "habitable", do they mean habitable by human standards (i.e., they are looking for alternate worlds for humans to colonize)? Or do they mean it in the sense of supporting any kind of life. Because when they say that conventional measures search for a planet that is Earth-like, my thought is that a large portion of Earth is not "habitable" by human standards. We can't live in the oceans that cover the vast majority of our home's surface; we are confined to the mounds of rock and soil that have jutted to the surface, and we need the additional comfort of a temperate climate and a nice thick ozone layer to protect our fragile cells. So theoretically, there could be many "habitable" planets that have not in fact given rise to any kind of life whatsoever.
If they are just looking for any kind of life, Heller and Armstrong's conclusion just seems like a "well, duh!" moment. In the realm of the entire universe, out of all that is theoretically possible, did people really think life only existed in the proverbial M class planet? ...huh...okaaaay... Well, to be fair, humanoid life would have the best chance of existing on such a planet...is that all they're looking for? A long, long time ago I remember watching something on Discovery about a theoretical planet on which life was based on Silicon instead of Carbon. The show talked about how all of the "plants" and "animals" would be very brittle and might actually break in high winds. It was all fake and the surreptitious goal was to make people learn about Silicon (damn you, science teachers!), but the idea is fascinating when you think about it.
But on the other hand, this is all theory until--and if--we actually find something.
I don't think it would be hard to construct an argument that the fact earth isn't "superinhabitable" is the reason we have developed as far as we have (well most of us).
In a warm,wet world without extreme weather the may not be the evolutionary pressure to evolve beyond the simplest organisms. Whereas life on earth had to struggle to survive and thus started an arms race from phytoplankton through the pinnacle of life on earth, the Youtube comments section troll.
Astronomers have found a few planets in "Goldie Locks" zones.
Given their distance away, has anyone else computed the number of centuries (multiply this number by about four to get the number of generations) that people would have to survive aboard a spacecraft to reach the nearest one?
Even if a spacecraft large enough to carry the required supplies could get up to one/tenth the speed of light?